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Millipore pbs edta
Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as <t>PBS-EDTA,</t> to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
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Images

1) Product Images from "Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy"

Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

Journal: PLoS ONE

doi: 10.1371/journal.pone.0152112

Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
Figure Legend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

Techniques Used: Concentration Assay, Buffer Exchange

(A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.
Figure Legend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

Techniques Used: Injection, Flow Cytometry, Size-exclusion Chromatography

(A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.
Figure Legend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

Techniques Used: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).
Figure Legend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

Techniques Used: Solubility, Centrifugation, Concentration Assay, Standard Deviation

2) Product Images from "Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy"

Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

Journal: PLoS ONE

doi: 10.1371/journal.pone.0152112

Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
Figure Legend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

Techniques Used: Concentration Assay, Buffer Exchange

(A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.
Figure Legend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

Techniques Used: Injection, Flow Cytometry, Size-exclusion Chromatography

(A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.
Figure Legend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

Techniques Used: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).
Figure Legend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

Techniques Used: Solubility, Centrifugation, Concentration Assay, Standard Deviation

3) Product Images from "Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy"

Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

Journal: PLoS ONE

doi: 10.1371/journal.pone.0152112

Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
Figure Legend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

Techniques Used: Concentration Assay, Buffer Exchange

(A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.
Figure Legend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

Techniques Used: Injection, Flow Cytometry, Size-exclusion Chromatography

(A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.
Figure Legend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

Techniques Used: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).
Figure Legend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

Techniques Used: Solubility, Centrifugation, Concentration Assay, Standard Deviation

4) Product Images from "Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy"

Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

Journal: PLoS ONE

doi: 10.1371/journal.pone.0152112

Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
Figure Legend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

Techniques Used: Concentration Assay, Buffer Exchange

(A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.
Figure Legend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

Techniques Used: Injection, Flow Cytometry, Size-exclusion Chromatography

(A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.
Figure Legend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

Techniques Used: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).
Figure Legend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

Techniques Used: Solubility, Centrifugation, Concentration Assay, Standard Deviation

5) Product Images from "Mesenchymal Stromal Cells Engage Complement and Complement Receptor Bearing Innate Effector Cells to Modulate Immune Responses"

Article Title: Mesenchymal Stromal Cells Engage Complement and Complement Receptor Bearing Innate Effector Cells to Modulate Immune Responses

Journal: PLoS ONE

doi: 10.1371/journal.pone.0021703

Blood exposure of MSCs activates complement and effector cells. Lepirudin-anticoagulated blood was incubated with MSCs (black), and blood treated with either PBS (white) or 10mM EDTA (shaded) served as active or inactive control, respectively. ( A ) Plasma levels of C3a (ng/ml, n = 13), and ( B ) Plasma level of soluble C5b-9 complex (AU/ml, n = 13) were detected with ELISA. ( C ) Flow cytometric analysis of PBMCs and MSCs after labeling of individual blood aliquots with specific antibodies and subsequent erythrocyte lysis; the cells were first gated according their scatter profile (top panel, scatter plot) and representative histograms for triggering of CD11b-expression on PMNs (green) or binding of C3-fragments to MSCs (red) are shown compared to EDTA-inactivated negative control blood (grey histograms). ( D ) Up-regulation of CD11b on PMNs in blood (MFI, n = 19). The median fluorescence intensity (MFI) of the cell-surface marker CD11b was assessed with flow cytometry. ( E ) Percentage of recovered MSCs after a 40 min exposure to active or EDTA-inactivated blood (n = 17). The data in figure A-E are means±SEM; with: ns = not significant; * *P
Figure Legend Snippet: Blood exposure of MSCs activates complement and effector cells. Lepirudin-anticoagulated blood was incubated with MSCs (black), and blood treated with either PBS (white) or 10mM EDTA (shaded) served as active or inactive control, respectively. ( A ) Plasma levels of C3a (ng/ml, n = 13), and ( B ) Plasma level of soluble C5b-9 complex (AU/ml, n = 13) were detected with ELISA. ( C ) Flow cytometric analysis of PBMCs and MSCs after labeling of individual blood aliquots with specific antibodies and subsequent erythrocyte lysis; the cells were first gated according their scatter profile (top panel, scatter plot) and representative histograms for triggering of CD11b-expression on PMNs (green) or binding of C3-fragments to MSCs (red) are shown compared to EDTA-inactivated negative control blood (grey histograms). ( D ) Up-regulation of CD11b on PMNs in blood (MFI, n = 19). The median fluorescence intensity (MFI) of the cell-surface marker CD11b was assessed with flow cytometry. ( E ) Percentage of recovered MSCs after a 40 min exposure to active or EDTA-inactivated blood (n = 17). The data in figure A-E are means±SEM; with: ns = not significant; * *P

Techniques Used: Incubation, Enzyme-linked Immunosorbent Assay, Flow Cytometry, Labeling, Lysis, Expressing, Binding Assay, Negative Control, Fluorescence, Marker, Cytometry

6) Product Images from "Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy"

Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

Journal: PLoS ONE

doi: 10.1371/journal.pone.0152112

Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
Figure Legend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

Techniques Used: Concentration Assay, Buffer Exchange

(A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.
Figure Legend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

Techniques Used: Injection, Flow Cytometry, Size-exclusion Chromatography

(A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.
Figure Legend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

Techniques Used: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).
Figure Legend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

Techniques Used: Solubility, Centrifugation, Concentration Assay, Standard Deviation

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    Millipore pbs edta
    Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as <t>PBS-EDTA,</t> to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.
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    Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

    Journal: PLoS ONE

    Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

    doi: 10.1371/journal.pone.0152112

    Figure Lengend Snippet: Representative absorbance spectra of AMB-PEG 2 and unconjugated AMB formulations prepared in buffers with varying hydrophobicity. 20 mM AMB-PEG 2 and unconjugated AMB formulations were prepared in DMSO and resuspended in 20% and 48% ACN buffers containing 4.3% acetic acid, as well as PBS-EDTA, to a final concentration of 2 mM AMB. As buffer hydrophobicity increases with higher ACN concentrations, the A 348 /A 409 ratio decreases, implying that AMB-PEG is increasingly in its monomeric form. As AMB-PEG 1 and 2 have similar UV-visible absorption profiles, with identical peak height ratios in all buffers tested, data for AMB-PEG 1 is not shown. AMB-PEG formulations that have been subjected to buffer exchange to PBS-EDTA through a 10 kDa centrifugal filter have the same UV-visible absorption spectra as the initial formulation of AMB-PEG in PBS-EDTA, which contains 10% DMSO.

    Article Snippet: AMB-PEG Particle Size Determination Using DLS 2 mM solutions of AMB-PEG were prepared in PBS-EDTA, and diafiltration carried out with PBS-EDTA using 10 kDa centrifugal filters (Millipore).

    Techniques: Concentration Assay, Buffer Exchange

    (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

    Journal: PLoS ONE

    Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

    doi: 10.1371/journal.pone.0152112

    Figure Lengend Snippet: (A) Reverse phase chromatogram of AMB-PEG and unconjugated AMB, with eluted peaks detected at 406 nm. 50 μL of AMB-PEG 1 and 2, and 10 μL of unconjugated AMB dispersed in PBS-EDTA and 48% ACN respectively were injected into a C18 reverse phase column and eluted isocratically in a 48% ACN buffer at a flow rate of 0.5 ml/min for 40 minutes. Peaks were detected at 406 nm. The AMB-PEG conjugate has a shorter retention time, implying that it is more hydrophilic. From the AMB-PEG samples, AMB-PEG conjugate and free AMB (based on the retention time of unconjugated AMB) fractions were collected for further analysis via size exclusion chromatography. (B) Size exclusion chromatogram of AMB-PEG 2 and unconjugated AMB, as well as the relevant fractions collected from RPC, in a 20% ACN mobile phase. 20 mM of AMB-PEG 2 formulations and unconjugated AMB in DMSO were prepared and resuspended at 2 mM in a 20% ACN buffer. 50 μL of these samples (unconjugated AMB diluted tenfold prior to analysis) and the peak fractions collected previously from RPC were passed through a size exclusion column and eluted peaks were detected at 406 nm. Unconjugated AMB was eluted later compared to the AMB-PEG conjugate, implying that it has a smaller hydrodynamic volume compared to AMB-PEG in 20% ACN. The previously collected AMB-PEG conjugate and free AMB peak fractions had similar retention times as the AMB-PEG 2 formulation and unconjugated AMB samples respectively, thus verifying their respective peak identities. AMB-PEG 1 and 2 have identical elution profiles. (C) Size exclusion chromatogram of AMB-PEG and unconjugated AMB dispersed in PBS-EDTA. 3 μL of 2 mM AMB-PEG formulations that have been retained by 10 kDa centrifugal filters (Millipore) and 50 μL of the supernatant obtained from unconjugated AMB were analysed using a Superdex 75 size exclusion column and eluted peaks detected at 406 nm. In a PBS-EDTA mobile phase, unconjugated AMB has a shorter retention time of 20 minutes compared to AMB-PEG at 40 minutes, implying that AMB-PEG has a smaller hydrodynamic volume under these experimental conditions.

    Article Snippet: AMB-PEG Particle Size Determination Using DLS 2 mM solutions of AMB-PEG were prepared in PBS-EDTA, and diafiltration carried out with PBS-EDTA using 10 kDa centrifugal filters (Millipore).

    Techniques: Injection, Flow Cytometry, Size-exclusion Chromatography

    (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

    Journal: PLoS ONE

    Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

    doi: 10.1371/journal.pone.0152112

    Figure Lengend Snippet: (A) AMB-PEG reaction scheme. The NHS ester on MS(PEG) 4 reacts with the primary amine (–NH2) group on AMB at a 1:1 molar ratio, generating conjugated AMB-PEG via amide bond formation. (B) Solubility of AMB-PEG at varying AMB:PEG molar ratios. AMB-PEG mixtures and unreacted AMB were prepared in DMSO, incubated for 2 hours and then (i) dispersed to a final concentration of 2 mM in PBS-EDTA, containing 10% DMSO by volume. (ii) The mixtures were then centrifuged to facilitate the observation of insoluble precipitates. Higher molar ratios yielded a suspension of yellow particles that precipitated upon centrifugation, similar to what was observed with unconjugated AMB.

    Article Snippet: AMB-PEG Particle Size Determination Using DLS 2 mM solutions of AMB-PEG were prepared in PBS-EDTA, and diafiltration carried out with PBS-EDTA using 10 kDa centrifugal filters (Millipore).

    Techniques: Mass Spectrometry, Solubility, Incubation, Concentration Assay, Centrifugation

    Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

    Journal: PLoS ONE

    Article Title: Characterization of a Polyethylene Glycol-Amphotericin B Conjugate Loaded with Free AMB for Improved Antifungal Efficacy

    doi: 10.1371/journal.pone.0152112

    Figure Lengend Snippet: Aqueous solubility of AMB-PEG 1 and 2. Increasing amounts of AMB-PEG formulations were added to PBS-EDTA, and post-centrifugation, the concentration of soluble AMB-PEG in the supernatants quantified based on their absorbance at 365 nm. Error bars denote the standard deviation between 3 independent formulations. Dotted line represents the theoretical condition where AMB formulation is completely soluble (i.e. concentration of total AMB = concentration of soluble AMB).

    Article Snippet: AMB-PEG Particle Size Determination Using DLS 2 mM solutions of AMB-PEG were prepared in PBS-EDTA, and diafiltration carried out with PBS-EDTA using 10 kDa centrifugal filters (Millipore).

    Techniques: Solubility, Centrifugation, Concentration Assay, Standard Deviation