Journal: Bioactive Materials
Article Title: Bone targeted microenvironment actuated engineered exosomes for precision therapy of IBD associated bone loss
doi: 10.1016/j.bioactmat.2026.04.034
Figure Lengend Snippet: Engineering and Characterization of an MMP-Responsive Bone-Targeted Exosome (ExoBIP) (see also Supporting ) (A) Schematic of ExoBIP construction and mechanism of action. IL-18BP was dual-functionalized with an MMP-cleavable linker (PLGVR) and a bone-targeting peptide (SDSSD) via NHS–amine chemistry. Separately, BMSC-derived exosomes (Exo) were treated with TCEP to expose surface thiol groups (-SH). The maleimide-terminated IL-18BP complex was then conjugated to the thiol-activated exosomes via thiol–maleimide coupling to form ExoBIP. Upon reaching MMP-rich bone resorption sites, the linker is cleaved, releasing IL-18BP to neutralize IL-18, while BMSC-derived exosomes preserve their inherent osteogenic potential. Some elements of this figure were created with BioRender.com (license number: YG28QKC6SI). (B) Representative TEM image of ExoBIP stained with uranyl acetate (left) and TEM image of ExoBIP bound to secondary antibody-linked gold nanoparticles (right). (C) Nanoparticle tracking analysis (NTA) and zeta potential characterization. (D) Western blot analysis of exosomal markers (CD9, CD63, CD81, TSG101) and IL-18BP conjugation. (E) Representative super-resolution confocal microscopy images of ExoBIP, with IL-18BP (red) and Exo membrane (green). (F) Line-scan analysis of Exo and IL-18BP fluorescence intensity. Signal profiles across individual particles confirmed spatial overlap and surface colocalization. (G) Protease-responsive release kinetics of IL-18BP from ExoBIP. ELISA demonstrated that recombinant MMP9 triggered sustained IL-18BP release from ExoBIP, which was abrogated by MMP inhibitor GM6001. (H) ELISA-based binding analysis showing that activity of IL-18BP released from ExoBIP is similar to the original IL-18BP. (I) Colloidal stability of ExoBIP. ExoBIP maintained stable particle size and surface charge over 7 days at 4 °C (J) Lyophilization and reconstitution of ExoBIP. Lyophilized ExoBIP powder reconstituted in PBS exhibited a distinct Tyndall effect. (K) Post-rehydration characterization of ExoBIP. Particle size and zeta potential remained stable after lyophilization, supporting storage and application feasibility. For (C, G-H, I), data are presented as mean ± s.d. Two-tailed unpaired Student's t-test was used for comparisons between two groups, and one-way ANOVA followed by Tukey's multiple-comparisons test was used for multiple groups. p < 0.05 was considered statistically significant. For C, zeta potential was measured five times; for G and H, ELISA assays were performed in triplicate; and for I, measurements were repeated three times.
Article Snippet: Cells were activated with plate-bound anti-CD3ε (1 μg/mL) and soluble anti-CD28 (1 μg/mL) in the presence of 0.5 ng/mL IL-2 for 24 h. Groups included a PBS control; 20 ng/mL recombinant IL-18 (RP02521, ABclonal); 20 ng/mL recombinant IL-18BP (50206-M08H, Sino Biological); 10 μM LY294002, a PI3K pathway inhibitor (S1737, Beyotime); 25 ng/mL IFN-γ (P6137, Beyotime); 25 ng/mL RANKL; 1 μg/mL IFN-γ Antagonist (HY-P4717, MCE); and 1 μg/mL Anti-Mouse RANKL Antibody (HY-P990165, MCE); 1 μM Ruxolitinib (HY-50856, MCE), a JAK1/2 pathway inhibitor; 5 μM BAY 11-7821 (HY-13453, MCE), an NF-κB pathway inhibitor.
Techniques: Derivative Assay, Staining, Zeta Potential Analyzer, Western Blot, Conjugation Assay, Confocal Microscopy, Membrane, Fluorescence, Enzyme-linked Immunosorbent Assay, Recombinant, Binding Assay, Activity Assay, Lyophilization, Two Tailed Test