Synthesis and Surface Modification of Mesoporous Silica Nanoparticles

MSNs were synthesized using the sol–gel emulsion described in [9 (link)]. In short, cetyltrimethylammonium bromide (CTAB, ≥99%, Sigma-Aldrich, Shanghai, China) served as a mesoporous template, followed by in situ polymerization using tetraethyl orthosilicate (TEOS, ≥99%, Sigma-Aldrich). After two hours, the surfactant CTAB was removed, and the resulting MSNs were filtered, washed, and dried under a high vacuum. Surface amine grafting was achieved through overnight refluxing by dried toluene (>99.3%, Honeywell Fluka, Seelze, Germany) and aminopropyl triethoxysilane (APTES, ≥99%, Sigma-Aldrich). Finally, the mixture was filtered and dried under vacuum to obtain MSN-NH₂. Successful synthesis of the MNSs was assessed transmission electron microscopy as described in [9 (link)]. To protect the conformation of the peptide, interactions between the peptide and the MSNs were inhibited by modifying the MSNs with PEG₄-N₃. As described in [34 (link)], N₃-PEG₄-COOH (1 eq., >97%, Biomatrik, Jiaxing, Zhejiang, China), HATU (2 eq., 99%, Alfa Aesar, Kendel, Germany), and DIPEA, (3 eq., ≥99%, Sigma-Aldrich) were added to a suspension of MSN-NH₂ in DMF (≥99.8%, Biosolve Chimie, Dieuze, France) and stirred overnight at room temperature, after which the MSNs were filtered and washed with water and ethanol to obtain MSN-PEG₄-N₃.