Amino acid as a biodegradation accelerator of mesoporous silica nanoparticles

In order to avoid cumulative toxicity of the remained mesoporous silica nanoparticles (MSNs) in biological systems, three amino acids (a (a) over caps), i.e., glycine (Gly), aspartic acid (Asp) and cysteine (Cys), were incorporated into MSNs for accelerating their biodegradation. a (a) over cap was conjugated with 3-isocyanatopropyl triethoxysilane (ICPTES) before reacting with tetraethyl orthosilicate to form a (a) over cap -MSNs via the sol-gel process based co-condensation. FTIR spectra confirmed the urea bond formation in a (a) over cap -ICPTES, whereas silicon resonances of T-2 and T-3 in Si-29 NMR spectrum indicated the incorporation of a (a) over cap in MSNs. Spherical bare-MSNs (112 nm) were obtained while the rod-like particles were formed in the case of Gly-MSNs (73 nm in length), Asp-MSNs (90 nm in length), and Cys-MSNs (163 nm in length). The trend of %Si dissolution rate analyzed from microwave plasma atomic emission spectrometer (MP-AES) of a (a) over cap -MSNs in phosphate buffer saline (PBS)/trypsin enzyme (pH 7.4) was 3-5 times higher than in PBS (pH 7.4) and 7-8 times higher than in acetate buffer (pH 5.2), respectively. The Asp-MSNs having two carboxylic groups showed the highest degradability, followed by Cys-MSNs, Gly-MSNs, and bare-MSNs in all three media. By capability of a (a) over cap as a dissolution promoter, the a (a) over cap -MSNs would be an effective and alternative material used as drug carrier in biomedical applications.