Formation mechanisms of chitosan-silica hybrid materials and its performance as solid support for KR-12 peptide adsorption: Impact on KR-12 antimicrobial activity and proteolytic stability

Abstract

Chitosan-silica materials offer a specific environment for the adsorption of biofunctional molecules, such as the antimicrobial peptide KR-12. The objective here is to rationalize the changes in the physicochemical properties of these chitosan-silica materials in function of the synthesis pH, using 0.02 w/v % chitosan as catalyst and aggregation agent and, to correlate these characteristics with the loading/delivery and activity/stability of KR-12 antimicrobial peptide. The CS-6 material, prepared at pH 6, exhibits higher surface area (745 m2/g) and total pore volume (0.58 cm3/g) due to the lower incorporation of chitosan swollen chains (9.36 wt %). Higher pHs produced denser materials (CS-7 and CS-8) with higher entangled chitosan incorporated (> 17 wt%). Adsorption of KR-12 peptide was found to take two different mechanisms depending on the chitosan-silica support, Langmuir-type for CS-6 material and Freundlich-type for CS-7 and CS-8 materials. According to the KR-12 release profiles, more hydrophobic interactions were observed in the CS-6 material exposing Lys and Arg residues from the peptide towards the material surface. This was correlated with the higher antimicrobial activity of this material against S. aureus strain (MIC = 128 μg/mL). Additionally, the KR-12 peptide adsorbed in the CS-6 hybrid support is 34 % more protected from the proteolytic action of α-chymotrypsin than the free one. In conclusion, the proposed models of different porous environments in the studied chitosan-silica materials supports the KR-12 peptide loading/delivery mechanisms, leading to biofunctionalized solid antimicrobial materials exhibiting proteolytic stability. This knowledge is useful for designing new antibacterial materials for biomedical applications. Keywords: Chitosan-silica particle mechanism formation, KR-12 peptide adsorption/delivery mechanisms, KR-12 controlled release, KR-12/chitosan-silica antimicrobial solid materials, Proteolysis stability