Incorporation of papain in ordered mesoporous silica

SBA-15 with highly ordered large mesopores, 2D hexagonal mesoporous structure and high surface area is very interesting for the incorporation of enzymes, such as papain that has poor stability. The goal of this work was to study the effect of incorporating papain into SBA-15 in relation the enzymatic and antimicrobial activity and cytotoxicity of papain. The papain (PPN) was incorporated into SBA-15 by incipient wetness impregnation (IWI) using post-synthesis methodology and water (W) and phosphate buffer solution (PBS) as solvent. The SBA-15:PPN mass ratio was equal to 2 (50 wt.%), 10 (10 wt.%) and 20 (5 wt.%). The SBA15PPN samples were analyzed using different characterization techniques: small angle X-ray scattering (SAXS), N2 adsorption-desorption isotherms (NAI), Fourier transformed infrared (FTIR) and scanning electron microscopy (SEM). The samples also were evaluated for its antimicrobial activity and cytotoxicity. SAXS (Fig 1) results showed reflections of a two-dimensional hexagonal mesoporous structure for all samples (SBA-15PPN), similar to SBA-15, indicating that the incorporation procedure does not change the pore structure of the SBA-15. SEM images also revealed that the SBA-15 particles in the samples (SBA15PPN) are similar to pure SBA-15, retaining the well-defined wheat-like macrostructure clusters of pure SBA-15 (Fig. 2). Analyzing the NAI (Fig. 3) results we observed that the samples have smaller superficial area and pore volume when compared with pure SBA-15, so we concluded that papain is inside the mesopores. FTIR results showed significant shifts for the SBA-15PPN samples, indicating slightly interaction between the papain and silica. Cytotoxicity results (IC50 and IC10) for SBA-15 and SBA-15PPN samples showed that these materials are non-toxic. Antimicrobial activity results showed that SBA-15 decreased proliferation of Staphylococcus aureus, Candida albicans, Pseudomona aeruginoa and Escherichia coli by approximately 80%. However, the antimicrobial activity for SBA-15PPN samples drastically decreases, exhibiting a slight activity against Candida albicans