Tailoring the surface chemistry of mesocellular foams for protein adsorption

Adsorption of bovine serum albumin (BSA) at pH 5 and lysozyme (LYS) at pH 8 on MCF silica functionalised with chloromethyl (CM), mercaptopropyl (MP), octyl (Oc) or aminopropyl (AP) groups was investigated and compared with that on the unmodified silica material. The results show that the adsorption performance of the solid (adsorption capacity and adsorption rates) can be tailored by incorporating a specific type and amount of functionality and, therefore, the material can be designed for a particular application. The material with 1.22 mmol g−1 of AP exhibits the highest adsorption capacity for BSA (711 mg g−1) but the smaller LYS molecules are almost completely excluded from the cells. Both proteins have more affinity for the solids containing relatively small amounts of CM and MP than for the silica, with the effect being more pronounced for LYS. On the contrary, the hydrophobicity and steric hindrance imparted to the surface by octyl or high amounts of CM groups causes significant reduction of the total amounts of LYS and BSA adsorbed. The adsorption rates of the proteins were found to be strongly dependent on the size and amount of the organic groups, especially for the large BSA. Incorporation of bulky (octyl) or high amounts of functional groups caused significant decrease of the adsorption rates. However, if protein–solid interactions are favorable and steric hindrance is relatively low, the adsorption rate can be considerably increased, as found for LYS on MCF materials with 1.26 and 2.29 mmol g−1 of CM or 0.86 and 1.11 mmol g−1 of MP.