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. Author manuscript; available in PMC: 2019 Jan 31.
Published in final edited form as: ACS Appl Mater Interfaces. 2018 Jan 16;10(4):3200–3209. doi: 10.1021/acsami.7b09071

Figure 2.

Figure 2

Schematics depicting the two approaches used to load the test protein bovine serum albumin (BSA). (a) Adsorption loading is performed at pH 4, which is lower than the isoelectric point of BSA. The cationic charge on the protein displays a strong electrostatic attraction to the negatively charged surface oxide of the particles. (b) Trapping of BSA is accomplished by loading the protein in the presence of high concentration of magnesium ion at pH 9. The orthosilicate product of SiO2 dissolution reacts with magnesium ions to form a stable silicate that immobilizes the protein within the pores.