Effect of Particle Size of Various Inorganic Milled Particles on Protein Adsorption Behavior

The size of inorganic particles used as adsorbents and drug carriers affects protein adsorption behavior.In this study, the protein adsorption behaviors of various inorganic milled particles, including activated bamboo charcoal (ABC), silica (SiO2), and hydroxyapatite (HAp), were investigated.Various inorganic particles were milled for different periods to reduce the particle size and enhance protein adsorption.A bicinchoninic acid test (BCA) kit was employed to assess the adsorption and desorption behaviors of bovine serum albumin (BSA) on inorganic particles.The increased amount of BSA adsorbed on the inorganic particles was correlated with the smaller sizes of the inorganic particles.Specifically, the maximum BSA adsorption capacity reached 10.18 mg/g for HAp, 4.47 mg/g for ABC, and 1.92 mg/g for SiO.Owing to the electrostatic interaction between the negatively charged carboxylate (COO ) groups of BSA and Ca 2+ ions on the surface of HAp, which is essential for the adsorption of acidic BSA molecules, HAp showed a higher ability to bind BSA.Desorption studies in phosphate buffer solution (PBS) showed a gradual release of protein from all inorganic-protein complexes; however, the cumulative release from HAp-BSA was markedly lower (13.14 0.36 %) than that from ABC-BSA (22.69 3.53 %%) or SiO-BSA (50.80 4.70 %), indicating stronger immobilization on HAp.These findings demonstrate that both particle size and physicochemical surface properties significantly influence the adsorption and release behavior of acidic proteins.