Effect of surface energy of solid surfaces on the micro- and macroscopic properties of adsorbed BSA and lysozyme

- Equilibrium surface energy of the adsorbed BSA on hydrophobic surface reaches at 6 h
- Equilibrium surface energy of the adsorbed BSA on hydrophilic surface reaches at 12 h
- Adsorbed BSA's surface energy passes through maximum at a concentration on hydrophilic surfaces.
- On octyl surface, a high surface energy is observed for proteins adsorbing from mixed proteins.

The surface energy, a macroscopic property, depends on the chemical functionality and micro- and macroscopic roughness of the surface. The adsorption of two widely used proteins bovine serum albumin (BSA) and lysozyme on surfaces of four different chemical functionalities were done to find out the interrelation between macroscopic and microscopic properties. We have observed the secondary structure of protein after its adsorption. In addition, we observed the variation of surface energy of proteins due to variation in adsorption time, change in protein concentration and effect of a mixture of proteins.Surfaces of three different chemical functionalities namely, amine, hydroxyl and octyl were obtained through self-assembled monolayer on silica surfaces and were tested for responses towards adsorption of lysozyme and BSA. The adsorbed lysozyme has higher surface energy than the adsorbed BSA on amine and octyl surfaces. On hydroxyl functional surface, the surface energy due to the adsorbed lysozyme or BSA increases slowly with time.The surface energy of the adsorbed protein increases gradually with increasing protein concentration on hydrophobic surfaces. On hydrophilic surfaces, with increasing BSA concentration in bulk solution, the surface energy of the adsorbed protein on GPTMS and amine surfaces is maximum at 1 μM concentration. During the adsorption from a mixture of BSA and lysozyme on octyl surface, first lysozyme adsorbs and subsequent BSA adsorption leads to a high surface energy.

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