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International audienceWe have studied kinetics of adsorption and properties of adsorbed bovine serum albumin (BSA) and fibrinogen (Fb) on a hydrophobic octyl surface, a hydrophilic amine surface, and a mixture of octyl and amine self-assembled monolayer (SAM) and newly synthesized hybrid SAM by using quartz crystal microbalance (QCM). In addition, we have proposed a combined kinetic and mass transfer constrained protein adsorption model. The model is fitted to a change in resonance frequency, Delta F-n/n versus time data obtained from QCM to get the kinetic rate constants, mass transfer coefficient, and spreading of adsorbed proteins. Initial rate of adsorption increases with a decrease in surface energy of the substrate. The equilibrium adsorbed amount of BSA on the hybrid surface is less than that on the mixed surface and lies in between that on octyl and amine surfaces and that of Fb is the least on hybrid surface. The analysis of variation of the dissipation factor, Delta D, with Delta F-n/n indicates that BSA is more flexible than Fb and the adsorbed layer of both proteins is softest on the hybrid surface. The relaxation times of adsorbed proteins are the slowest on the octyl surface, while those on the hybrid surface are the fastest. The analysis of secondary structures of proteins using ATR-FTIR suggests secondary structures of the proteins change during adsorption. The content of alpha-helix of the proteins increases due to adsorption on the amine surface, while that decreases on all other surfaces. The total content of a-helix and beta-sheet strongly depends on the adsorbed mass of the proteins and is weakly dependent related to elasticity and viscosity of the adsorbed proteins, respectively

Surface modification plays a vital role in regulating protein adsorption and subsequently cell adhesion. In the present work, we prepared nanoscaled modified surfaces using silanization and characterized them using Fourier-transform infrared spectroscopy (FTIR), water contact angle (WCA), and atomic force microscopy (AFM). Five different (amine, octyl, mixed, hybrid, and COOH) surfaces were prepared based on their functionality and varying wettability and their effect on protein adsorption and initial cell adhesion was investigated. AFM analysis revealed nanoscale roughness on all modified surfaces. Fetal bovine serum (FBS) was used for protein adsorption experiment and effect of FBS was analyzed on initial cell adhesion kinetics (up to 6 h) under three different experimental conditions: (a) with FBS in media, (b) with preadsorbed FBS on surfaces, and (c) incomplete media, i.e., without FBS. Various cell features such as cell morphology/circularity, cell area and nuclei size were also studied for the above stated conditions at different time intervals. The cell adhesion rate as well as cell spread area were highest in the case of surfaces with preadsorbed FBS. We observed higher surface coverage rate by adhering cells on hybrid (rate, 0.073 h–1) and amine (0.072 h–1) surfaces followed by COOH (0.062 h–1) and other surfaces under preadsorbed FBS condition. Surface treated with cells in incomplete media exhibited least adhesion rate, poor cell spreading and improper morphology. Furthermore, we found that initial cell adhesion rate and Δadhered cells (%) linearly increased with the change in α-helix content of adsorbed FBS on surfaces. Among all the modified surfaces and under all three experimental conditions, hybrid surface exhibited excellent properties for supporting cell adhesion and growth and hence can be potentially used as surface modifiers in biomedical applications to design biocompatible surfaces.

We study a system of grafted polymers in a poor solvent by self-consistent-field methods as well as Monte-Carlo simulation methods. We observe a number of different morphological structures including an inverted solvent micelle or hole in the polymer layer, a lamella-like micelle structure, and fused, spherical micelle structures. These structures can be obtained by either varying the grafting density or chain length. We also develop a scaling theory for the existence of these structures and find reasonable agreement between this theory and our numerical calculations.