Search

In this work, we applied total internal reflection microscopy (TIRM) to directly measure the interactions between three different kinds of macroscopic surfaces: namely bare polystyrene (PS) particle and bare silica surface (bare-PS/bare-silica), PS particle and silica surfaces both coated with bovine serum albumin (BSA) (BSA-PS/BSA-silica), and PS particle and silica surfaces both modified with polyethylene glycol (PEG) (PEG-PS/PEG-silica) polymers, in phosphate buffer solution (PBS) and fetal bovine serum (FBS). Our results showed that in PBS, all the bare-PS, BSA-PS, and PEG-PS particles were irreversibly deposited onto the bare silica surface or surfaces coated either with BSA or PEG. However, in FBS, the interaction potentials between the particle and surface exhibited both free-diffusing particle and stuck particle profiles. Dynamic light scattering (DLS) and elliposmeter measurements indicated that there was a layer of serum proteins adsorbed on the PS particle and silica surface. TIRM measurement revealed that such adsorbed serum proteins can mediate the surface-surface interactions by providing additional stabilization under certain conditions, but also promoting bridging effect between the two surfaces. The measured potential profile of the stuck particle in FBS thus was much wider than in PBS. These quantitative measurements provide insights that serum proteins adsorbed onto surfaces can regulate surface-surface interactions, thus leading to unique moving behavior and stability of colloidal particles in the serum environment. [ABSTRACT FROM AUTHOR]

The interaction and adsorption of enzyme, glucose oxidase (GOx), on poly(methyl methacrylate)−bovine serum albumin (PMMA−BSA) particles were studied by using a quartz crystal microbalance with dissipation (QCM-D) and laser light scattering (LLS). The enzyme was irreversibly immobilized on the PMMA−BSA particle surface. The amount of enzyme immobilized on PMMA−BSA particles and the enzymatic activity were determined by UV/vis measurements. The influences of pH and ionic strength on the adsorption indicate that the electrostatic interaction plays a major role on the immobilization. The adsorbed GOx can retain at least 80% of the free enzyme activity. Thermal stability studies reveal that the adsorbed GOx only losses 28% of its activity in comparison with a 64% activity loss of free GOx when it is incubated at 50 °C for 35 h. [ABSTRACT FROM AUTHOR]

Small well-defined core−shell poly(methyl methacrylate)−bovine serum albumin (PMMA-BSA) particles have been prepared in a direct one-step graft copolymerization of MMA from BSA at 75 °C in water with a trace amount of Cu 2+(5 μM). Initially, BSA generates free radicals and acts as a multifunctional macroinitiator, which leads to the formation of an amphiphilic PMMA-BSA grafting copolymer. Such formed copolymer chains act as a polymeric stabilizer to promote further emulsion polymerization of MMA inside, resulting in surfactant-free stable core−shell particles, confirmed by a transmission electron microscopic (TEM) analysis. The PMMA-BSA copolymers as well as PMMA homopolymer inside the particles were isolated by Soxhlet extraction and characterized by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry (TG). The highest grafting efficiency was ∼80%. Effects of the reaction temperature, the MMA/BSA ratio, and the concentrations of Cu 2+and BSA on such core−shell particle formation have been systematically studied. Due to their inert PMMA core and biocompatible BSA shell, these small polymer particles are potentially useful in biomedical applications. [ABSTRACT FROM AUTHOR]