BSA Adsorption on Differently Charged Polystyrene Nanoparticles using Isothermal Titration Calorimetry and the Influence on Cellular Uptake

BSA adsorption onto negatively and positively charged polystyrene nanoparticles was investigated. The nanoparticles were characterized in terms of particle size, zeta potential, surface group density, and morphology. The adsorption behavior of BSA on the particle surface, as a function of pH and overall charge of the particle, was studied using ITC. Different thermodynamic data such as enthalpy changes upon binding and stoichiometry of the systems were determined and discussed. The degree of surface coverage with BSA was calculated using the thermodynamic data. The cellular uptake of particles before and after BSA adsorption was studied using HeLa cells in the presence and absence of supplemented FCS in the cell culture medium. The interaction between differently functionalized polystyrene nanoparticles and BSA is studied. The maximum affinity is found for phosphonic‐acid‐functionalized nanoparticles, possibly because of the higher density of functional groups in this case and the inceased charge of the phosphonate groups. “Precoating” of the particle surfaces with BSA reduces the particle uptake into cells slightly.