Monolayers of the HSA dimer on polymeric microparticles-electrokinetic characteristics

Human serum albumin dimer (dHSA) enhances the accumulation and retention of anti-tumor drugs. In this work, monolayers of dHSA on polystyrene microparticles were prepared and thoroughly characterized. The changes in the electrophoretic mobility of microparticles upon the addition of controlled amounts of dHSA were measured using Laser Doppler Velocimetry (LDV) technique. These dependencies were quantitatively interpreted in terms of the 3D electrokinetic model. This allowed to determine the coverage of dHSA on microparticles under in situ conditions. Additionally, the maximum coverage of dHSA was precisely determined by the concentration depletion method. At physiological ionic strength, the maximum coverage of dHSA monolayer on microparticles was 1.05mg m^-2. This agrees with the theoretical value predicted from the random sequential adsorption approach by assuming a side-on orientation of molecules. A high stability of the monolayers under pH cycling was confirmed, which proved irreversibility of the protein adsorption on the microparticles. The obtained results can be exploited to prepare and characterize polymeric drug-capsule conjugated with albumin dimer.