Poly(Styrene‐Hydroxyethyl Methacrylate) Monodisperse Microspheres as Specific Sorbent in Dye Affinity Adsorption of Albumin

Abstract

In this study, human serum albumin (HSA) adsorption properties of reactive green HE‐4BD‐attached monodisperse poly(styrene‐2‐hydroxyethyl methacrylate) [poly(St‐HEMA)] microspheres were investigated. Poly(St‐HEMA) microspheres with an uniform size of 4.0 µm in diameter were produced by the dispersion copolymerization of St and HEMA in an ethanol–water medium. Reactive green HE‐4BD was covalently attached onto the poly(St‐HEMA) microspheres via a nucleophilic substitution reaction between the hydroxyl groups of HEMA and triazinyl chloro groups of dye with the equilibrium coupling capacity of 45.8 µmol dye (g polymer)−1. The poly(St‐HEMA) monodisperse microspheres were characterized by scanning electron microscopy. The effect of concentration of HSA, medium pH, and ionic strength on the adsorption efficiency of dye‐attached microspheres were studied in a batch system. The nonspecific adsorption of HSA on the poly(St‐HEMA) microspheres was 2.1 mg g−1. Reactive green HE‐4BD attachment significantly increased the HSA adsorption up to 221 mg g−1. The langmuir adsorption model was found to be applicable in interpreting HSA adsorption by reactive green HE‐4BD attached microspheres. Significant amount of the adsorbed HSA (up to 92%) was eluted in 1 hr in the elution medium containing 1.0‐M NaCl. To determine the effects of adsorption conditions on possible conformational changes of HSA structure, fluorescence spectrophotometry was employed. We resulted that poly(St‐HEMA) dye‐affinity microspheres can be applied for HSA adsorption without causing any significant conformational changes. Repeated adsorption/elution processes showed that these dye‐attached monodisperse microspheres are suitable for HSA adsorption.