Diamine-plasma treated and Cu(II)-incorporated poly(hydroxyethylmethacrylate) microbeads for albumin adsorption

Poly(2-hydroxyethylmethacrylate) (PHEMA) microbeads prepared by suspension polymerization were treated with diamine-plasmas (i.e. ethylene-diamine (ED A) and hexamethylene diamine (HMDA)) in a glow-discharge reactor in which t he exposure time and glow-discharge power were changed between 5 and 30 min and 5 and 20 W, respectively. The amount of nitrogen deposition increased both with increase in exposure time and glow-discharge power. The maximum a mounts of nitrogen deposition on the microbeads were 22.3 and 23.4 mu mol g (-1) with the EDA- and HMDA-plasmas. Then, Cu(II) ions were incorporated on to the PHEMA microbeads by chelating with the nitrogen-carrying functional groups. Different amounts of Cu(IT) ions (2.4-6.8 mg g(-1)) were in incorpo rated on the PHEMA microbeads by changing the initial concentration of Cu(I I) ions. Bovine serum albumin (BSA) adsorption onto the unmodified PHEMA, d iamine-plasma treated PHEMA, and diamine-plasma treated Cu(II)-incorporated PHEMA microbeads was investigated. The nonspecific adsorption of BSA on th e unmodified microbeads was very low (0.22 mg BSAg-1). Deposition of nitrog en increased the BSA adsorption (9.3 mg g(-1) for EDA-plasma and 12.7 mg g( -1) for HMDA-plasma). Cu(II)-incorporation significantly increased the BSA adsorption (154 mg g(-1) for EDA-plasma and 178 mg g(-1) for HMDA-plasma). Further increases in the albumin adsorption capacities of the polymer micro beads (185 mg g(-1) for EDA-plasma and 208 mg g(-1) for HMDA-plasma) were o bserved when human plasma was used. More than 92% of the adsorbed albumin m olecules was desorbed in 1 h in the desorption medium containing 0.5 M NaSC N at pH 8.0. Repeated adsorption-desorption cycles showed the feasibility o f these plasma-modified polymer microbeads.