Membrane filter modified by polyelectrolyte multilsyers for albumin preconcentration

Abstract

The layer-by-layer deposition technique (LbL) was used to modify the surface of cellulose acetate membrane (CA) as a membrane filter for preconcentration of trace amount of bovine serum albumin (BSA). By controlling the fabrication parameters, such as types of polyelectrolyte, pH of the weak polyelectrolyte, concentration of NaCl and the number of deposition layers, the thickness of multilayer films, morphology multilayer films and stability of multilayer films were evaluated and controlled. The suitable polyelectrolyte pairs are poly(diallyl dimethyl ammonium chloride) (PDADMAC) / poly(sodium 4-styrenesulfonate) (PSS) as a strong polyelectrolyte pair and poly(diallyl dimethyl ammonium chloride) (PDADMAC)/ poly (4-styrene sulfonic acid-co-maleic acid) copolymer (PSSMA) as a weak polyelectrolyte pair. The pH of 5.5 was found to be the best to fabricate PDADMAC/PSSMA. The polyelectrolyte multilayers (PEMs) film growth on the membrane was characterized using UV-Vis, ATR-FTIR and SEM. The optimum number of PEMs layers on the membrane filter of both PDADMAC/PSS and PDADMAC/PSSMA are 13 layers, in which PDADMAC is the outermost layer. The modified membranes were used to filter 1 ppm of BSA solution (pH 7.4). ATR-FTIR results showed that the BSA was adsorbed on the PDADMAC/PSS and PDADMAC/PSSMA via electrostatic interaction and the amount of adsorbed BSA increased with the numbers of coating layers of the thin film. The BSA adsorbed on the PDADMAC/PSS and PDADMAC/PSSMA membrane were then released using citric-citrate buffer solution pH 3.0 and measured quantitatively using the Bicinchoninic acid assay (BCA) and the urine test strip. Albumin concentration through the filtration process with PDADMAC/PSS and PDADMAC/PSSMA was found to be enhanced from 1 ppm to 29.6 ± 1.2 ppm and 41.6 ± 1.2 ppm, respectively. Furthermore, performance of PDADMAC/PSS membrane filter was found to be less interfered from interferences compared to PDADMAC/PSSMA membrane filter. The excellent repeatability of the preconcentration step was observed as evidenced by the standard deviation (SD) of 1.3, % relative standard deviation (%RSD) of 4.3 and % recovery of 90.8. Therefore, the proposed membrane filter would be useful as a simple and cost-effective preconcentration unit for screening test of renal failure at an early stage.