title: Protein adsorption on poly(N-isopropylacrylamide)-modified silicon surfaces: effects of grafted layer thickness and protein size.
abstract: In this work, we investigated the protein adsorption on the end-tethered thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes with varying grafted layer thickness prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) on initiator-immobilized silicon surfaces. The thickness of a grafted layer was modulated by adjusting reaction time and/or solvent composition. The surface properties as a function of thickness were investigated by water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). The influence of PNIPAAm-grafted layer thickness on human serum albumin (HSA) adsorption in phosphate-buffered saline (PBS) (pH 7.4) at different temperature was evaluated using a radiolabeling method. In a lower thickness range (<15 nm), protein adsorption on PNIPAAm-grafted layer shows a thermoresponsive change in a certain extent, but the variation is not remarkable. However, it is interesting to observe that these surfaces exhibit good protein-resistant property. For the surface with a PNIPAAm thickness of 13.4 nm, the HSA adsorption level measured at room temperature was approximately 7 ng/cm2, corresponding to a reduction of 97% compared to the unmodified silicon surface. For thicker PNIPAAm-grafted surface with thickness of 38.1 nm, the adsorption results of three proteins (HSA, fibrinogen, and lysozyme) with different sizes and charges indicate that the PNIPAAm-modified surface exhibits a size-sensitive property of protein adsorption.
authors.affiliation: State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, PR China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Yu
authors.forename: Yanxia
authors.initials: Y
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Zhaoqiang
authors.initials: Z
authors.lastname: Wu
authors.forename: He
authors.initials: H
authors.lastname: Huang
authors.forename: Chi
authors.initials: C
authors.lastname: Cheng
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D000180:Acrylic Resins; D000327:Adsorption; D005340:Fibrinogen / Q000737:chemistry*; D006801:Humans; D009113:Muramidase / Q000737:chemistry* / Q000378:metabolism; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D000178:Acrylamides; D000180:Acrylic Resins; D011108:Polymers; D012709:Serum Albumin; C052970:poly-N-isopropylacrylamide; D005340:Fibrinogen; D009113:Muramidase; D012825:Silicon