Nonfouling Poly(ethylene oxide) Layers End-Tethered to Polydopamine

Abstract

Nonfouling surfaces capable of reducing protein adsorption are highly desirable in a wide range of applications. Coating of surfaces with poly(ethylene oxide) (PEO), a water-soluble, nontoxic, and nonimmunogenic polymer, is most frequently used to reduce nonspecific protein adsorption. Here we show how to prepare dense PEO brushes on virtually any substrate by tethering PEO to polydopamine (PDA)-modified surfaces. The chain lengths of heterobifunctional PEOs were varied in the range of 45−500 oxyethylene units (M n = 2000−20 000). End-tethering of PEO chains was performed through amine and thiol headgroups from reactive polymer melts to minimize excluded volume effects. Surface plasmon resonance (SPR) was applied to investigate the adsorption of model protein solutions and complex biologic medium (human blood plasma) to the densely packed PEO brushes. The level of protein adsorption of human serum albumin and fibrinogen solutions was below the detection limit of the SPR measurements for all PEO chains end-tethered to PDA, thus exceeding the protein resistance of PEO layers tethered directly on gold. It was found that the surface resistance to adsorption of lysozyme and human blood plasma increased with increasing length and brush character of the PEO chains end-tethered to PDA with a similar or better resistance in comparison to PEO layers on gold. Furthermore, the chain density, thickness, swelling, and conformation of PEO layers were determined using spectroscopic ellipsometry (SE), dynamic water contact angle (DCA) measurements, infrared reflection− absorption spectroscopy (IRRAS), and vibrational sum-frequency-generation (VSFG) spectroscopy, the latter in air and water.

Polymer brushes based on PLLA-b-PEO colloids for the preparation of protein resistant PLA surfaces

“…The representative spectrum of the PLLAcontaining films is dominated by bands at 2997, 2947, and butions have been assigned to the PEO chains in helical conformation with a predominant perpendicular orientation with respect to the surface as in the case of the dense PEO brushes end-tethered directly to gold 39 or to a PDA anchor layer. 7,25 Thus the presence of these bands proves the brush structure of the PEO blocks in the top layer of the PLLA-b-PEO films in our study. Notably, the spectral contributions of PEO rise with increasing molecular weight of the PEO block.…”

“…7,23 Then, the PLLA film was prepared by spin-casting from the polylactide solution in chloroform (4 mg ml −1 , 180 µl on each SPR substrate, 60 µl on each glass slide) using a PWM32-PS-R790 spinner (Headway Research, Inc.) at 2750 rpm for 30 s at 24°C. The spin-cast films were annealed under vacuum at 120°C for 3 h. Finally, the copolymer surfaces were prepared by spincasting from suspensions in the acetone/methanol mixed solvent (1/9 v/v, copolymer concentration: 3 mg ml −1 ) on the PLLA surface.…”

“…4 For that purpose, besides other polymers, such as polybetaine-based polymers 1 or poly(vinyl alcohol), 5 poly(ethylene oxide), PEO, has been extensively studied and proved to be effective. 6,7 In general, the efficiency of the surface coating in preventing protein adsorption is attributed to the arrangement of the hydrophilic polymer chains into a brush conformation. The description of the theoretical model of polymer brushes and their mechanism and efficiency in suppressing the adsorption of proteins was reported by Szleifer 8,9 and Halperin, 10,11 and the important parameters of a polymer brush, such as chain distance, chain density, and the thickness of a polymer brush, have been established.…”

“…6 Recently, the formation of end-tethered PEO brushes on polydopamine-modified surfaces, thus applicable virtually to any substrate, prepared by the "grafting to" method and with a significantly reduced protein adsorption has been reported. 7 However, aliphatic polyesters, such as polylactide (PLA), which is a biodegradable polymer widely used for biomedical applications exhibiting a rather hydrophobic character which induces the non-specific protein adsorption, suffer from the lack of suitable functional groups for a direct modification with PEO as well as with bioactive compounds. Thus, for guided cell-surface interactions in the area of tissue engineering, physically-based surface modifications of PLLA by entrapment of PEO chains 13 or deposition of PEO-based copolymers have been mostly investigated.…”

Core-Shell MnO2-SiO2 Nanorods for Catalyzing the Removal of Dyes from Water

“…PDA is one kind of catechol amine. When MnO2@PDA was added to the polyethyleneimine (PEI) solution, PEI was bound to PDA through Michael addition of amines on the unsaturated indole rings and Schiff base formation reactions between the amines and catechols [30]. Thus, MnO2@PDA was coated with PEI forming MnO2@PDA-PEI.…”