IntroductionFouling impairs the function of all structures immersed in seawater, including ship hulls, aquaculture nets, and static structures. Prevention of marine fouling represents an unsolved challenge with the potential for huge savings in terms of reduced energy consumption due to reduced frictional drag losses and weight, as well as increased life-time and maintenance intervals for exposed components. [ 1 , 2 ] The high level of complexity in the biointerfacial processes involved in biofouling, and the many different length and time scales [ 3 ] involved, characterize the diffi culty in fi nding the most appropriate solution to the problem. Several strategies have been used in order to control fouling in the marine environment: besides a number of approaches to simplify the process of mechanical removal of the formed deposits, the use of antifouling paints incorporating biocides [ 4 ] is the most commonly employed approach. However, strategies that aim at the generation of passive, non-interacting, non-adhesive surface structures or coatings [ 5 ] are gaining more and more importance, and information gained from materials designed to combat fouling by proteins or biomedically important microorganisms are aiding the development of environmentally benign marine coatings. [ 6 ] The use of hydrophilic and uncharged polymers is often considered as a possible approach, and it has been shown that brush-forming polymers displaying hydration properties, that is, the capability to bind water around the polymer chain, [ 7 , 8 ] can be used to reduce the uptake of biological entities (e.g., macromolecules, cells, larvae) under various conditions. For example, the settlement (attachment) of zoospores of the marine alga Ulva linza and diatoms (unicellular slime-forming algae) and the adsorption of various proteins (fi brinogen, myoglobin, albumin, or full blood serum) have been shown to be signifi cantly reduced on poly(ethylene glycol) (PEG)-coated surfaces, [ 6 , 9 , 10 ] as well as on polymeric coatings incorporating PEGylated moieties; [11][12][13] the polymer poly(2-ethyl-2-oxazoline) (PEOXA) has been studied as a liposomal surface modifi er for drug-delivery vesicles with an effi ciency similar to PEG, [ 14 ] but has also been shown to be resistant to bovine serum albumin (BSA) adsorption; [ 15 ] poly(vinyl pyrrolidone) (PVP) has been shown to decrease fouling by lysozyme, BSA and fi brinogen; [16][17][18] poly(vinyl alcohol) (PVA) was found to be effective in reducing the adhesion of the diatom Amphora coffeaeformis independently of the shear rate the surfaces were subjected to, [ 19 ] and as a gel has been shown to reduce barnacle attachment; [ 20 , 21 ] and dextran has shown the ability to reduce adsorption of human-serum proteins. [ 22 , 23 ] Nonfouling Response of Hydrophilic Uncharged PolymersPolymeric ultrathin fi lms present a possible line of attack against marine biofouling for some applications. A protocol that provides a reliable comparison of the resistance of different polymers to biofouling ...
We report on the preparation and characterization of thin polyampholytic hydrogel gradient films permitting pH-controlled protein resistance via the regulation of surface charges. The hydrogel gradients are composed of cationic poly(2-aminoethyl methacrylate hydrochloride) (PAEMA), and anionic poly(2-carboxyethyl acrylate) (PCEA) layers, which are fabricated by Self-Initiated Photografting and Photopolymerization (SIPGP). Using a two-step UV exposure procedure, a polymer thickness gradient of one component is formed on top of a uniform layer of the oppositely charged polymer. The swelling of the gradient films in water and buffers at different pH were characterized by imaging spectroscopic ellipsometry. The surface charge distribution and steric interactions with the hydrogel gradients were recorded by direct force measurement with colloidal-probe atomic force microscopy. We demonstrate that formation of a charged polymer thickness gradient on top of a uniform layer of opposite charge can result in a region of charge-neutrality. This charge-neutral region is highly resistant to non-specific adsorption of proteins, and its location along the gradient can be controlled via the pH of the surrounding buffer. The pH-controlled protein adsorption and desorption was monitored in real-time by imaging surface plasmon resonance, while the corresponding redistribution of surface charge was confirmed by direct force measurements.
An in vitro methodology to simulate in vivo wearing of contact lenses has been proposed. The results suggest that certain lens materials show increased CoF after ageing, with potential clinical implications. The results indicate that the presence of a persistent wetting agent is of advantage to maintain a low CoF after prolonged wearing.
Biomaterials used in the ocular environment should exhibit specific tribological behavior to avoid discomfort and stress-induced epithelial damage during blinking. In this study, two macromolecules that are commonly employed as ocular biomaterials, namely, poly(vinylpyrrolidone) (PVP) and hyaluronan (HA), are compared with two known model glycoproteins, namely bovine submaxillary mucin (BSM) and α-acid glycoprotein (AGP), with regard to their nonfouling efficiency, wettability, and tribological properties when freely present in the lubricant, enabling spontaneous adsorption, and when chemisorbed under low contact pressures. Chemisorbed coatings were prepared by means of photochemically triggered nitrene insertion reactions. BSM and AGP provided boundary lubrication when spontaneously adsorbed in a hydrophobic contact with a coefficient of friction (CoF) of ∼0.03-0.04. PVP and HA were found to be excellent boundary lubricants when chemisorbed (CoF ≤ 0.01). Notably, high-molecular-weight PVP generated thick adlayers, typically around 14 nm, and was able to reduce the CoF below 0.005 when slid against a BSM-coated poly(dimethylsiloxane) pin in a tearlike fluid.
A versatile, photochemical surface-modification approach using nitrene-insertion reactions has been employed to develop an ultrathin, two-component, polymer-gradient coating. Perfluorophenyl azide (PFPA) acted as the photosensitive moiety, forming a nitrene radical upon 254 nm UV exposure. Cationic poly(allyl amine) was grafted with PFPA and surface-anchored onto silicon wafers by means of electrostatic self-assembly. After spin-coating of polystyrene (PS), the substrate was illuminated from behind a moving shutter, thereby controlling the azide-to-nitrene conversion degree across the substrate, and leading to a gradually varying PS density after rinsing. Backfilling with poly(vinyl pyrrolidone) (PVP) and re-exposing to UV light formed a two-component polymer-density gradient. The composition varied linearly following exposure to a linear UV exposure profile, as determined with spectroscopic ellipsometry (ELM) and X-ray photoelectron spectroscopy (XPS). High-spatial-resolution, time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed a high degree of mixing between the two incompatible polymers on the micrometer scale. The dynamic water-contact angle (dCA) was found to depend strongly on the sample history, suggesting adaptive properties of the coating, which was further confirmed by angle-resolved XPS (ARXPS). To confirm the applicability of the system for biological investigations, gradients were exposed to zoospores of the macrofouling alga Ulva linza , and a critical PS composition of 70% was identified, above which settlement started to increase. It has been shown that a two-component polymer-density gradient can provide a high-throughput platform for determining critical surface properties of polymer blend materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.