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Poly(2-(dimethylaminoethyl) methacrylate) (pDMAEMA) was grafted to low density polyethylene (LDPE) and silicone rubber (SR) in order to make them less susceptible to microbial biofilm formation. The direct grafting of DMAEMA using γ-rays was an efficient and fast procedure for obtaining modified materials, which could be quaternized in a second step using methyl iodide. Raman spectroscopy showed that the grafting occurred only at the surface of the LDPE, but both at the surface and in the bulk of the SR. Consequently, the grafted chains caused changes in the surface-related features of the LDPE (water contact angle and viscoelastic behavior in the dry state) and in the bulk-related properties of the SR (swelling and viscoelasticity in the swollen state). The microbiological assays revealed that the grafted DMAEMA reduced Candida albicans biofilm formation (almost no biofilm on SR), while the quaternized surfaces inhibited C. albicans and Staphylococcus aureus biofilm by more than 99% compared to pristine materials. Modified LDPE and SR were capable of holding considerable amounts of nalidixic acid, an anionic antimicrobial drug, and sustained the release for several hours. In addition, the grafted materials were cytocompatible (fibroblast cell survival > 70%). In conclusion, these materials have the ability to inhibit microbial biofilm formation and at the same time act as drug-eluting systems, and for that reason may hold great promise for anti-biofouling applications.

Polyethylene glycol (PEG) grafting has a great potential to create nonfouling and nonthrombogenic surfaces, but present techniques lack versatility and stability. The present work aimed to develop a versatile PEG grafting method applicable to most biomaterial surfaces, by taking advantage of novel primary amine-rich plasma-polymerized coatings. Star-shaped PEG covalent binding was studied using static contact angle, X-ray photoelectron spectroscopy (XPS), and quartz crystal microbalance with dissipation monitoring (QCM-D). Fluorescence and QCM-D both confirmed strong reduction of protein adsorption when compared to plasma-polymerized coatings and pristine poly(ethyleneterephthalate) (PET). Moreover, almost no platelet adhesion was observed after 15 min perfusion in whole blood. Altogether, our results suggest that primary amine-rich plasma-polymerized coatings offer a promising stable and versatile method for PEG grafting in order to create nonfouling and nonthrombogenic surfaces and micropatterns.

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Thromboelastography uses cups and pins made of CyroliteW plastic to analyze the rate of fibrin clot formation in blood samples. In this study, TEG cups and pins were modified by 4 distinct coating types using plasma-enhanced chemical vapor deposition (PECVD): carboxylated, amine-rich, hydrophobic, SiO 2 , and analyzed for surface chemistry and wettability. We tested the hypothesis that the coagulation kinetics of recalcified citrated blood plasma is controlled by surface chemistry, in the absence of clot activator. Only carboxylated surfaces became negatively charged upon wetting, and accelerated clot formation in a highly reproducible manner, whereas Cyrolite W and the other coatings had delayed and unpredictable clotting times. These data are consistent with a model whereby carboxylated surfaces selectively adsorb and activate factor XII while repelling other more abundant anionic blood proteins, resulting in reproducible clot kinetics.

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