Surface-grafted polysarcosine as a peptoid antifouling polymer brush

Poly(N-substituted glycine) "peptoids" are a class of peptidomimetic molecules receiving significant interest as engineered biomolecules. Sarcosine (i.e., poly(N-methyl glycine)) has the simplest side chain chemical structure of this family. In this Article, we demonstrate that surface-grafted polysarcosine (PSAR) brushes exhibit excellent resistance to nonspecific protein adsorption and cell attachment. Polysarcosine was coupled to a mussel adhesive protein-inspired DOPA-Lys pentapeptide, which enabled solution grafting and control of the surface chain density of the PSAR brushes. Protein adsorption was found to decrease monotonically with increasing grafted chain densities, and protein adsorption could be completely inhibited above certain critical chain densities specific to different polysarcosine chain lengths. The dependence of protein adsorption on chain length and density was also investigated by a molecular theory. PSAR brushes at high chain length and density were shown to resist fibroblast cell attachment over a 7 week period, as well as resist the attachment of some clinically relevant bacterial strains. The excellent antifouling performance of PSAR may be related to the highly hydrophilic character of polysarcosine, which was evident from high-pressure liquid chromatography measurements of polysarcosine and water contact angle measurements of the PSAR brushes. Peptoids have been shown to resist proteolytic degradation, and polysarcosine could be produced in large quantities by N-carboxy anhydride polymerization. In summary, surface-grafted polysarcosine peptoid brushes hold great promise for antifouling applications

Surface Assembly of Catechol-Functionalized Poly(L-lysine)-graft-poly(ethylene glycol) Copolymer on Titanium Exploiting Combined Electrostatically Driven Self-Organization and Blomimetic Strong Adhesion

Nonfouling coatings, based on surface-tethered, hydrophilic polymer chains, have widespread application in areas such as biosensing, medical devices, and biotechnology. Self-organization of polymers is a particularly attractive approach given its simplicity and cost-effectiveness in the application. Here we present a new class of polymers based on the polycationic poly(l-lysine)-graft-poly(ethylene glycol) copolymer (PLL-g-PEG) with a fraction of the amine-terminated lysine side chains covalently conjugated to 3,4-dihydroxyphenylacetic acid (DHPAA). This copolymer is shown to adsorb and self-organize as a confluent monolayer on negatively charged titanium oxide surfaces, driven by long-range electrostatic attraction, while the catechol groups of DHPAA spontaneously engage in strong, coordinative binding to the substrate surface, similar to the biomimetic dihydroxyphenylalanine (DOPA) found in mussel adhesive proteins. The adsorption kinetics and resulting polymer coverage are demonstrated to critically depend on (a) a rational design of the copolymer architecture with a compromise between sufficient positive charges in the PLL backbone and a minimal grafting density of DHPAA groups and (b) optimum choice of ionic strength and temperature of the assembly solution. PLL-graft-(DHPAA; PEG) adlayers exhibit excellent resistance to nonspecific protein (fibrinogen) adsorption. To test the chemical stability of the polymeric layer, coated substrates were exposed to high ionic salt solutions and proved to remain nonfouling thanks to stable catechol−substrate anchorage, in stark contrast to the control PLL-g-PEG copolymer that desorbed under these conditions as a consequence of screening of the (purely) electrostatic surface forces. Furthermore, polymer-coated substrates resisted attachment of the cyanobacterium Lyngbya sp. over a time frame of at least 100 days

Poly(ethylene glycol) Adlayers Immobilized to Metal Oxide Substrates Through Catechol Derivatives : Influence of Assembly Conditions on Formation and Stability

We have investigated Five different poly(ethylene glycol) (PEG, 5 kDa) catechol derivatives in terms of their spontaneous surface assembly from aqueous solution, adlayer stability, and resistance to nonspecific blood serum adsorption as a function of the type of catechol-based anchor, assembly conditions (temperature, pH), and type of substrate (SiO2, TiO2, Nb2O5), Variable-angle spectroscopic ellipsometry (VASE) was used for layer thickness evaluation, X-ray photoelectron spectroscopy (XPS) for layer composition, and ultraviolet-visible optical spectroscopy (UV-vis) for cloud point determination. Polymer surface coverage was influenced by the type of catechol anchor, type of the substrate, as well as pH and temperature (7) of the assembly solution. Furthermore, it was found to be highest for T close to the cloud point (T-CP) and pH of the assembly solution close to pK(a1) (dissociation constant of the first catechol hydroxy group) of the polymer and to the isoelectric point (1EP) of the substrate. T-CP turned out to depend on not only the ionic strength of the assembly solution, but also the type of catechol derivative and pH. PEG-coating dry thickness above 10 angstrom correlated with low serum adsorption. We therefore conclude that optimum coating protocols for catechol-based polymer assembly at metal oxide interfaces have to take into account specific physicochemical properties of the polymer, anchor, and substrate