Poly(N-acryloylsarcosine methyl ester) Protein-Resistant Surfaces

A novel dry chemical path way for diene and dienophile surface functionalization toward thermally responsive metal-polymer adhesion

In this paper, we report a new and easily up-scalable dry chemical method to functionalize with diene and dienophile groups a large range of surfaces, such as metal, polymer, or glass, and we demonstrate the potentiality of this technique to realize thermally responsive adhesion between these materials. A complete and extensive surface chemistry analysis of the grafted surfaces, based on the deposition of an anhydride-rich thin plasma polymer layer by using an atmospheric pressure dielectric barrier discharge (DBD) plasma process, and its subsequent gas phase aminolysis reaction with specific diene or dienophile compound is discussed. The optimization of the assembling condition for these tailored surfaces has led to achieve a Diels-Alder adhesion force up to 0.6 N/mm at ambient temperature, which can be reduced by a factor of 50 when the retro Diels-Alder is ignited at a heating temperature around 200 °C. The study of the failure interface produced after peeling tests is presented and a mechanism of failure is proposed, based on forensic analyses involving surface analytical techniques such as XPS, ToF-SIMS, and SEM combined to AFM analyses for the retrieving of chemical and morphological information.

A substrate-independent method for surface grafting polymer layers by atom transfer radical polymerization: reduction of protein adsorption

A general method for producing low-fouling biomaterials on any surface by surface-initiated grafting of polymer brushes is presented. Our procedure uses radiofrequency glow discharge thin film deposition followed by macro-initiator coupling and then surface-initiated atom transfer radical polymerization (SI-ATRP) to prepare neutral polymer brushes on planar substrates. Coatings were produced on substrates with variable interfacial composition and mechanical properties such as hard inorganic/metal substrates (silicon and gold) or flexible (perfluorinated poly(ethylene-co-propylene) film) and rigid (microtitre plates) polymeric materials. First, surfaces were functionalized via deposition of an allylamine plasma polymer thin film followed by covalent coupling of a macro-initiator composed partly of ATRP initiator groups. Successful grafting of a hydrophilic polymer layer was achieved by SI-ATRP of N,N'-dimethylacrylamide in aqueous media at room temperature. We exemplified how this method could be used to create surface coatings with significantly reduced protein adsorption on different material substrates. Protein binding experiments using labelled human serum albumin on grafted materials resulted in quantitative evidence for low-fouling compared to control surfaces.

Investigation of the hydration of nonfouling material poly(ethylene glycol) by low-field nuclear magnetic resonance

The strong surface hydration layer of nonfouling materials plays a key role in their resistance to nonspecific protein adsorption. Poly(ethylene glycol) (PEG) is an effective example of materials that can resist nonspecific protein adsorption and cell adhesion. Thus, the strong interaction between water molecules and PEG was investigated through each T(2) component in water/PEG mixtures using multiexponential inversion of T(2) relaxation time measured by the Carr-Purcell-Meiboom-Gill (CPMG) sequence of low-field nuclear magnetic resonance (LF-NMR). Results show that about one water molecule is tightly bound with one ethylene glycol (EG) unit, and additional water molecules over 1:1 ratio mainly swell the PEG matrix and are not tightly bound with PEG. This result was also supported by the endothermic behavior of water/PEG mixtures measured by differential scanning calorimetry (DSC). It is believed that the method developed could be also applied to investigate various interactions between macromolecules and other small molecules without using deuterium samples, which might open a novel route to quantitatively measure guest-host interactions in the future.

Surface actuation of smart nanoshutters

Patterned polymer brush surfaces have been fabricated using the molecular scratchcard lithography technique, where a functional top nanolayer (acting also as a resist) is selectively removed using a scanning probe tip to expose underlying atom-transfer radical polymerization (ATRP) initiator sites. The lateral spreading of grafted polymer brush patterns across the adjacent functional resist surface can be reversibly actuated via solvent exposure. Effectively, this methodology provides a means for hiding/unveiling functional surfaces on the nanoscale.

Construction of protein-resistant pOEGMA films by helicon plasma-enhanced chemical vapor deposition

This paper describes the formation of protein-resistant, poly(ethylene glycol) methyl ether methacrylate (pOEGMA) thin films by helicon plasma-enhanced chemical vapor deposition (helicon-PECVD). pOEGMA was successfully grafted onto a silicon substrate, as a model substrate, without any additional surface initiators, by plasma polymerization of OEGMA. The resulting pOEGMA films were characterized by ellipsometry, FT-IR spectroscopy, X-ray photoelectron spectroscopy and contact angle goniometry. To investigate the protein-resistant property of the pOEGMA films, four different proteins, bovine serum albumin, fibrinogen, lysozyme and ribonuclease A, were tested as model proteins for ellipsometric measurements. The ellipsometric thickness change for all the model proteins was less than 3 A, indicating that the formed pOEGMA films are protein-resistant.

Experimental and theoretical investigation of chain length and surface coverage on fouling of surface grafted polypeptoids

Numerous strategies exist to prevent biological fouling of surfaces in physiological environments; our strategy focuses on the modification of surfaces with poly-N-substituted glycine oligomers (polypeptoids). We previously reported the synthesis and characterization of three novel polypeptoid polymers that can be used to modify titanium oxide surfaces, rendering the surfaces resistant to adsorption of proteins, to adhesion of mammalian and bacterial cells and to degradation by common protease enzymes. In this study, we investigated the effect of polypeptoid chain length on the antifouling properties of the modified surfaces. For these experiments we used poly(N-methoxyethyl) glycines with lengths between ten and fifty repeat units and determined the influence of chain length on coating thickness and density as well as resistance to protein adsorption and cellular adhesion. Short-term protein resistance remained low for all polymers, as measured by optical waveguide lightmode spectroscopy, while fibroblast adhesion after several weeks indicated reduced fouling resistance for the polypeptoid-modified surfaces with the shortest chain length polymer. Experimental observations were compared to predictions obtained from a molecular theory of polymer and protein adsorption. Good agreement was found between experiment and theory for the chain length dependence of peptoid grafting density, and for protein adsorption as a function of peptoid grafting density. The theoretical predictions provide specific guidelines for the surface coverage for each molecular weight for optimal antifouling. The predictions show the relationship between polymer layer structure and fouling.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.