Non-adhesive behavior of new nanostructured PNIPAM surfaces towards specific neurodegenerative proteins: application to storage and titration of Tau proteins.

New nonfouling tubes are developed and their influence on the adhesion of neuroproteins is studied. The biomarkers are considered as single components (recombinant prion and Tau proteins) or in a solution of native and pathological forms. The samples are stored for 24 h at 4 °C in virgin and treated tubes layered with two different nanostructured coatings based on poly(N-isopropylacrylamide) with either a positive or a neutral charge, and the protein adhesion is monitored. The recombinant protein with a high pI is repelled from the nanostructured surface that has a negative ζ potential, whereas the recombinant protein with the lower pI is attracted. Furthermore, in the case of complex solutions, neutral nanostructured surfaces are able to retain all amyloid biomarkers.

Are the interactions between recombinant prion proteins and polymeric surfaces related to the hydrophilic/hydrophobic balance?

New non-fouling tubes are developed and their influence on the adhesion of neuroproteins is studied. Recombinant prion proteins are considered as a single component representative of hydrophobic proteins. Samples are stored for 24 h at 4 °C in tubes coated with two different coatings: poly(N-isopropylacrylamide) as a hydrophilic surface and a plasma-fluorinated coating as a hydrophobic one. The protein adhesion is monitored by ELISA tests, XPS and confocal microscopy. It appears that the highest recovery of recombinant prion protein in the liquid phase is obtained with the hydrophilic surface while the hydrophobic character of the storage tube induces an important amount of biological loss. However, the recovery is not complete even for tubes coated with poly(N-isopropylacrylamide).

A New Approach for Detection Improvement of the Creutzfeldt-Jakob Disorder through a Specific Surface Chemistry Applied onto Titration Well.

This work illustrates the enhancement of the sensitivity of the ELISA titration for recombinant human and native prion proteins, while reducing other non-specific adsorptions that could increase the background signal and lead to a low sensitivity and false positives. It is achieved thanks to the association of plasma chemistry and coating with different amphiphilic molecules bearing either ionic charges and/or long hydrocarbon chains. The treated support by 3-butenylamine hydrochloride improves the signal detection of recombinant protein, while surface modification with the 3,7-dimethylocta-2,6-dien-1-diamine (geranylamine) enhances the sensitivity of the native protein. Beside the surface chemistry effect, these different results are associated with protein conformation.

Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well.

The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic-phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface.

Surface treatment of polymeric materials controlling the adhesion of biomolecules.

This review describes different strategies of surface elaboration for a better control of biomolecule adsorption. After a brief description of the fundamental interactions between surfaces and biomolecules, various routes of surface elaboration are presented dealing with the attachment of functional groups mostly thanks to plasma techniques, with the grafting to and from methods, and with the adsorption of surfactants. The grafting of stimuli-responsive polymers is also pointed out. Then, the discussion is focused on the protein adsorption phenomena showing how their interactions with solid surfaces are complex. The adsorption mechanism is proved to be dependent on the solid surface physicochemical properties as well as on the surface and conformation properties of the proteins. Different behaviors are also reported for complex multiple protein solutions.

Elaboration of nano-structured grafted polymeric surface.

The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface.

Characterization of biomaterials polar interactions in physiological conditions using liquid-liquid contact angle measurements: relation to fibronectin adsorption.

Wettability of biomaterials surfaces and protein-coated substrates is generally characterized with the sessile drop technique using polar and apolar liquids. This procedure is often performed in air, which does not reflect the physiological conditions. In this study, liquid/liquid contact angle measurements were carried out to be closer to cell culture conditions. This technique allowed us to evaluate the polar contribution to the work of adhesion between an aqueous medium and four selected biomaterials widely used in tissue culture applications: bacteriological grade polystyrene (PS), tissue culture polystyrene (tPS), poly(2-hydroxyethyl methacrylate) film (PolyHEMA), and hydroxypropylmethylcellulose-carboxymethylcellulose bi-layered Petri dish (CEL). The contributions of polar interactions were also estimated on the same biomaterials after fibronectin (Fn) adsorption. The quantity of Fn adsorbed on PS, tPS, PolyHEMA and CEL surfaces was evaluated by using the fluorescein-labeled protein. PolyHEMA and CEL were found to be hydrophilic, tPS was moderately hydrophilic and PS was highly hydrophobic. After Fn adsorption on PS and tPS, a significant increase of the surface polar interaction was observed. On PolyHEMA and CEL, no significant adsorption of Fn was detected and the polar interactions remained unchanged. Finally, an inverse correlation between the polarity of the surfaces and the quantity of adsorbed Fn was established.

Probing fibronectin-surface interactions: a multitechnique approach.

The development of adhesive as well as antiadhesive surfaces is essential in various biomaterial applications. In this study, we have used a multidisciplinary approach that combines biological and physicochemical methods to progress in our understanding of cell-surface interactions. Four model surfaces have been used to investigate fibronectin (Fn) adsorption and the subsequent morphology and adhesion of preosteoblasts. Such experimental conditions lead us to distinguish between anti- and proadhesive substrata. Our results indicate that Fn is not able to induce cell adhesion on antiadhesive materials. On adhesive substrata, Fn did not increase the number of adherent cells but favored their spreading. This work also examined Fn-surface interactions using ELISA immunoassays, fluorescent labeling of Fn, and force spectroscopy with Fn-modified tips. The results provided clear evidence of the advantages and limitations of each technique. All of the techniques confirmed the important adsorption of Fn on proadhesive surfaces for cells. By contrast, antiadhesive substrata for cells avoided Fn adsorption. Furthermore, ELISA experiments enabled us to verify the accessibility of cell binding sites to adsorbed Fn molecules.

Surface treatment of polycarbonate films aimed at biomedical application.

Aiming to encapsulate pancreatic islets, a biocompatible polycarbonate membrane (Whatman) was treated with plasma argon in order to improve its surface properties. The argon plasma treatment decreased the hydrophobicity of the membrane by fixing polyvinylpyrrolidone (PVP) at the surface. The water angle contact decreased from 47 degrees to 20 degrees after this treatment, while the structure and pore diameter were preserved. The treatment also increased significantly the water permeability from 62 +/- 8 ml/min to 200 +/- 29 ml/min (P < 0.001). ToF-SIMS analyses revealed that the argon plasma treatment of the membrane allowed the installation of an uniform PVP layer at the surface. The concentration equilibrum in glucose was reached after 8 h diffusion for the treated membrane, while it was only 32.4 +/- 8.6% (P < 0.01) for the untreated membrane. The biocompatibility of the polycarbonate membrane was assessed after one month of implantation in rats and proved to be unaffected by the surface treatment. In conclusion, the present study provided sufficient information to establish a relationship between the physicochemical modifications of the PVP-plasma-treated polycarbonate membrane and the improvement in its permeability.

General properties of silated hydroxyethylcellulose for potential biomedical applications.

The general properties of hydroxyethylcellulose (HEC) grafted with 3-glycidoxypropyltrimethoxysilane (GPTMS) or 3-glycidoxypropylmethyldiethoxysilane (GPDMS) were studied for potential biomedical applications. The graft involved a Williamson reaction between the free hydroxyl function of HEC and the epoxy function of the two silanes. As the grafted silanes are in ionic form (sodium silanolate), this product remains in gel form at basic pH (>12.3) in aqueous solution. When pH decreases, sodium silanolate is transformed into silanol (2 or 3 silanol functions are carried by silicon, depending on the silane grafted). The silanols interreact, and the gel is transformed into a cross-linking form at room or body temperature. Studies were conducted to optimise this product for specific uses. Steam sterilization was used to compare self-hardening as a function of the silane grafted. Our previous work indicated that HEC grafted with GPTMS has good reactivity, but requires high pH for dissolution, whereas dissolution occurs at lower pH with GPMDS. The rate of silanol condensation for silated HEC was then determined as a function of pH, temperature, type of silane, and the percentage grafted. Condensation rates were ascertained by the viscosity method, and gels were neutralized by different solutions to obtain buffered forms at various pH. The time required to obtain 10(5) mPa x s, with an initial state of 2500 mPa x s, was then calculated. Condensation was catalysed in acid or basic medium at a lower rate at pH 5.5-6.5, and a temperature rise increased the condensation rate, regardless of the pH or silane studied. Silanetriol was more reactive than silanediol. However, as HEC lost considerable viscosity after sterilization, further studies will be conducted to develop new polysaccharides grafted with silane.

Synthesis and general properties of silated-hydroxypropyl methylcellulose in prospect of biomedical use.

Synthesis of grafting silane on a hydro soluble cellulose ether (HPMC) was described. In alkaline medium, this derivate is under gel form. With a decrease of the pH, a self-hardening occurs due to the silanol condensation. For potential biomedical use, we described the silated-HPMC synthesis, the gel behavior after steam sterilization and the parameters of the silanol condensation i.e. pH, silane percentage and temperature. Minimum kinetic of the condensation was observed for pH between 5.5 and 6.5. So temperature catalyzed the reaction and the self-hardening speed was increased by silane percentage.