Improvement of the adsorption of quaternary ammonium on polypropylene affinity membrane through the control of its surface properties.

Polypropylene fiber meshes were plasma-treated in order to attach new chemical functions corresponding to acidic or basic groups without altering the roughness of such thin material. An almost complete wettability of these plasma-treated materials is obtained. Because of the plasma-grafting of acid or amino moieties, such surface treatment allows increasing the adsorption rate of quaternary ammonium molecule like Aliquat 336. This increase was explained by specific interactions of ammonium head of the Aliquat 336 and hydrophilic group of plasma-treated PP, followed by the adsorption of a further layer of Aliquat 336 through hydrophobic interactions of its hydrocarbon chain. These interactions between the carrier and the polymeric surface were characterized leading to physisorption mechanism. Such new material could be applied to the extraction process since no evidence of aging was given.

Elaboration and surface modification of structured poly(L-lactic acid) thin film on various substrates.

Biosourced or biodegradable polymers like poly(lactic acid) (PLA) are often base-material for tissue-engineered scaffolds. However, in most of the cases, their bioadhesion properties are not satisfactory. Since the adhesion is controlled both by roughness and surface chemistry, PLA films were textured by applying the breath figure procedure and, then, plasma-treated. Depending on physicochemical characteristics of the breath figure technique, nice hexagonal structures were obtained. Their surface properties, i.e. hydrophobic-hydrophilic balance were controlled by plasma modification. However, their surface decoration could be only preserved with some specific plasma parameters depending on the applied energy and also on the induced surface chemistry.

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.

Design and sensing properties of an integrated optical gas sensor based on a multilayer structure.

In this paper, a new multilayer integrated optical sensor (MIOS) for ammonia detection at room temperature is proposed and characterized. The sensor is integrated on a single-mode TE0-TM0 planar polymer waveguide and based on polyaniline (PANI) sensitive material. A polymethyl methacrylate (PMMA) passive layer is deposited between the waveguide core and PANI sensitive layer in order to decrease optical losses induced by evanescent wave/sensitive material coupling. The design of this new sensor is discussed. Moreover, in order to investigate the feasibility of this sensor, the sensing properties to ammonia at room temperature are studied. A significant change is observed in the guided light output power after the sensor is exposed to ammonia gas, due to PANI absorption coefficient variation. This new ammonia sensor shows fast response and recovery times, good reversibility and repeatability. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region) and the PANI forms (doped and dedoped). The sensor has a logarithmic linear optical response within the ammonia concentration range between 92 to 4618 ppm. These experimental results demonstrate that the MIOS structure presents a potential innovation to elaborate integrated optical sensor based on non transparent (opaque) sensitive material.