Enzymes immobilized in Langmuir-Blodgett films: Why determining the surface properties in Langmuir monolayer is important?

ABSTRACT In this review we discuss about the immobilization of enzymes in Langmuir-Blodgett films in order to determine the catalytic properties of these biomacromolecules when adsorbed on solid supports. Usually, the conformation of enzymes depends on the environmental conditions imposed to them, including the chemical composition of the matrix, and the morphology and thickness of the film. In this review, we show an outline of manuscripts that report the immobilization of enzymes as LB films since the 1980’s, and also some examples of how the surface properties of the floating monolayer prepared previously to the transfer to the solid support are important to determine the efficiency of the resulting device

Chelating Langmuir-Blodgett film: a new versatile chemiluminescent sensing layer for biosensor applications

International audienceThe present study reports the achievement of a new chemiluminescent sensing layer able to simultaneously (i) play an active role on ligand immobilization and (ii) serve as a catalyst in detection processes for label-free biosensor applications. This new type of active Langmuir−Blodgett (LB) monolayer has been designed by using a chelating lipid (Ni-NTA-DOGS). Thanks to the chelated metallic cation, this peculiar lipid exhibits luminol chemiluminescence catalysis properties in the presence of hydrogen peroxide. Upon biomolecule interaction through imidazole ring chelation (mediated by the metallic cation bound to the lipid headgroup), the chemiluminescent signal can be modulated. The first chemiluminescent signal acquisition experiments have shown a strong and homogeneous signal of the chelating layer. Upon histamine interactions, a histidine derivative used as a marker of fresh food quality, we succeeded in obtaining as a proof of concept a chemiluminescent signal variation without any derivatization of the target molecule. This signal variation was shown to be directly correlated to the histamine concentration with a limit of detection of 2 μg/mL

Biomietic membranes and biomolecule immobilisation strategies for nanobiotechnology applications

International audienceBiological membranes constitute a source of inspiration for making supramolecular assemblies which can be used in the design of biomimetic sensors. At the same time, the concept of using biomolecules as an elementary structure to develop self-assembled entities has received considerable attention. More particularly, the ability of amphiphilic molecules like lipids, to spontaneously organise into bilayers, is suitable to achieve biomimetic membrane models. The potential of two-dimensional molecular self-assemblies is clearly illustrated by Langmuir monolayers of lipids formed at an air/water interface, which can be used as models to acquire knowledge about the molecular recognition process occurring in biological membranes. Langmuir-Blodgett (LB) technology, based on the transfer of this interfacial monomolecular film onto a solid support, allows building up lamellar lipid stack, with an accurate control of thickness and molecular organisation. This technique offers the possibility to prepare ultrathin layers suitable for biomolecule immobilisation. We are presenting herein an overview of work performed in our group that sheds light on the formation of biomimetic LB membranes associating protein in a well-defined orientation. Two points will be addressed: investigations of protein/lipid interactions using lipid monolayers as membrane models and biosensing applications. The objectives are to highlight advantages of interfacial Langmuir monolayers and supported Langmuir-Blodgett films to investigate molecular interactions between biomolecules and lipid membrane components or to elaborate biomimetic membranes as sensing layers, respectively. The present paper also draws a general picture of non-conventional methods for biomolecule immobilisation and their applications for biochip developments. The technologies presented are based either on original solid supports or on innovative immobilisation processes. First, ''Macromolecules to PDMS transfer'' technique relying on the direct entrapment of macromolecules spots during PDMS polymerisation is proposed as an alternative for the easy and simple PDMS surface modification. Then, the electro-addressing of biomolecule-aryl diazonium adducts at the surface of conducting biochips will be presented and shown to be an interesting alternative to immobilisation processes based on surface functionalisation

Chelating Langmuir-Blodgett film: a new versatile chemiluminescent sensing layer for biosensor applications

International audienceThe present study reports the achievement of a new chemiluminescent sensing layer able to simultaneously (i) play an active role on ligand immobilization and (ii) serve as a catalyst in detection processes for label-free biosensor applications. This new type of active Langmuir−Blodgett (LB) monolayer has been designed by using a chelating lipid (Ni-NTA-DOGS). Thanks to the chelated metallic cation, this peculiar lipid exhibits luminol chemiluminescence catalysis properties in the presence of hydrogen peroxide. Upon biomolecule interaction through imidazole ring chelation (mediated by the metallic cation bound to the lipid headgroup), the chemiluminescent signal can be modulated. The first chemiluminescent signal acquisition experiments have shown a strong and homogeneous signal of the chelating layer. Upon histamine interactions, a histidine derivative used as a marker of fresh food quality, we succeeded in obtaining as a proof of concept a chemiluminescent signal variation without any derivatization of the target molecule. This signal variation was shown to be directly correlated to the histamine concentration with a limit of detection of 2 μg/mL