Photochemical approach for multiplexed biofunctionalisation of gallium arsenide.

The optoelectronic properties of gallium arsenide (GaAs) hold great promise in biosensing applications, currently being held back by the lack of methodologies reporting the spatially selective functionalisation of this material with multiple biomolecules. Here, we exploit the use of a photoreactive crosslinker - a diazirine derivative - for spatially selective covalent immobilisation of multiple bioreceptors on the GaAs surface. As a proof of principle we show the immobilisation of two proteins: neutravidin and endosulfine alpha protein. X-ray photoelectron spectroscopy results showed the presence of the biomolecules on the GaAs regions selectively exposed to ultraviolet light. The approach presented here is applicable to the covalent attachment of other biomolecules, paving the way for using GaAs as a platform for multiplexed biosensing.

Biofunctionalisation of gallium arsenide with neutravidin.

Gallium arsenide (GaAs) is a promising candidate as a platform for optical biosensing devices due to its enabling optoelectronic properties. However, the biofunctionalisation of the GaAs surface has not received much attention compared to gold, carbon and silicon surfaces. Here we report a study presenting a physicochemical surface characterisation of the GaAs surface along the functionalisation with a high-affinity bioconjugation pair widely explored in the life sciences - biotin and neutravidin. Combined X-ray photoelectron spectroscopy (XPS), wettability measurements and spectroscopic ellipsometry were used for a reliable characterisation of the surface functionalisation process. The results suggest that a film with a thickness lower than 10 nm was formed, with a neutravidin to biotin ratio of 1:25 on the GaAs surface. Reduction of non-specific binding of the protein to the surface was achieved by optimising the protein buffer and rinsing steps. This study shows the feasibility of using GaAs as a platform for specific biomolecular recognition, paving the way to a new generation of optoelectronic biosensors.

On-Demand Electrical Switching of Antibody-Antigen Binding on Surfaces.

The development of stimuli-responsive interfaces between synthetic materials and biological systems is providing the unprecedented ability to modulate biomolecular interactions for a diverse range of biotechnological and biomedical applications. Antibody-antigen binding interactions are at the heart of many biosensing platforms, but no attempts have been made yet to control antibody-antigen binding in an on-demand fashion. Herein, a molecular surface was designed and developed that utilizes an electric potential to drive a conformational change in surface bound peptide moiety, to give on-demand control over antigen-antibody interactions on sensor chips. The molecularly engineered surfaces allow for propagation of conformational changes from the molecular switching unit to a distal progesterone antigen, resulting in promotion (ON state) or inhibition (OFF state) of progesterone antibody binding. The approach presented here can be generally applicable to other antigen-antibody systems and meets the technological needs for in situ long-term assessment of biological processes and disease monitoring on-demand.