A film that greatly enhances the photoelectric response of bacteriorhodopsin (bR), a retinal-containing protein, could pave the way towards new technology for bioelectronics, say scientists in Singapore. 

bR is one of the simplest biological energy converters and has become one of the most promising biomaterials for various applications in the bioelectronics field. The proteins contain molecules of retinal, also present in the eye, which changes conformation on light absorption. This conformation change transfers a proton across the protein membrane in a pump action generating a photoelectric current. The photoelectric response in bR is usually too low for practical applications, but Changming Li and colleagues from Nanyang Technological University have now made it six times more powerful. 

Li incorporated WO₃H₂O nanocrystals into a PVA matrix to engineer a novel bioorganic-inorganic interface with bR to enhance its practical use. The film increases the mass transport of protons through the protein membrane which increases the electric output, making it more attractive for applications in bioelectronic devices, says Li. 

'The coupling of a biologically photoactive material with an inorganic electron/proton conducting material to produce an electrical response is a significant step,' says Laurie Peter, an expert in bioelectronics from the University of Bath, in the UK. 'Developing a stable practical device based on the photochemical processes taking place in the hybrid system will be the next challenge,' he adds. 

'The challenges ahead are to further enhance the photoelectric responses using a nano-engineering approach to fabricate three-dimensional sensing devices,' says Li. This increased photoelectric response of bR using this new system could mean that bioelectronic applications such as artificial eyes are within our sights, he adds. 

Michael Brown 

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