There is increased demand both in developed and the developing countries for ready availability of biosensors [1-5]. In this context, self-assembled monolayer (Scheme I) based biosensors have recently attracted much interest due to their applications in health care, environmemtal, pharmaceuticals and food industry etc. This has been attributed to the use of ultra-thin layers for immobilization of desired sensing elements that may result in faster and stable biosesning devices. Biosensor has three major components: (i) a bio-recognition element such as DNA, enzyme, antibody etc. for recognition of an anlyte, (ii) a matrix such as a self-assembled monolayer (SAM), Langmuir-Blodgett film, thick polymer film, hydrogel and nanomaterials etc. for the immobilization of a biomolecule and (iii) a transducer unit for conversion and amplification of the biochemical reaction product into a recognizable. For fabrication of biosensors , appropriate immobilization of signal biomolecules on a transducer surface is presently a major area of concern. The thrust is, however, shifting towards the utilization of SAMs as matrices for proper and oriented immobilization of biomolecules. Using a SAM to functionalize noble metal surfaces provides a simple route to functionalize electrode surfaces by organic molecules (both aliphatic and aromatic) containing free anchor groups such as thiols, disulphides, amines,silanes, or acids for the immobilization of biomolecules. Among the various biochemical analytes such as glucose, galactose, uric acid, urea etc in biological samples to monitor human health, estimation of cholesterol has acquired the maximum attention since it is an indicator of abnormality in lipid metabolism and its abnormal level is associated with coronary artery disease, diabetes mellitus, hypothyroidism, anemia and wasting syndromes etc . I will focus on some of the recent developments that have occurred in our laboratories in the area of self-assembled monolayers based biosensors for cholesterol sensing [3-5].
Scheme 1. (a) Gold plate, (b) gold surface having terminal C–H group of P3HT SAM, (c) 1-fluro-2-nitro-4-azido-benzene modified SAM using nitrene reaction and (d) immobilized ChOx on SAM by displacing labile fluoro group at 37 ◦C. S.K. Arya et al., Biosensors and Bioelectronics 22 (2007) 2516–2524 2519.
Dr B.D.Malhotra received M.Sc (Physics, 1973) and Ph.D (1979) from the Department of Physics & Astrophysics, University of Delhi . He had stint as a Post Doctoral Fellow at the University of Strathclyde , Glasgow during 1979-1982 and is currently Scientist F & Head of the Biomolecular Electronics & Conducting Polymer Research Group at the National Physical laboratory, New Delhi, India. Dr Malhotra is a Fellow of the National Academy of Sciences, India, has published 121 papers, Seven Book Chapters and filed five Patents (India, USA and Europe). His publications (Cited > 2010 times), carry h-index of 25.
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