Biosensors & Bioelectronics

Ordered and self-organized nano-array structures have been developed by Mn 2+ doping in TiO 2 thin fi lms deposition on conducting substrates by dip coating technique. Mn doped TiO 2 thin fi lms exhibits better bioactivity for enzyme immobilization and cyclic voltammetry measurement has been used for qualitative characterization of electrochemical induction of oxidation-reduction process in TiO 2 and Mn doped TiO 2 fi lms. Due to presence of Mn 2+ ions at fi lm surface, current voltage characteristic of Mn doped TiO 2 matrix was enhanced by a factor of ten and it had also reduced the crystallite size and promoted transformation of anatase to rutile phase of TiO 2 . Urea concentration in the electrolyte was determined by observing chronoamperometry response on urease immobilized working electrodes. The urea detection sensitivity of the Mn doped TiO 2 thin fi lms base platform was 2.3 μ A mM − 1 cm − 2 which is about 15 times higher from only TiO 2 base platforms. Such kind of enzyme–TiO 2 /Mn nano-array electrode could contribute a potential prospect in low cost biomedical diagnosis.

A novel absorption-transmission based, miniaturized fi ber optic biosensor has been developed for the detection of cadmium in milk. Biosensor constitutes Bacillus badius whole cells with phenol red as an indicator co-immobilized onto circular plastic discs with sol-gel approach and a fi ber optic transducer system. Inhibition of urease enzyme by cadmium ion has been used as bioassay principle in the study. The detection limit of 0.1 g/l has been achieved. Sample volume could be miniaturized to 10 l; miniaturization of sample volume to this level has never been cited in literature. Storage stability of biocomponent was found to be more than 90 days when stored at 4°C in 10% glycerol. Conclusively the study resulted in development of a quick, reliable, miniaturized biosensor with lower detection limit and longer storage stability.