Chemical and biochemical sensors are presently the subject of extensive research and development for a wide variety of applications in environmental, industrial and biomedical monitoring. During the recent past, there has been an increasing demand for biosensors towards the determination of clinical parameters in biological fluids, such as blood, urine and serum. In this context, a number of biosensors for the estimation of glucose, urea, lactate, cholesterol etc. have been developed. [1][2][3][4][5] Lactate biosensors are found to be important for estimating the lactate levels in clinical biology and in food-processing industries. The lactate level in blood is known to find applications in sports medicine, and indicates various pathological states, such as respiratory insufficiencies, as well as heart and liver diseases. [6][7][8] Several materials, such as polymeric films/membranes, gels, carbon, graphite, silica and conducting polymers, have been utilized to fabricate optical, thermal, piezoelectric and electrochemical biosensors. [9][10][11][12] Among these, electrochemical biosensors are most popular among researchers because they combine the specificity of biological systems with the advantages of electrochemical transduction. [13][14][15] These may involve mediated or unmediated electrochemistry. Conducting polymers have been widely used as a transducing material in unmediated electrochemical biosensors because of considerable flexibility in their chemical structure and redox characteristics, which help in rapid electron transfer at the electrode surface. [16][17][18] Sol-gel derived materials have recently attracted much interest. This has been due to their excellent processability, ability to form films and chemical inertness for several biological applications, such as biocompatible implants, biomineralization and biosensors. [19][20][21][22] In this context, the sol-gel technique has recently attracted much attention for optical as well as electrochemical sensing. [23][24][25] Lev et al. 26 presented a brief account of sol-gel electrochemistry and its evolution. They described sol-gel based modified electrodes, solid electrolytes, electrochromic devices and corrosion protection coatings. A screen-printable "ink" has been prepared by dispersing the enzymes along with graphite powder and a binder (hydroxylpropyl cellulose) in a sol-gel solution.27 Such a solgel ink has been used to fabricate strip-type glucose-sensing electrodes. Revzin and coworkers 28 have recently fabricated glucose, lactate and pyruvate sensor arrays by depositing electrostatically complexed monolayers on lithographically patterned, individually addressable gold microelectrodes. They used photolithographic techniques in combination with metal deposition to fabricate gold arrays on both SiO2/Si and flexible mylar substrates. The sensitivities of glucose, lactate and pyruvate were found to be 0.26, 0.24 and 0.133 µA/mM, respectively. Though these redundant sensor arrays were reproducible, they were found to have a high standard deviat...
