1. Introduction Lei, Yang; Luo, Ning. A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for L-lactic acid detection. Nanoscale, 2012, 4, 3438-3443. Njagi, John; Ispas, Cristina; Andreescu, Silvana. Mixed ceria-based metal oxides biosensor for operation in oxygen restrictive environments. Analytical Chemistry, 2008,90,19,7266-7274. Rodriguez, M.; Rivas, G. Assembly of Glucose Oxidase and Different Polyelectrodes by Means of Electrostatic Layer-by-Layer Adsorption on Thiolated Gold Surface. Electroanalysis. 2004, 16, No. 20. Wiley Publishers. Lei, Yang; Luo, Ning. A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for L-lactic acid detection. Nanoscale, 2012, 4, 3438-3443. Njagi, John; Ispas, Cristina; Andreescu, Silvana. Mixed ceria-based metal oxides biosensor for operation in oxygen restrictive environments. Analytical Chemistry, 2008,90,19,7266-7274. Rodriguez, M.; Rivas, G. Assembly of Glucose Oxidase and Different Polyelectrodes by Means of Electrostatic Layer-by-Layer Adsorption on Thiolated Gold Surface. Electroanalysis. 2004, 16, No. 20. Wiley Publishers. The Role of Metal Oxide Layers in the Sensitivity of Lactate Biosensors Subjected to Oxygen-Limited Conditions Elizabeth Andreasen, Professor Lia Stanciu, Aytekin Uzunoglu School of Materials Engineering, Purdue University, West Lafayette, IN In-Situ Oxidative Polymerization via Spin Coating Method Results and Conclusions Future Work References Amperometric biosensors use the change in current to detect the concentration of the analyte in the medium. Lactate biosensors will improve ease in detecting athletic condition, septic shock, and cyanide intoxication. Detection depends on the oxidation of lactate, which produces H 2 O 2. The electro-oxidation of H 2 O 2 is detected on the electrode surface. Commercial amperometric sensor for hydrogen peroxide and other chemicals Biosensor construction via layer-by- layer assembly Positively charged polyethylenimine (PEI) and negatively charged lactate oxidase (LOx) Incorporation of metal oxide in the enzyme layer Results. Objectives Design an adequately sensitive and reliable sensor that can function in the absence of oxygen Examine the effect of oxygen storage capacity on the performance of the biosensor Improve the sensitivity of the biosensors Perform Electrochemical tests: Cyclic Voltammetry (CV) was conducted at 0.6 V. Lactate is introduced to the system to observe the magnitude of current change. Current response tests are repeated in an oxygen-free solution. Calibration curves are recorded by incrementally adding lactate. Sensor development with differing metal oxide solutions with varying oxygen storage capacities– Zr, Ti, Ge, Cu doped CeO 2 Improve biosensor stability Examine the surface microstructure Addition of metal oxide reduces the dependence on oxygen in the biosensor. Incorporation of CeO 2 extended the linear range. Lactate biosensors with a high sensitivity, selectivity, and wide linear range were constructed. The addition of a CeO 2 layer allows the sensor to remain sensitive in oxygen-free environments. It extends the linear range of current response to a measurable level (seen in Fig 1). Without oxygen, current response of CeO 2 coated sensors is twice that of non- CeO 2 sensors (seen in Fig 2). Figure 1 shows the comparison of sensitivity for sensors in an oxygen-free environment as a small, fixed amount of lactate is added incrementally. Figure 2 shows the increased response of Ceria coated sensors in an oxygen-free environment. A platinum electrode used for lactate sensing. Figure 3 shows the linear current response trend in oxide coated electrodes when oxygen is absent.