Enzymatic Strategies to Construct L-Lactate Biosensors Based on Polysulfone/Carbon Nanotubes Membranes

We present different strategies to construct amperometric L-lactate biosensors using the enzymes lactate dehydrogenase (LDH) and lactate oxidase (LOx). These biomolecules are incorporated into a polysulfone/carbon nanotubes composite matrix by means of an easy and rapid technique, i.e. inversion phase, and deposited onto carbon screen-printed electrodes. The use of redox mediators, Meldolas Blue and cobalt(II) phthalocyanine (CoPc) are necessary to reduce the working potential for the detection of NADH and H2O2 products. The working conditions for both biosensors have been optimized such as the pH, amount of immobilized enzyme and lifetime stability. LDH biosensor presents a linear interval range from 10-6 to 2 x 10(-5) M L-lactate and a 3.7 x 10(-7) M as limit of detection (LOD), and from 5 x 10(-6) to 5 x 10(-4) M and 3.4 x 10(-6) M, in case of LOx, respectively.