A novel photoelectrochemical (PEC) lactic dehydrogenase (LDH) biosensor was developed based on a multi-wall carbon nanotube (MWCNT)-TiO2 nanoparticle (TNP) composite platform. This composite platform can not only aid in regeneration of nicotinamide adenine dinucleotide (NAD+) in the enzymatic cycle, but also immobilize enzymes on electrode surface. TNPs were grown on MWCNT surface through a hydrothermal method and the composite was characterized by various spectroscopic techniques. The electrochemical performance of the LDH biosensors has demonstrated that the composite is a feasible immobilization matrix for LDH. The PEC experiments have confirmed that NAD(+) can be regenerated by the holes produced by irradiating MWCNT-TNP composite to fulfill the enzyme catalytic cycle. The analytical performance of the PEC LDH biosensor was studied by measuring its photocurrents. The dynamic range, sensitivity and limit of detection of the biosensor were estimated to be 0.5 to 120 mu M, 0.0242 mu A mu M-1 and 0.1 mu M respectively, which are superior to those of electrochemical LDH biosensors. (C) 2015 Elsevier Ltd. All rights reserved.