TiO₂ electrochemical biosensors represent an option for biomolecules recognition associated with diseases, food or environmental contaminants, drug interactions and related topics. The relevance of TiO₂ biosensors is due to the high selectivity and sensitivity that can be achieved. The development of electrochemical biosensors based on nanostructured TiO₂ surfaces requires knowing the signal extracted from them and its relationship with the properties of the transducer, such as the crystalline phase, the roughness and the morphology of the TiO₂ nanostructures. Using relevant literature published in the last decade, an overview of TiO₂ based biosensors is here provided. First, the principal fabrication methods of nanostructured TiO₂ surfaces are presented and their properties are briefly described. Secondly, the different detection techniques and representative examples of their applications are provided. Finally, the functionalization strategies with biomolecules are discussed. This work could contribute as a reference for the design of electrochemical biosensors based on nanostructured TiO₂ surfaces, considering the detection technique and the experimental electrochemical conditions needed for a specific analyte.

Folic acid (FA) is used as a recognition molecule to achieve selective internalization in cancer cells. Here functionalized gold nanoparticles with folic acid (AuNP-FA) are proposed as suitable therapeutic agents for cervix cancer cells by photothermal damage. The functionalized gold nanoparticles with folic acid were synthesized by mixing hydrogen tetrachloroaurate with folic acid in a molar ratio of 0.56/1 under radiation of mercury lamp (λmax=254 nm). HeLa cells were incubated with AuNP-FA during 48 h, then were irradiated and the cytotoxicity was analyzed 12 h after irradiation. The AuNP-FA were dose-dependent cytotoxic under irradiation and not cytotoxic in the absence of radiation. The viability of cancer cells treated with functionalized and non-functionalized gold nanoparticles (AuNPs), with and without near infrared light at 808 nm, was measured by MTT assays. This work provides useful guidance toward the synthesis of biocompatible nanomaterials for biological applications.