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Gold nanoparticles functionalized with folic acid toward the internalization into cancer cells have received considerable attention recently. Folic acid is recognized by folate receptors, which are overexpressed in several cancer cells; it is limited in normal cells. In this work, pterin-6-carboxylic acid is proposed as an agonist of folic acid since the pterin-6-carboxylic acid structure has a pterin moiety, the same as folic acid that is recognized by the folate receptor. Here a simple photochemical synthesis of gold nanoparticles functionalized with pterin-6-carboxylic acid is studied. These conjugates were used to cause photothermal damage of HeLa cells irradiating with a diode laser of 808 nm. Pterin-6-carboxylic acid-conjugated gold nanoparticles caused the death of the cell after near-infrared irradiation, dose-dependently. These results indicate a possible internalization of AuNPs via folate receptor-mediated endocytosis due to the recognition or interaction between the folate receptors of HeLa cells and pterin, P6CA., (© 2021. The Author(s), under exclusive licence to European Photochemistry Association, European Society for Photobiology.)

TiO 2 electrochemical biosensors represent an option for biomolecules recognition associated with diseases, food or environmental contaminants, drug interactions and related topics. The relevance of TiO 2 biosensors is due to the high selectivity and sensitivity that can be achieved. The development of electrochemical biosensors based on nanostructured TiO 2 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 TiO 2 nanostructures. Using relevant literature published in the last decade, an overview of TiO 2 based biosensors is here provided. First, the principal fabrication methods of nanostructured TiO 2 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 TiO 2 surfaces, considering the detection technique and the experimental electrochemical conditions needed for a specific analyte.