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.

In this paper we present a rapid and simple onepot method to obtain gold nanoparticles functionalized with folic acid using a photochemistry method. The bioconjugate folic acid-gold nanoparticle was generated in one step using a photo-reduction method, mixing hydrogen tetrachloroaurate with folic acid in different ratios and varying the illumination time of a mercury lamp (λ= 255 nm). Scanning electron microscopy showed a particle size of around 40-50nm and dynamic light scattering exhibited that the zeta potential varies from -41 to -50mV with different illumination times. Storage in the dark at 4°C prolongs the stability of folic acid-gold nanoparticle suspensions to up to 26 days. Ultraviolet visible and Fourier transform infrared spectroscopy showed a surface plasmon band of around 534nm and fluorescence spectroscopy exhibited a quenching effect on gold nanoparticles in the fluorescence emission of folic acid and thus confirmed the conjugation of folic acid to the surface of gold nanoparticles. In this study we demonstrate the use of a photochemistry method to obtain folic acid-gold nanoparticles in a simple and rapid way without the use of surfactants and long reaction times. The photochemical synthesis of FA-AuNPs opens new perspectives for creating novel functional nanomaterials for biomedical applications

The orientation of pterin-6-carboxylic acid on gold nanopillars was investigated by surface enhanced Raman spectroscopy and density functional theory methods. The experimentally vibrations from pterin-6-COOH free and attached to the Au surface display vibration features indicating chemical interaction of the pterin with the metal surface. The spectral feature evidenced that the pterin would adsorb on gold surface with a "lying down" configuration through the high intensity vibration of NH scissoring and rocking OH modes. The orientation study of pterins on gold nanopillars presented herein is believed to lead to new applications in biosensing field for detecting pterins of physiological importance.

<p>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 (λ_max=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.</p>

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.