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.

We herein demonstrate that capacitance spectroscopy (CS) experimentally allows access to the energy associated with the quantum mechanical ground state of many-electron systems. Priorly, electrochemical capacitance, C[ρ], was previously understood from conceptual and computational density functional theory (DFT) calculations. Thus, we herein propose a quantum mechanical experiment-based variational method for electron charging processes based on an experimentally-designed functional of the ground state electron density. In this methodology, the electron state density, ρ, and an energy functional of the electron density, E[ρ], can be obtained from CS data. CS allows the derivative of the electrochemical potential with respect to the electron density, (δ[ρ]/δρ), to be obtained as a unique functional of the energetically minimised system, i.e., β/C[ρ], where β is a constant (associated with the size of the system) and C[ρ] is an experimentally observable quantity. Thus the ground state energy (at a given fixed external potential) can be obtained simply as E[ρ], from the experimental measurement of C[ρ]. An experimental data-set was interpreted to demonstrate the potential of this quantum mechanical experiment-based variational principle.