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1.D.145.  The TiO2 Nanochannel (TiO2-NC) Family 

The level of hydrogen sulfide in the brain and vasculature is associated with human health and diseases. Hence, simple and robust analytical tools allowing determination of hydrogen sulfide levels are highly desirable. A biomineralization-driven ion gate in TiO2 nanochannel arrays for H2S sensing was designed and developed (Guo et al. 2019). The formed CuS precipitation decreased the transmembrane current in the presence of bovine serum albumin used as biological mineralizer. A label-free assay for sensing intracellular S2- was achieved based on changes in ionic current with a detection limit of 56 MCF-7 cells. The sensing strategy was promising for reusable application through dissolution of CuS in an acidic media (pH = 1) (Guo et al. 2019). 

Xu et al. 2023 developed an electrochemical platform based on a tandem recognition-reaction zone design in TiO2 nanochannels for the specific recognition of reducing enantiomers. In this system, MIL-125(Ti) Ti-metal-organic frameworks, in situ grown in TiO2 nanochannels, provided a homochiral recognition environment via postmodification with l-tartaric acid (l-TA); MnO2 nanosheets possessing both glucose oxidase (GOD)- and peroxidase (POD)-mimicking activities served as the target-reactive zone at the end of the nanochannels. The use of penicillamine (Pen) enantiomers as model-reducing targets facilitated the passage of d-Pen through the homochiral recognition zone, owing to its lower affinity with l-TA. The passed Pen molecules reached the responsive zone and induced a target concentration-dependent MnO2 disassembly. Such target recognition event impaired the cascade GOD- and POD-like activities of MnO2. Combining the enantioselectivity of the recognition nanochannels with the cascade enzyme-like activity of MnO2 toward glucose and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate), the quantitative identification of l- and d-Pen was achieved through the changes in transmembrane ionic current induced by the generated charged products. This recognition-reaction zone design paves an effective way for developing a promising electrochemical platform for the identification of reducing enantiomers with improved selectivity and sensitivity (Xu et al. 2023).

References associated with 1.D.145 family:

Guo, J., L. Yang, H. Xu, C. Zhao, Z. Dai, Z. Gao, and Y. Song. (2019). Biomineralization-Driven Ion Gate in TiO Nanochannel Arrays for Cell HS Sensing. Anal Chem 91: 13746-13751. 31559823
Xu, H., J. Guo, J. Zhao, Z. Gao, and Y.Y. Song. (2023). Enantioselective Target Transport-Mediated Nanozyme Decomposition for the Identification of Reducing Enantiomers in Asymmetric Nanochannel Arrays. Anal Chem 95: 14465-14474. 37699410