A Wearable PVA Film Supported TiO₂ Nanoparticles Decorated NaNbO₃ Nanoflakes‐Based SERS Sensor for Simultaneous Detection of Metabolites and Biomolecules in Human Sweat Samples

Abstract

Sweat is one of the non‐invasive diagnostic biofluids that provides critical information about human health. In this work, a wearable sweat sensor integrated with a polymer‐based fluid absorption layer modified with titanium oxide (TiO2) nanoparticles decorated sodium niobate (NaNbO3) nanoflakes in porous polyvinyl alcohol (PVA) film matrix is demonstrated for the detection of vital metabolites (such as glucose and urea) and biomolecules (ascorbic acid (AA) and uric acid (UA)) in human sweat samples via surface‐enhanced Raman scattering (SERS). The TiO2@NaNbO3/PVA (SERS patch) exhibits a low limit of detection (LOD) of 0.50, 0.80, 1.00, and 100 mm towards AA, glucose, UA, and urea, respectively. The SERS patch displays a high enhancement factor with a low accumulation time of 20s which can be ascribed to the surface coordination between the TiO2@NaNbO3 and the analytes leading to interfacial charge‐transfer transition (ICTT). Besides, the photo‐induced charge transfer (PICT) resonance significantly amplifies the SERS signal. The SERS patch is successful in the simultaneous determination of AA, glucose, UA, and urea in simulated sweat samples with minimal mutual interference. The high efficacy of the SERS patch proves it as an ideal platform for a wide range of wearable healthcare monitoring applications.

Flexible Sweat Sensors: From Films to Textiles

“…Before being used for formal monitoring, rhodamine (R6G) or crystal violet (CV) is generally used to characterize its performance and evaluate the adsorption effect of metal nanostructure surfaces. , Since a Raman spectrum is judged by the scattering of the molecular surface, SERS is generally only used for molecules such as metabolites in sweat, such as lactic acid, , glucose, , ascorbic acid, urea, , uric acid, etc., while physiological monitoring other than sweat can be extended to DNA , in blood. However, some people use SERS to monitor the pH value of sweat, and 4-MBA is needed to further modify the metal nanostructure. , Because of the high cost of SERS sensors due to the use of gold nanomaterials, transition metal oxides and their derivatives have been used to replace gold as SERS substrate material . On the other hand, some methods that can control the height and structure of nanostructures and large-scale ordered nanoarrays have also been used, such as porous anodic aluminum oxide (AAO). , The price of this process is relatively low.…”

“…166,169 Because of the high cost of SERS sensors due to the use of gold nanomaterials, transition metal oxides and their derivatives have been used to replace gold as SERS substrate material. 167 On the other hand, some methods that can control the height and structure of nanostructures and large-scale ordered nanoarrays have also been used, such as porous anodic aluminum oxide (AAO). 168,170 The price of this process is relatively low.…”

Recent Advancements in Physiological, Biochemical, and Multimodal Sensors Based on Flexible Substrates: Strategies, Technologies, and Integrations

“…The various components of human metabolites are closely related to human health status. The above analytes have been widely used in clinical diagnosis, athletes’ physical condition analysis, and medical health monitoring. − For details, see Table . ,− ,− …”

Dual‐Modal Fluorescence‐SERS Detection of Blood Glucose Engineered by Hierarchical Laser‐Induced Micro/Nano Structures for Diabetes Screening

“…First, the homogeneity of the substrate was verified by acquiring SERS spectra of R6G solution at 10 -3 mol L −1 from 50 × 50 points (2500 spectra, step size 200 µm in X direction, 200 µm in Y direction) covering the whole area of 10 mm × 10 mm. [40,41] The 1650 cm −1 Raman band of these spectra was then plotted in Figure S2 (Supporting Information) to give a spatial map of enhancement from the substrate. It can be seen that the substrate provides unambiguous and uniform SERS spectra over the whole tested area with a relative standard deviation (RSD) of 8.75%.…”