Functionalized Au@Ag nanorod-embedded triple-network hydrogel for wearable SERS analysis of azelaic acid, H2O2 and pH in sweat
![Quantitative SERS Detection of Uric Acid via Formation of Precise Plasmonic Nanojunctions within Aggregates of Gold Nanoparticles and Cucurbit[n]uril](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F61682.jpg&w=3840&q=50)
Xin Zhuang1, Jing Lin1, Jialun Lin1
1College of Chemistry and Materials Science, Fujian Provincial Key Laboratory of Advanced Oriented Chemical Engineer, Fujian Key Laboratory of Polymer Materials, Engineering Research Center of Industrial Biocatalysis, Fujian Province Higher Education Institutes, Fujian Normal University, Fuzhou, Fujian, 350007, China.
Abstract:
Skin inflammation is commonly accompanied by oxidative stress and changes in the local acid-base microenvironment, whereas molecular indicators reflecting inflammation-associated metabolic changes remain less explored in wearable sensing. Azelaic acid, a dicarboxylic acid associated with inflammatory skin conditions, represents a potential small-molecule target, yet its non-invasive analysis in sweat remains challenging. Herein, a wearable-compatible ratiometric surface-enhanced Raman scattering (SERS) platform was constructed by embedding functionalized Au@Ag nanorods into a TEMPO-oxidized cellulose nanofibers (TOCNF)/poly(vinyl alcohol) (PVA)/poly(acrylamide-co-acrylic acid) [P(AM-co-AA)]-Zn2+ triple-network hydrogel. The hydrogel architecture promoted nanoprobe dispersion and immobilization while maintaining flexibility and signal stability, yielding a spatial SERS relative standard deviation (RSD) of 5.19% and 77% signal retention after 100 days. Using Au@4-ATP@Ag nanorods (NRs) containing 4-ATP as a Raman-responsive reporter, azelaic acid was quantified through the ratiometric I1194/I1073 response over 1 × 10-12-1 × 10-7 M, with a detection limit of 7.8 × 10-13 M, and its analytical feasibility in sweat was further evaluated by spike-recovery analysis. To provide complementary information on inflammation-related microenvironmental changes, the same hydrogel architecture was further adapted for H2O2 and pH sensing using Au@4-MPBA@Ag and Au@4-MBA@Ag NRs, respectively. The H2O2 channel exhibited a concentration-dependent response over 1-500 μM, while the pH response agreed well with pH-meter measurements, with deviations within 0.07 pH units. These results demonstrate the analytical feasibility of azelaic acid as an underexplored inflammation-related sweat target and highlight the potential of the triple-network SERS hydrogel for integrating molecular and microenvironmental information in skin-related sweat analysis.
