A Smartphone-Integrated Coated Microneedle Sensor for In-Situ Extraction and Rapid Detection of Total Phenols in Fruits and Vegetables

Abstract

As interest in monitoring the nutritional and antioxidant levels in fruits and vegetables grows, the need for efficient, non-invasive detection methods increases. In this work, a novel coated microneedle colorimetric sensing platform is designed to rapidly and sensitively detect total phenolic compounds (TPC) in fruits and vegetables, which is the key indicator of their nutritional and antioxidant properties. The platform utilizes a swollen microneedle structure to efficiently collect juice samples, enhancing detection efficiency through colorimetric analysis and eliminating the complexity of traditional methods. The microneedles are fabricated from a composite material consisting of 10,12-pentacosadiynoic acid (PCDA) and methacrylated gelatin (GelMA), with a secondary layer containing α-cyclodextrin to selectively bind polyphenols, thereby inducing a visible color change for the specific detection of TPC. The colorimetric response is directly correlated with the concentration of TPC, facilitating on-site analysis. Using phenol as a model molecule, the detection range of the system for phenol is 10–60 mM, with an LOD of 0.5 mM. Furthermore, a mobile application enables portable detection and analysis, reducing detection time from several hours to just 30 min. This technology offers a promising approach for the rapid, reliable monitoring of phenolic content in fresh produce, with potential applications in food quality control, nutritional analysis, and agricultural monitoring.