Silk fibroin-based colorimetric microneedle patch for rapid detection of spoilage in packaged salmon samples

Spoiled salmon can cause foodborne diseases and severely affects human health. Herein, we report a pH-responsive colorimetric microneedle (MN) patch fabricated from bromothymol blue (BTB) and silk fibroin meth acryloyl (SilMA) (BTB/SilMA@MN patch) for sensing salmon spoilage. The needle tips of MN could penetrate food cling film and insert into fish to extract tissue fluids directly and transport the extracted fluids to the backing layer for color displaying. The color change of BTB/SilMA@MN patches depended on the pH variation resulting from the increase of total volatile basic nitrogen in salmon during storage. The color of MN patches changed from yellow to yellowish green and to final green, indicating salmon changed from fresh to medium fresh and then to putrefied, respectively. Salmon spoilage can be rapidly determined via naked eye recognition and also analyzed on a smartphone in a nondestructive way, allowing consumers to estimate food quality easily and reliably.