Tumor microenvironment-responsive touch sensor-based pH-triggered controllable conductive hydrogel

A tumor microenvironment-responsive wireless strain-pressure hydrogel sensor based on pH-induced controllable nanoparticles was designed for cancer detection in vitro–in vivo model, with excellent ability to distinguish between cancer and normal cells. The pH-responsive nanoparticles (CD-PNB), comprising diol–diol crosslinked semiconducting carbon dots (CDs) and non-conductive polymer (PNB), are sensitive to acidic tumor microenvironments and play crucial role in demonstrating tumor-selective strain-pressure responses. Upon application of strain and pressure, CD-PNB@PVA hydrogel produced distinct electronic signals in the presence of cancer cells (HeLa, PC-3), exhibiting higher strain–pressure sensitivity compared to the normal cells (MDCK, CHO-K1). The strain and pressure gage factors for cancer-cell-treated CD-PNB@PVA hydrogel were found to be 0.7439 and 5.3052 kPa⁻¹, which were higher than normal-cell-treated CD-PNB@PVA hydrogel (0.5009 and 4.2720 kPa⁻¹). CD-PNB@PVA hydrogel demonstrated excellent response in tumor-bearing mice based on in situ and ex situ measurements, with no inflammation during hydrogel implantation. Moreover, wireless sensing system was used along with CD-PNB@PVA hydrogel to simplify monitoring process and obtain real-time conductivity and strain–pressure profiles on smartphone. Thus, this approach constructs a tumor microenvironment-responsive strain–pressure hydrogel sensor and presents potential for sensitive and selective tumor detection in point-of-care diagnostic applications.