Wearable micromotor-based electrochemical microneedle sensors for monitoring tumor biomarkers in skin.

Wearable sensors show value in dynamic disease monitoring but face the challenge in efficiently detecting low-abundance biomarkers from trace skin interstitial fluid (ISF). Herein, we proposed an active microneedle sensor integrated with micromotors for highly sensitive, dynamic monitoring of trace tumor markers carcinoembryonic antigen (CEA) in ISF. The sensor employed a core-shell structured hydrogel microneedle array. The shell provided mechanical strength for minimally invasive skin penetration, while the water-soluble core dissolved upon contact with ISF, releasing self-propelled micromotors. These micromotors generated hydrogen bubbles that drove antibody-functionalized magnetic carriers, enhancing the capture efficiency of CEA and overcoming the limitations inherent in traditional passive diffusion modes. Following capture, the magnetic complexes bound with CEA were concentrated onto the surface of a screen-printed electrode, where quantitative detection was achieved by monitoring variations in the electrochemical current response. The in vivo results showed that the sensor could detect an early electrochemical response associated with tumor progression as early as day 2 after LLC-GFP-LUC cell inoculation, and the current signal showed a progressive decline with tumor development. By day 5, a significant increase in CEA concentration was measured by ELISA, while tumor volume remained undetectable by conventional physical methods. This micromotor-integrated sensor can provide early detection signals within a time window where traditional methods are unable to detect, offering a promising minimally invasive tool for monitoring tumor progression and evaluating treatment efficacy.