A Multiplexed SERS-Active Microneedle for Simultaneous Redox Potential and pH Measurements in Rat Joints

To detect redox potential and pH simultaneously in rat joints, a surface-enhanced Raman scattering (SERS)-active microneedle was structured with two separate grooves containing redox-sensitive and pH-sensitive SERS probes, respectively. The multiplexed SERS-active microneedles brought the two SERS probes into muscles with minimal invasion to sense their redox status and pH in 5 min, and they also detected the dynamical evolution of redox status and pH in muscles. The multiplexed SERS-active microneedles were also inserted into rat joints to sense their redox status and pH, which lack flowable fluids. The strategy of one SERS probe in one groove would allow SERS-active microneedles to become a multiplexed analytical tool for minimally invasive sampling in vivo and direct Raman detection ex vivo, and the multiplexed SERS-active microneedles would become a versatile analytical tool to promote research in biomedicines.