Plasmonic Cu_<i>x</i>S Nanocages for Enhanced Solar Photothermal Cell Warming

Highly efficient plasmonic photothermal nanomaterials are benefitial to the successful resuscitation of cells. Copper sulfide (CuxS) is a type of plasmonic solar photothermal semiconductor material that expands the light collecting range by altering its localized surface plasmonic resonance (LSPR) to the near- to mid-infrared (IR) spectral region. Particularly, nanocages (or nanoshells) have hybridized plasmon resonances as the result of superpositioned nanospheres and nanocavities, which extend their receiving range for the solar spectrum and increase light-to-heat conversion rate. In this work, for the first time, we applied colloidal hollow CuxS nanocages to revive cryopreserved HeLa cells via photothermal warming, which showed improved cell warming rate and cell viability after cell resuscitation. Moreover, we tested the photothermal performance of CuxS nanocages with concentrated light illumination, which exhibited extraordinary photothermal performance due to localized and enhanced illumination. We further quantified each band's contribution during the cell warming process via evaluating the warming rate of cryopreserved cell solution with illumination by monochromatic UV, visible, and NIR lasers. We studied the biosafety and toxicity of CuxS nanocages by analyzing the generated copper ion residue during cell warming and cell incubation, respectively. Our study shows that CuxS nanocages have huge potential for cell warming and are promising for vast range of applications, such as nanomedicine, life science, biology, energy saving, etc.