In Situ Shape Control of Thermoplasmonic Gold Nanostars on Oxide Substrates for Hyperthermia-Mediated Cell Detachment

Gold nanostars (AuNSTs) are biocompatible, have large surface areas, and are characterized by high near-infrared extinction, making them ideal for integration with technologies targeting biological applications. We have developed a robust and simple microfluidic method for the direct growth of anisotropic AuNSTs on oxide substrates including indium tin oxide and glass. The synthesis was optimized to yield AuNSTs with high anisotropy, branching, uniformity, and density in batch and microfluidic systems for optimal light-to-heat conversion upon laser irradiation. Surface-enhanced Raman scattering spectra and mesoscale temperature measurements were combined with spatially correlated scanning electron microscopy to monitor nanostar and ligand stability and microbubble formation at different laser fluences. The capability of the platform for generating controlled localized heating was used to explore hyperthermia-assisted detachment of adherent glioblastoma cells (U87-GFP) grafted to the capillary walls. Both flow and laser fluence can be tuned to induce different biological responses, such as ablation, cell deformation, release of intracellular components, and the removal of intact cells. Ultimately, this platform has potential applications in biological and chemical sensing, hyperthermia-mediated drug delivery, and microfluidic soft-release of grafted cells with single-cell specificity.