Intracellular gallium nitride microrod laser

Abstract

We report laser emission from gallium nitride (GaN) microrods that are introduced into mammalian cells and the application of these microrods for cell labeling. GaN microrods were grown on graphene-coated SiO 2 /Si substrates by metal-organic vapor phase epitaxy. The GaN microrods are easily detached from the substrates because of the weakness of the van der Waals forces between GaN and graphene. The uptake of microrods into HeLa cells via endocytosis and viability after uptake were investigated. Normal cellular activities, including migration and division, were observed over 2 weeks in culture. Furthermore, the photoluminescence spectra of the internalized microrods exhibited sharp laser emission peaks with a low lasing threshold of 270\u2009kW/cm 2 . A new technique for placing tiny lasers inside living cells could make it easier to selectively label targets during microscopy. Gyu-Chul Yi from Seoul National University in South Korea and colleagues report a procedure for growing gallium nitride (GaN), a biocompatible inorganic crystal capable of laser emission, into microscale rods. The team demonstrated that this morphology enabled the GaN crystals to be taken up into human cells in cell culture with no adverse effects on processes such as cell division. Optical characterization of the GaN-containing cells revealed they could emit narrow-band laser light using only moderate levels of excitation power. Because individual microrods could be identified by unique wavelength and intensity features in their laser spectra, this approach may prove advantageous for tagging and tracking large numbers of cells in complex environments. We demonstrate intracellular GaN microrod lasers for cell labeling applications. GaN microrods show excellent lasing signals under intracellular conditions with a low lasing threshold (~270\u2009kW/cm 2 ). The lasing spectra from individual intracellular microrods are distinguishable because each GaN microrod has different lasing peak wavelength, mode spacings, and relative PL intensities. This result suggests that GaN microrods can be candidates for cell labeling applications.