Lanthanum Fluoride Upconverting Nanoparticles For Photo-Biomodulation Of Cell Function

Inorganic fluorescent nanoprobes have been widely used as passive agents for intracellular imaging for decades. An emerging field of research is the development of these contrast agents and using them actively in a way that they respond to external stimulation by inducing photo-chemical, thermal or mechanical actions that enable control and modulation over cell function. To achieve such control, methods which are remote, non-invasive and with low-thermal means of stimulation is preferable. Among a large variety of candidates, lanthanide doped upconverting nanoparticles (UCNPs) are one of the most interesting class of fluorescent materials. Non-scattering, low energy near infrared (NIR) light can be used for excitation of UCNPs as on-demand light sources resulting in emission peaks throughout the near-UV and visible wavelengths. Towards this goal, we developed nano-size, hydrophilic, non-toxic and biocompatible core-shell nanoparticles with enhanced upconversion intensity for photo-biomodulation studies. Under this approach, un-doped LaF3 (inert) shell and Yb3+ doped LaF3 (active) shell are grown on core LaF3: 20% Yb, 2% Tm upconverting nanoparticles for enhanced luminescence for the first time with rapid microwave-assisted synthesis method that employs Polyvinylpyrrolidone (PVP) as biocompatible surfactant. The as-synthesized high efficiency UCNPs are analyzed through XRD, TEM, HRTEM, and Photoluminescence spectrum that is acquired under 980 nm laser excitation. Confocal microscopy is used to visualize nanoparticles in cells. The cellular response to NIR irradiation and upconverted light are visualized by luminescence microscopy.