(191cb) Luminescent Nanoparticles for High-Throughput Microfluidic Droplet Barcoding

Molecularly-targeted therapeutics and personalized medicine have dramatically increased the prognosis of patients suffering from cancer. However, one major challenge facing cancer patients is the presence of drug-resistant tumor cells. This is further complicated by the high patient-to-patient variability due to the heterogeneous, personalized nature of cancer. As such, multiple therapeutic combinations have required the development of new analytical methods capable of multiplexed high-throughput screening (HTS) technologies that can quantify ex vivo samples like patient biopsies. The use of droplet microfluidic devices has garnered significant interest as a means to facilitate high-throughput, single cell analysis of heterogeneous populations like tumor biopsies. Additionally, the inclusion downstream trapping arrays can facilitate droplet collection and dynamic investigation of the single cell response. However, these devices are still limited in their to assess multiple inputs such as combinations of drugs or different doses. While some droplet barcoding techniques exist, they are limited by overlapping fluorescence spectra between barcoding fluorophores and biochemical fluorophores. In this work, rare earth (RE)-doped nanoparticles are coupled with droplet microfluidics for a novel approach at droplet barcoding. The β-hexagonal NaYF₄ nanoparticles are roughly 750 nm in diameter and are doped with rare-earth emitters (Tb³⁺, Eu³⁺ or Dy³⁺). RE dopants have been extensively employed in solid-state applications due to their stability and wide excitation/emission pathways, allowing for visible luminescence with UV and IR excitation. Here, we use three different dopants (Eu³⁺, Tb³⁺, and Dy³⁺) incorporated into the nanoparticles which have a luminescence emission spectra in the red, green, and blue regions upon excitation with UV light. Using a droplet microfluidic trapping array, we have demonstrated that these particles are biologically inert and spectrally independent with common biological stains like GFP. Moreover, we have shown that the RE-doped nanoparticles do not interfere with fluorescent live and dead stains. To demonstrate the feasibility of these nanoparticles as droplet barcodes, we have co-encapsulated the nanoparticles with model cancer cell lines exposed to established therapeutic combinations to quantify concentration and time-dependent drug induced cell death. Thus, this work offers a novel antibody-free method for multiplexed droplet barcoding to facilitate high-throughput ex vivo screening of cancer therapeutics.