Surface-Enhanced Raman Scattering Based Microfluidics for Single-Cell Analysis.

The integration of surface-enhanced Raman scattering (SERS) with droplet microfluidics has the potential to improve our understanding of cellular systems. Herein, we present the first application of SERS droplet microfluidics for single-cell analysis. A microfluidic device was used to encapsulate single prostate cancer cells and wheat germ agglutin (WGA)-functionalized SERS nanoprobes in water-in-oil droplets that were subsequently locked into a storage droplet array for spectroscopic investigation. The stationary droplets enabled the rapid identification of SERS regions of interest in live cancer cells by allowing collection of "fast" coarse maps over an area of several square millimeters followed by "slower" detailed interrogation of the identified hotspots. We demonstrate SERS at cellular resolution via a proof-of-concept assay that detects glycan expression on the surface of prostate cancer cells using WGA-modified metallic nanoparticles. The data illustrates the potential of SERS optofluidic systems for high-throughput cell screening and illustrates a previously unobserved high degree of cell-to-cell variability in the size and number of glycan islands.

Emulsion technologies for multicellular tumour spheroid radiation assays.

A major limitation with current in vitro technologies for testing anti-cancer therapies at the pre-clinical level is the use of 2D cell culture models which provide a poor reflection of the tumour physiology in vivo. Three dimensional cell culture models, such as the multicellular spheroid, provide instead a more accurate representation. However, existing spheroid-based assessment methods are generally labour-intensive and low-throughput. Emulsion based technologies offer enhanced mechanical stability during multicellular tumour spheroid formation and culture and are scalable to enable higher-throughput assays. The aim of this study was to investigate the characteristics of emulsion-based techniques for the formation and long term culture of multicellular UVW glioma cancer spheroids and apply these findings to assess the cytotoxic effect of radiation on spheroids. Our results showed that spheroids formed within emulsions had similar morphological and growth characteristics to those formed using traditional methods. Furthermore, we have identified the effects produced on the proliferative state of the spheroids due to the compartmentalised nature of the emulsions and applied this for mimicking tumour growth and tumour quiescence. Finally, proof of concept results are shown to demonstrate the scalability potential of the technology for developing high-throughput screening assays.

Transitioning from multi-phase to single-phase microfluidics for long-term culture and treatment of multicellular spheroids.

When compared to methodologies based on low adhesion or hanging drop plates, droplet microfluidics offers several advantages for the formation and culture of multicellular spheroids, such as the potential for higher throughput screening and the use of reduced cell numbers, whilst providing increased stability for plate handling. However, a drawback of the technology is its characteristic compartmentalisation which limits the nutrients available to cells within an emulsion and poses challenges to the exchange of the encapsulated solution, often resulting in short-term cell culture and/or viability issues. The aim of this study was to develop a multi-purpose microfluidic platform that combines the high-throughput characteristics of multi-phase flows with that of ease of perfusion typical of single-phase microfluidics. We developed a versatile system to upscale the formation and long-term culture of multicellular spheroids for testing anticancer treatments, creating an array of fluidically addressable, compact spheroids that could be cultured in either medium or within a gel scaffold. The work provides proof-of-concept results for using this system to test both chemo- and radio-therapeutic protocols using in vitro 3D cancer models.