| Summary: | Label-free imaging of viruses and nanoparticles directly in complex solutions is important for virology, vaccine research, and rapid diagnostics. These fields would all benefit from tools that allow for more rapid and sensitive characterization of viruses. Traditionally, light microscopy has been used in laboratories for detection of parasites, fungi, and bacteria for both research and clinical diagnosis because it is portable and simple to use. However, virus particles typically cannot be explored using light microscopy without the use of secondary labels due to their small size and low contrast. Characterization and detection of virus particles therefore rely on more complex approaches such as electron microscopy, ELISA, or plaque assay. These approaches require a significant level of expertise, purification of the virus from its natural environment, and often offer indirect verification of the virus presence. A successful virus visualization technique should be rapid, sensitive, and inexpensive, while needing minimal sample preparation or user expertise. We have developed a disposable cartridge based platform for real-time, sensitive, and label free visualization of viruses and nanoparticles directly in complex solutions such as serum. To create this platform we combined an interference reflectance imaging technique (SP-IRIS) with a sealable microfluidic cartridge. Through empirical testing and numeric modelling, the cartridge parameters were optimized and a flow rate of ~3 µL/min was established as optimal. A complex 2-dimensional paper based capillary pump was incorporated into the polymer cartridge to achieve a constant flow rate. Using this platform we were able to reliably show virus detection in a 20 minute experiment. We demonstrate sensitivity comparable to laboratory-based assays such as ELISA and plaque assay, and equal or better sensitivity compared to paper based rapid diagnostic tests. These results display a platform technology that is capable of rapid multiplexed detection and visualization of viruses and nanoparticles directly in solution. This disposable cartridge based platform represents a new approach for sample-to-answer label-free detection and visualization of viruses and nanoparticles. This technology has the potential to enable rapid and high-throughput investigation of virus particle morphology, as well as be used as a rapid point-of-care diagnostic tool where imaging viruses directly in biological samples would be valuable.
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