I-Corps: Nanophosphors as Ultra-Sensitive Lateral Flow Reporters in a Lab-on-Phone Platform

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Diagnostic uncertainty or delay can exact a substantial toll on morbidity and mortality, especially with infectious diseases. For several critical medical conditions, reliable diagnostic tests currently have turnaround times of hours to days, besides requiring expensive equipment and trained personnel. Point-of-care (POC) diagnostics enable better disease management and patient care through decentralization and rapid time-to-result, and are rapidly growing in usage. Of all the existing and potential POC technologies and formats, the Lateral Flow Test (LFT), a nearly three decades-old technology, most readily meets the usability criteria and is, therefore, preferred over other formats when it is applicable and has sufficient sensitivity. However, commercially available LFTs for several critical diseases lack the analytical sensitivity and the cost-effective quantitative ability required to make a large clinical impact. When specific and stable antibodies to an analyte are used in combination with an LFT strip composed of the right components, the analytical sensitivity of an LFT is determined by the detectability of the reporter particle. The LFT reporters that have been developed thus far, to overcome the limitations of the colorimetric labels have not had a large impact in the POC market, and are likely to remain limited in their adoption, due to a combination of cost and practicality.The key innovation in the proposed technology is the use of 'nanophosphors', silica-encapsulated persistent luminescent nanoparticles, as Lateral Flow Test (LFT) reporters. Nanophosphors can enable the objective, ultrasensitive and quantitative measurement of analyte levels from complex samples through LFTs that use only a cell phone's built-in optics and an inexpensive plastic attachment for readout. The LFT is one of the most widely used point-of-care assay formats owing to its versatility and simplicity. LFTs have been hugely successful in applications including home pregnancy testing, but are not quantitative, and suffer from sensitivity and reproducibility limitations. Nanophosphors have an intense luminescence emission that lasts for several minutes after exposure to light available from inexpensive optical components like a cell phone flash. They are therefore more detectable than the currently used and visually-read colloidal gold, and when used as LFT reporters, allow the quantitative detection of much lower analyte concentrations.