Accelerating Lateral Flow Assay Development

Andre Alfaro is the director of assay development at nanoComposix. He holds a BS in human biology and a BA in clinical psychology from the University of California, San Diego. He spent several years characterizing surface markers on cancer stem cells for potential use as targets for nanoparticle delivery systems of cancer vaccines. He then joined Astute Medical in 2008 where he began a career developing and commercializing dozens of in vitro diagnostic tests on both the lateral flow and ELISA platforms for multiple disease indications. His work on the identification of acute kidney biomarkers led to a successful de novo 510(K) submission and CE mark of the NephroCheck test. In 2018, he joined the nanoComposix team to bring his 10+ years of development, quality, and regulatory training to the lateral flow group.

How do lateral flow assays work, and how are they currently used in clinical settings?

The core technology is very simple, and has been around for a long time. Essentially, it is an immunoassay—very similar to an ELISA (enzyme-linked immunosorbent assay)—that uses antibody affinities to capture target analytes at fixed positions as the fluids run through the nitrocellulose membrane. While the technology is not necessarily novel, the applications are. Lateral flow moves that technology out of the laboratory to the bedside or home environment. 

What are the advantages of plasmonic nanoparticles—such as gold nanoshells—in lateral flow assays?

All lateral flow is predicated on a detection system to determine if the target analyte binding event has occurred. An antibody itself is not visible without a reporter probe, which typically comes in two flavors: fluorescent and colorimetric. While both methods have their viability and uses, a significant drawback of fluorescence is that it requires a reader, which increases complexity and cost. A colorimetric test relies on plasmonic particles to generate a signal which can be interpreted by the naked eye. Pregnancy tests, for example, often use gold particles that produce a red line. This technology has not changed for decades, so we sought to improve upon colorimetric particles. 

One way to do this would be to make each particle more visible to the naked eye. This can be accomplished by increasing the size of the particle. The challenge is that increasing the particle size, thickness, and density will change the flow characteristics and make it more difficult for the particles to perform as desired within a lateral flow test strip. We developed a solution using nanoshells. Nanoshells are plasmonic reporter nanoparticles consisting of a silica core coated in a thin gold shell. They have similar flow characteristics as small gold colloids, but have the plasmonic properties of a large gold colloid. The resulting particles have a far greater per binding event signal versus the traditional small gold colloids, which really changed what we are able to achieve with colorimetric detection on lateral flow.

How can clinical labs accelerate the development of new lateral flow assays?

While lateral flow technology is not overly complex, the challenge is developing a test system that meets all the product requirements, and doing so efficiently. Given enough time, it is possible to put together a great assay, but a contract research organization has the expertise and experience to accelerate the process. Ultimately, this gets products to market faster, and reduces costs. 

How do you think novel lateral flow assays will impact diagnostics in the future?

The COVID-19 pandemic really shed light on the importance of rapid diagnostic tests. There has always been value in having test results in minutes instead of hours, but it was never considered necessary in most clinical settings with access to a central laboratory. The pandemic has made it very clear that we need access to rapid testing at home, and in the field. Widespread adoption of lateral flow is an inexpensive solution for preventative medicine.