A team of engineers from the University of Rhode Island (URI; RI, USA) has developed a novel paper-based platform that could be used for a range of complex medical diagnostic tests. The team invented a method of embedding fluid actuated valves into the paper, which allow for sequential manipulation of multiple reagents and sample fluids. This controlled manipulation allows the system to perform complex, multi-step immune-detection tests without human intervention.
Faghri, team leader Professor of Mechanical Engineering & Applied Mechanics at URI, explained that the platform could potentially be used for the diagnosis of a wide range of diseases, from Lyme disease and HIV to Ebola and malaria. “If someone comes up with a new biomarker for detecting a disease, we can create a test for it using our platform,” he recounted.
A patent with broad claims has been issued by the US Patent and Trademark Office for this technology, with two more pending. Paper-based lateral flow test strips, such as pregnancy tests, have been commercially successful for many years. In these devices, sample fluids wick along a strip of paper and react with embedded reagents to produce a colored signal result. More complex medical diagnostics, such as enzymatic assay protocols, require multiple reagents triggered at different points during analysis. This can be accomplished without human assistance using the proprietary microfluidic valve technique developed by the URI team.
“We combined the well-established test strip technology, micro-patterning techniques, and our innovative paper-based valves to create a new class of strip tests that are capable of autonomously handling multiple reagents,” Faghri described. “The sample fluid activated the flow of reagents in a predetermined sequence and time. When combined with an optical reader, which could even be a conventional smart phone, the lab-on-paper device provides quantitative results.”
The paper devices are constructed with layers of paper printed with wax, to create a three-dimensional structure of channels and valves. The fluid travels through this system, triggering the reagents at the appropriate time and generating a result. The new lab-on-paper device represents the next generation of the microchip-based device the team reported in 2011. “Our new paper-based system, however, doesn’t need any pumping because the fluid flows naturally along the paper channels via wicking,” Faghri explained. “It can perform enzymatic assays on paper autonomously with sensitivities close to laboratory techniques.”
The researchers, in collaboration with ProThera Biologics (RI, USA), have already performed a successful feasibility study of their technology by showing it can detect a biomarker for sepsis.