Application of the aqueous two-phase system and nanozyme signal enhancement for the improved detection of Plasmodium lactate dehydrogenase in serum.

Malaria is an infectious disease that can cause severe sickness and death if not diagnosed and treated in a timely manner. The current gold standard technique for malaria diagnosis is microscopy, which requires a dedicated laboratory setting and trained personnel and can have a long time to result. These requirements can be alleviated using paper-based diagnostic devices that enable rapid and inexpensive diagnosis at the point of care, which can allow patients to receive treatment before their symptoms progress when used for early detection of diseases. The lateral-flow immunoassay (LFA) is one such device, but currently available LFAs are susceptible to false negative results caused by low parasite density. To improve sensitivity and detection, we utilized the aqueous two-phase system (ATPS) to concentrate and purify the sample, and nanozyme signal enhancement to increase the intensity of the visible signal on the test strip. We were able to achieve a limit of detection (LOD) of 0.01 ng/mL for the malaria biomarker Plasmodium lactate dehydrogenase (pLDH) in human serum using a multi-step assay combining the LFA format with the ATPS and nanozyme signal enhancement.

Developments in integrating nucleic acid isothermal amplification and detection systems for point-of-care diagnostics.

Early disease detection through point-of-care (POC) testing is vital for quickly treating patients and preventing the spread of harmful pathogens. Disease diagnosis is generally accomplished using quantitative polymerase chain reaction (qPCR) to amplify nucleic acids in patient samples, permitting detection even at low target concentrations. However, qPCR requires expensive equipment, trained personnel, and significant time. These resources are not available in POC settings, driving researchers to instead utilize isothermal amplification, conducted at a single temperature, as an alternative. Common isothermal amplification methods include loop-mediated isothermal amplification, recombinase polymerase amplification, rolling circle amplification, nucleic acid sequence-based amplification, and helicase-dependent amplification. There has been a growing interest in combining such amplification methods with POC detection methods to enable the development of diagnostic tests that are well suited for resource-limited settings as well as developed countries performing mass screenings. Exciting developments have been made in the integration of these two research areas due to the significant impact that such approaches can have on healthcare. This review will primarily focus on advances made by North American research groups between 2015 and June 2020, and will emphasize integrated approaches that reduce user steps, reliance on expensive equipment, and the system's time-to-result.