Equipment-free, salt-mediated immobilization of nucleic acids for nucleic acid lateral flow assays.

As the world has been facing several deadly virus crises, including Zika virus disease, Ebola virus disease, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and Coronavirus disease 2019 (COVID-19), lateral flow assays (LFAs), which require minimal equipment for point-of-care of viral infectious diseases, are garnering much attention. Accordingly, there is an increasing demand to reduce the time and cost required for manufacturing LFAs. The current study introduces an equipment-free method of salt-mediated immobilization of nucleic acids (SAIoNs) for LFAs. Compared to general DNA immobilization methods such as streptavidin-biotin, UV-irradiation, and heat treatment, our method does not require special equipment (e.g., centrifuge, UV-crosslinker, heating device); therefore, it can be applied in a resource-limited environment with reduced production costs. The immobilization process was streamlined and completed within 30 min. Our method improved the color intensity signal approximately 14 times compared to the method without using SAIoNs and exhibited reproducibility with the long-term storage stability. The proposed method can be used to detect practical targets (e.g., SARS-CoV-2) and facilitates highly sensitive and selective detection of target nucleic acids with multiplexing capability and without any cross-reactivity. This novel immobilization strategy provides a basis for easily and inexpensively developing nucleic acid LFAs combined with various types of nucleic acid amplification.

Current state of diagnostic, screening and surveillance testing methods for COVID-19 from an analytical chemistry point of view.

Since December 2019, we have been in the battlefield with a new threat to the humanity known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this review, we describe the four main methods used for diagnosis, screening and/or surveillance of SARS-CoV-2: Real-time reverse transcription polymerase chain reaction (RT-PCR); chest computed tomography (CT); and different complementary alternatives developed in order to obtain rapid results, antigen and antibody detection. All of them compare the highlighting advantages and disadvantages from an analytical point of view. The gold standard method in terms of sensitivity and specificity is the RT-PCR. The different modifications propose to make it more rapid and applicable at point of care (POC) are also presented and discussed. CT images are limited to central hospitals. However, being combined with RT-PCR is the most robust and accurate way to confirm COVID-19 infection. Antibody tests, although unable to provide reliable results on the status of the infection, are suitable for carrying out maximum screening of the population in order to know the immune capacity. More recently, antigen tests, less sensitive than RT-PCR, have been authorized to determine in a quicker way whether the patient is infected at the time of analysis and without the need of specific instruments.

Recent advances in sensitive surface-enhanced Raman scattering-based lateral flow assay platforms for point-of-care diagnostics of infectious diseases.

This review reports the recent advances in surface-enhanced Raman scattering (SERS)-based lateral flow assay (LFA) platforms for the diagnosis of infectious diseases. As observed through the recent infection outbreaks of COVID-19 worldwide, a timely diagnosis of the disease is critical for preventing the spread of a disease and to ensure epidemic preparedness. In this regard, an innovative point-of-care diagnostic method is essential. Recently, SERS-based assay platforms have received increasing attention in medical communities owing to their high sensitivity and multiplex detection capability. In contrast, LFAs provide a user-friendly and easily accessible sensing platform. Thus, the combination of LFAs with a SERS detection system provides a new diagnostic modality for accurate and rapid diagnoses of infectious diseases. In this context, we briefly discuss the recent application of LFA platforms for the POC diagnosis of SARS-CoV-2. Thereafter, we focus on the recent advances in SERS-based LFA platforms for the early diagnosis of infectious diseases and their applicability for the rapid diagnosis of SARS-CoV-2. Finally, the key issues that need to be addressed to accelerate the clinical translation of SERS-based LFA platforms from the research laboratory to the bedside are discussed.