A Molecular Lateral Flow Assay for SARS-CoV-2 Quantitative Detection

Design and Validation of a Three-Dimensional Printer-Based System Enabling Rapid, Low-Cost Construction of the Biosensing Areas of Lateral Flow Devices for Immunoassays and Nucleic Acid Assays

The COVID-19 pandemic proved the great usefulness of lateral flow tests as self- and rapid tests. The rapid expansion of this field requires the design and validation of novel, affordable, and versatile technologies for the easy fabrication of a variety of lateral flow devices. In the present work, we have developed a new, simple, and cost-effective system for the dispensing of reagents on the membranes of lateral flow devices to be used for research purposes. The 3D printing technology is integrated, for the first time, with simple and inexpensive tools such as a technical pen and disposable pipet tips for the construction of the test and the control areas of the devices. We also used this system for the automated fabrication of spots on the membrane for multiplex analysis. The devices were applied for the detection of proteins/antibodies and single- and double-stranded DNA targets. Also, devices with multiple biosensing areas on the membrane were constructed for the simultaneous detection of different analytes. The proposed system is very simple, automated, and inexpensive and has provided rapid and reproducible construction of lateral flow devices. Compared to a commercially available automated dispenser, the devices showed similar detection capabilities and reproducibility in various real samples. Moreover, contrary to the existing dispensers, the proposed system does not require any gas or costly precision pumps and syringes for the deposition. In conclusion, the developed 3D printer-based system could be an extremely useful alternative for research laboratories for the construction of lateral flow devices of various assay configurations.

What to Do if the qPCR Test for SARS-CoV-2 or Other Pathogen Lacks Endogenous Internal Control? A Simple Test on Housekeeping Genes

Some of the products for the molecular diagnosis of infections do not have an endogenous internal control, and this is necessary to ensure that the result is not a false negative. The aim of the project was to design a simple low-cost RT-qPCR test that can confirm the expression of basic metabolism proteins, thus confirming the quality of genetic material for molecular diagnostic tests. Two successful equivalent qPCR assays for the detection of the GADPH and ACTB genes were obtained. The course of standard curves is logarithmic, with a very high correlation coefficient R2 within the range of 0.9955-0.9956. The reaction yield was between 85.5 and 109.7%, and the detection limit (LOD) with 95% positive probability was estimated at 0.0057 ng/µL for GAPDH and 0.0036 ng/µL for ACTB. These tests are universal because they function on various types of samples (swabs, cytology, etc.) and can complement the diagnosis of SARS-CoV-2 and other pathogens, as well as potentially oncological diagnostics.

Carrageenan from Gigartina skottsbergii: A Novel Molecular Probe to Detect SARS-CoV-2

The COVID-19 pandemic has caused an unprecedented health and economic crisis, highlighting the importance of developing new molecular tools to monitor and detect SARS-CoV-2. Hence, this study proposed to employ the carrageenan extracted from Gigartina skottsbergii algae as a probe for SARS-CoV-2 virus binding capacity and potential use in molecular methods. G. skottsbergii specimens were collected in the Chilean subantarctic ecoregion, and the carrageenan was extracted -using a modified version of Webber's method-, characterized, and quantified. After 24 h of incubation with an inactivated viral suspension, the carrageenan's capacity to bind SARS-CoV-2 was tested. The probe-bound viral RNA was quantified using the reverse transcription and reverse transcription loop-mediated isothermal amplification (RT-LAMP) methods. Our findings showed that carrageenan extraction from seaweed has a similar spectrum to commercial carrageenan, achieving an excellent proportion of binding to SARS-CoV-2, with a yield of 8.3%. Viral RNA was also detected in the RT-LAMP assay. This study shows, for the first time, the binding capacity of carrageenan extracted from G. skottsbergii, which proved to be a low-cost and highly efficient method of binding to SARS-CoV-2 viral particles.