New nanoimmunoassay can detect anti-SARS-CoV-2 antibodies in very low volume blood samples

The 2019 coronavirus disease pandemic (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been the largest global public health crisis in recent history. To date, it has been responsible for more than 158.3 million infections and more than 3.3 million deaths worldwide.

Managing this crisis, mitigating viral spread, and planning preparation for the next phase of the pandemic involves numerous testing and analysis regimens. Continuous monitoring of the spread of the virus to control the disease, the effectiveness of trial vaccines, current infection mortality rates, and post-vaccination health status, require significant blood sampling and testing to detect the seroprevalence of SARS-CoV-2.

In a recent study, researchers developed and validated a nanoimmunoassay (NIA) that analyzes 1,024 samples in parallel on a single microfluidic device the size of a USB stick. Anti-SARS-CoV-2 IgG antibodies were detected, achieving a sensitivity of 98% and a specificity of 100% from an analysis of 134 pre-pandemic sera (collected in 2013/2014 and 2018) and 155 transcription sera. reverse-polymerase chain reaction (RT-PCR) confirmed positive individuals of COVID-19. The study is published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

The results of the study indicated that an accurate binary classification of serum samples with NIA could be achieved. The study involves a detailed development and validation of the NIA method and a rigorous analysis and testing of very low volume whole blood collection.

In this study, the researchers analyzed samples obtained for more than 20 days after the onset of symptoms, and also samples obtained with less than 20 days of onset of symptoms, in both cases, the results of the NIA were be excellent. They demonstrated that NIA could be used to detect anti-SARS-CoV-2 antibodies in very low-volume whole blood samples (eliminating the need for venous puncture blood collection).

The capabilities of the platform can be expanded to include multiplexed analyzes, which allow four or more biomarkers (multiple antigens, cytokines, or inflammatory markers) to be tested for each sample to obtain information about infection and viral response.

Consumables, reagent consumption, and associated costs are negligible with NIA, which is an important consideration when compared to the high reagent cost of ELISAs and when considering the scarcity of potential reagents that can be found during the critical phases of a global pandemic ”.

Current testing methods, such as ELISA, chemiluminescent immunoassays (CLIA), or lateral flow assays (LFA), require venous puncture for blood collection, followed by sample pretreatment, and involve a cost reagents and testing procedures; all this prevents thorough testing and contributes to high healthcare costs. The main advantages presented here are that this assay is based on reused blood from a glucose test strip (finger pricked) and other low-cost blood sampling methods to eliminate the need for venous puncture and is capable of to analyze up to 1,024 samples per device. In addition, the consumption of NIA reagents and the corresponding costs are approximately 1,000 times lower than standard enzyme-linked immunosorbent assays (ELISA).

To implement this method, the researchers explained that the labs require a commercially available contact microarray and the ability to make masks, molds, and PDMS microfluidic devices, which can be easily manufactured using a spin coater, 80 ° C ovens, and stereomicroscope. The reading of the device is performed with a standard epifluorescence microscope equipped with an automated scenario.

The researchers tested two commercial blood collection devices: Mitra® from Neoteryx and HemaXisTM DB10 from DBS System SA, to show the possibility of reusing low-cost, widely available blood glucose test strips for the collection and shipping of blood. samples. Samples could be stored for up to 6 days at room temperature with minimal sample degradation. The researcher demonstrated that the three methods combined with NIA identified more positive samples than a standard ELISA performed on serum samples collected from the same individuals.

Researchers predict that a person can buy a simple blood sampling kit that contains a lancet, a blood sampling device, and a return mail envelope to a local pharmacy or supermarket. The individual can then collect the blood with a simple prick of the finger and send the device with the blood sample to a laboratory that will analyze one or more biomarkers, interpret the data and return the test results to the person by communication. electronics.

The method of this study can be used to analyze large samples collected as part of epidemiological studies, identify donors for plasma therapy, and provide support for vaccine testing. During a global pandemic, these technologies could enable the collection of critical epidemiological data, providing instrumental data for vaccine development and deployment, the researchers write.

The combination of a high-performance, highly specific and sensitive NIA and the ability to analyze small volumes of dried blood samples have enormous potential for SARS-CoV-2 serology, epidemiological studies, vaccine testing and therapeutic development. “