Emerging trends in point-of-care biosensing strategies for molecular architectures and antibodies of SARS-CoV-2

Plasmonic coffee-ring biosensing for AI-assisted point-of-care diagnostics

A major challenge in addressing global health issues is developing simple, affordable biosensors with high sensitivity and specificity. Significant progress has been made in at-home medical detection kits, especially during the COVID-19 pandemic. Here, we demonstrated a coffee-ring biosensor with ultrahigh sensitivity, utilizing the evaporation of two sessile droplets and the formation of coffee-rings with asymmetric nanoplasmonic patterns to detect disease-relevant proteins as low as 3 pg/ml, under 12 min. Experimentally, a protein-laden droplet dries on a nanofibrous membrane, pre-concentrating biomarkers at the coffee ring. A second plasmonic droplet with functionalized gold nanoshells is then deposited at an overlapping spot and dried, forming a visible asymmetric plasmonic pattern due to distinct aggregation mechanisms. To enhance detection sensitivity, a deep neural model integrating generative and convolutional networks was used to enable quantitative biomarker diagnosis from smartphone photos. We tested four different proteins, Procalcitonin (PCT) for sepsis, SARS-CoV-2 Nucleocapsid (N) protein for COVID-19, Carcinoembryonic antigen (CEA) and Prostate-specific antigen (PSA) for cancer diagnosis, showing a working concentration range over five orders of magnitude. Sensitivities surpass equivalent lateral flow immunoassays by over two orders of magnitude using human saliva samples. The detection principle, along with the device, and materials can be further advanced for early disease diagnostics.

Advances in Apolipoprotein-A4 Biosensing Assays for Depression Diagnosis

Apolipoprotein-A4 (Apo-A4) is a plasma protein that plays a role in various physiological and behavioral-emotional reactions when faced with stress. Studies have shown a close relationship between Apo-A4 and the onset of depression and its symptoms. However, there is currently no reliable laboratory approach to confirm the diagnosis of depression. Therefore, the development of a precise and effective technique to assess Apo-A4 might help in the early detection and screening of depression and other related psychiatric diseases, as well as in tracking and managing the course of treatment. As technology advances, biosensors have become quick, accurate, and sensitive tools for personal care and illness diagnosis. Biosensors for measuring and detecting Apo-A4 levels have recently been designed. These studies emphasized the development of accurate and sensitive diagnostic and measurement techniques. This review attempts to give a general overview of the role of Apo-A4 in depression and introduce established biosensors for its detection and measurement.

Evaluation of Preferential Cytokine Adsorption onto Biosensing Surface Modified with Glycopolymer

For the improvement of biosensor performance, the development of a molecular recognition material as well as a sensor platform is necessary. A glycopolymer is a molecular recognition material capable of recognizing specific proteins as natural glycans. However, the target molecules for biosensors using glycopolymers are limited to lectins that are already known for their specific interactions with glycan residues. The aim of this study is to investigate a glycopolymer-modified (GM) surface capable of recognizing non-lectin proteins. As non-lectin proteins, we focused on cytokines, in which the interaction preference to glycopolymers is unknown. The cytokine adsorption onto the GM surfaces was evaluated using a surface plasmon resonance imaging technique as a biosensing tool. Differences in cytokine adsorption onto the different glycan residues were revealed, which will be important for selective cytokine detection. This study indicates the possibility of a biosensing surface modified with glycopolymers for the detection of non-lectin proteins. The results are beneficial for expanding the use of glycopolymers as a molecular recognition material for future applications such as cell analysis and diagnostic devices.

Performance assessment of disposable carbon-based immunosensors for the detection of SARS-CoV-2 infections

We designed, developed, and clinically tested two rapid antigen-based immunosensors for SARS-CoV-2 detection, enabling diagnosis and viral load quantification for under USD $2. In a first clinical study, a screen-printed disposable carbon-based (SPC) sensor was assessed on prospectively recruited adult participants classified into three study groups: healthy donors (n = 46); SARS-CoV-2-infected symptomatic patients (n = 58); and co-habitants of patients without prior testing (n = 38). Nasopharyngeal aspirates (NA), oropharyngeal swabs (OS), and saliva (SA) samples were obtained from all participants. Performance was measured in terms of clinical sensitivity and specificity against a reference diagnostic RT-qPCR kit and analytical sensitivity (limit of detection, LoD) and specificity using recombinant material in lab tests. A second study was performed using the same sensor design, albeit with laser-induced graphene (LIG) electrodes, using nasopharyngeal swabs (NS) on 224 patient samples obtained at different stages of the pandemic, of which 110 tested negative and 114 positive via RT-qPCR. We find OS was the most informative sample, when compared to NA and SA. The SPC-based sensors had a 93.8% sensitivity and 61.5% specificity with OS samples, while the LIG-based sensors with NS had a lower sensitivity of 68.93%, albeit a significantly higher specificity of 86.17%. We believe specificity values for the SPC sensors were driven by positive results from co-habitants and healthy donors and were affected by the low sensitivity (75.5%) and high LoD (> 20,000 viral copies/mL) of the reference RT-qPCR kit used, and the lower sensitivity of the LIG-based was due to a reduced set of effective antigen-binding sites caused by the non-covalent LIG-mAb ligands used. The immunosensor's LoD to spike protein in phosphate-buffered saline (PBS) for both types of sensors was near 1 fg/mL and showed no cross-reactivity to recombinant structural proteins of Epstein-Barr and Influenza. Performance metrics and time-to-result (5 < 12 min) provide proof-of-principle of the immunosensor's applicability as a low-cost, rapid technology for determining SARS-CoV-2 infections. Changing the working electrode material to LIG, instead of SPC, improved specificity even in the presence of pathogen variants. Discordant results between our two immunosensor versions and RT-qPCR tests are attributed not only to limited antibody effectiveness in the former but also to the quality of RT-qPCR probes used at the height of the pandemic.

Hierarchical Nanobiosensors at the End of the SARS-CoV-2 Pandemic

Nanostructures have played a key role in the development of different techniques to attack severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Some applications include masks, vaccines, and biosensors. The latter are of great interest for detecting diseases since some of their features allowed us to find specific markers in secretion samples such as saliva, blood, and even tears. Herein, we highlight how hierarchical nanoparticles integrated into two or more low-dimensional materials present outstanding advantages that are attractive for photonic biosensing using their nanoscale functions. The potential of nanohybrids with their superlative mechanical characteristics together with their optical and optoelectronic properties is discussed. The progress in the scientific research focused on using nanoparticles for biosensing a variety of viruses has become a medical milestone in recent years, and has laid the groundwork for future disease treatments. This perspective analyzes the crucial information about the use of hierarchical nanostructures in biosensing for the prevention, treatment, and mitigation of SARS-CoV-2 effects.

An update on lateral flow immunoassay for the rapid detection of SARS-CoV-2 antibodies

Over the last three years, after the outbreak of the COVID-19 pandemic, an unprecedented number of novel diagnostic tests have been developed. Assays to evaluate the immune response to SARS-CoV-2 have been widely considered as part of the control strategy. The lateral flow immunoassay (LFIA), to detect both IgM and IgG against SARS-CoV-2, has been widely studied as a point-of-care (POC) test. Compared to laboratory tests, LFIAs are faster, cheaper and user-friendly, thus available also in areas with low economic resources. Soon after the onset of the pandemic, numerous kits for rapid antibody detection were put on the market with an emergency use authorization. However, since then, scientists have tried to better define the accuracy of these tests and their usefulness in different contexts. In fact, while during the first phase of the pandemic LFIAs for antibody detection were auxiliary to molecular tests for the diagnosis of COVID-19, successively these tests became a tool of seroprevalence surveillance to address infection control policies. When in 2021 a massive vaccination campaign was implemented worldwide, the interest in LFIA reemerged due to the need to establish the extent and the longevity of immunization in the vaccinated population and to establish priorities to guide health policies in low-income countries with limited access to vaccines. Here, we summarize the accuracy, the advantages and limits of LFIAs as POC tests for antibody detection, highlighting the efforts that have been made to improve this technology over the last few years.