Sensitive Detection of SARS-CoV-2 Using a Novel Plasmonic Fiber Optic Biosensor Design

Vagal nerve stimulation for the management of long COVID symptoms

This review investigates the therapeutic potential of vagal nerve stimulation (VNS) in managing long COVID, a condition marked by persistent symptoms following acute SARS-CoV-2 infection. Long COVID manifests as ongoing fatigue, cognitive impairment, and autonomic dysfunction, hypothesized to arise from sustained inflammatory and neurological dysregulation. The vagus nerve, central to modulating systemic inflammation and autonomic homeostasis, represents a promising therapeutic target for symptom alleviation through VNS. A comprehensive literature search was conducted across PubMed, Scopus, and Web of Science to identify studies evaluating VNS in the context of long COVID. Preliminary evidence from small-scale pilot studies suggests VNS may attenuate systemic inflammation through activation of the cholinergic anti-inflammatory pathway (CAP), thus restoring autonomic balance and ameliorating symptoms such as fatigue, cognitive dysfunction, and anxiety. In targeting the inflammatory cascade that underlies both acute COVID-19 pathophysiology and its prolonged sequelae, VNS holds potential as an innovative intervention for persistent post-viral symptoms. While these initial findings indicate promise, current data remain limited in scope and robustness, underscoring the need for larger, controlled trials to validate the efficacy and mechanisms of VNS in long COVID management. Establishing a clearer understanding of VNS's impact on inflammation and autonomic regulation in this context is crucial to inform clinical guidelines and therapeutic strategies for long COVID, potentially offering a targeted approach for mitigating this disabling condition.

Updates on the Biofunctionalization of Gold Nanoparticles for the Rapid and Sensitive Multiplatform Diagnosis of SARS-CoV-2 Virus and Its Proteins: From Computational Models to Validation in Human Samples

Since the outbreak of the pandemic respiratory virus SARS-CoV-2 (COVID-19), academic communities and governments/private companies have used several detection techniques based on gold nanoparticles (AuNPs). In this emergency context, colloidal AuNPs are highly valuable easy-to-synthesize biocompatible materials that can be used for different functionalization strategies and rapid viral immunodiagnosis. In this review, the latest multidisciplinary developments in the bioconjugation of AuNPs for the detection of SARS-CoV-2 virus and its proteins in (spiked) real samples are discussed for the first time, with reference to the optimal parameters provided by three approaches: one theoretical, via computational prediction, and two experimental, using dry and wet chemistry based on single/multistep protocols. Overall, to achieve high specificity and low detection limits for the target viral biomolecules, optimal running buffers for bioreagent dilutions and nanostructure washes should be validated before conducting optical, electrochemical, and acoustic biosensing investigations. Indeed, there is plenty of room for improvement in using gold nanomaterials as stable platforms for ultrasensitive and simultaneous "in vitro" detection by the untrained public of the whole SARS-CoV-2 virus, its proteins, and specific developed IgA/IgM/IgG antibodies (Ab) in bodily fluids. Hence, the lateral flow assay (LFA) approach is a quick and judicious solution to combating the pandemic. In this context, the author classifies LFAs according to four generations to guide readers in the future development of multifunctional biosensing platforms. Undoubtedly, the LFA kit market will continue to improve, adapting researchers' multidetection platforms for smartphones with easy-to-analyze results, and establishing user-friendly tools for more effective preventive and medical treatments.

Biomimetic nanoplasmonic sensor for rapid evaluation of neutralizing SARS-CoV-2 monoclonal antibodies as antiviral therapy

Monoclonal antibody (mAb) therapy is one of the most promising immunotherapies that have shown the potential to prevent or neutralize the effects of COVID-19 in patients at very early stages, with a few formulations recently approved by the European and American medicine agencies. However, a main bottleneck for their general implementation resides in the time-consuming, laborious, and highly-specialized techniques employed for the manufacturing and assessing of these therapies, excessively increasing their prices and delaying their administration to the patients. We propose a biomimetic nanoplasmonic biosensor as a novel analytical technique for the screening and evaluation of COVID-19 mAb therapies in a simpler, faster, and reliable manner. By creating an artificial cell membrane on the plasmonic sensor surface, our label-free sensing approach enables real-time monitoring of virus-cell interactions as well as direct analysis of antibody blocking effects in only 15 min assay time. We have achieved detection limits in the 102 TCID50/mL range for the study of SARS-CoV-2 viruses, which allows to perform neutralization assays by only employing a low-volume sample with common viral loads. We have demonstrated the accuracy of the biosensor for the evaluation of two different neutralizing antibodies targeting both Delta and Omicron variants of SARS-CoV-2, with half maximal inhibitory concentrations (IC50) determined in the ng/mL range. Our user-friendly and reliable technology could be employed in biomedical and pharmaceutical laboratories to accelerate, cheapen, and simplify the development of effective immunotherapies for COVID-19 and other serious infectious diseases or cancer.

The SARS-CoV-2 specific IgG antibodies biophotonic sensor

In this paper, we present the design and the principle of operation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific immunoglobulin G (IgG) biophotonic sensor, which is based on the single-mode telecommunication fiber. We fabricated the sensor head at the face of the single mode fiber-28. Due to the process of bio-functionalization, our sensor has the ability to selectively detect the SARS-CoV-2 specific IgG antibodies. The results of preliminary tests allowed us to correctly determine the presence of antibodies in less than 1 min in 5 μl in a volume sample of concentration of 10 μg/ml, which according to studies, corresponds to the concentration of IgG antibodies in human serum. Additionally, the tested sample can be smaller than 5 μl in volume.

Progress in Biosensors for the Point-of-Care Diagnosis of COVID-19

Coronavirus disease 2019 (COVID-19) is a highly virulent infection that has caused a pandemic since 2019. Early diagnosis of the disease has been recognized as one of the important approaches to minimize the pathological impact and spread of infection. Point-of-care tests proved to be substantial analytical tools, and especially lateral flow immunoassays (lateral flow tests) serve the purpose. In the last few years, biosensors have gained popularity. These are simple but highly sensitive and accurate analytical devices composed from a selective molecule such as an antibody or antigen and a sensor platform. Biosensors would be an advanced alternative to current point-of-care tests for COVID-19 diagnosis and standard laboratory methods as well. Recent discoveries related to point-of-care diagnostic tests for COVID-19, the development of biosensors for specific antibodies and specific virus parts or their genetic information are reviewed.

Nanoparticle-Based Visual Detection of Amplified DNA for Diagnosis of Hepatitis C Virus

Rapid, simple, and inexpensive diagnostic point-of-care tests (POCTs) are essential for controlling infectious diseases in resource-limited settings. In this study, we developed a new detection system based on nanoparticle–DNA aggregation (STat aggregation of tagged DNA, STAT-DNA) to yield a visual change that can be easily detected by the naked eye. This simplified optical detection system was applied to detect hepatitis C virus (HCV). Reverse transcription-polymerase chain reaction (RT-PCR) was performed using primers labeled with biotin and digoxigenin. Streptavidin-coated magnetic particles (1 μm) and anti-digoxigenin antibody-coated polystyrene particles (250–350 nm) were added to form aggregates. The limit of detection (LoD) and analytical specificity were analyzed. The STAT-DNA results were compared with those of the standard real-time PCR assay using serum samples from 54 patients with hepatitis C. We achieved visualization of amplified DNA with the naked eye by adding nanoparticles to the PCR mixture without employing centrifugal force, probe addition, incubation, or dilution. The LoD of STAT-DNA was at least 10¹ IU/mL. STAT-DNA did not show cross-reactivity with eight viral pathogens. The detection using STAT-DNA was consistent with that using standard real-time PCR.

High sensitivity detection of SARS-CoV-2 by an optofluidic hollow eccentric core fiber

Since the outbreak of coronavirus disease 2019 (COVID-19), efficient real-time monitoring has become one of the challenges faced in SARS-CoV-2 virus detection. A compact all-fiber Mach-Zehnder interferometer optofluidic sensor based on a hollow eccentric core fiber (HECF) for the detection and real-time monitoring of SARS-CoV-2 spike glycoprotein (SARS-CoV-2 S2) is proposed, analyzed and demonstrated. The sensor is comprised of fusion splicing single mode fiber (SMF), hollow core fiber (HCF) and HECF. After the incident light passes through the HCF from the SMF, it uniformly enters the air hole and the suspended micrometer-scale fiber core of the HECF to form a compact all-fiber Mach-Zehnder interferometer (MZI). HECF is side polished to remove part of the cladding that the suspended fiber core can contact the external environment. Subsequently, the mouse anti SARS-CoV-2 S2 antibody is fixed on the surface of the suspended-core for the sake of achieving high sensitivity and specific sensing of SARS-CoV-2 S2. The limit of detection (LOD) of the sensor is 26.8 pM. The proposed sensor has high sensitivity, satisfactory selectivity, and can be fabricated at low cost making it highly suitable for point-of-care testing and high-throughput detection of early stage of COVID-19 infection.

A Framework for Biosensors Assisted by Multiphoton Effects and Machine Learning

The ability to interpret information through automatic sensors is one of the most important pillars of modern technology. In particular, the potential of biosensors has been used to evaluate biological information of living organisms, and to detect danger or predict urgent situations in a battlefield, as in the invasion of SARS-CoV-2 in this era. This work is devoted to describing a panoramic overview of optical biosensors that can be improved by the assistance of nonlinear optics and machine learning methods. Optical biosensors have demonstrated their effectiveness in detecting a diverse range of viruses. Specifically, the SARS-CoV-2 virus has generated disturbance all over the world, and biosensors have emerged as a key for providing an analysis based on physical and chemical phenomena. In this perspective, we highlight how multiphoton interactions can be responsible for an enhancement in sensibility exhibited by biosensors. The nonlinear optical effects open up a series of options to expand the applications of optical biosensors. Nonlinearities together with computer tools are suitable for the identification of complex low-dimensional agents. Machine learning methods can approximate functions to reveal patterns in the detection of dynamic objects in the human body and determine viruses, harmful entities, or strange kinetics in cells.