Detection and Quantification of HspX Antigen in Sputum Samples Using Plasmonic Biosensing: Toward a Real Point-of-Care (POC) for Tuberculosis Diagnosis

Validation of a plasmonic-based serology biosensor for veterinary diagnosis of COVID-19 in domestic animals

The coronavirus disease 2019 (COVID-19) pandemic recently demonstrated the devastating impact on public health, economy, and social development of zoonotic infectious diseases, whereby viruses jump from animals to infect humans. Due to this potential of viruses to cross the species barrier, the surveillance of infectious pathogens circulation in domestic and close-to-human animals is indispensable, as they could be potential reservoirs. Optical biosensors, mainly those based on Surface Plasmon Resonance (SPR), have widely demonstrated its ability for providing direct, label-free, and quantitative bioanalysis with excellent sensitivity and reliability. This biosensor technology can provide a powerful tool to the veterinary field, potentially being helpful for the monitoring of the infection spread. We have implemented a multi-target COVID-19 serology plasmonic biosensor for the rapid testing and screening of common European domestic animals. The multi-target serological biosensor assay enables the detection of total SARS-CoV-2 antibodies (IgG + IgM) generated towards both S and N viral antigens. The analysis is performed in less than 15 min with a low-volume serum sample (<20 μL, 1:10 dilution), reaching a limit of detection of 49.6 ng mL-1. A complete validation has been carried out with hamster, dog, and cat sera samples (N = 75, including 37 COVID-19-positive and 38 negative samples). The biosensor exhibits an excellent diagnostic sensitivity (100 %) and good specificity (71.4 %) for future application in veterinary settings. Furthermore, the biosensor technology is integrated into a compact, portable, and user-friendly device, well-suited for point-of-care testing. This study positions our plasmonic biosensor as an alternative and reliable diagnostic tool for COVID-19 serology in animal samples, expanding the applicability of plasmonic technologies for decentralized analysis in veterinary healthcare and animal research.

Biosensors; nanomaterial-based methods in diagnosing of Mycobacterium tuberculosis

Diagnosis of Mycobacterium tuberculosis (Mtb) before the progression of pulmonary infection can be very effective in its early treatment. The Mtb grows so slowly that it takes about 6-8 weeks to be diagnosed even using sensitive cell culture methods. The main opponent in tuberculosis (TB) and nontuberculous mycobacterial (NTM) epidemiology, like in all contagious diseases, is to pinpoint the source of infection and reveal its transmission and dispersion ways in the environment. It is crucial to be able to distinguish and monitor specific mycobacterium strains in order to do this. In food analysis, clinical diagnosis, environmental monitoring, and bioprocess, biosensing technologies have been improved to manage and detect Mtb. Biosensors are progressively being considered pioneering tools for point-of-care diagnostics in Mtb discoveries. In this review, we present an epitome of recent developments of biosensing technologies for M. tuberculosis detection, which are categorized on the basis of types of electrochemical, Fluorescent, Photo-thermal, Lateral Flow, Magneto-resistive, Laser, Plasmonic, and Optic biosensors.

Bioactive Luminescent Silver Clusters Confined in Zeolites Enable Quick and Wash-Free Biosensing

The simultaneous capture and detection of biomolecules is crucial for revolutionizing bioanalytical platforms in terms of portability, response time and cost-efficiency. Herein, we demonstrate how the sensitivity to external stimuli and changes in the local electronic environment of silver clusters lead to an advantageous biosensing platform based on the fluorometric response of bioactive luminescent silver clusters (BioLuSiC) confined in faujasite X zeolites functionalized with antibodies. The photoluminescence response of BioLuSiC was enhanced upon immunocomplex formation, empowering a wash-free and quick biodetection system offering optimal results from 5 min. Proteins and pathogens (immunoglobulin G and Escherichia coli) were targeted to demonstrate the biosensing performance of BioLuSiC, and a human serum titration assay was also established. BioLuSiC will pave the way for innovative bioanalytical platforms, including real-time monitoring systems, point-of-care devices and bioimaging techniques.

Surface plasmon resonance biosensor chips integrated with MoS2-MoO3 hybrid microflowers for rapid CFP-10 tuberculosis detection

This study reports on the modification of surface plasmon resonance (SPR) chips with molybdenum disulfide-molybdenum trioxide (MoS2-MoO3) microflowers to detect the tuberculosis (TB) markers of CFP-10. The MoS2-MoO3 microflowers were prepared by hydrothermal methods with variations in the pH and amount of trisodium citrate (Na3Ct), which were projected to influence the shape and size of microflower particles. The analysis shows that optimum MoS2-MoO3 hybrid microflowers were obtained at neutral pH using 0.5 g Na3Ct. The modified SPR biosensor exhibits a ten times higher response than the bare Au. Moreover, increasing MoS2-MoO3 thickness results in a higher detection response, sensitivity, and a smaller limit of detection (LOD). Using the optimized material composition, the Au/MoS2-MoO3-integrated SPR sensor can demonstrate sensitivity and LOD of 1.005 and 3.45 ng mL-1, respectively. This biosensor also has good selectivity, stability, and reproducibility based on cross-sensitivity characterization with other analytes and repeated measurements on several chips with different storing times and fabrication batch. Therefore, this proposed SPR biosensor possesses high potential to be further developed and applied as a detection technology for CFP-10 in monitoring and diagnosing TB.

Disposable Device for Bacterial Vaginosis Detection

Due to the increasing demand for clinical testing of infectious diseases at the point-of-care, the global market claims alternatives for rapid diagnosis tools such as disposable biosensors, avoiding the need for specialized laboratories and skilled personnel. Bacterial vaginosis (BV) is an infectious disease that commonly affects reproductive-age women and predisposes the infection of sexually transmitted diseases. Especially in asymptomatic cases, BV can lead to pelvic inflammatory conditions, postpartum endometritis, and preterm labor. Conventionally, BV diagnosis involves the microscopic analysis of vaginal swab samples; it thus requires highly trained personnel. In response, we report a novel microfluidic paper-based analytical device for BV diagnosis. Sialidase, a biomarker overexpressed in BV, was detected by exploiting an immunosensing mechanism previously discovered by our team. This technology employs a graphene oxide-coated surface as a quencher of fluorescence; the fluorescence of the immunoprobes that do not experiment immunoreactions (antibody-antigen) are deactivated by graphene oxide via non-radiative energy transfer, whereas those immunoprobes undergoing immunoreactions preserve their photoluminescence due to the distance and the low affinity between the immunocomplex and the graphene oxide-coated surface. Our paper-based test was typically carried out within 20 min, and the sample volume was 6 μL. Besides, it was tested with 14 vaginal swabs specimens to discriminate clinical samples of women with normal microbiota from those with BV. Our disposable device represents a new tool to prevent the consequences of BV.

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.

Spotlight on mycobacterial lipid exploitation using nanotechnology for diagnosis, vaccines, and treatments

Tuberculosis (TB), historically the most significant cause of human morbidity and mortality, has returned as the top infectious disease worldwide, under circumstances worsened by the COVID-19 pandemic's devastating effects on public health. Although Mycobacterium tuberculosis, the causal agent, has been known of for more than a century, the development of tools to control it has been largely neglected. With the advancement of nanotechnology, the possibility of engineering tools at the nanoscale creates unique opportunities to exploit any molecular type. However, little attention has been paid to one of the major attributes of the pathogen, represented by the atypical coat and its abundant lipids. In this review, an overview of the lipids encountered in M. tuberculosis and interest in exploiting them for the development of TB control tools are presented. Then, the amalgamation of nanotechnology with mycobacterial lipids from both reported and future works are discussed.

Emergence of infectious diseases and role of advanced nanomaterials in point-of-care diagnostics: a review

Infectious outbreaks are the foremost global public health concern, challenging the current healthcare system, which claims millions of lives annually. The most crucial way to control an infectious outbreak is by early detection through point-of-care (POC) diagnostics. POC diagnostics are highly advantageous owing to the prompt diagnosis, which is economical, simple and highly efficient with remote access capabilities. In particular, utilization of nanomaterials to architect POC devices has enabled highly integrated and portable (compact) devices with enhanced efficiency. As such, this review will detail the factors influencing the emergence of infectious diseases and methods for fast and accurate detection, thus elucidating the underlying factors of these infections. Furthermore, it comprehensively highlights the importance of different nanomaterials in POCs to detect nucleic acid, whole pathogens, proteins and antibody detection systems. Finally, we summarize findings reported on nanomaterials based on advanced POCs such as lab-on-chip, lab-on-disc-devices, point-of-action and hospital-on-chip. To this end, we discuss the challenges, potential solutions, prospects of integrating internet-of-things, artificial intelligence, 5G communications and data clouding to achieve intelligent POCs.

Improved Conventional and New Approaches in the Diagnosis of Tuberculosis

Tuberculosis (TB) is a life-threatening infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis). Timely diagnosis and effective treatment are essential in the control of TB. Conventional smear microscopy still has low sensitivity and is unable to reveal the drug resistance of this bacterium. The traditional culture-based diagnosis is time-consuming, since usually the results are available after 3–4 weeks. Molecular biology methods fail to differentiate live from dead M. tuberculosis, while diagnostic immunology methods fail to distinguish active from latent TB. In view of these limitations of the existing detection techniques, in addition to the continuous emergence of multidrug-resistant and extensively drug-resistant TB, in recent years there has been an increase in the demand for simple, rapid, accurate and economical point-of-care approaches. This review describes the development, evaluation, and implementation of conventional diagnostic methods for TB and the rapid new approaches for the detection of M. tuberculosis.

Surface Plasmon Resonance (SPR) Spectroscopy and Photonic Integrated Circuit (PIC) Biosensors: A Comparative Review

Label-free direct-optical biosensors such as surface-plasmon resonance (SPR) spectroscopy has become a gold standard in biochemical analytics in centralized laboratories. Biosensors based on photonic integrated circuits (PIC) are based on the same physical sensing mechanism: evanescent field sensing. PIC-based biosensors can play an important role in healthcare, especially for point-of-care diagnostics, if challenges for a transfer from research laboratory to industrial applications can be overcome. Research is at this threshold, which presents a great opportunity for innovative on-site analyses in the health and environmental sectors. A deeper understanding of the innovative PIC technology is possible by comparing it with the well-established SPR spectroscopy. In this work, we shortly introduce both technologies and reveal similarities and differences. Further, we review some latest advances and compare both technologies in terms of surface functionalization and sensor performance.

Plasmonic nanosensors for point-of-care biomarker detection

Advancement of materials along with their fascinating properties play increasingly important role in facilitating the rapid progress in medicine. An excellent example is the recent development of biosensors based on nanomaterials that induce surface plasmon effect for screening biomarkers of various diseases ranging from cancer to Covid-19. The recent global pandemic re-confirmed the trend of real-time diagnosis in public health to be in point-of-care (POC) settings that can screen interested biomarkers at home, or literally anywhere else, at any time. Plasmonic biosensors, thanks to its versatile designs and extraordinary sensitivities, can be scaled into small and portable devices for POC diagnostic tools. In the meantime, efforts are being made to speed up, simplify and lower the cost of the signal readout process including converting the conventional heavy laboratory instruments into lightweight handheld devices. This article reviews the recent progress on the design of plasmonic nanomaterial-based biosensors for biomarker detection with a perspective of POC applications. After briefly introducing the plasmonic detection working mechanisms and devices, the selected highlights in the field focusing on the technology's design including nanomaterials development, structure assembly, and target applications are presented and analyzed. In parallel, discussions on the sensor's current or potential applicability in POC diagnosis are provided. Finally, challenges and opportunities in plasmonic biosensor for biomarker detection, such as the current Covid-19 pandemic and its testing using plasmonic biosensor and incorporation of machine learning algorithms are discussed.

Label-Free Plasmonic Biosensor for Rapid, Quantitative, and Highly Sensitive COVID-19 Serology: Implementation and Clinical Validation

Serological tests are essential for the control and management of COVID-19 pandemic (diagnostics and surveillance, and epidemiological and immunity studies). We introduce a direct serological biosensor assay employing proprietary technology based on plasmonics, which offers rapid (<15 min) identification and quantification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in clinical samples, without signal amplification. The portable plasmonic device employs a custom-designed multiantigen (RBD peptide and N protein) sensor biochip and reaches detection limits in the low ng mL^–1 range employing polyclonal antibodies. It has also been implemented employing the WHO-approved anti-SARS-CoV-2 immunoglobulin standard. A clinical validation with COVID-19 positive and negative samples (n = 120) demonstrates its excellent diagnostic sensitivity (99%) and specificity (100%). This positions our biosensor as an accurate and easy-to-use diagnostics tool for rapid and reliable COVID-19 serology to be employed both at laboratory and decentralized settings for the disease management and for the evaluation of immunological status during vaccination or treatment.

Novel Biorecognition Elements against Pathogens in the Design of State-of-the-Art Diagnostics

Infectious agents, especially bacteria and viruses, account for a vast number of hospitalisations and mortality worldwide. Providing effective and timely diagnostics for the multiplicity of infectious diseases is challenging. Conventional diagnostic solutions, although technologically advanced, are highly complex and often inaccessible in resource-limited settings. An alternative strategy involves convenient rapid diagnostics which can be easily administered at the point-of-care (POC) and at low cost without sacrificing reliability. Biosensors and other rapid POC diagnostic tools which require biorecognition elements to precisely identify the causative pathogen are being developed. The effectiveness of these devices is highly dependent on their biorecognition capabilities. Naturally occurring biorecognition elements include antibodies, bacteriophages and enzymes. Recently, modified molecules such as DNAzymes, peptide nucleic acids and molecules which suffer a selective screening like aptamers and peptides are gaining interest for their biorecognition capabilities and other advantages over purely natural ones, such as robustness and lower production costs. Antimicrobials with a broad-spectrum activity against pathogens, such as antibiotics, are also used in dual diagnostic and therapeutic strategies. Other successful pathogen identification strategies use chemical ligands, molecularly imprinted polymers and Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease. Herein, the latest developments regarding biorecognition elements and strategies to use them in the design of new biosensors for pathogens detection are reviewed.

Rapid and Sensitive Detection of Mycobacterium tuberculosis by an Enhanced Nanobiosensor

Tuberculosis (TB) mostly spreads from person to person through Mycobacterium tuberculosis (MTB). However, the majority of conventional detection methods for MTB cannot satisfy the requirements for actual TB detection. As one of the most promising powerful platforms, a silicon nanowire field-effect transistor (SiNW-FET) biosensor shows good prospect in TB detection. In this study, an enhanced SiNW-FET biosensor was developed for the rapid and sensitive detection of MTB. The surface functional parameters of the biosensor were explored and optimized. The SiNW-FET biosensor has good sensitivity with a detection limit of 0.01 fg/mL toward protein. The current change value shows a linear upward trend with the increase in protein concentration in the range of 1 fg/mL to 100 μg/mL. One whole test cycle can be accomplished within only 30 s. More importantly, a good distinction was realized in the sputum without pretreatment between normal people and TB patients, which greatly shortened the TB detection time (only 2-5 min, considering the dilution of sputum). Compared with other methods, the SiNW-FET biosensor can detect MTB with a remarkably broad dynamic linear range in a shorter time.

Facile Determination of COVID-19 Seroconversion via Nonradiative Energy Transfer

Serological tests are crucial in a pandemic scenario, since they are a valuable tool to spot those citizens with potential immunity, specific regions with herd immunity or particular at-risk populations, as well as acquired immunity after vaccination. Hence, high-throughput, fast, cost-effective, and straightforward technologies facilitating interrogation of COVID-19 seroconversion are an existing need. Herein, we developed an innovative assay for the determination of COVID-19 seroconversion. Fluorophore-labeled SARS-CoV-2 spike receptor-binding domain recombinant protein (F-RBD) was discovered to operate as a bioprobe that emits a strong fluorescence upon COVID-19 antibody detection; however, F-RBD fluorescence was deactivated by graphene oxide-decorated surfaces when COVID-19 antibodies are absent in the sample. With a cost of less than 0.5 USD per test (at laboratory scale), the biosensing system offers optimum results within 42 min. To demonstrate that this technology is technically sound in a relevant environment, 34 human serum samples were analyzed and clearly differentiated, requiring a tiny amount of serum (1 μL to be later diluted in saline buffer).

Advances in airborne microorganisms detection using biosensors: A critical review

Humanity has been facing the threat of a variety of infectious diseases. Airborne microorganisms can cause airborne infectious diseases, which spread rapidly and extensively, causing huge losses to human society on a global scale. In recent years, the detection technology for airborne microorganisms has developed rapidly; it can be roughly divided into biochemical, immune, and molecular technologies. However, these technologies still have some shortcomings; they are time-consuming and have low sensitivity and poor stability. Most of them need to be used in the ideal environment of a laboratory, which limits their applications. A biosensor is a device that converts biological signals into detectable signals. As an interdisciplinary field, biosensors have successfully introduced a variety of technologies for bio-detection. Given their fast analysis speed, high sensitivity, good portability, strong specificity, and low cost, biosensors have been widely used in environmental monitoring, medical research, food and agricultural safety, military medicine and other fields. In recent years, the performance of biosensors has greatly improved, becoming a promising technology for airborne microorganism detection. This review introduces the detection principle of biosensors from the three aspects of component identification, energy conversion principle, and signal amplification. It also summarizes its research and application in airborne microorganism detection. The new progress and future development trend of the biosensor detection of airborne microorganisms are analyzed.

Emerging point-of-care biosensors for rapid diagnosis of COVID-19: current progress, challenges, and future prospects

Coronavirus disease 2019 (COVID-19) pandemic is currently a serious global health threat. While conventional laboratory tests such as quantitative real-time polymerase chain reaction (qPCR), serology tests, and chest computerized tomography (CT) scan allow diagnosis of COVID-19, these tests are time-consuming and laborious, and are limited in resource-limited settings or developing countries. Point-of-care (POC) biosensors such as chip-based and paper-based biosensors are typically rapid, portable, cost-effective, and user-friendly, which can be used for COVID-19 in remote settings. The escalating demand for rapid diagnosis of COVID-19 presents a strong need for a timely and comprehensive review on the POC biosensors for COVID-19 that meet ASSURED criteria: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end users. In the present review, we discuss the importance of rapid and early diagnosis of COVID-19 and pathogenesis of COVID-19 along with the key diagnostic biomarkers. We critically review the most recent advances in POC biosensors which show great promise for the detection of COVID-19 based on three main categories: chip-based biosensors, paper-based biosensors, and other biosensors. We subsequently discuss the key benefits of these biosensors and their use for the detection of antigen, antibody, and viral nucleic acids. The commercial POC biosensors for COVID-19 are critically compared. Finally, we discuss the key challenges and future perspectives of developing emerging POC biosensors for COVID-19. This review would be very useful for guiding strategies for developing and commercializing rapid POC tests to manage the spread of infections.Graphical abstract.