Development of ESAT-6 Based Immunosensor for the Detection of Mycobacterium tuberculosis

Quantum Dot-Based Nanosensors for In Vitro Detection of Mycobacterium tuberculosis

Despite the existing effective treatment methods, tuberculosis (TB) is the second most deadly infectious disease, its carriers in the latent and active phases accounting for more than 20% of the world population. An effective method for controlling TB and reducing TB mortality is regular population screening aimed at diagnosing the latent form of TB and taking preventive and curative measures. Numerous methods allow diagnosing TB by directly detecting Mycobacterium tuberculosis (M.tb) biomarkers, including M.tb DNA, proteins, and specific metabolites or antibodies produced by the host immune system in response to M.tb. PCR, ELISA, immunofluorescence and immunochemical analyses, flow cytometry, and other methods allow the detection of M.tb biomarkers or the host immune response to M.tb by recording the optical signal from fluorescent or colorimetric dyes that are components of the diagnostic systems. Current research in biosensors is aimed at increasing the sensitivity of detection, a promising approach being the use of fluorescent quantum dots as brighter and more photostable optical tags. Here, we review current methods for the detection of M.tb biomarkers using quantum dot-based nanosensors and summarize data on the M.tb biomarkers whose detection can be made considerably more sensitive by using these sensors.

Bioreceptor modified electrochemical biosensors for the detection of life threating pathogenic bacteria: a review

The lack of reliable and efficient techniques for early monitoring to stop long-term effects on human health is an increasing problem as the pathogenesis effect of infectious bacteria is growing continuously. Therefore, developing an effective early detection technique coupled with efficient and continuous monitoring of pathogenic bacteria is increasingly becoming a global public health prime target. Electrochemical biosensors are among the strategies that can be utilized for accomplishing that goal with promising potential. In recent years, identifying target biological analytes by interacting with bioreceptors modified electrodes is among the most commonly used detection techniques in electrochemical biosensing strategies. The commonly employed bioreceptors are nucleic acid molecules (DNA or RNA), proteins, antibodies, enzymes, organisms, tissues, and biomimetic components such as molecularly imprinted polymers. Despite the advancement in electrochemical biosensing, developing a reliable and effective biosensor for detecting pathogenic bacteria is still in the infancy stage with so much room for growth. A major milestone in addressing some of the issues and improving the detection pathway is the investigation of specific bacterial detection techniques. The present study covers the fundamental concepts of electrochemical biosensors, human PB illnesses, and the latest electrochemical biosensors based on bioreceptor elements that are designed to detect specific pathogenic bacteria. This study aims to assist researchers with the most up-to-date research work in the field of bio-electrochemical pathogenic bacteria detection and monitoring.

Integrating pathogen- and host-derived blood biomarkers for enhanced tuberculosis diagnosis: a comprehensive review

This review explores the evolving landscape of blood biomarkers in the diagnosis of tuberculosis (TB), focusing on biomarkers derived both from the pathogen and the host. These biomarkers provide critical insights that can improve diagnostic accuracy and timeliness, essential for effective TB management. The document highlights recent advancements in molecular techniques that have enhanced the detection and characterization of specific biomarkers. It also discusses the integration of these biomarkers into clinical practice, emphasizing their potential to revolutionize TB diagnostics by enabling more precise detection and monitoring of the disease progression. Challenges such as variability in biomarker expression and the need for standardized validation processes are addressed to ensure reliability across different populations and settings. The review calls for further research to refine these biomarkers and fully harness their potential in the fight against TB, suggesting a multidisciplinary approach to overcome existing barriers and optimize diagnostic strategies. This comprehensive analysis underscores the significance of blood biomarkers as invaluable tools in the global effort to control and eliminate TB.

A novel enzyme-linked ligand-sorbent assay (ELLSA) to screening pulmonary tuberculosis: a retrospective cross-sectional study

BACKGROUND

Little knowledge of antigen existence in the pulmonary tuberculosis (PTB) patient serum impeded its development in antigen detection technology, despite its considerable potential.

METHODS

Human ligand proteins and their adsorbent Mycobacterium tuberculosis (M.tb) proteins in the serum of PTB patients were identified using human protein chip (HuProt™) and LC-MS/MS, successively. The monoclonal antibody of ligand proteins, C5orf24, and polyclonal antibody of 9 M.tb proteins were prepared on mice and rabbits which were used to develop a novel enzyme-linked ligand-sorbent assay (ELLSA). The 412 volunteers were divided into the PTB group (n = 250) and the healthy control (n = 162). The PTB group was further divided into ATB (n = 131), LTBI (n = 18), Clinical diagnosis (n = 18), and Suspected (n = 73). All samples were tested by ELLSA to evaluate the diagnostic performance of ELLSA in PTB patients.

RESULTS

Nine ligand proteins specific to PTB patients were identified on chips, with Chromosome 5 Open Reading Frame 24 (C5orf24) and kinocilin (KNCN) showing significantly higher signals. Proteomic analysis of the C5orf24-and KNCN-adsorbent protein complexes revealed 10 and 10 of the M.tb proteins, respectively. According to the composition reference of standard, the ELLSA based on C5orf24 ligand demonstrated a higher sensitivity of 69.6% and specificity of 90.18% in ATB patients and had a sensitivity of 64.22% in bacterial negative pulmonary tuberculosis, whereas the sensitivity of MGIT 960 and Xpert M.tb/RIF were 0%, respectively.

CONCLUSIONS

M.tb proteins in serum can be enriched by ligand proteins and detected by ELLSA which proved to have excellent diagnostic performance for PTB.

Surface-Activated Ti3C2Tx Adsorption of Acetylene Black Coupled with Polyaniline as a Signal Tag for the Detection of the ESAT-6 Antigen of Mycobacterium tuberculosis

Early secretory antigenic target-6 (ESAT-6) is regarded as the most immunogenic protein produced by Mycobacterium tuberculosis, whose detection is of great clinical significance for tuberculosis diagnosis. However, the detection of the ESAT-6 antigen has been hampered by the expensive cost and complex experimental procedures, resulting in low sensitivity. Herein, we developed a titanium carbide (Ti3C2Tx)-based aptasensor for ESAT-6 detection utilizing a triple-signal amplification strategy. First, acetylene black (AB) was immobilized on Ti3C2Tx through a cross-linking reaction to form the Ti3C2Tx-AB-PAn nanocomposite. Meanwhile, AB served as a conductive bridge, and Ti3C2Tx can synergistically promote the electron transfer of PAn. Ti3C2Tx-AB-PAn exhibited outstanding conductivity, high electrochemical signals, and abundant sites for the loading of ESAT-6 binding aptamer II (EBA II) to form a novel signal tag. Second, N-CNTs were adsorbed on NiMn layered double hydride (NiMn LDH) nanoflowers to obtain NiMn LDH/N-CNTs, exhibiting excellent conductivity and preeminent stability to be used as electrode modification materials. Third, the biotinylated EBA (EBA I) was immobilized onto a streptavidin-coated sensing interface, forming an amplification platform for further signal enhancement. More importantly, as a result of the synergistic effect of the triple-signal amplification platform, the aptasensor exhibited a wide detection linear range from 10 fg mL-1 to 100 ng mL-1 and a detection limit of 4.07 fg mL-1 for ESAT-6. We envision that our aptasensor provides a way for the detection of ESAT-6 to assist in the diagnosis of tuberculosis.

The role of ESAT-6 in tuberculosis immunopathology

Despite major global efforts to eliminate tuberculosis, which is caused by Mycobacterium tuberculosis (Mtb), this disease remains as a major plague of humanity. Several factors associated with the host and Mtb interaction favor the infection establishment and/or determine disease progression. The Early Secreted Antigenic Target 6 kDa (ESAT-6) is one of the most important and well-studied mycobacterial virulence factors. This molecule has been described to play an important role in the development of tuberculosis-associated pathology by subverting crucial components of the host immune responses. This review highlights the main effector mechanisms by which ESAT-6 modulates the immune system, directly impacting cell fate and disease progression.

Fluorescent nanodiamond immunosensors for clinical diagnostics of tuberculosis

Fluorescent nanodiamonds (FNDs) are carbon nanoparticles containing a dense ensemble of nitrogen-vacancy defects as color centers. These centers have exceptional photostability and unique quantum properties, making them useful for ultrasensitive biosensing applications. This work employed FNDs conjugated with antibodies as magneto-optical immunosensors for tuberculosis (TB) diagnostics using competitive spin-enhanced lateral flow immunoassay (SELFIA). ESAT6 (6-kDa early secretory antigenic target) of Mycobacterium tuberculosis is a clinical marker of TB. We evaluated the assay's performance using the recombinant ESAT6 antigen and its antibodies noncovalently coated on FNDs. A detection limit of ∼0.02 ng mL-1 was achieved with the lateral flow membrane strip pre-structured with a narrow channel of 1 mm width. Adopting a cut-off value of 24.0 ng mm-1 for 100-nm FNDs on the strips, the method detected 49 out of 50 clinical samples with Mycobacterium tuberculosis complexes. In contrast, none of the assays for 10 clinical samples with non-tuberculous mycobacteria (NTM) isolates exhibited the presence of ESAT6. These results suggest that the SELFIA platform is applicable for TB detection and can differentiate TB from NTM infections, which also affect the human respiratory system. The FND-enabled immunosensing techniques are versatile and promising for early detection of TB and other diseases, opening a new avenue for biomedical applications of carbon-based nanomaterials.

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.

Mycobacterium tuberculosis virulence protein ESAT-6 influences M1/M2 polarization and macrophage apoptosis to regulate tuberculosis progression

BACKGROUND

Tuberculosis (TB) is an infectious disease caused by infection with Mycobacterium tuberculosis (Mtb), and it remains one of the major threats to human health worldwide. To our knowledge, the polarization of M1/M2 macrophages were critical innate immune cells which play important roles in regulating the immune response during TB progression.

OBJECTIVE

We aimed to explore the potential mechanisms of M1/M2 macrophage polarization in TB development.

METHODS

THP-1 macrophages were treated with early secreted antigenic target of 6 kDa (ESAT-6) protein for an increasing time. The polarization profiles, apoptosis levels of M1 and M2 macrophages were detected by RT-qPCR, immunofluorescence, Western blot and flow cytometry.

RESULTS

ESAT-6 initially promoted the generation of pro-inflammatory M1-polarized macrophages in THP-1 cells within 24 h, which were suppressed by further ESAT-6 treatment at 30-42 h. Interestingly, ESAT-6 continuously promoted M2 polarization of THP-1 cells, thereby maintaining the anti-inflammatory response in a time-dependent manner. In addition, ESAT-6 promoted apoptotic cell death in M1-polarized macrophages, which had little effects on apoptosis of M2-phenotype of macrophages. Then, the potential underlying mechanisms were uncovered, and we verified that ESAT-6 increased the protein levels of TLR4, MyD88 and NF-κB to activate the TLR4/MyD88/NF-κB pathway within 24 h, and this signal pathway was significantly inactivated at 36 h post-treatment. Interestingly, the following experiments confirmed that ESAT-6 TLR4/MyD88/NF-κB pathway-dependently regulated M1/M2 polarization and apoptosis of macrophage in THP-1 cells.

CONCLUSION

Our study investigated the detailed effects and mechanisms of M1/M2 macrophages in regulating innate responses during TB development, which provided a new perspective on the development of treatment strategies for this disease.

MXene-incorporated C60NPs and Au@Pt with dual-electric signal outputs for accurate detection of Mycobacterium tuberculosis ESAT-6 antigen

Rapid and effective detection of Mycobacterium tuberculosis (MTB) is the crux of minimizing tuberculosis (TB) spread. Consequently, a new electrochemical aptasensor based on dual-signal output for ultrasensitive detection of MTB early secreted antigenic target 6 (ESAT-6) antigen was developed. Especially, a new nanocomposite MXene/C60NPs/Au@Pt was synthesized for signal generation and amplification. In this biosensing architecture, dual independent signal outputs were achieved by coupling the electrochemical redox activity of fullerene nanoparticles (C60NPs) with the effective electrocatalytic activity of Au@Pt nanoparticles. MXene possesses a large specific surface area, allowing densely loaded of these two electroactive materials, further improved sensing capability. In addition, specific ESAT-6 antigen binding aptamers were attached to Au@Pt to create the tracer label. With a typical sandwich format along with the introduction of the gold nanoparticle-loaded molybdenum disulfide (MoS2-Au) as the sensing interface, the limit of detection (LOD) of the proposed aptasensor was 2.88 fg mL-1 (DPV measurement) and 13.50 fg mL-1 (IT measurement), respectively, with a broad linear range of 100 fg mL-1 to 50 ng mL-1. Significantly, it exhibited better specificity and accuracy with a sensitivity of 97.5% and a specificity of 96.7% to distinguish healthy donors, other lung diseases and TB patients compared to commercial ELISA assay, holding a promising prospect in clinical diagnosis.

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.

An electrochemical aptasensor for Mycobacterium tuberculosis ESAT-6 antigen detection using bimetallic organic framework

A label-free electrochemical aptasensor is reported for sensitive detection of the 6-kDa early secreted antigenic target (ESAT-6). For the first time, the bimetallic organic framework (b-MOF) of Zr-MOF-on-Ce-MOF was decorated with nitrogen-doped graphene (NG) and applied as the matrix for electroactive toluidine blue (Tb) to form the NG@Zr-MOF-on-Ce-MOF@Tb nanohybrid. The prepared nanohybrid with excellent hydrophilicity, dispersibility, and large specific surface exhibited significant electrochemical response. This nanohybrid could be directly used for anchoring ESAT-6 binding aptamers (EBA) through the interaction between the 5'-phosphate group (PO₄^3-) of EBA and Zr⁴⁺ of Zr-MOF. The signal response before and after incubating the ESAT-6 antigen has been evaluated by cyclic voltammetry at a scan rate of 100 mV s^-1 from - 0.7 to 0.3 V (vs. SCE). Under optimal conditions, the proposed aptasensor displayed a wide linear range from 100 fg mL^-1 to 10 ng mL^-1 with a limit of detection (LOD) of 12 fg mL^-1. The developed method showed good reproducibility with a relative standard deviation (RSD) of 2.27%. The aptasensor showed favorable results in the analysis of the real samples. With these merits, the aptasensor has exceptional potential as a diagnostic tool for tuberculosis in clinical practice.