A label-free IFN-γ aptasensor based on target-triggered allosteric switching of aptamer beacon and streptavidin-inorganic hybrid composites

Dimeric-molecular beacon based intramolecular strand displacement amplification enables robust analysis of miRNA

Given the critical role of miRNAs in regulating gene expression and their potential as biomarkers for various diseases, accurate and sensitive miRNA detection is essential for early diagnosis and monitoring of conditions such as cancer. In this study, we introduce a dimeric molecular beacon (Di-MB) based isothermal strand displacement amplification (ISDA) system (Di-MB-ISDA) for enhanced miRNA detection. The Di-MB system is composed of two monomeric MBs (Mono-MBs) connected by a double-stranded DNA linker with single-stranded sequences in the middle, facilitating binding with the flexible arms of the Mono-MBs. This design forms a compact, high-density structure, significantly improving biostability against nuclease degradation. In the absence of target miRNA, the Di-MB maintains its stable structure. When target miRNA is present, it binds to the stem-loop regions, causing the hairpin structure to unfold and expose the stem sequences. These sequences serve as templates for the built-in primers, triggering DNA replication through an intramolecular recognition mechanism. This spatial confinement effect accelerates the strand displacement reaction, allowing the target miRNA to initiate additional reaction cycles and amplify the detection signal. The Di-MB-ISDA system addresses key challenges such as poor biostability and limited sensitivity seen in traditional methods. By enhancing biostability and optimizing reaction conditions, this system demonstrates robust performance for miRNA detection with a detection limit of 100 pM. The findings highlight the potential of Di-MB-ISDA for sensitive and accurate miRNA analysis, paving the way for its application in biomedical study and disease diagnosis in complex biological samples.

Unrevealing the connection between real sample analysis and analytical method. The case of cytokines

Cytokines are compounds that belong to a special class of signaling biomolecules that are responsible for several functions in the human body, being involved in cell growth, inflammatory, and neoplastic processes. Thus, they represent valuable biomarkers for diagnosing and drug therapy monitoring certain medical conditions. Because cytokines are secreted in the human body, they can be detected in both conventional samples, such as blood or urine, but also in samples less used in medical practice such as sweat or saliva. As the importance of cytokines was identified, various analytical methods for their determination in biological fluids were reported. The gold standard in cytokine detection is considered the enzyme-linked immunosorbent assay method and the most recent ones have been considered and compared in this study. It is known that the conventional methods are accompanied by a few disadvantages that new methods of analysis, especially electrochemical sensors, are trying to overcome. Electrochemical sensors proved to be suited for the elaboration of integrated, portable, and wearable sensing devices, which could also facilitate cytokines determination in medical practice.

Point-of-care electrochemical testing of biomarkers involved in inflammatory and inflammatory-associated medical conditions

Recent years have shown that the diagnosis and monitoring of biomarkers involved in inflammatory-associated medical conditions such as cancer, neurological disorders, viral infections, or daily physical activities offer real benefits in increasing the quality of medical care and patient life quality. In this context, the use of integrated and portable platforms as point-of-care testing devices for biomedical analysis to enable early disease diagnosis and monitoring, which can be successfully used even at the patient's bed, is an emergency nowadays. The development of low-cost, miniaturized, and portable, user-friendly devices that provide an answer in a timely manner, such as electrochemical sensors, is relevant for the elaboration of point-of-care testing devices. This review focuses on the recent progress in bioanalysis of both specific biomarkers and inflammatory-associated biomarkers present in several diseases like neoplasia, severe neurological disorders, viral infections, and usual physical activity and provides an overview of the state of the art over the most recent electrochemical (bio)sensors for the detection of inflammation-related biomarkers. Future perspectives of point-of-care testing to improve healthcare management are also discussed.

Interferon-γ detection in point of care diagnostics: Short review

Interferon (IFN)-γ is a cytokine secreted by immune cells. The elevated levels of IFN-γ are an early indicator of multiple diseases such as tuberculosis and autoimmune diseases. This short review focuses on different sensing methods based on optical, electrochemical, and mechanical principles. We explain how specific biorecognition molecules such as antibodies and aptamers are employed in the sensing methods. We also compare different surface functionalization methods and their details. Although the review gives an overview of only IFN-γ sensing, the same strategies can be applied to sensing other analytes with appropriate modifications.

Recent advances in the detection of interferon-gamma as a TB biomarker

Tuberculosis (TB) is one of the main infectious diseases worldwide and accounts for many deaths. It is caused by Mycobacterium tuberculosis usually affecting the lungs of patients. Early diagnosis and treatment are essential to control the TB epidemic. Interferon-gamma (IFN-γ) is a cytokine that plays a part in the body’s immune response when fighting infection. Current conventional antibody-based TB sensing techniques which are commonly used include enzyme-linked immunosorbent assay (ELISA) and interferon-gamma release assays (IGRAs). However, these methods have major drawbacks, such as being time-consuming, low sensitivity, and inability to distinguish between the different stages of the TB disease. Several electrochemical biosensor systems have been reported for the detection of interferon-gamma with high sensitivity and selectivity. Microfluidic techniques coupled with multiplex analysis in regular format and as lab-on-chip platforms have also been reported for the detection of IFN-γ. This article is a review of the techniques for detection of interferon-gamma as a TB disease biomarker. The objective is to provide a concise assessment of the available IFN-γ detection techniques (including conventional assays, biosensors, microfluidics, and multiplex analysis) and their ability to distinguish the different stages of the TB disease.

Sensitive electrochemical detection of oxytetracycline based on target triggered CHA and poly adenine assisted probe immobilization

Here, we developed a homogeneous electrochemical biosensor for the sensitive determination of antibiotic by the CHA reaction and the consecutive adenine mediated probe fixation. The binding of target to the target recognition sequences in the triple-helix DNA can release the trigger. It can initiate the catalytic hairpin assembly (CHA) to generate lots of mimic targets, which were labeled with electroactive substance ferrocene (Fc). Because the generated mimic target has consecutive sequence of adenines (PolyA), they can be self-assembled on the AuNPs modified electrode and finally realize electrochemical detection. Under optimal conditions, this developed biosensor achieved a satisfactory limit of detection of 0.089 nM (S/N = 3) and a linear range from 0.1 nM to 100 nM for sensitive detection of oxytetracycline with good specificity. The whole process is carried out in homogeneous solution, not only realizes signal amplification, but also avoids the complex modification process of electrode surface. Compared with some reported electrochemical sensors, the method is easier to operate and has good precision.

Selective analysis of interferon-alpha in human serum with boronate affinity oriented imprinting based plastic antibody

Interferons are important biomolecules in human immune system. Cytokine interferon alpha (IFN-α), a type I interferon, is one of the major components of the innate immune response involved in autoimmune diseases. Thus, the analysis of interferons is of great importance for both biological and pharmaceutical purposes. In this work, an IFN-α specific plastic antibody is prepared via boronate affinity oriented surface imprinting. By combing with the magnetic nanoparticles, the imprinted material exhibits several advantages, including strong affinity (K_d: 75.2 nM), high specificity (cross reactivity<25%), excellent efficiency (imprinting efficiency: 44.1%), tolerance to interferences, and easy manipulation. By employing the prepared imprinted material as sorbent for selective enrichment of IFN-α, a good linearity is achieved in the range of 50 ng/mL-10 μg/mL, and the detection and quantifcation limits are 10 ng/mL and 50 ng/mL respectively. The recoveries of this approach are found within 75.8%-82.2% with relative standard deviations of 6.4-9.7%. Furthermore, the IFN-α in spiked human serum is analyzed with acceptable reliability (recovery: 77.3%, RSD: 7.9%). Because of these highly desirable properties, the IFN-α specific plastic antibody can find more applications in medical and pharmaceutical industry.

Organic-Inorganic Hybrid Nanoflower Production and Analytical Utilization: Fundamental to Cutting-Edge Technologies

Over the past decade, science has experienced a growing rise in nanotechnology with ground-breaking contributions. Through various laborious technologies, nanomaterials with different architectures from 0 D to 3 D have been synthesized. However, the 3 D flower-like organic-inorganic hybrid nanomaterial with the most direct one-pot green synthesis method has attracted widespread attention and instantly become research hotspot since its first allusion in 2012. Mild synthesis procedure, high surface-to-volume ratio, enhanced enzymatic activity and stability are the main factor for its rapid development. However, its lower mechanical strength, difficulties in recovery from the reaction system, lower loading capacity, poor reusability and accessibility of enzymes are fatal, which hinders its wide application in industry. This review first discusses the selection of non-enzymatic biomolecules for the synthesis of hybrid nanoflowers followed by the innovative advancements made in organic-inorganic hybrid nanoflowers to overcome aforementioned issues and to enhance their extensive downstream applications in transduction technologies. Besides, the role of hybrid nanoflower has been successfully utilized in many fields including, water remediation, biocatalyst, pollutant adsorption and decolourization, nanoreactor, biosensing, cellular uptake and others, accompanied with several quantification technologies, such as ELISA, electrochemical, surface plasmon resonance (SPR), colorimetric, and fluorescence were comprehensively reviewed.

Espinosa R, Lavín A, Holgado M. A Point-of-Care Based on Label-Free Interferometric Optical Detection Method to Evaluate Interferon Gamma (IFN-γ): A Correlation with the ELISA Technique

Interferon-gamma (IFN-γ) is a cytokine associated with inflammatory diseases, virus, infection, etc. The quantification of interferon-gamma concentration levels is studied to relate the immune system response to the progression of disease. In this work, we used a label-free point-of-care device based on the increase relative optical power (IROP) and a biosensor based on photonic transducers called BICELLs (Biophotonic Sensing Cells) to evaluate interferon-gamma concentrations. The BICELLs' sensing surface size used is 100 μm in diameter. The bioreceptor is attached to the surface by streptavidin-biotin affinity. This label-free IROP-based device can work with a low concentration of reagents and a low sample volume for measurements. Furthermore, this new device was compared with an ELISA technique in the same conditions. A good correlation was achieved between both techniques. This device is easy to use, and it is a cost-effective tool for monitoring an analyte in a disease.

Grafting homogenous electrochemical biosensing strategy based on reverse proximity ligation and Exo III assisted target circulation for multiplexed communicable disease DNA assay

Rapid and effective diagnosis of communicable disease is one of the critical issues of the modern society, especially for detecting different targets at the same time. In this work, a grafting homogenous electrochemical biosensing strategy is proposed by integrating of reverse proximity ligation and exonuclease III (Exo III) assisted target circulation to analyze hepatitis B (HBV) and human immunodeficiency (HIV). Specially, a two-wing nanodevice (TWD) with two detection paths is elaborately designed based on analogous proximity ligation assay. The reverse proximity ligation process provides a new way of signal conversion and amplification, what accomplished by demolishing the TWD in the presence of targets. Meanwhile, a vast number of signal probes are released via Exo III assisted target circulation. Then the signal probes are grafted on the universal sensing interface, which is decorated with graftable tetrahedron DNA (GTD). These lead to a highly amplified electrochemical signal. Compared with the conventional strategies, the grafting homogenous electrochemical biosensing strategy not only achieves convenient sensitive detection of multiple communicable diseases DNA simultaneously, but also performs well in the detection of sole target. This strategy effectively decreases the background, homogenizes the distribution of probes, and avoids the complex and time-consuming modification process of the working electrode, which holds great potential application in early diagnosis for communicable disease in the future.

Immunoassay of interferon gamma by quartz crystal microbalance biosensor

Interferon gamma (IFNγ) is a cytokine and an immunochemical marker that can be used for revealing of infectious diseases and especially for distinguishing of viral and some types of bacterial infections. Blood tests for IFNγ are typically based on immunoassays like Enzyme-Linked Immunosorbent Assay (ELISA). In this paper, a biosensor working on the principle of quartz crystal microbalance (QCM) was developed as an alternative to the standard analytical methods for IFNγ. The biosensor contained antibodies against IFNγ immobilized on QCM and also on gold nanoparticles. A sandwich containing QCM, gold nanoparticles and IFNγ was formed and formation of the sandwich caused decrease of oscillation frequency. The assay exerted limit of detection 5.7 pg/ml for a sample sized 50 μl and one measuring cycle was finished within 90 min. The assay by biosensor fully correlated to standard ELISA. In a conclusion, the biosensor appears to be a fully applicable analytical tool for a simple assay of IFNγ. Overall simplicity and no special requirement on staff and equipment are the major advantages of the here presented assay.

A "signal-on" electrochemical biosensor based on DNAzyme-driven bipedal DNA walkers and TdT-mediated cascade signal amplification strategy

In this work, a dual amplified signal enhancement approach based on coupling deoxyribozyme (DNAzyme)-driven bipedal DNA walkers (BDW) and terminal deoxynucleotidyl transferase (TdT)-mediated DNA elongation signal amplifications has been developed for highly sensitive and label-free electrochemical detection of thrombin in human serums. In presence of thrombin, the BDW complex, which is comprised from the target thrombin and two DNAzyme-containing probes, can exhibit autonomous cleavage behavior on the surface of the substrate DNA (SD) modified electrode, and remove the cleaved DNA fragment from the electrode surface. Subsequently, the TdT can catalyze the elongation of the SD with free 3'-OH termini and formation of many G-quadruplex sequence replicates with the presence of 2'-deoxyaguanosine-5'-triphosphate (dGTP) and adenosine 5'-triphosphate (dATP) at a molar ratio of 6:4. These G-quadruplex sequences bind hemin and generate drastically amplified current response for sensitive detection of thrombin in a "signal-on" and completely label-free fashion. Under optimized conditions, the response peak current was linear with the concentration of thrombin in the range from 0.5 pM to 100000 pM with detection limit of 0.31 pM. This research provides us a sustainable idea for the hyphenated multiple amplification strategies and a stable and effective method for the detection of protein biomarkers.