Label-free electrochemical homogeneous detection of the depression marker human apolipoprotein A4 based on proximity hybridization triggered rolling circle amplification

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.

Supradecoration induced homogenous electrochemical sensing: development of Ru(ii) half sandwich complex as isoniazid and rifampicin dual sensor

Homogenous electrochemical sensing using unmodified electrodes remove electrode fabrication challenges and prove effective for detecting sensitive bio-analytes without chances of surface degradation. This work envisages design and optimization of a ruthenium(ii) half-sandwich complex as supradecorated homogeneous electrochemical sensor for simultaneous detection of rifampicin (RIF) and isoniazid (INH) as first-line anti-tuberculosis drugs in aqueous environments. The electrochemical profile of GCE/ruthenium(ii) half-sandwich complex sensor was analyzed using cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy (EIS). The results indicate significant electrochemical parameters corroborating enhanced sensing propensity of GCE/ruthenium(ii) half-sandwich complex over bare GCE for simultaneous estimation of RIF and INH binary mixture. The RIF and INZ analytical figure of merit has been corroborated with their relative supra interactional propensity. Supra interactional propensity has also been predicted to be the plausible mechanism of RIF and INZ electrochemical sensing. Under optimized conditions GCE/ruthenium(ii) half-sandwich complex sensor depicted INH detection limits of 1.2 μM, and RIF detection limit of 32 nM. The comparative study of RIF and INZ analytes individually depicted high sensitivity of 24.57 μA μM-1 cm-2 and 1.69 μA μM-1 cm-2 under a linear response in the range of 0.29-3.72 μM and 4.9-82.22 μM for RIF and INH respectively. The analytical figure of merit of homogenous sensor has been compared to other GCE modified electrodes for RIF and INZ analytes. A significant antibiotic contaminant recovery of RIF and INZ drugs in pharmaceutical formulations, municipal water supplies and Dal lake water under spiked as well as unspiked conditions was observed portraying real time sensing application propensity. The homogenous GCE/ruthenium(ii) half-sandwich complex expresses excellent stability and reproducibility. The GCE/ruthenium(ii) half-sandwich complex in the presence of potential redox active biological interfering agents confirmed selectivity towards RIF and INZ analytes.

Electrochemical biosensors for depression: Diagnosis and therapeutic monitoring

Electrochemical biosensors have revolutionized the detection of biomarkers related to depression and the quantification of antidepressant drugs. These biosensors leverage nanomaterials and advanced assay designs to achieve high sensitivity and selectivity for clinically relevant analytes. Key neurotransmitters implicated in depression, such as serotonin, dopamine, and glutamate, can be accurately measured via biosensors, providing insights into the effects of antidepressant treatments on neurotransmission. Biosensors can also detect biomarkers of inflammation, oxidative stress, and neuronal health that are altered in depression. Real-time biosensing techniques such as fast-scan cyclic voltammetry enable monitoring of dynamic neurotransmitter changes during depressive episodes and pharmacological interventions. Advancements incorporating graphene, gold nanoparticles, and other nanomaterials have enhanced biosensor performance, enabling the detection of low biomarker concentrations. Closed-loop biosensing systems hold promise for precision medicine by automating antidepressant dosage adjustments on the basis of neurotransmitter levels. A wide range of depression biomarkers, including apolipoprotein A4, heat shock protein 70, brain-derived neurotrophic factor, microRNAs, proteins, and combinatorial biomarker panels, have been detected via sophisticated biosensor platforms. Emerging biosensors show selectivity for antidepressant drugs such as serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, and selective serotonin reuptake inhibitors in biological samples. This review emphasizes the transformative potential of electrochemical biosensors in combating depression. By facilitating earlier and more accurate diagnoses, these biosensors can revolutionize patient care and enhance treatment outcomes.

Immuno-Rolling Circle Amplification (Immuno-RCA): Biosensing Strategies, Practical Applications, and Future Perspectives

In the rapidly evolving field of life sciences and biomedicine, detecting low-abundance biomolecules, and ultraweak biosignals presents significant challenges. This has spurred a rapid development of analytical techniques aiming for increased sensitivity and specificity. These advancements, including signal amplification strategies and the integration of biorecognition events, mark a transformative era in bioanalytical precision and accuracy. A prominent method among these innovations is immuno-rolling circle amplification (immuno-RCA) technology, which effectively combines immunoassays with signal amplification via RCA. This process starts when a targeted biomolecule, such as a protein or cell, binds to an immobilized antibody or probe on a substrate. The introduction of a circular DNA template triggers RCA, leading to exponential amplification and significantly enhanced signal intensity, thus the target molecule is detectable and quantifiable even at the single-molecule level. This review provides an overview of the biosensing strategy and extensive practical applications of immuno-RCA in detecting biomarkers. Furthermore, it scrutinizes the limitations inherent to these sensors and sets forth expectations for their future trajectory. This review serves as a valuable reference for advancing immuno-RCA in various domains, such as diagnostics, biomarker discovery, and molecular imaging.

Sensitive and Cost-Effective Tools in the Detection of Ovarian Cancer Biomarkers

Women diagnosed with late-stage ovarian cancer suffer a very high rate of mortality. Accordingly, it is imperative to detect and diagnose the disease as early as possible in its development. Achievement of this aim implies relatively large-scale screening of women at an age of clinical significance through assay of biomarkers for disease present in blood or serum. Biosensor detection offers an attractive technology for the automated detection of such species. Among several biomarkers that have been identified that are present in patients with ovarian cancer, the only one that is commonly tested for in clinical use is cancer antigen 125, which is considered to be a poor biomarker for the disease. Here, we describe several biosensors that developed in the past decade for the detection of ovarian cancer biomarkers such as CA125, human epididymis protein 4 (HE4) and apolipoprotein A1. The challenges presented by the fabrication of biosensor devices for detecting ovarian cancer and the limited number of biosensors developed for this purpose are discussed.

Advances in biosensors for major depressive disorder diagnostic biomarkers

Depression is one of the most common mental disorders and is mainly characterized by low mood or lack of interest and pleasure. It can be accompanied by varying degrees of cognitive and behavioral changes and may lead to suicide risk in severe cases. Due to the subjectivity of diagnostic methods and the complexity of patients' conditions, the diagnosis of major depressive disorder (MDD) has always been a difficult problem in psychiatry. With the discovery of more diagnostic biomarkers associated with MDD in recent years, especially emerging non-coding RNAs (ncRNAs), it is possible to quantify the condition of patients with mental illness based on biomarker levels. Point-of-care biosensors have emerged due to their advantages of convenient sampling, rapid detection, miniaturization, and portability. After summarizing the pathogenesis of MDD, representative biomarkers, including proteins, hormones, and RNAs, are discussed. Furthermore, we analyzed recent advances in biosensors for detecting various types of biomarkers of MDD, highlighting representative electrochemical sensors. Future trends in terms of new biomarkers, new sample processing methods, and new detection modalities are expected to provide a complete reference for psychiatrists and biomedical engineers.

A novel electrochemical immunosensor for sensitive detection of depression marker Apo-A4 based on bipyridine-functionalized covalent organic frameworks

A novel electrochemical immunosensor for detecting potential depression biomarker Apolipoprotein A4 (Apo-A4) was developed using a multi-signal amplification approach. Firstly, the sensor utilized a modified electrode material, NG-PEI-COF, combining bipyridine-functionalized covalent organic framework (COF) and polyethyleneimine-functionalized nitrogen-doped graphene (NG-PEI), providing high surface area and excellent electron transfer capability for the first-stage amplification in electrical signal conduction. Subsequently, gold nanoparticles (AuNPs) were further electrodeposited onto the electrode, providing good biocompatibility and abundant binding sites for immobilizing the target antigen, thus achieving the second-stage amplification in target recognition and binding. To address the lack of redox properties of the antigen, a tracer probe was formed by loading AuNPs, anti-Apo-A4, and toluidine blue (TB) successively onto COF, leading to the third-stage amplification in signal conversion. The constructed electrochemical immunosensor TB/Ab/AuNPs/COF-Apo-A4/AuNPs/NG-PEI-COF/GCE exhibited excellent detection performance against Apo-A4 with a linear range of 0.01 to 300 ng mL-1 and had a low detection limit of 2.16 pg mL-1 (S/N = 3). In addition, the biosensor had good reproducibility (RSD = 2.31%), stability, and significant anti-interference performance toward other depression biomarkers. The sensor has been successfully used for the quantitative detection of Apo-A4 in serum, providing potential applications for detecting Apo-A4 in the clinic and serving as a reference for constructing sensing methods based on COF.

Proximity hybridization induced bipedal DNA walker and rolling circle amplification for label-free electrochemical detection of apolipoprotein A4

Apolipoprotein A4 (Apo-A4) is considered as a prospective molecular biomarker for diagnosis of depression due to its neurosynaptic toxicity. We develop a proximity hybridization-induced DNAzyme-driven bipedal DNA walker strategy for Apo-A4 quantification based on rolling circle amplification (RCA) triggered by poly adenine binding to Ag nanoparticles (AgNPs). With the help of DNAzyme, the free-running bipedal DNA walker can quickly and sequentially shear a molecular beacon that acts as a primer to initiate the RCA process, producing a large number of long DNA strands containing numerous adenines. The long repetitive adenine strands then absorb large amounts of AgNPs on the electrode interface, which is then electrochemically stripped of the AgNPs. The method has a linear detection range of 0.001 ∼ 100 ng mL-1 and a detection limit of 0.46 pg mL-1. The presented detection strategy is label-free, which allows high sensitivity and selectivity for detection of a wide range of protein targets by corresponding DNA-based affinity probes, which have potential applications in bioanalysis.

Label-free SERS detection of apolipoprotein A4 based on DNAzyme-driven molecular machine

Apolipoprotein A4 has a wide range of synaptic toxicity and can be used as a reliable molecular biomarker for the detection of depressive disorder. It has certain clinical requirements for simple, rapid and selective detection of apolipoprotein A4. Here, based on the DNA biped walker driven by DNAzyme, we designed a label-free surface-enhanced Raman scatting sensor for rapid detection of apolipoprotein A4. Compared with the typical DNA walker, the biped DNA walker has the advantages of large walking range and high magnification efficiency. The magnesium-dependent DNAzyme drives the DNA walker, which can cut the MBs sequentially. The resulting MBs fragments were then hybridized with AuNPs modified by repetitive adenine to make Au NPs proliferate on the substrate surface, resulting in a large number of cycles. Using 736 cm-1 adenine as the internal marker, surface enhanced Raman scattering analysis showed that the linear detection range of human apolipoprotein A4 was 10∼1000 ng mL-1, the detection limit was 4.7 pg/mL, and it had significant specificity, which could meet the needs of clinical detection and showed great application potential.

Proximity hybridization induced bipedal DNA walker for label-free electrochemical detection of apolipoprotein A4 based on DNA meditated Ag nanoparticles growth

Apolipoprotein A4 (Apo-A4) is considered as a prospective molecular biomarker for diagnosis of depression due to its neurosynaptic toxicity. Here, we propose a neighboring hybridization induced catalyzed hairpin assembly (CHA) driven bipedal DNA walker that mediates hybridization of Ag nanoparticles (Ag NPs) with DNA probes for highly sensitive electrochemical quantitative detection of Apo-A4. Driven by CHA, this bipedal DNA walker can spread all over the surface of the sensor, induce the HP1-HP2 double chain structure, make the surface of the sensor negatively charged, and adsorb a large number of Ag ions. After chemical reduction with hydroquinone, the Ag NPs formed provide signal tracers for electrochemical dissolution analysis of the target. The Ag NPs formed by chemical reduction of hydroquinone can provide signal traces for electrochemical stripping analysis of target thrombin. The linear range of this method is from 10 pg mL-1 to 1000 ng mL-1, and the detection limit is 5.1 pg mL-1. This enzyme-free and labeling detection method provides a new strategy for rapid clinical detection of Apo-A4 and accurate identification of depression.

Recent advances in electrochemical proximity ligation assay

Proximity ligation assay (PLA) is a vigorously developed homogeneous immunoassay assisted by DNA combining dual recognition of target protein by pairs of proximity probes, in which the detection of protein is tactfully converted to the detection of DNA. The booming developments in PLA have enabled a variety of ultrasensitive assays for the detection of protein and this concept of PLA is also extended to the detection of nucleic acids and some small molecule. The association between PLA and electrochemical method, defined as electrochemical proximity ligation assay (ECPLA), has gained much interests in disease diagnosis, food safety and environmental assays with the advantages, such as broad range of targets, simplicity, low cost and rapid response. In this review, we took a different perspective to present the history of PLA, the classical ECPLA biosensing methodology as well as the developments of ECPLA based on several key parameters, such as sensitivity, selectivity, reusability and generalization. In addition, the developments of PLA with electrochemiluminescence as readout are also presented. Finally, perspective and some unresolved challenges in ECPLA that can potentially be addressed have also been discussed.

Translation of aptamers toward clinical diagnosis and commercialization

The dominance of antibodies in diagnostics has gradually changed following the discovery of aptamers in the early 1990s. Aptamers offer inherent advantages over traditional antibodies, including higher specificity, higher affinity, smaller size, greater stability, ease of manufacture, and low immunogenicity, rendering them the best candidates for point-of-care testing (POCT). In the past 20 years, the research community and pharmaceutical companies have made great efforts to promote the development of aptamer technology. Macugen® (pegaptanib) was the first aptamer drug approved by the US Food and Drug Administration (FDA), and various aptamer-based diagnostics show great promise in preclinical research and clinical trials. In this review, we introduce recent literature, ongoing clinical trials, commercial reagents of aptamer-based diagnostics, discuss the FDA regulatory mechanisms, and highlight the prospects and challenges in translating these studies into viable clinical diagnostic tools.