Ultrasensitive immunoassay of proteins based on in-situ enzymatic formation of quantum dots and microliter-droplet anodic stripping voltammetry

Immunocolorimetric assay based on amplified gold nanoparticles and magnetic separation beads for detection of sesame allergens in food

We have developed a magnetic separation-based immunocolorimetric assay to detect sesame allergens. Sesame monoclonal antibody (Ab) was modified onto gold nanoparticles (AuNPs) to create signal probes (AuNPs-Ab), and sesame allergens (SA) were attached to carboxyl-functionalized magnetic polystyrene microspheres (MPMs) to act as capture probes (MPMs-SA). Based on the competition format, the capture probes competed with the sesame allergens in the sample to bind the corresponding signal probes. When sesame allergens were present, two immune complexes (AuNPs-Ab@MPMs-SA and AuNPs-Ab@SA) were formed. The immune complex AuNPs-Ab@SA was used to quantify the sesame allergens in the sample. This immunoassay had a detection linear range from 50 to 800 μg L^-1 with a limit of detection (LOD) of 45.53 μg L^-1. Based on the optimized conditions, the recovery of sesame allergens in bread, biscuit, almond beverage, and energy bar samples was between 82.50% and 116.67%. The LODs for the bread, biscuit, almond beverage, and energy bar samples were 0.36, 0.36, 0.27, and 0.55 mg kg^-1, respectively.

Sensitive impedimetric detection of troponin I with metal-organic framework composite electrode

Metal-organic frameworks (MOFs) are promising materials for biosensing applications due to their large surface to volume ratio, easy assembly as thin films, and better biocompatibility than other nanomaterials. Their application in electrochemical biosensing devices can be realized by integrating them with other conducting materials, like polyaniline (PANI). In the present research, a composite of a copper-MOF (i.e., Cu3(BTC)2) with PANI has been explored to develop an impedimetric sensor for cardiac marker troponin I (cTnI). The solvothermally synthesized Cu3(BTC)2/PANI composite has been coated as a thin layer on the screen-printed carbon electrodes (SPE). This electroconductive thin film was conjugated with anti-cTnI antibodies. The above formed immunosensor has allowed the impedimetric detection of cTnI antigen over a clinically important concentration range of 1-400 ng mL-1. The whole process of antigen analysis could be completed within 5 min. The detection method was specific to cTnI even in the co-presence of other possibly interfering proteins.

A phenol phosphorescent microsensor of mesoporous molecularly imprinted polymers

Based on the optical quenching phenomenon, a smart mesoporous phosphorescent microsensor was built. It is a phenol microsensor, which inherits a high selectivity of molecularly imprinted polymers (MIPs) and room-temperature phosphorescence (RTP) properties of Mn-doped ZnS quantum dots (QDs). On the surface of silane-modified Mn-doped ZnS QDs, the phenol microsensor was synthesized by a sol–gel process. Because of the presence of a porogenic agent, a mesoporous structure played an important role in increasing the detection sensitivity. The MPTS-modified Mn-doped ZnS QDs were used as solid supports and auxiliary monomers. Under optimal conditions, the experiment for the detection of phenol had a linear range of 5.0 to 50 μmol L⁻¹ with a correlation coefficient of 0.9983 and a high imprinting factor (IF) of 3.28. In addition, the as-prepared Mn-doped ZnS QD@ms-MIPs were successfully applied for phenol determination and selectivity in water samples. Therefore, this study provides a highly selective and sensitive mesoporous phosphorescent microsensor for the detection of phenol.

Based on the optical quenching phenomenon, a smart mesoporous phosphorescent microsensor was built.

A fluorescent microsensor for the selective detection of bifenthrin

Based on the fluorescence quenching phenomenon, a smart fluorescent microsensor was synthesized. The bifenthrin (BI) microsensor inherited the high selectivity of molecular imprinted polymers (MIPs) and the excellent fluorescence properties of aqueous CdTe quantum dots (QDs). Aqueous CdTe QDs are functionalized by octadecyl-4-vinylbenzyl-dimethyl-ammonium chloride (OVDAC). A type of functional monomer, 4-vinylphenylboronic acid (VPBA), was used and its boronic acid groups could covalently combine with a cis-diol compound for direct imprinting polymerization. The OVDAC-functionalized aqueous CdTe QDs were used as solid supports and auxiliary monomers. Under optimal conditions, experimentation showed that BI had a linear detection range of 10 to 300 μmol L⁻¹ with a correlation coefficient of 0.9968 and a high imprinting factor (IF) of 4.53. In addition, the prepared MIP-OVDAC/CdTe QDs were successfully used to detect BI in water samples. Therefore, this work provided a highly selective and sensitive fluorescence probe for the detection of BI. In addition, the fluorescence probe could be used to detect other targets by changing the functional monomers.

Based on the fluorescence quenching phenomenon, a smart fluorescent microsensor was synthesized.

Point-of-Care Compatibility of Ultra-Sensitive Detection Techniques for the Cardiac Biomarker Troponin I-Challenges and Potential Value

Cardiac biomarkers are frequently measured to provide guidance on the well-being of a patient in relation to cardiac health with many assays having been developed and widely utilised in clinical assessment. Effectively treating and managing cardiovascular disease (CVD) relies on swiftly responding to signs of cardiac symptoms, thus providing a basis for enhanced patient management and an overall better health outcome. Ultra-sensitive cardiac biomarker detection techniques play a pivotal role in improving the diagnostic capacity of an assay and thus enabling a better-informed decision. However, currently, the typical approach taken within healthcare depends on centralised laboratories performing analysis of cardiac biomarkers, thus restricting the roll-out of rapid diagnostics. Point-of-care testing (POCT) involves conducting the diagnostic test in the presence of the patient, with a short turnaround time, requiring small sample volumes without compromising the sensitivity of the assay. This technology is ideal for combatting CVD, thus the formulation of ultra-sensitive assays and the design of biosensors will be critically evaluated, focusing on the feasibility of these techniques for point-of-care (POC) integration. Moreover, there are several key factors, which in combination, contribute to the development of ultra-sensitive techniques, namely the incorporation of nanomaterials for sensitivity enhancement and manipulation of labelling methods. This review will explore the latest developments in cardiac biomarker detection, primarily focusing on the detection of cardiac troponin I (cTnI). Highly sensitive detection of cTnI is of paramount importance regarding the rapid rule-in/rule-out of acute myocardial infarction (AMI). Thus the challenges encountered during cTnI measurements are outlined in detail to assist in demonstrating the drawbacks of current commercial assays and the obstructions to standardisation. Furthermore, the added benefits of introducing multi-biomarker panels are reviewed, several key biomarkers are evaluated and the analytical benefits provided by multimarkers-based methods are highlighted.

Effect of Electrode Shape and Flow Conditions on the Electrochemical Detection with Band Microelectrodes

In this work, we report the analysis of the electrochemical detection of electroactive species with band microelectrodes that operate under controlled convection. The study focuses on the determination of the collection efficiency of the analyte as a function of inlet flow velocity and microband geometry (inlaid, bumped and recessed), also providing a straightforward method for the theoretical determination of the lower detection limit. The analysis has been carried out by simulating the dimensionless mass transport with the finite element method, delivering the stationary limiting current density. Simulations have been performed on systems consisting of single and double band electrodes to investigate the trail effect on the electrochemical detection. We show that the obtained dimensionless results can be easily turned into dimensional data, providing a tool for the design of devices. The proposed method is general and can easily be extended to systems with different geometry.