A potentiometric sensor for the trace level determination of hemoglobin in real samples using multiwalled carbon nanotube based molecular imprinted polymer

Recent Advances in Biosensor Technologies for Point-of-Care Urinalysis

Human urine samples are non-invasive, readily available, and contain several components that can provide useful indicators of the health status of patients. Hence, urine is a desirable and important template to aid in the diagnosis of common clinical conditions. Conventional methods such as dipstick tests, urine culture, and urine microscopy are commonly used for urinalysis. Among them, the dipstick test is undoubtedly the most popular owing to its ease of use, low cost, and quick response. Despite these advantages, the dipstick test has limitations in terms of sensitivity, selectivity, reusability, and quantitative evaluation of diseases. Various biosensor technologies give it the potential for being developed into point-of-care (POC) applications by overcoming these limitations of the dipstick test. Here, we present a review of the biosensor technologies available to identify urine-based biomarkers that are typically detected by the dipstick test and discuss the present limitations and challenges that future development for their translation into POC applications for urinalysis.

Glycated Hemoglobin Electrochemical Immunosensor Based on Screen-Printed Electrode

An electrochemical HbA1c sensor with high sensitivity and good specificity is proposed based on the electrochemical immune principle. The reproducibility and conductivity of the electrode are improved by depositing gold nanoparticles (AuNPs) on the surface of the screen-printed electrode (SPE). The HbA1c antibodies are immobilized on the surface of the modified electrode by adsorption to capture the HbA1c in the sample. The hindering effect of HbA1c on the electrode transfer reaction was exploited as the HbA1c detection mechanism. The electrode's properties were characterized by electrochemical impedance spectroscopy (EIS), and the measurement properties of the electrode were analyzed using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The experimental results show that the peak current signal of the electrochemical immunosensor produced a linear response to HbA1c in the concentration range of 20-200 μg/mL, a linear relationship coefficient of 0.9812, a detection limit of 15.5 µg/mL, and a sensitivity of 0.0938 µA/µg·mL^-1. The sensor delivered satisfactory repeatability, stability, and anti-interference performance. Due to its small size, high sensitivity, and wide linear detection range, it is expected to play a significant role in managing diabetes at home.

Ag nanoparticles/PbTiO3 with in-situ photocatalytic process and its application in an ultra-sensitive molecularly imprinted hemoglobin detection

An electrochemical sensor based on loading molecularly imprinted polymers (MIP) on the material surface can improve the specificity towards the object. In this work, a T-shaped PbTiO₃ with a high active-exposed (110) facet was prepared by a hydrothermal process. Then, Ag nanoparticles (Ag NPs) modified T-shaped PbTiO₃ was obtained by in-situ photocatalytic reduced method under UV irradiation, where a hetero-junction was formed with a well lattice matching between the (111) facet of Ag⁰ and the (110) facet of PbTiO₃. A MIPs modified by Ag nanoparticles (NPs)/PbTiO₃ (MAP) electrodes was prepared via electro polymerization process by o-Phenylenediamine (o-PD) in the presence of the template molecule, bovine hemoglobin (BHb), i.e., the detected molecule. The response peak current and concentration of BHb is demonstrated with a good linear relationship in the range of 0.00294-0.41 nM (R² =0.98), and the detection limit at 0.23 pM (S/N = 3). A heterojunction between Ag NPs and high- active facet of PbTiO₃ is beneficial to oxidizing electroactive material ([Fe (CN)₆]^3-/4-), generating more BHb-imprinting cavities on the modified electrode and improving the sensitivity of sensor. The electrochemical sensor is with a simple, stable structure and high sensitivity to BHb detection. Furthermore, the sensor was successfully applied to detect BHb in the bovine serum samples.

Molecularly Imprinted Polymers in Diagnostics: Accessing Analytes in Biofluids

Bio-applied molecularly imprinted polymers (MIPs) are biomimetic materials with tailor-made synthetic recognition sites, mimicking biological counterparts known for their sensitive and selective analyte detection. MIPs, specifically designed for biomarker analysis...

Specific recognition of protein by deep eutectic solvent-based magnetic β-cyclodextrin molecularly imprinted polymer

A magnetic β-cyclodextrin (MCD) surface molecularly imprinted polymer (MIP) based on deep eutectic solvents (DESs) as cross-linker and functional monomer (MCD@DES-MIP) was successfully synthesized for the specific recognition of bovine hemoglobin (BHb). The adsorption behavior of MCD@DES-MIP for BHb was investigated by adsorption thermodynamics, adsorption kinetics, and pH control experiments. The maximum adsorption capacity of MCD@DES-MIP for BHb under the optimized conditions was 195.94 mg g^-1 and the imprinting factor was 4.68. In addition, the competitive adsorption experiments demonstrated that MCD@DES-MIP showed excellent selective extraction ability for BHb in the binary mixture of BHb and bovine serum albumin (BSA). The actual sample analysis manifested that MCD@DES-MIP effectively separated BHb from complex samples. The results of circular dichroism spectra proved that the secondary structure of BHb did not change during elution. The result indicated that MCD@DES-MIP can be used as a new imprinting material for the separation and purification of BHb.Graphical abstract Magnetic imprinted microspheres (MCD@DES-MIP) were prepared by free radical polymerization using magnetic β-cyclodextrin (MCD) as carrier, deep eutectic solvents (DESs) as functional monomer and cross-linker. MCD@DES-MIP show high adsorption capacity and excellent selectivity for BHb.

New Generation of Electrochemical Sensors Based on Multi-Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNT) have provided unprecedented advances in the design of electrochemical sensors. They are composed by sp2 carbon units oriented as multiple concentric tubes of rolled-up graphene, and present remarkable active surface area, chemical inertness, high strength, and low charge-transfer resistance in both aqueous and non-aqueous solutions. MWCNT are very versatile and have been boosting the development of a new generation of electrochemical sensors with application in medicine, pharmacology, food industry, forensic chemistry, and environmental fields. This work highlights the most important synthesis methods and relevant electrochemical properties of MWCNT for the construction of electrochemical sensors, and the numerous configurations and successful applications of these devices. Thousands of studies have been attesting to the exceptional electroanalytical performance of these devices, but there are still questions in MWCNT electrochemistry that deserve more investigation, aiming to provide new outlooks and advances in this field. Additionally, MWCNT-based sensors should be further explored for real industrial applications including for on-line quality control.