Methylated DNA impedimetric immunosensor based on azo-polymer-AuNPs dots and 5-methylcytosine antibody using dissolved oxygen as a redox probe

Development of an electrochemical impedance spectroscopy immunosensor for insulin monitoring employing pyrroloquinoline quinone as an ingestible redox probe

Contemporary electrochemical impedance spectroscopy (EIS)-based biosensors face limitations in their applicability for in vivo measurements, primarily due to the necessity of using a redox probe capable of undergoing oxidation and reduction reactions in solution. Although previous investigations have demonstrated the effectiveness of EIS-based biosensors in detecting various target analytes using potassium ferricyanide as a redox probe, its unsuitability for blood or serum measurements, attributed to its inherent toxicity, poses a significant challenge. In response to this challenge, our study adopted a unique approach, focusing on the use of ingestible materials, by exploring naturally occurring substances within the body, with a specific emphasis on pyrroloquinoline quinone (PQQ). Following an assessment of PQQ's electrochemical attributes, we conducted a comprehensive series of EIS measurements. This involved the thorough characterization of the sensor's evolution, starting from the bare electrode and progressing to the immobilization of antibodies. The sensor's performance was then evaluated through the quantification of insulin concentrations ranging from 1 pM to 100 nM. A single frequency was identified for insulin measurements, offering a pathway for potential in vivo applications by combining PQQ as a redox probe with EIS measurements. This innovative approach holds promise for advancing the field of in vivo biosensing based on the EIS method.

Impedimetric Polyaniline-Based Aptasensor for Aflatoxin B1 Determination in Agricultural Products

An impedimetric aptasensor based on a polyaniline (PAni) support matrix is developed through the surface modification of a screen-printed carbon electrode (SPE) for aflatoxin B₁ (AFB₁) detection in foodstuffs and feedstuffs for food safety. The PAni is synthesized with the chemical oxidation method and characterized with potentiostat/galvanostat, FTIR, and UV-vis spectroscopy techniques. The stepwise fabrication procedure of the PAni-based aptasensor is characterized by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The impedimetric aptasensor is optimized using the EIS technique, and its feasibility of detecting AFB₁ in real sample matrices is evaluated via a recovery study in spiked foodstuffs and feedstuffs, such as pistachio nuts, cinnamons, cloves, corn, and soybeans, with a good recovery percentage, ranging from 87.9% to 94.7%. The charge transfer resistance (R_CT) at the aptasensor interface increases linearly with the AFB₁ concentration in the range of 3 × 10^-2 nM to 8 × 10^-2 nM, with a regression coefficient (R²) value of 0.9991 and detection limit of 0.01 nM. The proposed aptasensor is highly selective towards AFB₁ and partially selective to AFB₂ and ochratoxin A (OTA) due to their similar structures that differ only at the carbon-carbon double bond located at C₈ and C₉ and the large molecule size of OTA.

Flexible Label-Free Platinum and Bio-PET-Based Immunosensor for the Detection of SARS-CoV-2

The demand for new devices that enable the detection of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) at a relatively low cost and that are fast and feasible to be used as point-of-care is required overtime on a large scale. In this sense, the use of sustainable materials, for example, the bio-based poly (ethylene terephthalate) (Bio-PET) can be an alternative to current standard diagnostics. In this work, we present a flexible disposable printed electrode based on a platinum thin film on Bio-PET as a substrate for the development of a sensor and immunosensor for the monitoring of COVID-19 biomarkers, by the detection of L-cysteine and the SARS-CoV-2 spike protein, respectively. The electrode was applied in conjunction with 3D printing technology to generate a portable and easy-to-analyze device with a low sample volume. For the L-cysteine determination, chronoamperometry was used, which achieved two linear dynamic ranges (LDR) of 3.98-39.0 μmol L^-1 and 39.0-145 μmol L^-1, and a limit of detection (LOD) of 0.70 μmol L^-1. The detection of the SARS-CoV-2 spike protein was achieved by both square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) by a label-free immunosensor, using potassium ferro-ferricyanide solution as the electrochemical probe. An LDR of 0.70-7.0 and 1.0-30 pmol L^-1, with an LOD of 0.70 and 1.0 pmol L^-1 were obtained by SWV and EIS, respectively. As a proof of concept, the immunosensor was successfully applied for the detection of the SARS-CoV-2 spike protein in enriched synthetic saliva samples, which demonstrates the potential of using the proposed sensor as an alternative platform for the diagnosis of COVID-19 in the future.

Bach-Type Polycondensation with the Aid of Hemoglobin as an Oxygen Supplier, and Synthetic/Bio-Composite

We developed a new Bach-type reaction in the presence of oxy-hemoglobin as an oxygen supplier to synthesize polyazobenzene by traditional Bach reaction. The resultant product is a form of polymeric dye/hemoglobin copolymer. The advantage of this research is that it involves a new reaction using the function of biomolecules, as well as the formation of plastics and biomaterials. The bio-based material may have good affinity with life forms, which may lead to applications in medical science.