Cuprous oxide coated silver/graphitic carbon nitride/cadmium sulfide nanocomposite heterostructure: Specific recognition of carcinoembryonic antigen through sandwich-type mechanism

Graphitic carbon nitride/1-pyrenebutyric acid N-hydroxysuccinimide/polythiophene nanocomposite photoelectrochemical biosensor for CA 19-9 detection

A photoelectrochemical (PEC) biosensor composed entirely of carbon nanomaterials was synthesized to detect carbohydrate antigen 19-9 (CA 19-9). The biosensor platform integrated graphitic carbon nitride (GCN), known for its light sensitivity, polythiophene (PTh), an organic conductive and optically active material, and 1-pyrenebutyric acid N-hydroxysuccinimide (PBASE), which functions both as a biolinker to conjugate CA 19-9 antibody and antigen and as an electron mediator to facilitate electron transfer from GCN to PTh. The formation of a Schottky heterojunction between PTh and GCN reduced the bandgap of GCN from 2.66 to 1.96 eV, which enhanced transfer of photogenerated electrons for cathodic photocurrent generation. The improvement of charge transfer due to heterojunction formation and π-π stacking between GCN and the pyrene group of PBASE is confirmed by cyclic voltammetry (CV), electron impedance spectroscopy (EIS), and chronoamperometry (CA) findings. The highest current of 1.31 μA is observed for combination of 5 wt% PTh with a GCN/PBASE ratio of 1:0.5. Besides evaluating the electron mobility of GCN/PBASE/PTh, CV, EIS, and CA were also used to evaluate the sensor performance. Optimization studies revealed that 0.6 μg of CA 19-9 antibody and 1 h of antigen-antibody immobilization time significantly improved the biosensor response. The GCN/PBASE/PTh biosensor demonstrated high sensitivity to CA 19-9 antigen across a concentration of 50-1000 U/ml and a detection limit as low as 0.052 U/ml. The reported working range is within the limits required for diagnostic testing of patients with hepatic and heart problems as well as for post-treatment monitoring of colorectal and pancreatic cancer patients.

Emerging electrochemical biosensors for lung cancer-associated protein biomarker and miRNA detection

Lung cancer remains a major driver of global morbidity and mortality, and diagnosing lung tumors early in their development is vital to maximizing treatment efficacy and patient survival. Several biomarkers, including CYFRA 21-1, NSE, ProGRP, CEA, and miRNA, have been identified as reliable indicators for early lung cancer detection and monitoring treatment progress. However, the minute changes in the levels of these biomarkers during the early stages of disease necessitate advanced detection platforms. In this space, electrochemical biosensors have currently emerged as robust tools for early lung cancer screening and diagnosis owing to their low costs, rapid responses, and superior sensitivity and selectivity. This review provides an up-to-date overview of the application of electrochemiluminescence, photoelectrochemical, and other electrochemical analytical strategies for detecting lung cancer-associated protein biomarkers, and miRNA. This review compares these techniques to provide a concise overview of the principles underlying these electrochemical analytical methods, the preparation of their components, and the performance of the resulting biosensors. Lastly, a discussion of the challenges and opportunities associated with electrochemical biosensors detection of lung cancer-associated biomarkers are provided.

A multiple signal amplification photoelectrochemical biosensor based on biotin-avidin system for kanamycin sensing in fish and milk via synergism of g-C3N4 and Ru@SiO2

BACKGROUND

The residues of kanamycin can accumulate in the human body for a long time and pose serious health risks, including hearing loss, kidney poisoning, and drug allergic reactions. Therefore, it is crucial to develop a rapid, highly sensitive, and low-cost method for detecting kanamycin residues in foods. However, the current methods have limitations such as low sensitivity, expensive instruments, and multiple steps, which make them impractical for use in resource-limited environments and emergencies. In this study, the creation of a multiple-signal amplification photoelectrochemical biosensor to address these aforementioned issues is discussed.

RESULTS

Herein, we proposed a multiple signal amplification photoelectrochemical (PEC) biosensor based on carboxylated g-C3N4 and avidin functionalized Ru@SiO2 for the ultrasensitive detection of kanamycin. The carboxylated g-C3N4 was a highly efficient photoactive substance for amplifying photoelectric signals and a substrate for aptamer immobilization. The DOS and PDOS of g-C3N4 were studied by simulation, and the sensing mechanism of the probe at the molecular level was revealed. Meanwhile, using Ru@SiO2 as a signal amplifying unit, through the cooperative work between Ru@SiO2 and g-C3N4, the photoelectric signal could be double amplified to produce an excellent photocurrent response. Under optimized conditions, the photocurrent response of the PEC biosensor to kanamycin was obtained at concentrations from 0.1 nM to 1000 nM with a lower detection limit of 4.1052 × 10-11 mol L-1. This protocol demonstrates high sensitivity, brilliant specific recognition ability, excellent reproducibility, and acceptable stability.

SIGNIFICANCE

The first combination of g-C3N4 and avidin-Ru@SiO2 as photocurrent materials greatly enhanced the sensitivity of the PEC biosensors. Moreover, the specificity and sensitivity of the PEC biosensor were further improved through the specific interaction between kanamycin and aptamer. The photoelectric conversion mechanism based on g-C3N4 and two pathways for enhancing the photocurrent by Ru(byp)32+ were proposed. Through simulations of the DOS and PDOS of g-C3N4, the sensing mechanism of the probe at the molecular level was revealed. Under the optimum conditions, the PEC biosensor exhibited a wide linear concentration range and a low detection limit.

Cadmium Sulfide Nanoparticles: Preparation, Characterization, and Biomedical Applications

Cadmium sulfide nanoparticles (CdS NPs) have been employed in various fields of nanobiotechnology due to their proven biomedical properties. They are unique in their properties due to their size and shape, and they are popular in the area of biosensors, bioimaging, and antibacterial and anticancer applications. Most CdS NPs are generally synthesized through chemical, physical, or biological methods. Among these methods, biogenic synthesis has attracted more attention due to its high efficiency, environmental friendliness, and biocompatibility features. The green approach was found to be superior to other methods in terms of maintaining the structural characteristics needed for optimal biomedical applications. The size and coating components of CdS NPs play a crucial role in their biomedical activities, such as anticancer, antibacterial, bioimaging, and biosensing applications. CdS NPs have gained significant interest in bioimaging due to their desirable properties, including good dispersion, cell integrity preservation, and efficient light scattering. Despite these, further studies are necessary, particularly in vivo studies to reduce NPs' toxicity. This review discusses the different methods of synthesis, how CdS NPs are characterized, and their applications in the biomedical field.

Redox-labelled detection probe enabled immunoassay for simultaneous detection of multiple cancer biomarkers

Some of the cancer biomarkers often lack specificity and sensitivity; thus, simultaneous detection of multiple biomarkers can make the diagnosis more accurate. Also, simple sensing system without utilization of extra reagents like mediator or substrate during detection event is desirable for point-of-care testing. To address this, mediator and substrate-free amperometric biosensor for simultaneous detection of cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) have been demonstrated by designing two different redox-labelled detection probes. Colloidal nanoparticles of polyaniline-pectin conjugated with AFP antibody along with ferrocene and silver nanoparticles conjugated with CEA antibody along with anthraquinone were used as redox probes to bind with AFP and CEA during the detection event. Sensor constructed using carboxylic acid tethered polyaniline as immobilization matrix displayed 5 times wider linear range than conventional polyaniline for AFP and CEA detection by sandwich electrochemical assay. The detection limit was 30 pg mL^-1 for AFP and 80 pg mL^-1 for CEA. The biosensor displayed appropriate sensitivity, good specificity, and negligible cross-reactivity between the two targets. The proposed sensor was used to determine APF and CEA in human blood serum. The strategy demonstrated can be further extended for detection of panel of cancer biomarkers by designing appropriate redox probes.

Photoelectrochemical biosensor based on DNA aptamers and dual nano-semiconductor heterojunctions for accurate and selective sensing of chloramphenicol

Nanosheets of anatase TiO₂ and CdS quantum dots modified with thioglycolic acid (TGA-CdS QDs) were prepared and hierarchically modified on the indium tin oxides (ITO) electrodes. The heterojunction structure is formed to improve the light capture ability and carrier migration, significantly enhancing the sensitivity of photoelectrochemical (PEC) biosensors. Specific DNA sequences labeled with TGA-CdS QDs were placed on the electrodes to prepare a biosensor for the detection of chloramphenicol with ultrahigh selectivity. In addition, the heterojunction structure and the principle of photocurrent signal amplification on the electrode are described in detail. Under the optimal conditions, the photoelectrochemical biosensors showed good reproducibility and stability for chloramphenicol with a linear response in the range 10-10,000 pM and a limit of detection (LOD) of 0.23 pM. Due to the specific recognition of base pairs, the sensor has excellent anti-interference ability in practical applications. An effective method was developed for the accurate detection of antibiotics with far reaching prospects.