Boosted photoelectrochemical immunosensing of metronidazole in tablet using coral-like g-C3N4 nanoarchitectures

Two-Dimensional Graphitic Carbon Nitride (g-C3N4) Nanosheets and Their Derivatives for Diagnosis and Detection Applications

The early diagnosis of certain fatal diseases is vital for preventing severe consequences and contributes to a more effective treatment. Despite numerous conventional methods to realize this goal, employing nanobiosensors is a novel approach that provides a fast and precise detection. Recently, nanomaterials have been widely applied as biosensors with distinctive features. Graphite phase carbon nitride (g-C3N4) is a two-dimensional (2D) carbon-based nanostructure that has received attention in biosensing. Biocompatibility, biodegradability, semiconductivity, high photoluminescence yield, low-cost synthesis, easy production process, antimicrobial activity, and high stability are prominent properties that have rendered g-C3N4 a promising candidate to be used in electrochemical, optical, and other kinds of biosensors. This review presents the g-C3N4 unique features, synthesis methods, and g-C3N4-based nanomaterials. In addition, recent relevant studies on using g-C3N4 in biosensors in regard to improving treatment pathways are reviewed.

Polymeric carbon nitride-based materials: Rising stars in bioimaging

Polymeric carbon nitrides (CN), due to their unique physicochemical properties, versatile surface functionalization, ultra-high surface area, and good biocompatibility, have attracted considerable interest in diverse biomedical applications, such as biosensors, drug delivery, bioimaging, and theranostics. In this review, the recent advances in bioimaging of CN-based nanomaterials are summarized according to the imaging modalities, including optical (fluorescence and Raman) imaging, magnetic resonance imaging (MRI), photoacoustic imaging (PAI), computed tomography (CT), and multimodal imaging. The pros and cons of CN bioimaging are comprehensively analyzed and compared with those in previous reports. In the end, the prospects and challenges of their future bioimaging applications are outlooked.

Recent Advances of Nanostructured Materials for Photoelectrochemical Bioanalysis

Nowadays, the emerging photoelectrochemical (PEC) bioanalysis has drawn intensive interest due to its numerous merits. As one of its core elements, functional nanostructured materials play a crucial role during the construction of PEC biosensors, which can not only be employed as transducers but also act as signal probes. Although both chemical composition and morphology control of nanostructured materials contribute to the excellent analytical performance of PEC bioassay, surveys addressing nanostructures with different dimensionality have rarely been reported. In this review, according to classification based on dimensionality, zero-dimensional, one-dimensional, two-dimensional, and three-dimensional nanostructures used in PEC bioanalysis are evaluated, with an emphasis on the effect of morphology on the detection performances. Furthermore, using the illustration of recent works, related novel PEC biosensing patterns with promising applications are also discussed. Finally, the current challenges and some future perspectives in this field are addressed based on our opinions.

Porous Inorganic Materials for Bioanalysis and Diagnostic Applications

Porous inorganic materials play an important role in adsorbing targeted analytes and supporting efficient reactions in analytical science. The detection performance relies on the structural properties of porous materials, considering the tunable pore size, shape, connectivity, etc. Herein, we first clarify the enhancement mechanisms of porous materials for bioanalysis, concerning the detection sensitivity and selectivity. The diagnostic applications of porous material-assisted platforms by coupling with various analytical techniques, including electrochemical sensing, optical spectrometry, and mass spectrometry, etc., are then reviewed. We foresee that advanced porous materials will bring far-reaching implications in bioanalysis toward real-case applications, especially as diagnostic assays in clinical settings.

Design of ultrathin nanosheet subunits ZnIn2S4 hollow nanocages with enhanced photoelectric conversion for ultrasensitive photoelectrochemical sensing

Herein, a high-efficiency photoactive material, hollow ZnIn₂S₄ nanocages (ZIS-HNCs) composed of ultrathin nanosheets were creatively synthesized via a metal-organic framework (MOF) derived solvothermal method. It had been specified the underlying mechanism of the ZIS-HNCs evolution under the MOF templated surface. Subsequently, the obtained ZIS-HNCs combined with annealing TiO₂ modified electrode (ZIS-HNCs@TiO₂), and the ZIS-HNCs@TiO₂ exhibited intense transient photocurrent. The enhanced photocurrent signal benefited from the multiple light capture effect of ZIS-HNCs, ultrathin nanosheet subunits of ZIS-HNCs, and typical type Ⅱ heterojunction, which could effectively retard the photoexcited electron-hole pairs recombination, and accelerated charge separation and transfer. Taking antibiotic lincomycin (Lin) as a model, a signal-off photoelectrochemical (PEC) aptasensor based on the ZIS-HNCs@TiO₂ was established and manifested a high sensitive detection for Lin with a linear response range from 0.0001 to 0.1 nM as well as an ultralow detection limit of 0.084 pM. Additionally, the proposed PEC aptasensor showed acceptable stability and remarkable selectivity. Therefore, this study provides a promising strategy to design nanomaterials with superior photoelectric activity for PEC sensing applications.

Graphite-like carbon nitride-laden gold nanoparticles as signal amplification label for highly sensitive lateral flow immunoassay of 17β-estradiol

Conventional gold nanoparticles-based lateral flow immunoassays (AuNPs-LFIA) lack sensitivity. In this work, we developed a graphite-like carbon nitride-laden AuNPs (g-C₃N₄@Au) assisted LFIA to improve sensitivity for 17β-estradiol (E2) in foods. g-C₃N₄ nanosheets were applied as carriers, because of their excellent chemical stability, large surface areas and low-cost, loading large numbers of AuNPs to amplify signals and improve the overall response of g-C₃N₄@Au-based LFIA (g-C₃N₄@Au-LFIA). The lowest visual limit of detection (vLOD) of E2 is 0.5 ng mL^-1 for g-C₃N₄@Au-LFIA, which exhibit a significantly three-fold improved analytical performance compared with that of AuNPs-LFIA. Additionally, this method was successfully used to the detection of E2 in four spiked food samples, offering a great potential of the g-C₃N₄@Au based LFIA for its application in food products.

Fabrication of carbon dots@restricted access molecularly imprinted polymers for selective detection of metronidazole in serum

A custom-tailored design was proposed for the fabrication of carbon dots coupled with restricted access materials and molecularly imprinted polymers (CDs@RAM-MIPs) to detect metronidazole (MNZ). Biomass carbon dots (CDs) were derived from longan peels assisted with high pressure microwave, and had the merits of eco-friendly, excellent photostability and low toxicity. In this work, glycidyl methacrylate was used as a co-polymeric monomer to increase hydroxyl groups on the surface of synthetic materials, which eliminated the interference of biological macromolecules. The specific binding cavities of CDs@RAM-MIPs were formed after removing the template molecule (MNZ). The obtained CDs@RAM-MIPs can selectively capture MNZ through the specific interaction between recognition sites and MNZ, and obey photoinduced electron transfer fluorescence quenching mechanism. The highly sensitive and selective fluorescent sensor based CDs@RAM-MIPs had a wide linear range (50-1200 ng mL^-1) and a low detection limit (17.4 ng mL^-1) for MNZ. It has been utilized to detect MNZ in serum with recoveries of 93.5%-102.7%, and the relative standards (RSDs) were 1.9%-3.6%, respectively. This work provides a thoughtful strategy for preparation and application of CDs@RAM-MIPs, which presages its great potential for detecting trace compounds in real samples.

Recent developments of photoelectrochemical biosensors for food analysis

Recent developments of photoelectrochemical biosensors for food analysis are summarized and the future prospects in this field are discussed.

A carbon-rich nanofiber framework based on a conjugated arylacetylene polymer for photocathodic enzymatic bioanalysis

The metal-free photocathode fabricated by porous carbon-rich nanofiber framework of PTEB film realized “signal-off” photocathodic bioanalysis of glucose.