Covalent Organic Frameworks-Based Electrochemical Sensors for Food Safety Analysis

Fabrication of hybrid nanocomposites for electrochemical evaluation of food-based preservative and bioactive targets of hydrogen peroxide and rutin in real fruit and drug samples

Development of a reliable tool to detect hydrogen peroxide (H2O2) and rutin in food-derived products and bioactive flavonoids is essential for food safety. Nevertheless, food/drug-based real samples are complex matrices that affect the sensor's specificity and sensitivity. For this purpose, we developed a simple electrochemical detection platform using covalent organic framework‑silver nanoparticles (COF-AgNPs). Based on spectral and electrochemical tests, COF-AgNPs displayed enhanced electroactive sites and facile electron transfer. For H2O2 and rutin, the designed sensor surface exhibited outstanding concentration linearity of 0.5 nM-1000 μM and 1 nM-900 μM, respectively, along with superior detection limits of 0.126 nM and 0.133 nM. Additionally, it demonstrated acceptable reproducibility and interference capability. In practical analysis, H2O2 and rutin were detected in milk, fruits, and drug samples with high recovery rates of 94.60-99.31 % (n = 3). Consequently, the designed sensor is ideal for screening targets for H2O2 and rutin in food sources and for food research.

Ultrasensitive detection of circulating tumor DNA using a CRISPR/Cas9 nickase-driven 3D DNA walker based on a COF-AuNPs sensing platform

A electrochemical biosensor was designed utilizing a CRISPR Cas9n-driven DNA walker combined with gold-nanosphere-like covalent organic frameworks (COFs-AuNPs) to detect breast cancer markers (PIK3CA E545K ctDNA). The DNA walker probe is activated only in the presence of circulating tumor deoxyribonucleic acid (ctDNA), binding to a support probe to form a double strand that is then specifically cleaved by the Cas9n/sgRNA complex. This cleavage produces numerous DNA fragments for signal amplification. The COF-AuNPs as electrode materials facilitate electronic transfer and provide additional active sites for the immobilization of nucleic acid probes. This setup achieves a detection limit of 1.76 aM, demonstrating high sensitivity. Additionally, Cas9n improves the specificity of the sensor, accurately distinguishing a pair of base-mismatched sequences, and reducing the occurrence of false positives. Overall, the sensor exhibits excellent selectivity, reproducibility, and potential for early diagnosis of breast cancer.

Not Only Graphene Two-Dimensional Nanomaterials: Recent Trends in Electrochemical (Bio)sensing Area for Biomedical and Healthcare Applications

Two-dimensional (2D) nanomaterials (e.g., graphene) have attracted growing attention in the (bio)sensing area and, in particular, for biomedical applications because of their unique mechanical and physicochemical properties, such as their high thermal and electrical conductivity, biocompatibility, and large surface area. Graphene (G) and its derivatives represent the most common 2D nanomaterials applied to electrochemical (bio)sensors for healthcare applications. This review will pay particular attention to other 2D nanomaterials, such as transition metal dichalcogenides (TMDs), metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXenes, applied to the electrochemical biomedical (bio)sensing area, considering the literature of the last five years (2018-2022). An overview of 2D nanostructures focusing on the synthetic approach, the integration with electrodic materials, including other nanomaterials, and with different biorecognition elements such as antibodies, nucleic acids, enzymes, and aptamers, will be provided. Next, significant examples of applications in the clinical field will be reported and discussed together with the role of nanomaterials, the type of (bio)sensor, and the adopted electrochemical technique. Finally, challenges related to future developments of these nanomaterials to design portable sensing systems will be shortly discussed.