"Five birds one stone" tri-modal monitoring driven lab-on-magnetic aptasensor for accurate pathogen detection and enhanced germicidal application

Carbon dots: An emerging food analysis nanoprobes for detection of contaminants

Carbon dots are the new class of nanomaterials with a size range of 10 nm or less. These are associate with the important material properties such as good biocompatibility, fluorescent nature, small size and easy to synthesize with low toxicity which make them the first choice over the fluorescent inorganic materials and dyes, to be used as biocompatible nanoprobes for the detection of food adulterations. Herein, we have focused on the methods of synthesis of these tiny zero dimensions, fluorescent nanomaterials (CDs), their properties, mechanism of fluorescence, and lastly their wide applications in food analysis which include the detection of additives, heavy metal ions, organic pollutants, foodborne microbes, antibiotic and pesticides. Further, these nanomaterials open the scope to be used as nanoprobes in the food safety concern. Additionally, we discussed the challenges and future scope of CDs as an auspicious and emerging nanomaterial to be used in the food industries.

Au@Fe3O4 Nanoparticle-Based Colorimetric Aptasensor for Noninvasive Screening of Colorectal Cancer via Detection of Parvimonas micra

Colorectal cancer (CRC) is a common malignancy requiring early screening to improve patient outcomes. Current screening methods such as colonoscopy and fecal occult blood tests have several limitations including high cost, poor specificity, invasiveness, and inconvenience. Recent research has identified specific bacterial communities associated with CRC, notably Parvimonas micra (P. micra), which serves as a biomarker for early screening and diagnosis owing to its accumulation in the malignant tissues and feces of CRC patients. Herein, we employed the whole-bacterium systematic evolution of ligands by the exponential enrichment (SELEX) method to isolate high-affinity aptamers against P. micra using 17 selection cycles. These aptamers were subsequently bound to Au@Fe3O4 nanoparticles, and the interaction of P. micra and aptamers inhibited the peroxidase-like activity of Au@Fe3O4 nanoparticles, thereby blocking the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction and resulting in a measurable reduction in absorbance. This colorimetric detection strategy demonstrated a linear response across a range of 100-108 CFU/mL for P. micra with a limit of detection of 11 CFU/mL. Using a colorimetric aptasensor, we assessed the abundance of P. micra in clinical fecal samples and found significantly higher levels in the feces of CRC patients as compared to that of healthy individuals, which was consistent with the quantitative polymerase chain reaction results. This study therefore represents the first successful identification of an aptamer with high affinity and specificity for P. micra, leading to the development of a highly specific and sensitive aptasensor for its detection. The presented approach has a significant potential for CRC screening and diagnosis.

"Four - in - one" platform based on multifunctional nanozyme for ultra - accurate detection and on - demand disinfection of Listeria monocytogenes

The inability to integrate detection and disinfection hindered building a unified pathogen monitoring platform, risking secondary contamination. Herein, a novel "four - in - one" platform for monitoring foodborne Listeria monocytogenes (L. monocytogenes) was presented. The magnetic daptomycin - functionalized Fe3O4 (Dap/Fe3O4) could selectively bind to L. monocytogenes, enhancing detection accuracy. The separated bacteria were captured by aptamers - functionalized Fe - doped - silica nanoparticles (Apt/Fe@SiNPs) for tri - mode detection. Besides fluorescence, the Apt/Fe@SiNPs converted 3,3',5,5' - tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) via peroxidase activity, allowing colorimetric and subsequent photothermal detection upon irradiation, as low as 2.06 CFU/mL. Magnetic - induced aggregation of Apt/Fe@SiNPs generated toxic hydroxyl radicals around L. monocytogenes, achieving ∼99.6% disinfection. Furthermore, the biofilm of L. monocytogenes was effectively inhibited by the action of hydroxyl radicals. The platform might offer a promising prospect to control L. monocytogenes in food industries.

Carbon dots-based fluorescent probe for detection of foodborne pathogens and its potential with microfluidics

Concern about food safety triggers demand on rapid, accurate and on-site detection of foodborne pathogens. Among various fluorescent probes for detection, carbon dots (CDs) prepared by carbonization of carbon-rich raw materials show extraordinary performance for their excellent and tailorable photoluminescence property, as well as their facilely gained specificity by surface customization and modification. CDs-based fluorescent probes play a crucial role in many pathogenic bacteria sensing systems. In addition, microfluidic technology with characteristics of portability and functional integration is expected to combine with CDs-based fluorescent probes for point-of-care testing (POCT), which can further enhance the detection property of CDs-based fluorescent probes. Here, this paper reviews CDs-based bacterial detection methods and systems, including the structural modulation of fluorescent probes and pathogenic bacteria detection mechanisms, and describes the potential of combining CDs with microfluidic technology, providing reference for the development of novel rapid detection technology for pathogenic bacteria in food.

Smart Nanozymes for Diagnosis of Bacterial Infection: The Next Frontier from Laboratory to Bedside Testing

The global spread of infectious diseases caused by pathogenic bacteria significantly poses public health concerns, and methods for sensitive, selective, and facile diagnosis of bacteria can efficiently prevent deterioration and further spreading of the infections. The advent of nanozymes has broadened the spectrum of alternatives for diagnosing bacterial infections. Compared to natural enzymes, nanozymes exhibit the same enzymatic characteristics but offer greater economic efficiency, enhanced durability, and adjustable dimensions. The importance of early diagnosis of bacterial infection and conventional diagnostic approaches is introduced. Subsequently, the review elucidates the definition, properties, and catalytic mechanism of nanozymes. Eventually, the detailed application of nanozymes in detecting bacteria is explored, highlighting their utilization as biosensors that allow for accelerated and highly sensitive identification of bacterial infections and reflecting on the potential of nanozyme-based bacterial detection as a point-of-care testing (POCT) tool. A brief summary of obstacles and future perspectives in this field is presented at the conclusion of this review.

Colorimetry/fluorescence dual-mode detection of Salmonella typhimurium based on a "three-in-one" nanohybrid with high oxidase-like activity for AIEgen

A colorimetry/fluorescence dual-mode assay based on the aptamer-functionalized magnetic covalent organic framework-supported CuO and Au NPs (MCOF-CuO/Au@apt) was developed for Salmonella typhimurium (S. typhimurium) biosensing. The nanohybrid combined three functions in one: good magnetic separation characteristic, excellent oxidase-mimic activity for tetrap-aminophenylethylene (TPE-4A), and target recognition capability. The attachment of MCOF-CuO/Au@apt onto the surface of S. typhimurium resulted in a significant reduction in the oxidase-mimicking activity of the nanohybrid, which could generate dual-signal of colorimetry and fluorescence through the catalytic oxidation of TPE-4A. Based on this, S. typhimurium could be specifically detected in the linear ranges of 102- 106 CFU·mL-1 and 101- 106 CFU·mL-1, with LODs of 7.6 and 2.1 CFU·mL-1, respectively in colorimetry/fluorescence modes. Moreover, the smartphone and linear discrimination analysis-based system could be used for on-site and portable testing. In addition, this platform showed applicability in detecting S. typhimurium in milk, egg liquid and chicken samples.