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Foodborne illnesses can be infectious and dangerous, and most of them are caused by bacteria. Some common food-related bacteria species exist widely in nature and pose a serious threat to both humans and animals; they can cause poisoning, diseases, disabilities and even death. Rapid, reliable and cost-effective methods for bacterial detection are of paramount importance in food safety and environmental monitoring. Polymerase chain reaction (PCR), lateral flow immunochromatographic assay (LFIA) and electrochemical methods have been widely used in food safety and environmental monitoring. In this paper, the recent developments (2013–2023) covering PCR, LFIA and electrochemical methods for various bacterial species (Salmonella, Listeria, Campylobacter, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)), considering different food sample types, analytical performances and the reported limit of detection (LOD), are discussed. It was found that the bacteria species and food sample type contributed significantly to the analytical performance and LOD. Detection via LFIA has a higher average LOD (24 CFU/mL) than detection via electrochemical methods (12 CFU/mL) and PCR (6 CFU/mL). Salmonella and E. coli in the Pseudomonadota domain usually have low LODs. LODs are usually lower for detection in fish and eggs. Gold and iron nanoparticles were the most studied in the reported articles for LFIA, and average LODs were 26 CFU/mL and 12 CFU/mL, respectively. The electrochemical method revealed that the average LOD was highest for cyclic voltammetry (CV) at 18 CFU/mL, followed by electrochemical impedance spectroscopy (EIS) at 12 CFU/mL and differential pulse voltammetry (DPV) at 8 CFU/mL. LOD usually decreases when the sample number increases until it remains unchanged. Exponential relations (R2 > 0.95) between LODs of Listeria in milk via LFIA and via the electrochemical method with sample numbers have been obtained. Finally, the review discusses challenges and future perspectives (including the role of nanomaterials/advanced materials) to improve analytical performance for bacterial detection. [ABSTRACT FROM AUTHOR]

In this work, biomass-derived carbon quantum dots (CQDs) with excellent water solubility, strong fluorescence and favorable biocompatibility were synthesized via one-step hydrothermal treatment of purple perilla for the first time. The functional group composition, morphology, and pH stability of the synthesized CQDs were systematically investigated. And based on fluorescence quenching of CQDs, the as-prepared CQDs were innovatively developed as an effective "signal-off" fluorescent probe for selective and sensitive detection of silver ion (Ag+) with two linear ranges of 0–10 and 10–3000 nM, and a detection limit 1.4 nM. The specificity and selectivity of this fluorescent probe were also verified through challenging the detection by using similarmetallic cations or in real water samples. In addition, the as-prepared CQDs exhibit a low cytotoxicity and a good biocompatibility, revealing its potential bioimaging applications in living cells. Image 1 • CQDs were synthesized via one-step hydrothermal treatment of purple perilla. • Selective and sensitive detection of Ag+ were achieved based on as-prepared CQDs. • The obtained CQDs have low cytotoxicity and good biocompatibility. • Fluorescence quenching of CQDs by Ag+ was revealed following a static mechanism. [ABSTRACT FROM AUTHOR]

Real-time in-situ visualization and sensitive detection of thimbleful tumor-related microRNAs (miRNAs) in living cells is still unmet. Especially, poor amplification efficiency and resistance against complex intracellular environment hinder amplifiers' widespread applications in vivo. Herein, we report enzyme-free self-propelled quantum dots-based spherical nucleic acids (QDs-based SNAs, also named TSD-QDs) as a ratiometric amplifier for stable, efficient, and sensitive detection and imaging of miRNAs in biological samples and living cells. The ratiometric amplifier is proved possesses outstanding stability in human serum and cells, as well as prominent recognition capability for miRNAs. More importantly, the ingeniously designed tail sequence of fuel strand (FS) could lead to high operating efficiency and excellent detection performance of TSD-QDs for non-enzyme detection in vitro (in the range of 10 fM-150 nM with a limit of detection (LOD) of 5.8 fM). Furthermore, the spherical nucleic acids (SNAs) structure can endow TSD-QDs with favorable photostability and high resistance against to the nuclease, thus benefit its applications in intracellular miRNA-21 monitoring via fluorescence imaging. With these advantages, the proposed TSD-QDs based amplifier enables accurate and effective monitoring of the miRNAs expression levels in living cells (A549, normal QSG-7701, Hela and MCF-7 cells), and poses great potential in medical diagnostics and biomedical applications. [Display omitted] • Self-propelled quantum dots-based spherical nucleic acids (TSD-QDs) were constructed. • TSD-QDs as ratiometric amplifier enabled sensitive detection of intracellular miRNAs. • The ratiometric amplifier possessed outstanding photostability and biostability. • Tactfully designed tail sequence of FS accelerated operating efficiency of TSD-QDs. • High selectivity and sensitivity with a low LOD 5.8 fM were favorably obtained. [ABSTRACT FROM AUTHOR]

[Display omitted] • A quantitative method for analyzing photochromism was described. • A photo-responsive film serving as a sensitive UV sensor was demonstrated. • A facile low-cost photo-patterning technique was developed. Photochromic materials are widely applied in many fields, but their applications are partly limited by the complexity in both synthesis and device-fabrication, as well as the difficulty in quantitative analysis. We developed a photochromic compound (DHAIA) capable of changing color and fluorescence upon UV radiation. The change can be quantitatively analyzed via CIELAB color space, further yielding color shift (Δ E Lab) values that can be either recognized by instruments or detected by naked eyes. The compound can be fabricated into a photo-responsive film to serve as a sensitive UV sensor, allowing a low detection limit down to 20 μW/cm2 (UV radiation intensity). In addition, a photo-patterning technique was demonstrated, wherein patterns can be printed using either UV light or sunlight. [ABSTRACT FROM AUTHOR]

• The CDs@ZIF-8 composites have been fabricated via an in-situ embedding strategy. • The CDs@ZIF-8 demonstrates uniform size and excellent FL efficiency. • A fluorescent sensor for DA detection was favorably developed based on CDs@ZIF-8. • By virtue of synergy of ZIF-8 and CDs properties, sensor exhibits good performance. By embedding high quantum yield blue-emitting carbon dots (CDs) into zeolitic imidazolate framework-8 (ZIF-8), the luminescent metal-organic frameworks (LMOFs) - CDs@ZIF-8 composites were fabricated facilely and served as the fluorescent probe for selective and sensitive detection of dopamine (DA). In which the sustainable pores within ZIF-8 would not only provide a natural habitat for analyte but also can selectively capture and concentrate the DA molecules via the interaction between the analyte DA and the basic site of the frame. Meanwhile, the CDs can be served as the signal probes to transform chemical signals of the interaction between CDs and analytes into fluorescent signals. Thus, the as-synthesized CDs@ZIF-8 composites generate new sensing performance when compared with CDs. As a consequence, a wide concentration dynamic range of 0.1–200 μM with a low detection limit (LOD) 16.64 nM was favorably obtained for the CDs@ZIF-8 composites based detection method for DA. Besides, the practicality and viability of the fluorescent composites were also successfully verified via challenging the CDs@ZIF-8 based sensing method to detect DA in complicated serum and urine. [ABSTRACT FROM AUTHOR]