Platinum ions mediate the interactions between DNA and carbon quantum dots: diagnosis of MRSA infections

Comprehensive review on fluorescent carbon dots and their applications in nucleic acid detection, nucleolus targeted imaging and gene delivery

Carbon dots (CDs), including carbon quantum dots, graphene quantum dots, carbon nanodots, and polymer dots, have gained significant attention due to their unique structural and fluorescence characteristics. This review provides a comprehensive overview of the classification, structural characteristics, and fluorescence properties of CDs, followed by an exploration of various fluorescence sensing mechanisms and their applications in gene detection, nucleolus imaging, and gene delivery. Furthermore, the functionalization of CDs with diverse surface ligand molecules, including dye molecules, nucleic acid probes, and metal derivatives, for sensitive nucleic acid detection is systematically examined. Fluorescence imaging of the cell nucleolus plays a vital role in examining intracellular processes and the dynamics of subcellular structures. By analyzing the mechanism of fluorescence and structure-function relationships inherent in CDs, the nucleolus targeting abilities of CDs in various cell lines have been discussed. Additionally, challenges such as the insufficient organelle specificity of CDs and the inconsistent mechanisms underlying nucleolus targeting have also been highlighted. The unique physical and chemical properties of CDs, particularly their strong affinity toward deoxyribonucleic acid (DNA), have spurred interest in gene delivery applications. The use of nuclear-targeting peptides, polymers, and ligands in conjunction with CDs for improved gene delivery applications have been systematically reviewed. Through a comprehensive analysis, the review aims to contribute to a deeper understanding of the potential and challenges associated with CDs in biomedical applications.

Detection of Methicillin-Resistant Staphylococcus Aureus using vancomycin conjugated silica-based fluorescent nanoprobe

Methicillin-Resistant Staphylococcus Aureus (MRSA) is a worldwide major pathogenic bacteria that has emerged over the past three decades as the leading cause of nosocomial and community-acquired infections. Biosensors can provide rapid, sensitive, and selective detection of the presence and number of bacteria in various environments. Herein, a novel fluorescence nanoprobe was designed as a biosensor for MRSA detection using dye-incorporated silica nanoparticles (FSiNP). Based on the results of specific surface area analysis using the Brauner Emmett-Teller (BET) method, the surface area of the nanoparticles was obtained at 377.127 m2/g, and the X-ray diffraction (XRD) analysis confirmed that it was in the amorphous phase. Vancomycin, as the bioreceptor, was immobilized on the silica surface through a hydrosilylation reaction, generating the biosensing platform FSiNP-Van. Each modification step was corroborated by the Fourier Transform Infra-Red (FTIR) spectroscopy. The sensing principle was based on the fluorescence-quenching mechanism of FSiNP-Van at 515 nm obtaining a rapid response time of 20 min. The FSiNP-Van nanoprobe provided a wide linear concentration range of 10-106 CFU/mL with a limit of MRSA detection calculated at 1 CFU/mL. The fluorescent nanoprobe demonstrated here is expected to find applications in point-of-care (POC) diagnostics to detect the presence of MRSA bacteria.

Constructing DNAzyme-driven three-dimensional DNA nanomachine-mediated paper-based photoelectrochemical device for ultrasensitive detection of miR-486-5p

As a unique class of dynamic nanostructures, biomimetic DNA walking machines that exhibit geometrical complexity and nanometre precision have gained great success in photoelectrochemical (PEC) bioanalysis. Despite certain achievements, the slow reaction kinetics and low processivity severely restrict the amplification efficiency of the DNA walker-mediated biosensors. Herein, by taking advantage of efficient DNA rolling machines, a three-dimensional (3D) DNA nanomachine-mediated paper-based PEC device for speedy ultrasensitive detection of miR-486-5p was successfully constructed. To achieve it, a novel In2S3/SnS2 sensitized heterojunction was firstly in-situ grown on the Au-modified paper fibers and implemented as the photoanode with effective separation of photogenerated carriers to achieve an enhanced initial photocurrent. Subsequently, the copper hexacyanoferrate(II)-modified CuO nanosphere was introduced as a multifunctional signal regulator via the competitive capture of electron donors and photon energy with the photoelectric layer for efficiently quenching the PEC signal. With the introduction of targets, the DNAzyme-driven DNA nanomachine with editable motion modes was gradually activated and it could continuously cleave the tracks DNA labeled quenching probes, finally achieving the recovery of PEC signal. As a proof of concept, the elaborated paper-based PEC device presented a wide linear range from 0.1 fM to 100 pM and a detection limit of 35 aM for miR-486-5p bioassay. This work provides an innovative insight to the exploitation of DNA nanobiotechnology and nucleic acid signal amplification strategy.

Carbon-dot-triggered aggregation/dispersion of gold nanoparticles for colorimetric detection of nucleic acids and its application in visualization of loop-mediated isothermal amplification

In this study, cationic carbon dots (CDs) were prepared from p-phenylenediamine (pPDA) via a one-step hydrothermal method and used to trigger the aggregation and dispersion of gold nanoparticles (AuNPs) for the colorimetric detection of nucleic acids. Physicochemical characterization results revealed that the CDs are enriched with positively charged surface functional groups with an average size of ∼11 nm. The interaction between the CDs and AuNPs was confirmed via fluorescence and absorption studies. Absorption spectroscopic results revealed that the primary surface plasmon resonance (SPR) band of the AuNPs decreased upon introduction of CDs, and a new band emerged at ∼600 nm, indicating the aggregated assembly of AuNPs. Upon the introduction of double-stranded deoxyribonucleic acid (DNA), the band corresponding to the aggregated AuNPs showed a continuous decrease, accompanied by a simultaneous increase in the primary SPR band, leading to a noticeable purple-to-red color transformation. Based on this phenomenon, a colorimetric assay for DNA was developed, which relies on the interaction between negatively charged DNA and cationic CDs, leaving the AuNPs dispersed. The assay exhibited a linear response within a DNA concentration range of 0.7-14 nM with a detection limit of 1.70 nM. Selectivity results showed that colorimetric assays are specific for both DNA and single-stranded DNA (ssDNA). Smartphone-assisted detection was developed by monitoring the colorimetric response of a AuNPs/CDs probe. As a proof-of-concept experiment, the AuNPs/CDs probe was used to visualize the loop-mediated isothermal amplification (LAMP) of Escherichia coli (E. coli), a robust indicator of sewage contamination in water.

Recent Advances in Nanozyme-Mediated Strategies for Pathogen Detection and Control

Pathogen detection and control have long presented formidable challenges in the domains of medicine and public health. This review paper underscores the potential of nanozymes as emerging bio-mimetic enzymes that hold promise in effectively tackling these challenges. The key features and advantages of nanozymes are introduced, encompassing their comparable catalytic activity to natural enzymes, enhanced stability and reliability, cost effectiveness, and straightforward preparation methods. Subsequently, the paper delves into the detailed utilization of nanozymes for pathogen detection. This includes their application as biosensors, facilitating rapid and sensitive identification of diverse pathogens, including bacteria, viruses, and plasmodium. Furthermore, the paper explores strategies employing nanozymes for pathogen control, such as the regulation of reactive oxygen species (ROS), HOBr/Cl regulation, and clearance of extracellular DNA to impede pathogen growth and transmission. The review underscores the vast potential of nanozymes in pathogen detection and control through numerous specific examples and case studies. The authors highlight the efficiency, rapidity, and specificity of pathogen detection achieved with nanozymes, employing various strategies. They also demonstrate the feasibility of nanozymes in hindering pathogen growth and transmission. These innovative approaches employing nanozymes are projected to provide novel options for early disease diagnoses, treatment, and prevention. Through a comprehensive discourse on the characteristics and advantages of nanozymes, as well as diverse application approaches, this paper serves as a crucial reference and guide for further research and development in nanozyme technology. The expectation is that such advancements will significantly contribute to enhancing disease control measures and improving public health outcomes.

A Continuously Tunable Full-Color Emission Nitrogen-Doped Carbon Dots and for Ultrasensitive and Highly Selective Detection of Ascorbic Acid

Nitrogen-doped carbon dots exhibiting excitation-dependent full-color emissions (F-NCDs) were prepared via the one-step hydrothermal method with citric acid and phenylenediamine. Specifically, the emission wavelength of the F-NCDs tuned from 452 nm to 602 nm due to the introduction of new energy levels by C=O and C=N functional groups. We exploited its stability in illumination, ionic strength, and pH, as well as its specificity, sensitivity, especially in ascorbic acid (AA) detection. F-NCDs could measure the AA concentration in the linear ranges of 0~0.1 and 0.1~1 mmol/L with the detection limit (LOD, S/N = 3) as low as 2.6 nmol/L. Additionally, we successfully detected AA in bovine serum with our F-NCDs and obtained the result within 1 min. Because of full-color emission features, we believe our F-NCDs have a great potential in fluorescent sensor detection.

Application of Nanomaterials in Isothermal Nucleic Acid Amplification

Because of high sensitivity and specificity, isothermal nucleic acid amplification are widely applied in many fields. To facilitate and improve their performance, various nanomaterials, like nanoparticles, nanowires, nanosheets, nanotubes, and nanoporous films are introduced in isothermal nucleic acid amplification. However, the specific application, roles, and prospect of nanomaterials in isothermal nucleic acid amplification have not been comprehensively reviewed. Here, the application of different nanomaterials (0D, 1D, 2D, and 3D) in isothermal nucleic acid amplification is comprehensively discussed and recent progress in the field is summarized. The nanomaterials are mainly used for reaction enhancer, signal generation/amplification, or surface loading carriers. In addition, 3D nanomaterials can be also functioned as isolated chambers for digital nucleic acid amplification and the tools for DNA sequencing of amplified products. Challenges and future recommendations are also proposed to be better used for recent covid-19 detection, point-of-care diagnostic, food safety, and other fields.

Sulfur-doped carbon dots synthesis under microwave irradiation as turn-off fluorescent sensor for Cr(III)

This study synthesized a facile and high sensitive fluorescent probe based on sulfur-doped carbon dots (S-CDs) using a one-step microwave irradiation method. The probe exhibited a strong blue emission and a high quantum yield (QY) of 36.40%. In the detection, the presence of trivalent chromium (Cr(III)) strongly quenched the PL intensity of S-CDs by the inner filter effect (IFE) quenching mechanism of Cr(III) on the S-CDs. The S-CDs exhibited good sensitivity to turn-off Cr(III) detection with a linear range concentration of 0–45 μM and a detection limit of 0.17 μM. Furthermore, the proposed method has been successfully applied for Cr(III) detection in natural water samples with the 93.68–106.20% recoveries.

Short DNA-catalyzed formation of quantum dot-DNA hydrogel for enzyme-free femtomolar specific DNA assay

Fast, sensitive, specific, and user-friendly DNA assay is a key technique for the next generation point-of-care molecular diagnosis. However, high-cost, time-consuming, and complicated enzyme-based DNA amplification step is essential to achieve high sensitivity. Herein, a short target DNA-catalyzed formation of quantum dot (QD)-DNA hydrogel is proposed as a new DNA assay platform satisfying the above requirements. A single-stranded target DNA catalyzes the opening cycle of DNA hairpin loops, which are quickly self-assembled with DNA-functionalized QDs to generate QD-DNA hydrogel. The three-dimensional hydrogel network allows efficient resonance energy transfer, dramatically lowering the limit of detection down to ~6 fM without enzymatic DNA amplification. The QD-DNA hydrogel also enables a rapid detection (1 h) with high specificity even for a single-base mismatch. The clinical applicability of the QD-DNA hydrogel is demonstrated for the Klebsiella pneumoniae carbapenemase gene, one of the key targets of drug-resistant pathogenic bacteria.