Cu-Fe Oxide Nanozymes with Enhanced Peroxidase-like Activity for Sensitive H2O2 Colorimetric Detection

Highly sensitive colorimetric and paper-based detection for sildenafil in functional food based on monodispersed spherical magnetic graphene composite nanozyme

Prussian blue nanoparticles as peroxidase mimetics for sensitive colorimetric detection of hydrogen peroxide and glucose

Sodium percarbonate fuel-driven magnetic micromotor for rapid detection and efficient removal of tetracycline: Synergistic effect of oxygen vacancy and dissolved oxygen.

Sensitive and portable colorimetric detection of copper in water by cotton thread based pre-concentration

Sensitive colorimetric detection of heparin using reverse modulation of peroxidase- and oxidase-mimetic activities in Fe3O4@PDA@MnO2 nanocomposites

Facile preparation of Fe3O4 nanospheres/reduced graphene oxide nanocomposites with high peroxidase-like activity for sensitive and selective colorimetric detection of acetylcholine

A facile and green approach to the preparation of peroxidase-like nanozymes by reducing and functionalizing graphene oxide (rGO) with Ganoderma polysaccharide (GP) has been achieved in this work. Our results showed that the as-fabricated nanozyme, namely rGO-GP, possessed the excellent property of simulating peroxidase with higher catalytic activity compared with GO or rGO obtained by using chitosan, which may be due to the better dispersion of rGO-GP in the solution. Steady-state kinetics studies further showed that the catalytic process conformed to Michaelis-Menten equation and ping-pong mechanism. Benefiting from the excellent peroxidase property of rGO-GP, we have also successfully established a highly sensitive and selective colorimetric detection approach to trace detection of L-cysteine (L-Cys). The limit of detection (LOD) of L-cysteine is 0.1μM and the linear detection range is 2-30μM. Furthermore, the nanozyme was successfully applied for detecting L-cysteine in serum. This work therefore demonstrates the advantages of rGO-GP as an effective nanozyme in both its green synthesis and detecting application.

To meet the demand for more cost-effective rapid and sensitive nucleic acid detection methods to benefit various applications, we introduce a novel technique that uses a modified triggerable guanine quadruplex-based peroxidase (POD)-tagged primer. This technique allows sensitive colorimetric detection by activating an inactive POD tag during polymerase chain reaction amplification, which, importantly, functions independently of the type of DNA polymerase used.

Optical biosensors for rapid detection of significant foodborne pathogens are steadily gaining popularity due to its simplicity and sensitivity. While nanomaterials such as gold nanoparticles (AuNPs) are commonly used as signal amplifiers for optical biosensors, AuNPs can also be utilized as a robust biosensing platform. Many reported optical biosensors were designed for individual pathogen detection in a single assay and have high detection limit (DL). Salmonella spp. is one of the major causative agents of foodborne sickness, hospitalization and deaths. Unfortunately, there are around 2,000 serotypes of Salmonella worldwide, and rapid and simultaneous detection of multiple strains in a single assay is lacking. In this study, a comprehensive and highly sensitive simultaneous colorimetric detection of nineteen (19) environmental and outbreak Salmonella spp. strains was achieved by a novel optical biosensing platform using oligonucleotide-functionalized AuNPs. A pair of newly designed single stranded oligonucleotides (30-mer) was displayed onto the surface of AuNPs (13 nm) as detection probes to hybridize with a conserved genomic region (192-bases) of ttrRSBCA found on a broad range of Salmonella spp. strains. The sandwich hybridization (30 min, 55°C) resulted in a structural formation of highly stable oligonucleotide/AuNPs-DNA complexes which remained undisturbed even after subjecting to an increased salt concentration (2 M, final), thus allowing a direct discrimination via color change of target (red color) from non-target (purplish-blue color) reaction mixtures by direct observation using the naked eye. In food matrices (blueberries and chicken meat), nineteen different Salmonella spp. strains were concentrated using immunomagnetic separation and then simultaneously detected in a 96-well microplate by oligonucleotide-functionalized AuNPs after DNA preparation. Successful oligonucleotide/AuNPs-DNA hybridization was confirmed by gel electrophoresis while AuNPs aggregation in non-target and control reaction mixtures was verified by both spectrophotometric analysis and TEM images. Results showed that the optical AuNP biosensing platform can simultaneously screen nineteen (19) viable Salmonella spp. strains tested with 100% specificity and a superior detection limit of <10 CFU/mL or g for both pure culture and complex matrices setups. The highly sensitive colorimetric detection system can significantly improve the screening and detection of viable Salmonella spp. strains present in complex food and environmental matrices, therefore reducing the risks of contamination and incidence of foodborne diseases.

Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes

The construction of DNA nanostructures with various sizes and shapes has significantly advanced during the past three decades, yet the application of these DNA nanostructures for solving real problems is still in the early stage. On the basis of microRNA-triggered, catalytic self-assembly formation of the functional "DNAzyme ferris wheel" nanostructures, we show here a new signal amplification platform for highly sensitive, label-free and non-enzyme colorimetric detection of a small number of human prostate cancer cells. The microRNA (miR-141), which is catalytically recycled and reused, triggers isothermal self-assembly of a pre-designed, G-quadruplex sequence containing hairpin DNAs into "DNAzyme ferris wheel"-like nanostructures (in association with hemin) with horseradish peroxidase mimicking activity. These DNAzyme nanostructures catalyze an intensified color transition of the probe solution for highly sensitive detection of miR-141 down to 0.5 pM with the naked eye, and the monitoring of as low as 283 human prostate cancer cells can also, theoretically, be achieved in a colorimetric approach. The work demonstrated here thus offers new opportunities for the construction of functional DNA nanostructures and for the application of these DNA nanostructures as an effective signal amplification means in the sensitive detection of nucleic acid biomarkers.

Sensitive and selective colorimetric detection of Cu (II) in water samples by thiazolylazopyrimidine-functionalized TiO2 nanoparticles.

Gallotannin functionalized gold nanoparticles for rapid, selective and sensitive colorimetric detection of Ag+ in aqueous medium: Approach to eco-friendly water analysis

A universal platform for sensitive and selective colorimetric DNA detection based on Exo III assisted signal amplification

A simple colorimetric and paper-based-smartphone sensing platform based on the enhanced peroxidase-like activity of Al doping Prussian blue for point-of-care detection of GSH.