A turn-on fluorescent aptasensor for ampicillin detection based on gold nanoparticles and CdTe QDs

A fluorescence aptamer sensor utilizing WS2 nanosheets for sensitive detection of patulin: enhanced specificity and wide applicability

A tungsten disulfide (WS2) nanosheet-based aptamer sensor was developed to detect patulin (PAT). The 5'-end of the PAT aptamer was modified with a cyanine 3 (Cy3) fluorophore, which self-assembled on WS2 nanosheets. The interaction between the Cy3 fluorophore at the 5'-end of the PAT aptamer and the WS2 nanosheets resulted in reduced fluorescence (FL) intensity due to fluorescence resonance energy transfer (FRET). The introduction of PAT into this sensing system led to hybridization with the PAT aptamer, forming a G-quadruplex/PAT complex with low affinity for the WS2 nanosheet surface. This hybridization increased the distance between the Cy3 fluorophore and the WS2 nanosheets, inhibiting FRET and producing a strong FL signal. Under optimal experimental conditions, the FL intensity of the sensing system demonstrated an excellent linear correlation with PAT concentrations ranging from 0.5 to 40.0 ng mL-1, and it achieved a detection limit (S/N = 3) of 0.23 ng mL-1. This sensing system offers enhanced specificity for PAT detection and has the potential for broad application in detecting other toxins by substituting the sequence of the recognition aptamer.

Carbon-based nanozymes: design, catalytic mechanisms, and environmental applications

Carbon-based nanozymes are synthetic nanomaterials that are predominantly constituted of carbon-based materials, which mimic the catalytic properties of natural enzymes, boasting features such as tunable catalytic activity, robust regenerative capacity, and exceptional stability. Due to the impressive enzymatic performance similar to various enzymes such as peroxidase, superoxide dismutase, and oxidase, they are widely used for detecting and degrading pollutants in the environment. This paper presents an exhaustive review of the fundamental design principles, catalytic mechanisms, and prospective applications of carbon-based nanozymes in the environmental field. These studies not only serve to augment the comprehension on the intricate operational mechanism inherent in these synthetic nanostructures, but also provide essential guidelines and illuminating perspectives for advancing their development and practical applications. Future studies that are imperative to delve into the untapped potential of carbon-based nanozymes within the environmental domain was needed to be explored to fully harness their ability to deliver broader and more impactful environmental preservation and management outcomes.

Development of a highly sensitive ampicillin sensor utilizing functionalized aptamers

To develop a sensitive and simple ampicillin (AMP) sensor for trace antibiotic residue detection, the influencing factors of the modification effect of nanogold-functionalized nucleic acid sequences (Adenine: A, Thymine: T) were comprehensively analyzed in this study, including the modification method, base length and type. It was found that under the same base concentration, longer chains are more likely to reach saturation than shorter chains; and when the base concentration and length are both the same, A exhibits a higher saturation modification level compared to T. Based on these research findings, a highly sensitive fluorescence aptamer sensor for detecting ampicillin was constructed using the optimized functionalized sequence (ployA6-aptamer) and experimental conditions (6 hours binding time between nucleic acid aptamer and complementary strand, pH 7 working solution, 20 minutes detection time) based on the principle of fluorescence resonance energy transfer. The sensor has a detection range of 0.18 ng ml-1 to 3.11 ng ml-1 for ampicillin, with a detection limit of 0.04 ng ml-1. It exhibits significant selectivity and achieves an average recovery rate of 98.71% in tap water and 91.83% in milk. This method can be used not only for residual ampicillin detection, but also for highly sensitive detection of various antibiotics and small biological molecules by replacing the aptamer type. It provides a research basis for the design of highly sensitive fluorescence aptamer sensors and further applications of nanogold@DNA composite structures.

Signal-off nanozyme-based colorimetric aptasensor for sensitive detection of ampicillin using MnO2 nanoflowers and gold nanoparticles

The combination of nanomaterials possessing distinct characteristics and the precision of aptamers facilitates the creation of biosensors that exhibit exceptional selectivity and sensitivity. In this manuscript, we present a highly sensitive aptasensor that utilizes the distinctive characteristics of MnO2 nanoflowers and gold nanoparticles to selectively detect ampicillin (AMP). In this aptasensor, the mechanism of signal change is attributed to the difference in the oxidase-mimicking activity of MnO2 nanoflowers in the presence of a free sequence. The inclusion of AMP hindered the creation of a double-stranded DNA configuration through its binding to the aptamer, resulting in an observable alteration in absorbance. The relative absorbance varied linearly with the concentration of AMP in the range of 70 pM to 10 nM with a detection limit of 21.7 pM. In general, the colorimetric aptasensor that has been developed exhibits exceptional selectivity and remarkable stability. It also demonstrates favorable performance in human serum, making it a highly reliable diagnostic tool. Additionally, its versatility is noteworthy as it holds great potential for detecting various antibiotics present in complex samples by merely replacing the utilized sequences with new ones.

Recent Advances in Biomolecular Detection Based on Aptamers and Nanoparticles

The fast, accurate detection of biomolecules, ranging from nucleic acids and small molecules to proteins and cellular secretions, plays an essential role in various biomedical applications. These include disease diagnostics and prognostics, environmental monitoring, public health, and food safety. Aptamer recognition (DNA or RNA) has gained extensive attention for biomolecular detection due to its high selectivity, affinity, reproducibility, and robustness. Concurrently, biosensing with nanoparticles has been widely used for its high carrier capacity, stability and feasibility of incorporating optical and catalytic activity, and enhanced diffusivity. Biosensors based on aptamers and nanoparticles utilize the combination of their advantages and have become a promising technology for detecting of a wide variety of biomolecules with high sensitivity, reliability, specificity, and detection speed. Via various sensing mechanisms, target biomolecules have been quantified in terms of optical (e.g., colorimetric and fluorometric), magnetic, and electrical signals. In this review, we summarize the recent advances in and compare different aptamer-nanoparticle-based biosensors by nanoparticle types and detection mechanisms. We also share our views on the highlights and challenges of the different nanoparticle-aptamer-based biosensors.

Plasmonic quenching and enhancement: metal-quantum dot nanohybrids for fluorescence biosensing

Plasmonic metal nanoparticles and semiconductor quantum dots (QDs) are two of the most widely applied nanomaterials for optical biosensing and bioimaging. While their combination for fluorescence quenching via nanosurface energy transfer (NSET) or Förster resonance energy transfer (FRET) offers powerful ways of tuning and amplifying optical signals and is relatively common, metal-QD nanohybrids for plasmon-enhanced fluorescence (PEF) have been much less prevalent. A major reason is the competition between fluorescence quenching and enhancement, which poses important challenges for optimizing distances, orientations, and spectral overlap toward maximum PEF. In this feature article, we discuss the interplay of the different quenching and enhancement mechanisms (a mixed distance dependence of quenching and enhancement - "quenchancement") to better understand the obstacles that must be overcome for the development of metal-QD nanohybrid-based PEF biosensors. The different nanomaterials, their combination within various surface and solution based design concepts, and their structural and photophysical characterization are reviewed and applications toward advanced optical biosensing and bioimaging are presented along with guidelines and future perspectives for sensitive, selective, and versatile bioanalytical research and biomolecular diagnostics with metal-QD nanohybrids.

Optical Sensing of Toxic Cyanide Anions Using Noble Metal Nanomaterials

Water toxicity, one of the major concerns for ecosystems and the health of humanity, is usually attributed to inorganic anions-induced contamination. Particularly, cyanide ions are considered one of the most harmful elements required to be monitored in water. The need for cyanide sensing and monitoring has tempted the development of sensing technologies without highly sophisticated instruments or highly skilled operations for the objective of in-situ monitoring. Recent decades have witnessed the growth of noble metal nanomaterials-based sensors for detecting cyanide ions quantitatively as nanoscience and nanotechnologies advance to allow nanoscale-inherent physicochemical properties to be exploited for sensing performance. Particularly, noble metal nanostructure e-based optical sensors have permitted cyanide ions of nanomolar levels, or even lower, to be detectable. This capability lends itself to analytical application in the quantitative detection of harmful elements in environmental water samples. This review covers the noble metal nanomaterials-based sensors for cyanide ions detection developed in a variety of approaches, such as those based on colorimetry, fluorescence, Rayleigh scattering (RS), and surface-enhanced Raman scattering (SERS). Additionally, major challenges associated with these nano-platforms are also addressed, while future perspectives are given with directions towards resolving these issues.