Colorimetric detection of ciprofloxacin in aqueous solution based on an unmodified aptamer and the aggregation of gold nanoparticles

Graphene oxide mediated CdSe quantum dots fluorescent aptasensor for high sensitivity detection of fluoroquinolones

In view of the urgent need for fluoroquinolones contamination detection in the fields of food safety, a novel aptasensor based on the fluorescence quenching property of graphene oxide (GO) and the fluorescence characteristic of cadmium selenide quantum dots (CdSe QDs) was developed for fluoroquinolones highly sensitive detection in this work. The CdSe QDs with carboxyl-rich surface were synthesized successfully and fluoresced at 525 nm under the optimal excitation light of 366 nm. Based on the hydrophobic and π-π stacking between GO and aptamer, aptamer labeled by CdSe QDs fluorescence (CdSe QDs-apt) were adsorbed by GO and the fluorescence of CdSe QDs was quenched. After the aptamer combined specifically with fluoroquinolones, greater specific force lead to the desorption of CdSe QDs-apt from GO and fluorescence recovery. Represented by Ciprofloxacin (CIP), a member of fluoroquinolones, the fluorescence emission increased with the increasing of CIP concentrations from 8 nM to 500 nM, and the detection limit was 0.42 nM. The spiked recoveries in real samples of honey and milk were 91.5-96.9 % and 90.3-95.2 %, respectively, indicating that the aptasensor was reliable. Moreover, the fluorescence responses of multiple members of fluoroquinolones were found to be consistent, denoting that the fluorescence aptasensor can be used to detect the total amount of multiple members of fluoroquinolones. These results showed that the aptasensor can be used as a promising platform for fluoroquinolones detection.

Ratiometric fluorescence sensing of hazardous ciprofloxacin based on aggregation induced emission enhancement of thiolate-protected gold nanoclusters induced by La3+ ion

In this research work, ultrasensitive and reliable ratiometric sensor was designed for assay of ciprofloxacin (CIPRO). The platform consists of thiolate-protected gold nanoclusters (GSH@AuNCs) with high fluorescence quantum yield and long-term stability. In the existence of lanthanum (La3+) ion, the GSH@AuNCs emission was sharply raised owing to the formation of La3+/GSH@AuNCs system accompanied with aggregation-induced emission enhancement (AIEE). Addition of CIPRO, a good La3+ ion coordinator, decreased the fluorescence emission of La3+/GSH@AuNCs system at 610 nm significantly as a result of disaggregation caused by the removal of La3+ ion from GSH@AuNCs surface. Furthermore, the blue emission of La3+-CIPRO coordination complex appears at 440 nm. Under optimized conditions, the fluorescence ratios (F440/F610) were linearly increased with increasing the CIPRO amount within the range of 0.003-200 µM with a limit of detection equal to 0.2 nM (S/N = 3). The as-fabricated La3+/GSH@AuNCs system possesses outstanding reliability and sensitivity for the detection of CIPRO. The system was effectively used to assay CIPRO in human urine and milk specimens with recoveries % of 97.6-102.3 % and 96.7-105.7 % for urine and milk samples, respectively and RSD % did not exceed 2.5 %, suggesting the accuracy of the method.

Rapid and naked-eye colorimetric detection of ultra trace sumatriptan in drinking water, saliva, and human urine samples based on the aggregation of gold nanoparticles

In this study, the determination of sumatriptan (SUM) was performed using a simple, rapid, and precise colorimetric method based on the surface plasmon resonance (SPR) feature of gold nanoparticles (AuNPs). By adding SUM, the aggregation was observed in AuNPs with red-to-blue color shifts. The size distribution of NPs was estimated before and after adding SUM via dynamic light scattering (DLS), which was found to be 15.34 and 97.45 nm, respectively. Characterization of AuNPs, SUM, and AuNPs in combination with SUM was investigated using transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Examining the effect of pH, the volume of buffer, the concentration of AuNPs, interaction time, and ionic strength revealed that their optimal values were 6, 100 μL, 5 μM, 14 min, and 12 μg L-1, respectively. The suggested method was able to determine the amount of SUM in a linear range of 10 to 250 μg L-1 with a limit of detection (LOD) and limit of quantification (LOQ) of 0.392 and 1.03 μg L-1, respectively. This approach was successfully applied to determine SUM in drinking water, saliva, and human urine samples with relative standard deviations (RSD) lower than 0.03%, 0.3%, and 1.0%, respectively.

Development of Novel Peptide-Modified Silver Nanoparticle-Based Rapid Biosensors for Detecting Aminoglycoside Antibiotics

The detection and monitoring of aminoglycoside antibiotics (AGAs) have become of utmost importance due to their widespread use in human and animal therapy, as well as the associated risks of exposure, toxicity, and the emergence of antimicrobial resistance. In this study, we successfully synthesized casein hydrolysate peptides-functionalized silver nanoparticles (CHPs@AgNPs) and employed them as a novel colorimetric analytical platform to demonstrate remarkable specificity and sensitivity toward AGAs. The colorimetric and spectral response of the CHPs@AgNPs was observed at 405 and 520 nm, showing a linear correlation with the concentration of streptomycin, a representative AGA. The color changes from yellow to orange provided a visual indication of the analyte concentration, enabling quantitative determination for real-world samples. The AgNP assay exhibited excellent sensitivity with dynamic ranges of approximately 200-650 and 100-700 nM for streptomycin-spiked tap water and dairy whey with limits of detection found to be ∼98 and 56 nM, respectively. The mechanism behind the selective aggregation of CHPs@AgNPs in the presence of AGAs involves the amine groups of the target analytes acting as molecular bridges for electrostatic coupling with hydroxyl or carboxyl functionalities of adjacent NPs, driving the formation of stable NP aggregates. The developed assay offers several advantages, making it suitable for various practical applications. It is characterized by its simplicity, rapidity, specificity, sensitivity, and cost-effectiveness. These unique features make the method a promising tool for monitoring water quality, ensuring food safety, and dealing with emergent issues of antibiotic resistance.

AFB1 colorimetric aptamer sensor for the detection of AFB1 in ten different kinds of miscellaneous beans based on gold nanoparticles and smartphone imaging

A simple, rapid, low-cost, sensitive, intuitive, visual, label-free, colorimetric smartphone-assisted assay was developed for the measurement of aflatoxin B1 in miscellaneous beans. Ten different kinds of miscellaneous beans were treated and measured by modified QuEChERS(Quick、Easy、Cheap、Effective、Rugged、Safe) method with aflatoxin B1 nucleic acid aptamer as a recognition element and gold nanoparticles as indicators. Several factors influencing its sensitivity were investigated, including consumes and NaCl concentrations, as well as incubation time and specificity. The results showed a good linear relationship between concentrations of 0.2-8.0 ng/g under optimal conditions. With a detection limit of 0.08 ng/g, the linear regression equation was Y = 0.024X + 0.4615 (R = 0.9989). Sensor specificity is good. The content of aflatoxin B1 in bean samples was determined successfully. The recovery of aflatoxin B1 ranged from 87.18% to 110.24%. The whole thing took 15 min. This smartphone-assisted colorimetric aptamer sensor can be used to detect aflatoxin B1 in beans.

Gold Nanoparticles-Based Colorimetric Assays for Environmental Monitoring and Food Safety Evaluation

Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.

γ-Cyclodextrin-graphene quantum dots-chitosan modified screen-printed electrode for sensing of fluoroquinolones

An innovative electrochemical approach based on screen-printed carbon electrodes (SPCEs) modified with graphene quantum dots (GQDs) functionalized with γ-cyclodextrin (γ-CD) and assembled to chitosan (CHI) is designed for the assessment of the total content of fluoroquinolones (FQs) in animal source products. For the design of the bionanocomposite, carboxylated graphene quantum dots synthesized from uric acid as precursor were functionalized with γ-CD using succinic acid as a linker. Physic-chemical and nanostructural characterization of the ensuing nanoparticles was performed by high-resolution transmission scanning microscopy, dynamic light scattering, Z potential measurement, Fourier transformed infrared spectroscopy and X-ray diffraction. Electrochemical properties of assembled bionanocomposite like potential difference, kinetic electronic transfer constant and electroactive area among other parameters were assessed by cyclic voltammetry and differential pulse voltammetry using potassium ferricyanide as redox probe. The oxidation behaviour of four representative quinolones with distinctive structures was studied, obtaining in all cases the same number of involved e^- (2) and H⁺ (2) in their oxidation. These results led us to propose a single and consistent oxidation mechanism for all the checked analytes. The γ-CD-GQDs-CHI/SPCE sensor displayed a boosted electroanalytical performance in terms of linear range (4-250 µM), sensibility (LOD = 1.2 µM) and selectivity. This electrochemical strategy allowed the determination of FQs total amount in complex processed food like broths, bouillon cubes and milkshakes at three concentration levels (150, 75 and 37.5 µM) for both equimolar and different ratio FQs mixtures with recovery values ranging from 90 to 106%.

An enhanced fluorescent probe through the strategy of using MgWO4 nanosheets to enhance terbium ion luminescence for highly sensitive and point-of-care visual quantitative testing of ciprofloxacin integrated with a low-cost smartphone-based platform

In this work, MgWO₄ nanosheets have been successfully synthesized by a simple hydrothermal method, and the morphology and composition of the MgWO₄ nanosheets are characterized by SEM, TEM, XPS, and UV-vis. The results show that the as-prepared MgWO₄ nanosheets have a triclinic symmetry phase and an obvious two-dimensional layered structure. Studies have shown that the MgWO₄ semiconductor nanosheets can adjust the energy level, which significantly enhances the visible light absorption and the separation and transfer of photogenerated electrons, which facilitates the generation of photogenerated electrons. We use this feature to boost a terbium ion (Tb³⁺)-ciprofloxacin (CIP) system to enhance the luminescence, so as to achieve highly sensitive detection of CIP. The mechanism of Tb³⁺-MgWO₄ for CIP detection is the effective energy transfer from WO₄^2- in MgWO₄ nanosheets to Tb³⁺-CIP, thereby enhancing the characteristic emission of Tb³⁺ and enhancing the sensitivity of CIP detection. The linear response of the Tb³⁺-MgWO₄ enhanced fluorescent probe is in the range from 10 nM to 20 μM, and the detection limit (LOD) is 2 nM. In addition, we tested the recovery in spiked river water and mouse serum. Experiments have shown that the recovery of spiked samples is 97-102.2%, while the relative standard deviation (RSD) is less than 5.53%. The possible interfering substances in environmental samples will not interfere with the detection of CIP with the Tb³⁺-MgWO₄ enhanced fluorescent probe. At the same time, the development of a smartphone-based portable device provides the possibility of CIP on-site detection. Our work provides a simple, fast, highly sensitive and stable method for detecting CIP in living organisms and the environment. Importantly, the strategy of MgWO₄ nanosheet boosted terbium ion luminescence expands the application range of semiconductor nanomaterials.