Analytical Methods最新文献

The detection of anions using carbon dots (CDs) has received less attention compared to cations. Therefore, the present study aimed to develop a fluorescence sensor based on carbon dots (CDs) capable of detecting S²⁻ in real water samples. The CDs were successfully prepared from the residues of a traditional Chinese herb, Gardenia, which emitted green photoluminescence (PL) under ultraviolet light irradiation. The as-prepared CDs were quasi-spherical in shape and ranged in size from 10 to 30 nm. Different detailed analyses proved that the CDs had good morphology, various functional groups, high water solubility, great optical features, and excellent stability under diverse environmental conditions. The ion detection showed that only Ag⁺ had the strongest fluorescence quenching effect on the CDs, however, the addition of S²⁻ could recover their fluorescence. Based on these results, an “off–on” fluorescence sensor was achieved to selectively detect the concentration of S²⁻ in real water samples with a limit of detection (LOD) of 39 μM, which further expanded the application of residues from traditional Chinese herbal medicine.

We present a sensitive and selective lateral flow immunoassay (LFIA) for cotinine (COT), the primary metabolite of nicotine. COT is widely recognized as a superior biomarker to evaluate tobacco smoke exposure. The LFIA uses a competitive assay format where the COT–BSA capture competes with the target COT in urine samples for binding to the monoclonal antibody against COT (mAb–COT) conjugated with gold nanoparticles (mAb–COT–AuNPs). To improve the sensitivity and selectivity of the LFIA-COT, we focused on optimizing the diameter of AuNPs, the conjugation of mAb–COT, and the concentration of the COT–BSA capture. Our findings reveal that the utilization of 40 nm AuNPs in conjugation with a concentration of 4 mg mL⁻¹ of mAb–COT demonstrated significantly greater efficacy compared to LFAs utilizing 20 nm AuNPs. Under the optimal conditions, the LFIA-COT demonstrated sensitive detection of COT at a level of 150 ng mL⁻¹ within 15 min, as observed by the naked eye. It possesses a linear range of 25 to 200 ng mL⁻¹ of COT, with the limit of detection (LOD) of 11.94 ng mL⁻¹ in human urine samples when the color intensity is analyzed using ImageJ software. Our LFIA described here is simple and requires less time for COT detection. It can be used for the rapid and quantitative detection of COT in urine samples in clinical settings.

Sensitive and accurate determination of glyphosate (GLYP) is vital for food safety and environmental protection. Herein, a novel electrochemical ratiometric biosensor was designed for the accurate quantification of GLYP through one-step electrodeposition of MWCNTs-Cu MOF films. MWCNTs-Cu MOF nanostructures were directly electro-synthesized in situ on the electrode from the precursor solution. The combination of Cu MOFs with MWCNTs not merely improved the conductivity of MOFs, but also enhanced the sensitivity of the biosensor. Furthermore, Cu sites within Cu MOFs were turned into CuCl to further amplify the current signal and enable the specific recognition of GLYP through competing reactions with the transformation of CuCl into non-electroactive Cu-GLYP. Meanwhile, internal reference molecules of methylene blue (MB) were incorporated to improve the measurement accuracy of GLYP for reducing unpredictable measurement errors aroused by environmental deviations. The ratiometric electrochemical sensor exhibited a high linearity with the logarithmic value of GLYP concentration from 0.5 nM to 400 nM. The detection limit was estimated to be as low as 0.014 nM. Finally, the present sensor with ratiometric signal export was applied for GLYP analysis in real samples with high sensitivity and accuracy. The simplicity and reliability of the ratiometric sensor make it a worthy and powerful tool for food and environmental monitoring. This design strategy also provides an avenue for the development of simple and efficient biosensors for other substances.

Melanoma inhibitory activity protein (MIA) does obviously offer the potential to reveal clinical manifestations of melanoma. Despite a pressing need for effective diagnosis of this highly fatal disease, there are no clinically approved MIA detection ELISA kits available. A recommended MIA threshold has not yet been defined, mostly by reason of variability in immunoglobulins' affinity and stability, the difference in sample preparation and assay conditions. Here we present a pair of high-affinity DNA aptamers developed as an alternative recognition and binding element for MIA detection. Their stability and reproducible synthesis are expected to ensure this analysis under standard conditions. The devised aptamer-based solid-phase microassay of model standard and control human sera involves luciferase NLuc as a highly sensitive reporter. Bioluminescence dependence on MIA concentration ranges in a linear manner from 2.5 to 250 ng mL⁻¹, providing a MIA detection limit of 1.67 ± 0.57 ng mL⁻¹.