Rapid and accurate quantification of amphetamine and methamphetamine in human urine by antibody decorated magnetite nanoparticles coupled with matrix-assisted laser desorption ionization time-of-flight mass spectrometer analysis

Enzyme-aided amplification strategy for sensitive detection of methamphetamine based on fluorescence aptamer sensor

Methamphetamine (METH) abuse poses a serious risk to human health and social stability. It is critical to develop sensitive and selective methods for detecting METH. Here, we develop a fluorescence aptamer sensor to detect METH based on DNA exonuclease III (Exo III), graphene oxide (GO), and FAM-labeled aptamer. First, the sensor used GO's strong binding capacity to adsorb and quench the fluorescence of the aptamer attached to GO surface. When METH was added to the system, the formation of stable complex for aptamer and METH dissociated from the surface of GO, leading to a fluorescence restoration. Then, the fluorescence signal was further amplified by using Exo III to liberate target METH for cyclic hybridization. And the gel electrophoresis experiment further verified the reliability of this strategy. This aptamer sensor exhibited a low detection limit (0.52 nM) and excellent selectivity under optimal conditions. Notably, this sensor has been successfully validated in the detection of METH in urine and saliva samples, exhibited commendable recovery (94.00-104.65%). Its benefits include facile, sensitive, and rapid. Expected to be used in practical METH detection.

Single drop analysis of mercury ions by rational design of peptide coated gold nanoparticles integrated with MALDI-MS measurement

In this study, a novel and rapid method for specific identification and accurate quantification of Hg²⁺ in environmental water was developed by using laser cleavable cysteine containing peptides modified gold nanoparticles coupled with high resolution matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF MS) measurement. First, gold nanoparticles were prepared by the reduction of tetrachloroauric (III) acid (HAuCl₄) solution. Various cysteine containing peptides, photolabile linkers, including mercury ion binding motif with a proper molecular mass and amino acids were synthesized by solid phase peptide synthesis (SPPS). Subsequently, thiol-containing peptides were coated onto the surface of gold nanoparticles via the formation of gold-thiol (Au-S) bond. The resulting cysteine containing peptides modified gold nanoparticles were designed to specifically capture Hg²⁺ in water samples. After conjugated complex formation, ions of Hg²⁺-peptide complex were directly liberated by ultraviolet laser radiation by way of MALDI-MS using α-Cyano-4-hydroxycinnamic acid (CHCA) as matrix. The linear dynamic range of Hg²⁺ concentration in this study was 1-100 pmol/μL with coefficient of determination 0.9987. The limit of detection (LOD) and limit of quantification (LOQ) were 0.19 and 0.63 pmol/μL, respectively. Notably, the developed method allows rapid quantification of Hg²⁺ in 5 min and the desired sample volume was down to few μL.

Enrichment of boron element in follicular fluid and its potential effect on the immune function

The blood-follicle barrier (BFB) between the blood and follicular fluid (FF) can maintain the microenvironment balance of oocyte. Boron, an exogenous environmental trace element, has been found to possibly play an important role in oocyte maturation. This study aimed to examine the distribution characteristics of boron across the BFB and find the potential effect of boron on FF microenvironment. We analyzed the concentration of boron in paired FF and serum collected from 168 women undergoing in vitro fertilization and embryo transfer in Beijing City and Shandong Province, China. To explore the potential health impact of boron enrichment in oocyte maturation, a global proteomics analysis was conducted to tentatively correlate the protein levels with the boron enrichment. Interestingly, the results showed that the concentration of boron in FF (34.5 ng/mL) was significantly higher than that in serum (22.0 ng/mL), with a median concentration ratio of 1.52. Likewise, the concentrations of boron in FF and serum were positively correlated (r = 0.446), suggesting that boron concentration in serum can represent its concentration in follicular fluid to a large extent.. This is the first time to observe the enrichment of boron in the FF to our knowledge. It is interesting to observe a total of 13 proteins, which mainly belong to immunoglobulin class, were positively correlated with boron concentration in FF. We concluded that boron, as one environmental trace element, was enriched in FF from blood validated by two area in north china, which may be involved in an increased level of immune processes of immunoglobulins.

Application of Carbonic Nanosheets Based on Urea Precursors as Dispersive Solid Phase Extraction Adsorbent for Extraction of Methamphetamine from Urine Samples

Purpose: This paper established the application of synthesized graphitic carbon nitride nanosheets (GCNNs) as an influential dispersive solid phase extraction (DSPE) adsorbent in extracting methamphetamine from complicated urine media coupled with high performance liquid chromatography.

Methods: The graphitic carbon nitride nanosheets (GCNNs) was synthesized easily and applied as adsorbent in the extraction process. The effective extraction parameters were investigated by one-parameter-at-a-time. Under optimized conditions the method was validated.

Results: The calibration curve was plotted in the concentration range of 50-1500 ng/mL through the optimized conditions and the proposed method was validated. The method was used for the analysis of positive urine samples and showed satisfactory results with the average 99.7% relative recovery.

Conclusion: The results persuade the capability of this novel method in analyzing of the positive urine samples in diverse clinical and forensic laboratories.

Rapid analysis of ketamine with in-house antibody conjugated boronic acid modified silver chip on MALDI-TOF MS measurement

An antibody conjugated boronic acid modified silver chip (ABAS ship) is fabricated as a simple, rapid, accurate, sensitive and cost-effective sample preparation method for abused drug quantification in human urine. Ketamine, one common abused drug, was applied as proof of concept for ABAS chip with high resolution matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF MS) analysis. The overall testing process required 10 min at part per billion (ppb) sensitivity level, where current drug testing method necessitated several hours with similar sensitivity. The ABAS chip manufacture process started with slide glass by way of silver mirror reaction to form silver conductive glass for further chemical conjugation. Boronic acid functional group was decorated on silver conductive glass through the formation of silver-thiol (Ag-S) bond. Anti-ketamine antibody was covalently conjugated to boronic acid modified silver conductive glass through the formation of cyclic boronate ester between the boronic acid and the cis-diol groups on the glycans of antibody, which maintain the correct orientation to maximally capture its antigen. The resulting ABAS chip were designed to specifically capture ketamine in human urine samples, that could be directly analyzed by addition of MALDI α-Cyano-4-hydroxycinnamic acid (CHCA) matrix solution. The linear dynamic range of concentration in this method was 10-500 ng/mL with coefficient of determination 0.996. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0 and 7.0 ng/mL, respectively. Importantly, the proposed method allows rapid and accurate quantification of ketamine from suspects' urine samples in 10 min and small sample volume of 1 μL was required. The resulting data were consistent with traditional gas chromatography-mass spectrometry (GC-MS) analysis. Our homemade ABAS chip could thus provide a powerful tool not only for forensic science but also for most clinical diagnosis of disease as many expression antibodies for the occurrence of diverse diseases could be simply produced and purchased.

Effects of different quantities of antibody conjugated with magnetic nanoparticles on cell separation efficiency

Antibody-conjugated magnetic nanoparticles (Ab-MNPs) have received considerable attention in bioseparation and clinical diagnostics assays due to their unique ability to detect and isolate a variety of biomolecules and cells. Because antibodies can be expensive, a key challenge for bioconjugation is to determine the optimal amount of antibodies with reasonable antigen-capturing activity. We designed an approach to determine the minimum amounts of antibodies for efficient coating. Different quantities of Herceptin (anti-human epidermal growth factor receptor 2: HER2) antibody were applied and immobilized on the surface of MNPs. Antibody binding was then checked by using an anti-human antibody conjugated with fluorochrome and flow cytometry. When the ratio of MNPs to antibodies increased from 0.79 to 795.45, mean fluorescence intensity (MFI) of conjugated MNPs decreased markedly from 185.56 to 20.07, indicating lower surface antibody coverage. We then investigated the relation between antibody content and isolation efficiency. Three Ab-MNP samples with different MFI were used to isolate SK-BR-3, a HER2-positive breast cancer cell line, from mixtures of whole blood or mononuclear cells. After isolation in a magnetic field, separation efficiency was evaluated by fluorescence microscopy and flow cytometry-based techniques. Our results collectively showed that the amount of anti-HER2 antibodies for conjugation with MNPs could be decreased by as much as one-fifteenth without compromising isolation efficiency, which in turn can reduce the cost of immunoassay biosensors.