Development of a new synchronous fluorescence spectrometry combined with Al3+ sensitized for simultaneous and rapid determination of trace flumequine, ciprofloxacin and doxycycline hydrochloride residues in wastewater.

Antibiotics are a new type of environmental pollutants. Due to its wide application in many fields, antibiotic residues are ubiquitous in the wastewater environments. Given their potential threat on water ecosystem functioning and public health, the detection of antibiotic residues in wastewater environments has become very necessary. Based on the complexation of Al3+ with flumequine (FLU), ciprofloxacin (CIP) and doxycycline hydrochloride (DOX), their molecular conjugated area were increased and fluorescence intensity were enhanced, combined with synchronous fluorescence spectrometry (SFS) had good selectivity and high sensitivity, a novel method of Al3+ sensitized synchronous fluorescence spectrometry for the determination of FLU, CIP and DOX residues in wastewater was established. When the wavelength difference (Δλ) was selected 115.0 nm, synchronous fluorescence spectra of the three antibiotics could be well separated and the interference of wastewater matrix were eliminated primely. The new SFS made good use of spectral separation instead of conventional chemical separation, and the actual wastewater sample could be directly determined after simple filtration. The experiment results showed that the concentrations of FLU, CIP and DOX in the range of 0.5000-800.0 ng·mL-1, 0.5000-640.0 ng·mL-1 and 10.00-3500 ng·mL-1 had a good linear relationship with fluorescence intensity. The detection limits of three antibiotics were 0.02054 ng·mL-1, 0.03956 ng·mL-1 and 0.8524 ng·mL-1, respectively. Recovery rates of three antibiotics in wastewater samples were 90.72%-98.23%, 88.68%-95.08% and 85.94%-96.70%. The new SFS established in this experiment had the advantages of simple, rapid, sensitive, accurate and good selectivity. Simultaneous and rapid detection of FLU, CIP and DOX residues in wastewater was successfully realized. It had good application prospects in real-time water quality monitoring.

Facile and green chemistry-compatible fluorescence spectroscopic applications of acid red 87 used to evaluate eletriptan, antimigraine, in its pharmaceutical and biological samples.

Eletriptan (ETR), a selective pharmaceutical agent agonist of the 5-hydroxytryptamine1 receptor subtype, are primarily used to treat acute migraine attacks. ETR is a triptan-class medication that works by narrowing cerebral blood vessels and reducing chemicals that produce headache pain, light and sound sensitivity, and nausea. Due to its effectiveness in reducing migraine symptoms, it is a worthwhile choice for those looking for quick and efficient treatment. A green, raid, one-pot and straightforward fluorescence spectrometric method was employed to evaluate ETR in tablets and biological samples. By introducing the ETR drug and the fluorescent ligand, Acid red 87, in an acidic buffer, a quenching of the ligand native fluorescent was promptly produced. The quenching action was simply attributed to the selective ion-pair complex generation between the cationic target and the selected ligand. An increase in ETR concentration was linearly proportional to the quenching response in the 50.0 - 500.0 ng/mL range. The optimal configurations for adjusting the system's variable parameters were determined by examining the ETR-Acid red 87 system's response. Additionally, the sensor that was developed met the standards set by the International Council for Harmonisation of Technical Requirements of Pharmaceuticals for Human Use. The sensitivity thresholds of the approach were 13.8 and 42.0 ng/mL for the detection and quantification parameters, respectively, LOD and LOQ. This approach proficiently evaluated the pharmaceutical and biological samples of ETR. Finally, the proposed approach not only simplifies the analysis process but also limits the badimpact on the environment, making it a promising technique for analytical applications.

Influence of fluoride characteristics on tooth surface protection in an erosive condition: A multifaceted characterization approach.

OBJECTIVE: To evaluate the effect of fluoride consistency and composition to protect enamel and dentin against the dental erosion. MATERIALS AND METHODS: Bovine enamel and dentin specimens were treated with artificial saliva, neutral fluoride gel (NFG), acidulated phosphate fluoride gel (AFG), neutral fluoride foam (NFF), and acidulated phosphate fluoride foam. The samples were subjected to cycling. Micro energy-dispersive X-ray fluorescence spectrometry, surface roughness (Ra), contact angle (CA), and scanning electron microscopy (SEM) were performed. Composition, CA and Ra data were analyzed by ANOVA and multiple comparison test (p < 0.05). RESULTS: The dentin protected had a significantly higher mineral content than in the control. Eroded unprotected enamel had higher Ra values than normal surfaces. Fluoride treatments increased the Ra in dentin samples. AFG increased the CA in enamel. Fluoride foams increased CA in dentin with reduced mineral loss. SEM analysis found a deposited layer on enamel treated with AFG and remnants of deposits on dentin treated with NFG and NFF. CONCLUSION: Regardless of the form of application, fluoride provided protection against erosion, however with different levels. CLINICAL SIGNIFICANCE: Applying the adequate fluoride form is relevant since the formulations have different effects on both enamel and dentin.

High enrichment and sensitive measurement of oxytetracycline in tea drinks by thermosensitive magnetic molecular imprinting based magnetic solid phase extraction coupled with boron doped carbon dots.

As a typical kind of new pollutants, there are still some challenges in the rapid detection of antibiotics. In this work, a sensitive fluorescent probe based on boron-doped carbon dots (B-CDs) in combination with thermo-responsive magnetic molecularly imprinted polymers (T-MMIPs) was constructed for the detection of oxytetracycline (OTC) in tea drinks. T-MMIPs were designed, fabricated and employed to enrich OTC at trace level from tea drinks, and B-CDs were utilized as the fluorescent probe to detect the concentration of OTC. The proposed method exhibited good linear relationship with OTC concentration from 0.2 to 60 µg L-1 and the limit of detection was 0.1 µg L-1. The established method has been successfully validated with tea beverages. Present work was the first attempt application of T-MMIPs in combination with CDs in detection of OTC, and demonstrated that the proposed method endowed the detection of OTC with high selectivity, sensitivity, reliability and wide application prospect, meanwhile offered a new strategy for the method establishment of rapid and sensitive detection of trace antibiotics in food and other matrices.

Itemized determination of As, Sb, Bi, Se, and Ge in graphite sample by HG-AFS with high-temperature microwave digestion.

In this paper, we optimized a method for fast and accurate determination of five impurity elements (As, Sb, Bi, Se, and Ge) in graphite samples to overcome the shortcomings of existing methods, such as complicated equipment, cumbersome process, multiple-time preparation, separate determination, and large error in results. Graphite samples were digested with HNO3-H2SO4-HClO4-HF in a high-temperature and high-pressure microwave digestion apparatus, and the elements were extracted and determined separately by AFS (atomic fluorescence spectrometry). There is no element loss during the processing and analysis of this method. The spike recoveries (As: 90.30%-102.3%, Sb: 90.73%-110.0%, Bi: 90.00%-99.67%, Se: 93.33%-110.0%, Ge: 92.26%-104.2%) and precision (RSD%; As: 1.34%-8.96%, Sb: 2.67%-7.10%, Bi: 1.83%-4.58%, Se: 0.36%-3.25%, Ge: 4.41%-8.65%) meet the requirements of the corresponding quality specifications. The method has some advantages (such as no elemental loss, fast testing, strong element targeting, and accurate results), and thus can achieve batch determination of graphite samples. The optimized method for graphite sample and final solution preparations can be used for diverse spectrometric technologies, and that for spectrometer conditions have reference value for HG-AFS instruments.

Imaging metabolic mechanisms and the binding behavior of nutrients/transporters of edible Matricaria flowers VOCs.

To promote the consumption of flowers and to utilize the nutritional value of proteins, the efficacy of the beneficial components of flowers has been intensively studied. Anthemis nobilis was used as the study object, and all its volatile components (VOCs) were fingerprinted using headspace solid-phase micro-extraction gas-mass spectrometry (HS-SPME/GC-MS). GC-MS fingerprints of five parts of Anthemis nobilis were established using three proteins, bovine lactoferrin (BLF), bovine lactoglobulin (ß-Lg), and human serum albumin (HSA), as nutrient transporters. The interactions between the volatile components from different parts of the mother chrysanthemum plant and the nutrient/transport proteins were investigated. The results of fingerprinting showed that the flavor components were dominated by alkenes. In addition, this study revealed that among the three nutrient transporters, the strongest binding to the adsorbed volatile components was HSA, followed by BLF, and ß-Lg was second. In addition, a characteristic molecule, camphene, was screened. Integrated molecular simulation using fluorescence spectroscopy was used to validate the results of the interaction of the nutrient/transport proteins systems with characteristic molecule. The properties of the characteristic molecules such as absorption, distribution, metabolism, excretion and toxicity in vivo were analyzed using ADMET to provide a theoretical basis for the preparation of flower-flavored dairy products.

Green Emissive Molybdenum Nanoclusters for Selective and Sensitive Detection of Hydroxyl Radical in Water Samples.

In this work, Cassia tora (C. tora) have been used as a template to synthesize green fluorescent C. tora molybdenum nanoclusters (C. tora-MoNCs) through a green chemistry approach. These C. tora-MoNCs showed a quantum yield (QY) of 7.72% and exhibited a significant emission peak at 498 nm when excited at 380 nm. The as-prepared C. tora-MoNCs had an average size of 3.48 ± 0.80 nm and showed different surface functionality. The as-synthesized C. tora-MoNCs were successfully identified the hydroxyl radical (•OH) via a fluorescence quenching mechanism. Also, fluorescence lifetime and Stern-Volmer proved that after the addition of •OH radicals it was quenched the fluorescence intensity via a static quenching mechanism. The limit of detection is 9.13 nM, and this approach was successfully utilized for sensing •OH radicals in water samples with a good recovery rate.

A novel synchronous fluorescence spectrometry combined with fluorescence sensitization for the highly sensitive and simultaneous detection of enoxacin, ofloxacin and tetracycline hydrochloride residues in wastewater.

The synergistic effect of sodium dodecyl sulfate (SDS) and Mg2+ could significantly enhance the fluorescence intensity of enoxacin (ENO) at λex/λem = 269.2 nm/385.6 nm, ofloxacin (OFL) at λex/λem = 290.8 nm/466.2 nm and tetracycline hydrochloride (TCH) at λex/λem = 372.6 nm/514.8 nm. Moreover, when the wavelength difference (Δλ) was chosen 135 nm, the synchronous fluorescence spectra of the three antibiotic complexes could be well separated and the interference of the samples matrix were eliminated primely. Therefore, only one synchronous fluorescence scan was needed to simultaneously determine the three antibiotics. Based on these facts, a synchronous fluorescence spectrometry combining fluorescence sensitization for highly sensitive and selective determination of ENO, OFL and TCH residues in wastewater was developed for the first time. The experimental results showed that the concentrations of ENO, OFL and TCH in the range of 0.5-550 ng mL-1, 1-1500 ng mL-1 and 10-5500 ng mL-1 showed a good linear relationship with fluorescence intensity. The limits of detection were 0.0599 ng mL-1, 0.115 ng mL-1 and 0.151 ng mL-1, respectively. The recoveries of the actual sample were 87.50%-99.99 %, 93.00%-98.50 % and 85.70%-98.42 %, respectively. Overall, the novel synchronous fluorescence spectrometry established in the experiment has the advantages of high sensitivity, good selectivity, fast detection speed and high accuracy. It has been successfully applied to the detection of residual amounts of ENO, OFL and TCH in wastewater with satisfactory results.

Probing binding mode between sodium acid pyrophosphate and albumin: multi-spectroscopic and molecular docking analysis.

Sodium acid pyrophosphate (SAPP) food additive is widely used as a preservative, bulking agent, chelating agent, emulsifier and pH regulator. It is also used as an improver of color and water retention capacity in the processing of various types of seafood, canned food, cooked meat and flour products. For the first time, we evaluated the SAPP interaction with bovine serum albumin (BSA) using spectroscopic methods including UV-Vis absorption, fluorescence spectroscopy, and surface plasmon resonance, and docking analysis to understand the mechanisms of complex formation and binding. The fluorescence intensity of BSA reduces when titrated with various concentrations of SAPP by forming a complex with BSA via a static quenching mechanism. The binding constant between BSA and SAPP decreased from 123,300 to 15,800 (M-1) with rising temperature, which indicates a decrement in complex formation owing to the interaction of SAPP with BSA. A negative ΔG° value means that SAPP binds spontaneously to BSA at all temperatures, and both ΔH° and ΔS° negative values indicate that hydrogen bonds (H-bonding) and van der Waals forces are the primary forces involved in the binding processes. The UV-Vis spectrum of BSA reduced upon increasing SAPP concentrations due to forming a new ground state complex between SAPP and BSA. Molecular docking study shows that residues Arg256, Ser259, Ser286, Ile 289 and Ala 290 play an important role in SAPP binding process to site I (subdomain IIA) of BSA through H-bonding and van der Waals forces, which is supported by the thermodynamic study.Communicated by Ramaswamy H. Sarma.

3-aminophenylboronic acid modified carbon nitride quantum dots as fluorescent probe for selective detection of dopamine and cell imaging.

Dopamine (DA) is the most abundant catecholamine neurotransmitter in the brain and plays an extremely essential role in the physiological activities of the living organism. There is a critical need for accurately and efficiently detecting DA levels in organisms in order to reflect physiological states. Carbon nitride quantum dots (C3N4) were, in recent years, used enormously as electrochemical and fluorescence probes for the detection of metal ions, biomarkers and other environmental or food impurities due to their unique advantageous optical and electronic properties. 3-Aminophenylboronic acid (3-APBA) can specifically combine with DA through an aggregation effect, providing an effective DA detection method. In this work, 3-APBA modified carbon nitride quantum dots (3-APBA-CNQDs) were synthesized from urea and sodium citrate. The structure, chemical composition and optical properties of 3-APBA-CNQDs were investigated by XRD, TEM, UV-visible, and FT-IR spectroscopy. The addition of DA could induce fluorescence quenching of 3-APBA-CNQDs possibly through the inner filter effect (IFE). 3-APBA-CNQDs shows better selectivity and sensitivity to DA than other interfering substances. By optimizing the experiment conditions, good linearity was obtained at 0.10-51µM DA with a low detection limit of 22.08 nM. More importantly, 3-APBA-CNQDs have been successfully applied for the detection of DA in human urine and blood samples as well as for bioimaging of intracellular DA. This study provides a promising novel method for the rapid detection of DA in real biological samples.

A pathological lesion or a postmortem artefact? An interdisciplinary approach to deal with an interesting early medieval case.

OBJECTIVE: This study evaluates a case of pseudopathology and the effects that postmortem taphonomic changes and environmental influences can have on bone. MATERIAL: A skeleton of a young male from the early medieval site Staré Mesto, dated to the 9th-10th century CE. METHODS: The skeletal remains were subjected to detailed macroscopic and X-ray examination, and then a CT scan and XRF analysis were performed. RESULTS: X-ray examination of the mandible revealed unusually dense structures, whose appearance was not consistent with any known pathology. Based on the results of CT scanning, it was hypothesized that these were cavities filled with alluvial sediment. X-ray fluorescence spectrometry (XRF), focusing on the determination of the silica content, revealed a high intensity of silica in the samples of the affected area of the bone. CONCLUSION: The hypothesis that the inclusions were composed of waterborne sediment was supported. SIGNIFICANCE: Although it is well known that soil can infiltrate bones buried in the ground, its appearance on plain radiographs is not that commonly known. The case illustrates the usefulness of differentiating true pathologies from postmortem alterations to avoid inappropriate interpretations. LIMITATIONS: No similar cases have been described. SUGGESTION FOR FURTHER RESEARCH: In palaeopathological evaluation, the use of multiple imaging and evaluative techniques should be implemented to differentiate pathological lesions from pseudopathology.

Evaluation of Monochromatic Excitation X-ray Fluorescence Spectrometry for Rapid Thallium Detection in Biological Samples Using Animal Models.

Monochromatic excitation X-ray fluorescence (ME-XRF) spectrometry is a novel technique for trace element analysis, characterized by its simplicity, rapidity, and low cost. The objective of this study was to evaluate the applicability of ME-XRF technique for the measurement of thallium in biological samples. Acute and subacute thallium poisoning experiments were conducted to simulate various scenarios, with blood, urine, and 10 distinct organs collected. Detection was initially performed using ME-XRF technique, followed by validation with inductively coupled plasma mass spectrometry (ICP-MS). Excellent agreement between ME-XRF and ICP-MS values was demonstrated by means of paired sample t-tests and intraclass correlation coefficients. Subsequently, the practical implementation of the proposed technique was demonstrated through an actual case study. In conclusion, this study validates ME-XRF as a suitable alternative to ICP-MS for the measurement of trace heavy metals in biological samples. These efforts promote the development of simpler and faster techniques for heavy metal detection, thereby presenting novel avenues for the prevention and diagnosis of heavy metal poisoning.

Study on the Interactions Between Cisplatin and Cadherin by Fluorescence Spectrometry and Atomic Force Microscopy.

Cisplatin is an important platinum drug in cancer chemotherapy in clinical practice. It is well established that the main target of cisplatin is nuclear DNA. However, recent studies have demonstrated that platinum drugs may act on some important functional proteins in the human body. E-cadherin is a newly discovered glycoprotein that has been regarded as an important sign of the occurrence and development of some tumors. This study examines the interactions between cisplatin and E-cadherin by fluorescence spectrometry and atomic force microscopy (AFM). The fluorescence spectrometry results indicated that cisplatin can efficiently quench the fluorescence of E-cadherin. The calculated binding constant Kb was 3.20 × 106 (25 ℃), 1.36 × 106(31 ℃), and 8.22 × 105 L mol-1 (37 ℃). These results reveal that the fluorescence quenching effect of cisplatin on E-cadherin is static quenching. The obtained thermodynamic parameters ΔH < 0, ΔS < 0, and ΔG < 0, indicate that the binding of cisplatin on E-cadherin is a spontaneous process dominated by hydrogen bonds and Van der Waals forces. The AFM results revealed that E-cadherins are interlaced with each other to form a spherical-chain structure. The addition of cisplatin can significantly disrupt the interlaced structure of the E-cadherin molecules.

Synthesis of copper nanoclusters from Bacopa monnieri leaves for fluorescence sensing of dichlorvos.

In this work, a facile one-step green synthesis was developed for the fabrication of blue fluorescent copper nanocluster (Brahmi-CuNCs) from the extract of Bacopa monnieri (common name is Brahmi) via a microwave method. The as-prepared Brahmi-CuNCs emitted blue fluorescence at 452 nm when excited at 352 nm and showed a quantum yield of 31.32%. Brahmi-derived blue fluorescent CuNCs acted as a probe for fluorescence sensing of dichlorvos. Upon the addition of dichlorvos, the blue emission for Brahmi-CuNCs was gradually turned off, favouring establishment of a calibration graph in the range 0.5-100 µM with a detection limit of 0.23 µM. The as-synthesized Brahmi-CuNCs exhibited marked sensitivity and selectivity towards dichlorvos, favourable for assaying dichlorvos in various samples (cabbage, apple juice, and rice).

Paper-based sensor based on lead-free manganese halide for the determination of water content in organic solvents.

A highly stable and luminescent lead-free manganese(II) halide hybrid MnBr4(TMN)2 (C34H42Br4MnN4) was designed and synthesized by introducing a large cationic organic spacer. The MnBr4(TMN)2 displays high luminescence with quantum yields up to 77% and possesses turn-off fluorescence behavior (Ex/Em=365/546 nm) for water. These properties make the MnBr4(TMN)2 a promising candidate as an alternative indicator for the detection of water with potential applications for the fabrication of LEDs. Herein, a paper-based sensor based on MnBr4(TMN)2 is described for the determination of water content in organic solvents. The mechanism of water sensing can be tentatively explained by fluorescence quenching originating from the destruction of water due to the Mn-Br bonds of MnBr4(TMN)2. The MnBr4(TMN)2-based paper sensor exhibits an excellent discrimination ability of water content in the range 0-25.0% with a detection limit of 0.27%. Satisfactory recoveries (94.91±4.09% to 103.23±2.38%) are obtained in spiked ethanol solvent samples, which demonstrate that the MnBr4(TMN)2-based paper sensor is capable of detecting water content in real ethanol solvent samples.

Highly selective and sensitive determination of doxycycline integrating enrichment with thermosensitive magnetic molecular imprinting nanomaterial and carbon dots based fluorescence probe.

Doxycycline (DOX), a typical tetracycline antibiotic, is widely used because of its excellent antibacterial activity. To develop effective method for DOX has attracted much more attention. Herein, a new detection technology integrating magnetic solid phase extraction (MSPE) based on thermosensitive magnetic molecularly imprinted polymers (T-MMIPs) and fluorescence spectrometry based on carbon dots (CDs) was established. Thermosensitive magnetic molecularly imprinted polymers (T-MMIPs) was designed for selective enrichment of trace DOX. The synthesized T-MMIPs showed excellent selectivity for DOX. The adsorption performance of T-MMIPs varied with temperature in different solvents, which could achieve the enrichment and rapid desorption of DOX. In addition, the synthesized CDs had stable fluorescent property and better water-solubility, and the fluorescence of CDs was significantly quenched by DOX due to the internal filtration effect (IFE). Under the optimized conditions, the method resulted in good linearity over the range from 0.5 to 30 µg L-1, and the limit of detection was 0.2 µg L-1. The constructed detection technology was validated with real water samples, and excellent spiked recoveries from 92.5 % to 105.2 % were achieved. These data clearly indicated that the proposed technology was rapid, highly selective, environmentally friendly, and possessed significant potential application and development prospects.

Unveiling the mechanisms behind the chemical vapor generation of plumbane for trace analysis of lead.

The mechanisms controlling the generation of PbH4 by reaction of inorganic Pb(II) with aqueous NaBH4 were investigated both in the presence and in the absence of the additive K3Fe(CN)6. For the first time PbH4 has been identified in analytical chemical vapor generation (CVG) by using gas chromatographic mass spectrometry (GC-MS), which allows the use of deuterium labelled experiments. In the absence of the additive, under reaction conditions typically employed for trace lead determination by CVG, Pb(II) is converted to solid species and no volatile lead species can be detected by either atomic or mass spectrometry for Pb(II) concentration up to 100 mg L-1. In alkaline conditions Pb(II) substrates are unreactive towards NaBH4. In the presence of K3Fe(CN)6, deuterium labelled experiments clearly indicated that the generated PbH4 is formed by the direct transfer of hydride from borane to lead atoms. Kinetic experiments were carried out to evaluate the rate of reduction of K3Fe(CN)6 by NaBH4, the rate of hydrolysis of NaBH4 both in the presence and in the absence of K3Fe(CN)6, and the rate of dihydrogen evolution following NaBH4 hydrolysis. The effect of delayed addition of Pb(II) to NaBH4-HCl- K3Fe(CN)6, and K3Fe(CN)6 to NaBH4-HCl-Pb(II) reaction mixtures on the efficiency of plumbane generation was investigated by continuous flow CVG coupled with atomic fluorescence spectrometry. The collected evidences, complemented with thermodynamic considerations and literature data, have made it possible to clarify long-standing controversial aspects related to the mechanism of plumbane generation and the role of K3Fe(CN)6 additive.

Characterization of lignite deposits of Barmer Basin, Rajasthan: insights from mineralogical and elemental analysis.

The geochemistry of fly ash produced from the combustion of coal at thermal power plants presents a significant challenge for disposal and environmental impact due to its complex mineralogical and elemental composition. The objective of this study was to investigate the mineralogical and elemental distribution of thirty lignite samples from the Barmer Basin using advanced techniques such as X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). XRD analysis revealed the presence of minerals such as haematite (Fe2O3), nepheline, anhydrite, magnesite, andalusite, spinel and anatase. Other minor minerals included albite, siderite, periclase, calcite, mayenite, hauyne, pyrite, cristobalite, quartz, nosean and kaolinite. XRF analysis demonstrated that the most abundant elements in the Barmer Basin lignite ash were iron oxide (Fe2O3), sulphur oxide (SO3), calcium oxide (CaO), and quartz (SiO2) followed by minor traces of toxic oxides (SrO, V2O5, NiO, Cr2O3, Co2O3, CuO) that are known to have adverse effects on human health and the environment. The rare earth element (REE) composition showed higher concentrations of Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc at the Giral and lower concentrations at Sonari mine. The Barmer lignites recorded higher concentration of trace elements such as V, Cr, Co, Ni, Cu and Sr while lower concentration of Rb, Cs, Ba, Pb, As, Th and U were observed within optimal range. The study findings revealed the predominant mineral concentration, elemental makeup, trace elements and rare earth elements associated with lignite reserves in the Barmer Basin.

Encapsulating functionalized graphene quantum dot into metal-organic framework as a ratiometric fluorescent nanoprobe for doxycycline sensing.

A distinctive fluorescent nanoprobe with the function of doxycycline identification was designed by encapsulating histidine and serine-functionalized graphene quantum dots (His-GQDs-Ser) into the luminescent metal-organic frameworks (MOF). The synthesized nanoprobe displayed the merits of prominent selectivity, wide detection range, and high sensitivity. The interaction of doxycycline and the fabricated fluorescent nanoprobe contributed to the phenomenon of the suppression of the fluorescence of the His-GQDs-Ser and enhancement of the MOF fluorescence. Linear relation between the concentration of doxycycline and the ratio fluorescence intensity of the nanoprobe was observed, which evidenced the brilliant capability in the ranges 0.003-6.25 µM and 6.25-25 µM with a detection limit of 1.8 nM. Additionally, the practicability of the probe was verified in analysis of spiked milk sample, and the satisfactory recoveries of doxycycline varied from 97.39 to 103.61%, with relative standard deviations in the range 0.62-1.42%. A proportional fluorescence sensor for doxycycline detection in standard solution was constructed, which provides a potential for the development of other fluorescence detection systems.

Single hair analysis by X-ray fluorescence spectrometry detects small changes in dietary zinc intake: A nested randomized controlled trial.

The aim of this study was to determine whether X-ray fluorescence spectrometry (XRF) could be used to detect changes in hair zinc concentration in response to a modest daily increase in zinc from the consumption of zinc biofortified wheat flour. This study was conducted as part of an effectiveness trial (BiZiFED2) exploring the potential for zinc biofortified wheat to alleviate zinc deficiency in adolescent girls aged 10-16 years in Pakistan (trial registration ID ISRCTN17107812). A randomized controlled design was used. Participants received either control flour or zinc biofortified flour for 6 months. Consumption of biofortified flour resulted in an average daily increase in dietary zinc intake of 1.5 mg per day above that of the control flour. At baseline and at the end of the intervention, individual hair samples (control: n = 59, intervention: n = 64) were analyzed for zinc and sulfur content by XRF. Data were analyzed using linear mixed effects models to contrast between trial groups the changes from baseline to end point and also to compare baseline and end point values within each trial group. Increases from baseline to endpoint in both sulfur and zinc were significantly greater in the intervention group compared to control (sulfur counts. CONTROL: baseline = 119.87 ± 20.33 and endpoint = 121.58 ± 23.58/intervention: baseline = 122.67 ± 24.19 and endpoint = 131.60 ± 21.34); (Zinc counts. CONTROL: baseline = 50.88 ± 14.33 and endpoint = 54.82 ± 14.61/intervention: baseline = 49.61 ± 10.77 and endpoint = 58.79 ± 12.20). For these parameters, there were also significant increases from baseline to endpoint in the intervention group but not in control. Furthermore, for Zn:S count ratio there were no differences in terms of the magnitude of the change from baseline to endpoint in the control group, although significant increases from baseline to endpoint were evident in the intervention group (Zn:S count ratio. CONTROL: baseline = 0.42 ± 0.10 and endpoint = 0.45 ± 0.08/intervention: baseline = 0.41 ± 0.08 and endpoint = 0.45 ± 0.08). A modest increase in dietary zinc over 6 months resulted in a detectable increase in both sulfur and zinc counts in individual hairs measured using XRF. This offers a sensitive, non-invasive method to monitor changes within subjects in response to dietary zinc interventions.