Highly luminescent water-dispersed silicon quantum dots for fluorometric determination of oxytetracycline in milk samples

Triplex hairpin oligosensor for ultrasensitive determination of miRNA-155 as a cancer marker using Si quantum dots and Au nanoparticles

In this study, a new triplex hairpin oligosensor was developed for the determination of a breast cancer biomarker using silicon quantum dots (Si QD) (λex = 370 nm, λem = 482 nm) as donor and gold nanoparticles (GNP) as an acceptor in a FRET (fluorescence resonance energy transfer) mechanism. In the triplex hairpin oligosensor, a triplex-forming oligonucleotide (TFO) labeled with Si QD and a single-strand DNA labeled with GNP form a hairpin shape with a triplex structure at the hairpin stem. In a turn-on mechanism, the triplex hairpin stem is opened in the presence of sequence-specific miRNA-155 which leads to the release of the Si QD-labeled TFO probe and recovery of the fluorescence signal. About 80 % of the fluorescence intensity of the Si QD-TFO is quenched in the triplex hairpin structure of the oligosensor and in the presence of 800 pM miRNA-155, the fluorescence signal recovered to 57.7 % of its initial value. The LOD of about 10 pM was obtained. The designed triplex-based biosensor can discriminate concentrations of breast cancer biomarkers with high selectivity.

Evaluation of antibiotic residues in honey: a systematic review and meta-analysis

Nowadays, incorrect apply of antibiotics to treat infections in honey has led to health risks for humans and antibiotic resistance. Current systematic review and meta-analysis conducted to study antibiotic residues in honey. Data were obtained through searching the databases, including Scopus, Web of Science, PubMed, and other internal databases. The pooled concentration of antibiotic residues was 5.032 (µg/kg) that ranged from 4.72 to 5.33 (µg/kg). The ranking of antibiotics concentration was found in order of fluoroquinolone (8.59 µg/kg) > tetracycline (5.68 µg/kg) > sulfonamides (5.54 µg/kg) > macrolides (4.19µg/kg), respectively. Liquid chromatography-mass spectrometry (LC-MS) method (37.9.7%), high-performance liquid chromatography (HPLC) method (34.4%), and enzyme-linked immunosorbent assay (ELISA) method (27.5.8%) were the most used methods in various studies. In order to avoid contamination, proper use of antibiotics, placement of hives at a suitable distance from agricultural environment, and regular control of antibiotic residues in honey seems to be necessary.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH₂-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH₂-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH₂-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH₂-UIO-66 (Zr). The introduction of NH₂-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH₂-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 μg mL^-1, with a detection limit of 0.012 μg mL^-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH₂-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

Green and rapid synthesis of biomass carbon dot-based fluorescence sensing for the sensitive determination of oxytetracycline

Eco-friendly biomass carbon dots (CDs) with blue fluorescence emission were rapidly synthesized by a microwave method. Based on the inner filter effect (IFE) between oxytetracycline (OTC) and CDs, the fluorescence of CDs could be selectively quenched by OTC. Therefore, a simple and time-saving fluorescence sensing system for the detection of OTC was established. Under optimal experimental conditions, the concentration of OTC showed a good linear relationship with fluorescence quenching values (ΔF) in the range of 4.0-100.0 μmol L^-1, a corresponding correlation coefficient (r) of 0.9975, and a detection limit of 0.12 μmol L^-1. The method has the advantages of low cost, time-saving, and green synthesis that could be used for the determination of OTC. Moreover, possessing high sensitivity and specificity, this fluorescence sensing method was successfully applied for detecting OTC in milk, indicating its potential applications in food safety.

UiO-66-NH2 based fluorescent sensing for detection of tetracyclines in milk

In this work, a fluorescent sensor based on a zirconium-based metal organic framework was prepared for the detection of tetracyclines (TCs) in milk. The UiO-66-NH2 fluorescent sensor was synthesized by a simple microwave-assisted method with 2-aminoterephthalic acid and zirconium chloride as precursors. In the presence of target TCs, the synergistic effect of the inner filter effect (IFE) and photo-induced electron transfer (PET) was responsible for the fluorescence quenching of UiO-66-NH2, and the fluorescence sensor showed a rapid fluorescence quenching response (5 min) to target TCs. The proposed UiO-66-NH2 sensor had good sensitivity and selectivity, and under the optimal conditions possessed detection limits of 0.449, 0.431, and 0.163 μM for tetracycline (TET), oxytetracycline (OTC), and doxycycline (DOX), respectively. Besides, the UiO-66-NH2 sensor was successfully applied to the quantitative detection of TCs in milk samples with reasonable recoveries of 93.26-115.17%, and the detection results achieved from the as-fabricated fluorescence sensing assay were consistent with those of high-performance liquid chromatography (HPLC), indicating the potential applicability of the UiO-66-NH2 sensor for detecting TCs in actual food samples.

Multifunctional theranostic nanoplatform loaded with autophagy inhibitor for enhanced photothermal cancer therapy under mild near-infrared irradiation

Photothermal therapy (PTT) usually causes hyperthermia and damages healthy tissues. Developing a PTT platform with enhanced therapeutic effects and reduced side effects to normal tissues attracts increasing attention. Herein, we developed a multifunctional theranostic nanoplatform using poly(lactic-co-glycolic acid) (PLGA) loaded with near-infrared (NIR) photothermal agent (new indocyanine green IR820), fluorescence imaging agent (ZnCdSe/ZnS quantum dots, QDs) and autophagy inhibitor (chloroquine, CQ). These PLGA/IR820/Fluorescence imaging agent/CQ co-loading nanoparticles (termed PIFC NPs) displayed photothermal effects, enhanced the stability of IR820 in vivo, and enabled QDs to have stable fluorescent signals in vitro and in vivo. The PIFC NPs with particle size around 240 nm aggregated to tumor sites through the high permeability and retention effects of solid tumors. The intracellular delivery of CQ molecules through PIFC NPs significantly attenuated the degradation of autophagic lysosomes in tumor cells and effectively inhibited the autophagy mediated repair of photothermal damaged cells. Under milder NIR irradiation conditions, PIFC NPs exhibited high antitumor effect. By regulating autophagy, PTT can be effectively sensitized, which will provide a new idea for future cancer treatment research.

Designing prototype rapid test device at qualitative performance to detect residue of tetracycline in chicken carcass

Background and Aim:

Human health problems due as a microbial resistance or tumors and cancers because consumption of the carcasses containing residues of tetracycline are main global problems in the context of fight against antimicrobial resistance phenomena. Explanation of the sustainable development goals, particularly point 3, is well recognized that all animal products for human consumption must be safe to live a healthy life. This study aimed to design a prototype of rapid test devices (RTD) based on principles of precipitate to obtain a specific color change after the process of reactions as an indicator to determine tetracycline residues in the carcass.

Materials and Methods:

Five samples of tetracycline-containing poultry carcasses using artificial add the tetracycline at pharmaceutics grade were examined using a prototype of a strong reaction solution for tetracycline fixation based on the concept bonded by ion Fe(III) at atom O in position atom C-1 at the ring of tetracycline and ion N⁺ as the functional branch of tetracycline. RTD detection was evaluated using a yellow color presentation and an absorbance spectrometric technique at a wavelength of 273 nm.

Results:

The following chemicals were used to create the best-fixed tetracycline residue: HCl and H₂SO₄ dissolved in H₂O, chromatographic grade of 0.1 N and 0.5 N of HNO₃, and 1% Fe (III) Cl. The RTD had a higher limit of detection (LOD) than the ultraviolet-visible spectrophotometer.

Conclusion:

The results of this study revealed that RTD, as constructed in this study, can be used to detect residue at LOD 44.764 mg/mL during 120 min of exposure through a light-emitting diode at 980 nm wavelength (p<0.05). The necessity for using RTD was because of the apparent limitations of conventional devices.

Quantum dots based sensitive nanosensors for detection of antibiotics in natural products: A review

Residual antibiotics in food products originated from administration of the antibiotics to animals may be accumulated through food metabolism in the human body and endanger safety and health. Thus, developing a prompt and accurate way for detection of antibiotics is a crucial issue. The zero-dimensional fluorescent probes including metals based, carbon and graphene quantum dots (QDs), are highly sensitive materials to use for the detection of a wide range of antibiotics in natural products. These QDs demonstrate unique optical properties like tunable photoluminescence (PL) and excitation-wavelength dependent emission. This study investigates the trends related to carbon and metal based QDs preparation and modification, and their diverse detection application. We discuss the performance of QDs based sensors application in various detection systems such as photoluminescence, photoelectrochemical, chemiluminescence, electrochemiluminescence, colorimetric, as well as describing their working principles in several samples. The detecting mechanism of a QDs-based sensor is dependent on its properties and specific interactions with particular antibiotics. This review also tries to describe environmental application and future perspective of QDs for antibiotics detection.