Novel magnetic fluorescence probe based on carbon quantum dots-doped molecularly imprinted polymer for AHLs signaling molecules sensing in fish juice and milk

Emerging advances in biosensor technologies for quorum sensing signal molecules

Quorum sensing is a physiological phenomenon of microbial cell-to-cell information exchange, which relies on the quorum sensing signal molecules (QSSMs) to communicate and coordinate collective processes. Quorum sensing enables bacteria to alter their behavior as the population density and species composition of the bacterial community change. Effective detection of QSSMs is paramount for regulating microbial community behavior. However, traditional detection methods face the shortcomings of complex operation, high costs, and lack of portability. By combining the advantage of biosensing and nanomaterials, the biosensors play a pivotal significance in QSSM detection. In this review, we first briefly describe the QSSM classification and common detection techniques. Then, we provide a comprehensive summary of research progress in biosensor-based QSSM detection according to the transduction mechanism. Finally, challenges and development trends of biosensors for QSSM detection are discussed. We believe it offers valuable insights into this burgeoning research area.

Electrochemical Detection of Pseudomonas aeruginosa Quorum Sensing Molecule (S)-N-Butyryl Homoserine Lactone Using Molecularly Imprinted Polymers

Pseudomonas aeruginosa is a multidrug-resistant Gram-negative bacterium that poses a significant threat to public health, necessitating rapid and on-site detection methods for rapid recognition. The goal of the project is therefore to indirectly detect the presence of P. aeruginosa in environmental water samples targeting one of its quorum-sensing molecules, namely, (S)-N-butyryl homoserine lactone (BHL). To this aim, molecularly imprinted polymers (MIPs) were synthesized via bulk free-radical polymerization using BHL as a template molecule. The obtained MIP particles were immobilized onto screen-printed electrodes (MIP-SPEs), and the BHL rebinding was analyzed via electrochemical impedance spectroscopy (EIS). To study the specificity of the synthesized MIPs, isotherm curves were built after on-point rebinding analysis performed via LC-MS measurements for both MIPs and NIPs (nonimprinted polymers, used as a negative control), obtaining an imprinting factor (IF) of 2.8 (at C f = 0.4 mM). The MIP-SPEs were integrated into an electrochemical biosensor with a linear range of 1 × 101-1 × 103 nM and a limit of detection (LoD) of 31.78 ± 4.08 nM. Selectivity measurements were also performed after choosing specific interferent molecules, such as structural analogs and potential interferents, followed by on-point analysis performed in spiked tap water to prove the sensor's potential to detect the presence of the quorum-sensing molecule in environmentally related real-life samples.

Rational synthesis of 1,3,4-thiadiazole based ESIPT-fluorescent probe for detection of Cu2+ and H2S in herbs, wine and fruits

Here, 1,3,4-thiadiazole unit was employed as novel excited state intramolecular proton transfer (ESIPT) structure to prepare favorable fluorescent probe. High selectivity and rapid response to Cu2+ was obtained and the settling reaction was also used to recover ESIPT characteristics of probe to achieve sequential detection of H2S. Remarkable color change of solution from colorless to bright yellow and fluorescence emission from green to dark realized the visual detection of Cu2+ by naked eyes and transition of probe into portable fluorescent test strips. As expected, L-E could be utilized to quantitatively sense Cu2+ and H2S in different actual water and food samples including herbs, wine and fruits. The limits of detection for Cu2+ and H2S were as low as 34.5 nM and 38.6 nM. Also, probe L-E achieved real-time, portable, on-site quantitative detection of Cu2+ via a colorimeter and a smartphone platform with limit of detection to 90.3 nM.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Trace detection of methcathinone in sewage using targeted extraction based on magnetic molecularly imprinted polymers coupled with liquid chromatography-tandem mass spectrometry

Methcathinone, a new psychoactive substance (NPS), poses a serious threat to public health. Therefore, there is an urgent need to develop a reliable, selective, sensitive and simple analytical technique for monitoring trace amounts of this target NPS in complex matrices. For this purpose, magnetic molecularly imprinted polymers (MMIPs) based on MIPs combined with nano-sized magnetic Fe3O4 were developed for the specific enrichment of methcathinone in wastewater. The binding properties and selectivity of MMIPs toward methcathinone were evaluated and compared with non-imprinted polymer (MNIPs). For sensitive and selective extraction and determination of the target methcathinone, magnetic solid-phase extraction (MSPE) based on MMIPs was combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Under optimized conditions, the proposed method was successfully used for the detection of methcathinone in wastewater, which provided a low limit of detection of 0.3 ng L-1 and a limit of quantification of 1.0 ng L-1 with relative standard deviations of less than 6.89% for intra- and inter-day analyses. Good linearity in the range of 1-2000 ng L-1 with a coefficient of determination (R2) greater than 0.98 was observed. Moreover, a certified reference material of water sample was successfully analyzed with satisfactory results and the recoveries of spike experiments ranged from 96.35-116.7%.

Application of molecular imprinting technology based on new nanomaterials in adsorption and detection of fluoroquinolones

Irrational use of fluoroquinolones (FQs) can lead to allergic reactions, adverse reactions to the heart and damage of the liver; thus, it is of great significance to establish rapid, sensitive and accurate detection methods for FQs. Molecularly imprinted polymers (MIPs) with specific structures synthesized by molecular imprinting technology (MIT) are widely used for the detection of FQs due to their high specificity, high sensitivity and stable performance. Recently, new functional nanomaterials with different morphologies and sizes, which can provide rich sites for surface chemical reactions, have attracted more and more attention of the researchers. Thus, the application status and development prospects of MIT based on new nanomaterials in the adsorption and detection of FQs were summarized in this study, providing a theoretical basis and technical guarantee for the development of new and efficient food safety analysis strategies based on MIPs.

Bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite-based lateral flow immunoassay for ultrasensitive detection of streptomycin and dihydrostreptomycin in milk, muscle, liver, kidney, and honey

In this study, bifunctional magnetic ZnCdSe/ZnS quantum dots nanocomposite (MQNs) were synthesized, and firstly used to develop a lateral flow immunoassay (LFIA) for streptomycin (STR) and dihydrostreptomycin (DHSTR) detection in milk, muscle, liver, kidney, and honey simultaneously. The fluorescence signal of MQNs was 9-fold stronger than that of the original quantum dots. The detection limits of the established MQNs-LFIA for STR and DHSTR in five samples were 0.08-1.78 μg/kg, the quantitation limits were 0.26-5.87 μg/kg, the recoveries were between 85.0% and 120.0%, and the coefficient of variations were between 0.8% and 19.3%, respectively. The sensitivity was up to 42-fold more sensitive than the reported LFIAs. The single blind test results of 25 samples were consistent with that of the confirmation method (R² ≥ 0.99). Besides, a portable reader was self-developed and used for rapid quantification. Our study demonstrated MQNs as a promising signal-amplifying tag can be used for ultrasensitive detection of chemical contaminants in foods.

A Novel Sulfonamide, Molecularly Imprinted, Upconversion Fluorescence Probe Prepared by Pickering Emulsion Polymerization and Its Adsorption and Optical Sensing Performance

A novel, molecularly imprinted, upconversion fluorescence probe (UCNP@MIFP) for sulfonamide sensing was fabricated by Pickering emulsion polymerization using UCNP@SiO₂ particles as the stabilizer and sulfamethazine/sulfamerazine as the co-templates. The synthesis conditions of the UCNP@MIFP were optimized, and the synthesized probe was characterized by scanning electron microscopy, Fourier transform infrared spectrometer, thermogravimetric analyzer, and fluorescence spectrometer. The UCNP@MIFPs showed a good adsorption capacity and a fast kinetic feature for the template. The selectivity experiment revealed that the UCNP@MIFP has a broad-spectrum molecular recognition capability. Good linear relationships were obtained over the concentration range of 1-10 ng/mL for sulfamerazine, sulfamethazine, sulfathiazole, and sulfafurazole, with low limits of detection in the range of 1.37-2.35 ng/mL. The prepared UCNP@MIFP has the potential to detect four sulfonamide residues in food and environmental water.

Carbon nanomaterial-based molecularly imprinted polymer sensors for detection of hazardous substances in food: recent progress and future trends

The presence of various harmful substances in food is significantly risky to human health. Therefore, simple, rapid, and selective food hazard analysis tools have become a focus of sensing research. At present, molecularly imprinted polymers (MIPs) have attracted more and more attention because of their easy preparation and high selectivity. Due to their simple preparation, low cost, large specific surface area, and high conductivity, carbon nanomaterial can be used as sensing substrate carriers. Therefore, the combination of carbon nanomaterial with MIPs has attracted great attention. This paper summarizes the development, composition, and preparation methods of MIPs, as well as the latest research progress in carbon nanomaterials for the detection of various food hazards using sensors. In addition, the practical applications of carbon nanomaterial-based MIP sensors, their current challenges and future trends, and the ongoing efforts devoted to developing new and efficient carbon nanomaterial-based MIP sensing platforms are also introduced.

Molecularly Imprinted Polymer-Based Luminescent Chemosensors

Molecularly imprinted polymer (MIP)-based luminescent chemosensors combine the advantages of the highly specific molecular recognition of the imprinting sites and the high sensitivity with the luminescence detection. These advantages have drawn great attention during the past two decades. Luminescent molecularly imprinted polymers (luminescent MIPs) towards different targeted analytes are constructed with different strategies, such as the incorporation of luminescent functional monomers, physical entrapment, covalent attachment of luminescent signaling elements on the MIPs, and surface-imprinting polymerization on the luminescent nanomaterials. In this review, we will discuss the design strategies and sensing approaches of luminescent MIP-based chemosensors, as well as their selected applications in biosensing, bioimaging, food safety, and clinical diagnosis. The limitations and prospects for the future development of MIP-based luminescent chemosensors will also be discussed.

ZnO/C nanocomposite grafted molecularly imprinted polymers as photoelectrochemical sensing interface for ultrasensitive and selective detection of chloramphenicol

Nanomaterials-based photoelectrochemical (PEC) detection is becoming a rapidly-developing analytical technique in chemical and biological assays due to its unique advantages of easy miniaturization, high sensitivity, and rapid turnaround time. Herein, a molecularly imprinted polymer-assisted PEC sensor based on ZnO/C nanocomposite was successfully fabricated for the highly sensitive and selective determination of chloramphenicol (CAP). Benefiting from the hydrophilic functional groups (-OH, -COOH) and large surface area of bio-templated ZnO/C nanocomposite, the tight grafting of MIP with excellent recognition ability on substrate is easier and more stable than traditional PEC sensor, thus significantly increasing the performance. Under optimal conditions, the PEC sensor exhibited significant CAP detection performance in the range of 0.01-5000 ng mL^-1 with a detection LOD of 5.08 pg mL^-1 (S/N = 3) and successfully applied to the detection of CAP in milk sample. Our results show that ZnO/C nanocomposite and MIP can act as an efficient photo-responsible matrix to fabricate PEC sensor, providing important application potentials for pollutants control in food and environment.

Molecularly imprinted probe based on CdTe QDs and magnetic nanoparticles for selective recognition of malachite green in seawater and its sensing mechanisms

A magnetic molecularly imprinted probe (MMIP@QD) was synthesized by reverse microemulsion method using CdTe QDs, Fe₃O₄, and molecularly imprinted polymer as the fluorophore, magnetic carrier, and recognition sites, respectively. The nanoparticle was characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and vibrating sample magnetometry (VSM). In the optimal experimental condition, fluorescent emission intensity (measured at excitation wavelengths of 350 nm) was quenched linearly with increasing malachite green (MG) concentration from 0.8 to 28.0 μM with LOD of 0.67 μM. Simultaneously, it was observed that the maximum absorption wavelength was blue shifted gradually with the increase of MG concentration. The inner filter effect, static quenching, and band gap transition were interpreted as the mechanisms of fluorescence quenching and wavelength shift. Thermodynamic studies indicated that the quenching reaction proceeded spontaneously. The developed sensor was applied to detect MG in seawater samples. Satisfactory recoveries of MG in spiked seawater ranged from 83.6 to 122.1% with RSD < 1.8%.

An advantageous application of molecularly imprinted polymers in food processing and quality control

In the global market era, food product control is very challenging. It is impossible to track and control all production and delivery chains not only for regular customers but also for the State Sanitary Inspections. Certified laboratories currently use accurate food safety and quality inspection methods. However, these methods are very laborious and costly. The present review highlights the need to develop fast, robust, and cost-effective analytical assays to determine food contamination. Application of the molecularly imprinted polymers (MIPs) as selective recognition units for chemosensors' fabrication was herein explored. MIPs enable fast and inexpensive electrochemical and optical transduction, significantly improving detectability, sensitivity, and selectivity. MIPs compromise durability of synthetic materials with a high affinity to target analytes and selectivity of molecular recognition. Imprinted molecular cavities, present in MIPs structure, are complementary to the target analyte molecules in terms of size, shape, and location of recognizing sites. They perfectly mimic natural molecular recognition. The present review article critically covers MIPs' applications in selective assays for a wide range of food products. Moreover, numerous potential applications of MIPs in the food industry, including sample pretreatment before analysis, removal of contaminants, or extraction of high-value ingredients, are discussed.

A novel terbium (III) and aptamer-based probe for label-free detection of three fluoroquinolones in honey and water samples

Fluoroquinolones, a family of synthetic broad-spectrum antibiotics, are widely used in clinical medicine, farm animals and aquaculture. Residues of fluoroquinolones in samples have attracted much attention because of growing food safety and public health concerns. Here, a novel Tb³⁺ ion-enrofloxacin aptamer coordination probe was prepared to develop a sensitive and rapid label-free fluorescence assay for specific detection three fluoroquinolones. In presence of the target, Tb³⁺ ion- enrofloxacin aptamer probe specifically bound with enrofloxacin, norfloxacin and ciprofloxacin, leading to a sharp increase in fluorescence emission of the probe. Under the optimized conditions, fluorescence increased linearly in the 1.0-100.0 ng/mL range for the three fluoroquinolones, with 0.053 ng/mL limit of detection for ciprofloxacin, 0.020 ng/mL limit of detection for norfloxacin and 0.061 ng/mL limit of detection for enrofloxacin. Satisfactory recovery (80.10-102.48%) in spiked honey and water samples were obtained for the three fluoroquinolones with relative standard deviations between 0.21% and 5.44% (n = 3).

A gel fluorescence sensor based on CDs@SiO2/FeS2@MIPs for the visual detection of p-chlorophenol

There is a critical need for the rapid detection of p-chlorophenol produced by pesticide abuse and industrial wastewater discharge, which has been an urgent problem in the realm of environmental protection. Here, a green and environmentally friendly method was developed to prepare stable and low toxicity quantum dots. First, blue-green fluorescent FeS₂ quantum dots (B-FeS₂ QDs) were prepared with FeCl₃·6H₂O (an iron source) and L-cysteine (a capping agent) by the solvothermal method. By combining B-FeS₂ QDs with orange carbon dots (O-CDs), a CDs@SiO₂/FeS₂@MIPs visual fluorescence sensor for the selective detection of p-chlorophenol was constructed. Under optimum conditions, this sensor exhibited a detection limit of 1.265 μM with a linear range of 5.00-50.00 μM and was successfully applied to detect p-chlorophenol in real samples. Moreover, this sensor was successfully applied to visual semi-quantitative detection of p-chlorophenol. This work demonstrated that these sensors, based on FeS₂ QDs and CDs, had potentials for in situ and visual detection of environmental contaminants.

Mitochondria-Targeted Fluorescent Turn-On Probe for Rapid Detection of Bisulfite/Sulfite in Water and Food Samples

Bisulfite (HSO₃^-)/Sulfite (SO₃^2-) is widely used as a food additive, but excessive use often leads to serious consequences, so the detection of HSO₃^-/SO₃^2- is of great importance. In this paper, a novel 1,4-diethylpiperazine-modified coumarin-benzopyran derivative (probe QLP) has been synthesized and characterized. In PBS (10 mM, pH = 7.4), QLP displays good selectivity and is sensitive for HSO₃^-/SO₃^2- over various analytes with fluorescent "OFF-ON" rapid responding (2 min), long-wavelength emission (600 nm), and a detection limit of 177 nM. With the treatment of HSO₃^-/SO₃^2-, the color of the QLP solution obviously changes from blue-green to yellow, and the fluorescent color of QLP changes from colorless to amaranth. The fluorescence-enhanced mechanism is qualitatively evaluated by density functional theory calculations using the CAM-B3LYP/6-31G (d) method, which reveals that the photoinduced electron transfer leads to the fluorescence emission of the QLP-SO₃H adduct. Importantly, nontoxic QLP can be used to detect HSO₃^-/SO₃^2- in sugar, natural water samples, and living cells and localized to the mitochondria and monitor the mitochondrial HSO₃^-/SO₃^2- level.

Application progress of magnetic molecularly imprinted polymers chemical sensors in the detection of biomarkers

Specific recognition and highly sensitive detection of biomarkers play an essential role in identification, early diagnosis and prevention of many diseases. Magnetic molecularly imprinted polymers (MMIPs) have been widely used to capture biomimetic receptors for targets in various complex matrices due to their superior recognition ability, structural stability, and rapid separation characteristics, which overcome the existing deficiencies of traditional recognition elements such as antibodies, aptamers. The integration of MMIPs as recognition elements with chemical sensors opens new opportunities for the development of advanced analytical devices with improved selectivity and sensitivity, shorter analysis time, and lower cost. Recently, MMIPs-chemical sensors (MMIPs-CS) have made significant progress in detection, but many challenges and development spaces remain. Therefore, this review focuses on the research progress of the sensor based on biomarker detection and introduces the surface modification of the magnetic support material used to prepare high selective MMIPs, as well as the selective extraction of target biomarkers by MMIPs from the complex biological sample matrix. Based on the understanding of optical sensors and electrochemical sensors, the applications of MMIPs-optical sensors (MMIPs-OS) and MMIPs-electrochemical sensors (MMIPs-ECS) for biomarker detection were reviewed and discussed in detail. Moreover, it provides an overview of the challenges in this research area and the potential strategies for the rational design of high-performance MMIPs-CS, accelerating the development of multifunctional MMIPs-CS.

Dipeptide nanoparticle and aptamer-based hybrid fluorescence platform for enrofloxacin determination

A novel fluorescence platform was fabricated for enrofloxacin determination by using cDNA-modified dipeptide fluorescence nanoparticles (FDNP-cDNA) and aptamer-modified magnetic Fe₃O₄ nanoparticles (Fe₃O₄-Apt). The FDNP were prepared via tryptophan-phenylalanine self-assembling. When magnetic Fe₃O₄-Apt incubated with standard solution or sample extracts, the target enrofloxacin was selectively captured by the aptamer on the surface of the Fe₃O₄ nanoparticles. After removing interference by washing with phosphate-buffered saline, the FDNP-cDNA was added, which can bind to the aptamer on the surface of the Fe₃O₄ nanoparticles not occupied by the analyte. The higher the concentration of the target enrofloxacin in the standard or sample solution is, the less the FDNP-cDNA can be bound with the Fe₃O₄ nanoparticles, and the more the FDNP-cDNA can be observed in the supernatant. Fluorescence intensity (E_x/E_m = 310/380 nm) increased linearly in the enrofloxacin concentration range 0.70 to 10.0 ng/mL with a detection limit of 0.26 ng/mL (S/N = 3). Good recoveries (88.17-99.30%) were obtained in spiked lake water, chicken, and eel samples with relative standard deviation of 2.7-6.2% (n = 3).

Recyclable Magnetic Fluorescence Sensor Based on Fe3O4 and Carbon Dots for Detection and Purification of Methcathinone in Sewage

Sensitive, rapid, and low-cost detection of drug traces in sewage is very important for drug monitoring and control. In this study, a dual functional and recyclable magnetic fluorescent molecularly imprinted polymers (MFMIPs) sensor with high sensitivity for rapid detection and purification of methcathinone in sewage was developed. MFMIPs was prepared via molecular imprinting and conjugation with carbon dots as a fluorescent reporter on Fe₃O₄ (Fe₃O₄-MIPs@CDs). With strong recognition and adsorption toward methcathinone by the specific cavities on the surface of MFMIPs, the fluorescence of the sensor could dramatically be quenched once anchored with methcathinone. Under optimal conditions, the MFMIPs sensor presented high sensitivity with a linear range of 0.5-100 nM and a detection limit of 0.2 nM, which would be used to monitor drug prevalence and consumption within a certain region. This sensor was applied to the assay of methcathinone in sewage samples collected from Yuebeiyuan, Yanghu, and Xujiahu sewage pumping stations of Yuelu District. The calculated concentrations of methcathinone were 4.80, 15.33, and 8.59 nM in sewage samples, which were in good agreement with data tested by LC-MS/MS. For another function, MFMIPs exhibited purification toward methcathinone and the adsorption capacity was about 0.27 mg/g in a real sewage sample. Moreover, the sensor could be recycled and reused at least five times with the aid of an external magnetic field. Collectively, with good analytical performance and excellent recognition and selectivity to methcathinone, the proposed sensing system based on the magnetic core and molecularly imprinted polymers would open a door to establish highly sensitive and effective sensing systems for sewage analysis and purification.

Mycotoxins detection: view in the lens of molecularly imprinted polymer and nanoparticles

Molecularly imprinted polymers (MIPs) are tailor-made functional composites which selectively recognize and bind the target molecule of interest. MIP composites are products of the massively cross-linked polymer matrices, generated via polymerization, with bio-inspired recognition cavities that are morphologically similar in size, shape and spatial patterns to the target conformation. These features have enabled researchers to expand the field of molecular recognition, more specifically for target with peculiar requirements. Nevertheless, MIPs alone are characterized with weak sensitivity. Besides, nanoparticles (NPs) are remarkably sensitive but also suffer from poor selectivity. Intriguingly, the combination of the two results in a highly sensitive and selective MIP composite. For instance, the conjugation of different functional NPs with MIPs can generate new flexible target capture tools, either a dynamic sensor or a novel drug delivery system. In this regard, although the technology is considered an established and feasible approach, it is still perceived as a burgeoning technology for various fields, which makes it unceasingly worthy reviewing. Therefore, in this review, we attempt to give an update on various custom-made biosensors based on MIPs in combination with various NPs for the detection of mycotoxins, the toxic secondary metabolites of fungi. We first summarize the classification, prevalence, and toxicological characteristics of common mycotoxins. Next, we provide an overview of MIP composites and their characterization, and then segment the role of NPs with respect to common types of MIP-based sensors. At last, conclusions and outlook are discussed.

Ultrafast Ratiometric Detection of Aflatoxin B1 Based on Fluorescent β-CD@Cu Nanoparticles and Pt2+ Ions

Rapid detection of aflatoxin B1 (AFB1) is a very important task in food safety monitoring. However, it is still challenging to achieve highly sensitive detection without antibody or aptamer biomolecules. In this work, a rapid detection of aflatoxin B1 was achieved using a ratiometric fluorescence probe without antibody or aptamer for the first time. In the ratiometric fluorescence system, the fluorescence emission of AFB1 at 433 nm was significantly enhanced due to the β-cyclodextrin-AFB1 host-guest interaction and the complexation of AFB1 and Pt²⁺. Meanwhile, the inclusion of aflatoxin B1 also quenched the fluorescence emission of β-CD@Cu nanoparticles (NPs) at 650 nm based on inner filter effect mechanism. On the basis of the above effects, the ratiometric detection of aflatoxin B1 was achieved in the range of 0.03-10 ng/mL with a low detection limit of 0.012 ng/mL (3σ/s). In addition, the β-CD@Cu NPs based nanoprobe could achieve stable response within 1 min to AFB1. The above ratiometric detection also demonstrated excellent application potential in the rapid on-site detection of AFB1 in food due to the advantages of convenience, rapidness, and high accuracy.

Development of silica molecularly imprinted polymer on carbon dots as a fluorescence probe for selective and sensitive determination of cetirizine in saliva and urine

A fluorescence probe based on carbon dots (CDs) coated with silica molecularly imprinted polymer (MIPs) was synthesized for selective and sensitive determination of cetirizine (CTZ). Green source carbon dots were firstly derived from orange peels through a microwave method, and had the merits of eco-friendly and low toxicity. Then a thin silica film was formed on the surface of CDs by reverse microemulsion technique, and molecularly imprinted polymer coated on silica-carbon dots. In this scene, CTZ, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were employed as a template, a functional monomer and cross linker, respectively. The obtained CDs-MIPs can selectively bind CTZ through the specific interaction between recognition sites and template, and obey photoinduced electron transfer fluorescence quenching mechanism. Fluorescence dropped linearly in the range of 0.5-500 ng mL^-1, under the optimal conditions, with a detection limit of 0.41 ng mL^-1. Furthermore, the proposed method was successfully intended for the determination of trace CTZ in human saliva and urine samples without the interference of other molecules and ions. And recoveries ranged from 95.8% to 99.8% with relative standard deviation less than 3.0%.

An anthracene-based microporous metal–organic framework for adsorbing CO2 and detecting TNP sensitivity

An anthracene-based microporous MOF of CUST-607 was synthesized by a solvothermal method. CUST-607 possesses a large surface area and shows strong adsorption toward CO2. In the fluorescence experiments, CUST-607 exhibits total quenching for TNP.

Fast Determination of Carbamates in Environmental Water Based on Magnetic Molecularly Imprinted Polymers as Adsorbent

Magnetic molecularly imprinted polymers (MMIPs) were prepared with isoprocarb as template molecule and applied to extraction of carbamates pesticides in different water samples. This method based on magnetic solid-phase extraction (SPE) avoided the time-consuming column-passing process of loading large volume samples in conventional SPE. In the study, only 0.1 g MMIPs could be used to obtain satisfactory recoveries, due to the high-surface area and excellent adsorption capacity of these nano-magnetic adsorbents. Owing to the excellent selectivity of MMIPs, in high-performance liquid chromatography-mass spectrometry analysis, the matrix effects of this technique were obviously lower than the conventional SPE method. Under the optimal conditions, the detection limits of carbamates were in the range of 2.7-11.7 ng L-1. The relative standard deviations of intra-day and inter-day were 2.5-7.4% and 3.6-8.4%, respectively. At all the spiked level, the recoveries of four analyzed carbamates in environmental water samples were in the range of 74.2-94.2%. The significant positive results were achieved in the proposed method for the determination of four carbamates in water samples from different lakes and rivers. In the three samples we tested, the carbaryl was found in the lake water obtained from Yitong River, and the content was 2.4 ng L-1.

Mitochondria-Targeted Red-Emission Fluorescent Probe for Ultrafast Detection of H2S in Food and Its Bioimaging Application

Hydrogen sulfide (H₂S) contributes to human health and prolongs the storage time of postharvest fruits and vegetables. At the same time, H₂S can cause a negative impact on some foodstuffs and beverages, so an efficient probe to detect H₂S is needed. Herein, a fluorescent turn-on responding probe SPy-DNs for H₂S detection has been designed and synthesized. SPy-DNs exhibited a red emission (608 nm), large Stokes shift (111 nm), and a detection limit of a nanomolar level (356 nM) in a dimethylformamide/phosphate-buffered saline (DMF/PBS) (1:1, v/v, 10 mM, pH 7.4) solution. SPy-DNs can detect H₂S with ultrafast response within 4 s, which is faster than the response of other reported probes. In addition, the applicability of SPy-DNs to detect H₂S has been determined in the actual water samples, targeted mitochondria, and imaged H₂S in living cells. Moreover, SPy-DNs was successfully used as a tool to judge H₂S levels in beer, which indicates that SPy-DNs possesses the advantage of rapid detection of H₂S in foodstuffs.

Facile synthesis of orange fluorescence multifunctional carbon dots for label-free detection of vitamin B12 and endogenous/exogenous peroxynitrite

In this work, orange emission fluorescent multifunctional carbon dots (O-CDs) were designed for the label-free detection of vitamin B₁₂ (VB₁₂)，endogenous/exogenous peroxynitrite (ONOO^-) sensing, cell imaging, and fluorescent flexible film preparation. The O-CDs with excitation-independent were prepared using safranine T and ethanol as precursors via one-step hydrothermal process. VB₁₂ was utilized as a quencher to quench the fluorescence of O-CDs due to the internal filtration effect (IFE). Two-segment linear ranges are 1-65 μM and 70-140 μM, and the detection limit was calculated as 0.62 μM. Besides, ONOO^- can reduce the fluorescence intensity of O-CDs based on static quenching (SQ). The linear ranges are 0.3-9 μM and 9-48 μM, and the detection limit was 0.06 μM. Moreover, the O-CDs were exploited as a cellular imaging reagent for intracellular VB₁₂ and endogenous/exogenous ONOO^- imaging owing to its great biocompatibility, low toxicity and strong photostability. These results indicate that O-CDs have the potential to be used as a sensitive fluorescence probe to rapidly monitor VB₁₂ and endogenous/exogenous ONOO^- with high selectivity in living cells. Also, the as-proposed O-CDs can be employed to fabricate O-CDs/PVA composites as fluorescent flexible films. All of the above prove that the O-CDs present great prospect in multiple applications such as biosensing, cellular labeling, biomedical optical imaging, and fluorescent films.

Development of a molecularly imprinted photoelectrochemical sensing platform based on NH2-MIL-125(Ti)-TiO2 composite for the sensitive and selective determination of oxtetracycline

In this work, a molecularly imprinted photoelectrochemical (MIP-PEC) sensor based on a novel PEC composite of metal-organic frameworks (MOFs) and TiO₂ (NH₂-MIL-125(Ti)-TiO₂) was established for the ultrasensitive and selective detection of oxytetracycline (OTC). This is the first attempt of applying MOFs in the construction of MIP-PEC sensor. The NH₂-MIL-125(Ti)-TiO₂ was synthesized by a simple one-step solvothermal method and modified onto the surface of indium tin oxide (ITO) electrode as the photosensitive layer. Subsequently, molecularly imprinted polymer (MIP) was modified as recognition element by electropolymerization. The NH₂-MIL-125(Ti)-TiO₂ showed an enhanced photocurrent response due to stronger light absorption capacity and matched energy band. Furthermore, MIP greatly improved the selectivity and sensitivity of the constructed PEC sensor. The photocurrent response of the MIP-PEC sensor was reduced after OTC recognition because the specific binding of OTC to the imprinted cavities blocked the electron transfer of the electrode. Under optimal experimental conditions, the MIP-PEC sensor exhibited a wide detection range from 0.1 nM to 10 μM with a low limit of detection (LOD) of 60 pM, as well as certain reproducibility, stability and good applicability in real samples. The proposed sensor provides ideas for the application of MOFs in the construction of PEC sensors and will offer an alternative method for the detection of other pollutants in the field of food safety.

A review of the incorporation of QDs and imprinting technology in optical sensors – imprinting methods and sensing responses

This review aims to cover the simultaneous method of using molecularly imprinted technology and quantum dots (QDs) as well as its application in the field of optical sensors.

Fluorescent Carbonized Polymer Dots Prepared from Sodium Alginate Based on the CEE Effect

In recent years, as a new type of carbon dots, carbonized polymer dots (CPDs) have attracted more and more attention in many fields. In this experiment, a new kind of CPDs was synthesized by the hydrothermal treatment of the chemically cross-linked sodium alginate (SA) via glutaraldehyde. The fluorescence of CPDs was greatly enhanced because of the cross-linking enhanced emission effect. The formation process of CPDs at different reaction temperatures was explored. In addition, it was found that CPDs have stable fluorescence properties in mild acidic/basic and metal-ion environments. The in vitro toxicity of CPDs was tested, and based on their nontoxic property, SA films with anti-ultraviolet aging properties were prepared by using CPDs as the additive.

Molecularly Imprinted Polymer Micro- and Nano-Particles. A review

In recent years, molecularly imprinted polymers (MIPs) have become an excellent solution to the selective and sensitive determination of target molecules in complex matrices where other similar and relative structural compounds could coexist. Although MIPs show the inherent properties of the polymers, including stability, robustness, and easy/cheap synthesis, some of their characteristics can be enhanced, or new functionalities can be obtained when nanoparticles are incorporated in their polymeric structure. The great variety of nanoparticles available significantly increase the possibility of finding the adequate design of nanostructured MIP for each analytical problem. Moreover, different structures (i.e., monolithic solids or MIPs micro/nanoparticles) can be produced depending on the used synthesis approach. This review aims to summarize and describe the most recent and innovative strategies since 2015, based on the combination of MIPs with nanoparticles. The role of the nanoparticles in the polymerization, as well as in the imprinting and adsorption efficiency, is also discussed through the review.