A NIR-responsive up-conversion nanoparticle probe of the NaYF4:Er,Yb type and coated with a molecularly imprinted polymer for fluorometric determination of enrofloxacin

Novel Iminocoumarin-substituted Tetraphenylethylene-based Near-infrared Fluorescent Probe for Ratiometric Detection of F- and H2S

An iminocoumarin and tetraphenylethylene compound that exhibits aggregation-induced emission (AIE) and a significant Stokes shift (Δλ = 135 nm) in THF was created via the Knoevenagel condensation method. TPICBT could also be used as a ratiometric near-infrared fluorescent probe for the naked color identification of F- and H2S. It showed a large red shift (˃ 90 nm), good selectivity, and anti-interference. Test strip detection and cell imaging had both been accomplished using the probe. In addition, the probe could conveniently detect H2S produced during food spoilage without laboratory instruments.

Pentacenequinone-Modulated 2D GdSn-PQ Nanosheets as a Fluorescent Probe for the Detection of Enrofloxacin in Biological and Environmental Samples

The fate and effects of fluoroquinolone antibacterial (FQ) on the environment are important since there appears to be a surge in FQ resistance like enrofloxacin (ENR) in both environmental and clinical organisms. Numerous reports indicate that the sensing capabilities of these antibiotics need to be improved. Here, we have investigated the interaction of ENR with our synthesized pentacenequinone-modulated gadolinium-tin (GdSn-PQ) nanosheets and the formation of intermolecular interactions that caused the occurrence of aggregation-induced emission enhancement. The concept for designing hybrid metallic nanosheets comes from the unique features inherited from the parent organic precursor. Due to the distinct interaction between ENR and GdSn-PQ, the interstate conversion (ISC) between GdSn-PQ and ENR induces a significant wavelength shift in photoluminescence (PL), improving reliability, selectivity, and visibility compared to quenching- or AIEE-based methods without peak shifts, allowing for highly sensitive and visually detectable analyses. The fluorescence signal of GdSn-PQ exhibited a linear relationship (R2 = 0.9911), with the added ENR concentrations ranging from 5 to 90 nM, with a detection limit of 0.10 nM. We have demonstrated its potential and wide use in the detection of ENR in biological samples (human urine and blood serum) and environmental samples (tap water and seawater) with a recovery rate of 98- 108%. The current approach has demonstrated that the 2D GdSn-PQ nanosheet is a novel and powerful platform for future biological and environmental studies.

Efficient Sequential Detection of Two Antibiotics Using a Fiber-Optic Surface Plasmon Resonance Sensor

Antibiotic residues have become a worldwide public safety issue. It is vital to detect multiple antibiotics simultaneously using sensors. A new and efficient method is proposed for the combined detection of two antibiotics (enrofloxacin (Enro) and ciprofloxacin (Cip)) in milk using surface plasmon resonance (SPR) sensors. Based on the principle of immunosuppression, two antibiotic antigens (for Enro and Cip) were immobilized on an optical fiber surface with conjugates of bovine serum albumin using dopamine (DA) polymerization. Each single antigen was bound to its corresponding antibody to derive standard curves for Enro and Cip. The fiber-optic sensor's sensitivity was 2900 nm/RIU. Detection limits were calculated to be 1.20 ng/mL for Enro and 0.81 ng/mL for Cip. The actual system's recovery rate was obtained by testing Enro and Cip in milk samples; enrofloxacin's and ciprofloxacin's mean recoveries from the milk samples were 96.46-120.46% and 96.74-126.9%, respectively. In addition, several different regeneration solutions were tested to analyze the two target analytes' regeneration ability; NaOH and Gly-HCl solutions were found to have the best regeneration ability.

Nanomaterial-based fluorescent biosensors for the detection of antibiotics in foodstuffs: A review

Antibiotics are widely used as bacteriostatic or bactericidal agents against various microbial infections in humans and animals. The excessive use of antibiotics has led to an accumulation of their residues in food products, which ultimately poses a threat to human health. In light of the shortcomings of conventional methods for antibiotic detection (primarily cost, proficiency, and time-consuming procedures), the development of robust, accurate, on-site, and sensitive technologies for antibiotic detection in foodstuffs is important. Nanomaterials with amazing optical properties are promising materials for developing the next generation of fluorescent sensors. In this article, advances in detecting antibiotics in food products are discussed with respect to their sensing applications, with a focus on fluorescent nanomaterials such as metallic nanoparticles, upconversion nanoparticles, quantum dots, carbon-based nanomaterials, and metal-organic frameworks. Furthermore, their performance is evaluated to promote the continuation of technical advances.

Fluorescence Detection of Carbofuran in Aqueous Extracts Based on Dual-emission SiO2 @Y2 O3 :(Eu3+ ,Tb3+ )@MIP Core-shell structurally Nanoparticles

A novel double-windows fluorescent sensor for carbofuran (CF) detection was successfully developed based on rare-earth Eu, Tb-doped Y₂ O₃ @SiO₂ -based molecularly imprinted nanoparticles (MINs) with multilayer core-shell structure. The recognition process of the MINs for CF was fairly fast and merely need ca. 8 min to reach a dynamic equilibrium. Interestingly, one fluorescent attenuation window was found with an increase of CF concentration (Q) from 0.1 to 10 μg mL^-1 with the limit of detection (LOD) of 0.04 μg mL^-1 at 544 nm belonging to the Tb³⁺ emission, as well as the other fluorescence enhanced window within the range of CF concentration from 10 to 100 μg mL^-1 (LOD = 4 μg mL^-1 ) at 617 nm of Eu³⁺ emission in the dispersed rare-earth doped MINs colloidal aqueous solution. Simultaneously, it was obviously observed that the luminescent resonance energy transfer from CF to Eu³⁺ , and an inner filter effect of CF towards Tb³⁺ as well from the two independent detection windows. The competition experiment displayed hardly any remarkable interference during the detection of CF by addition of its analogues (carbaryl, isoprocarb, aldicarb, methomyl and etofenprox). Moreover, the MINs could also be applied to accurately detect CF in the rhubarb and wolfberry samples with the recoveries of 85.7%-92.2%. The sensing system has high specific recognition and wide detection range to CF and provides new opportunities in pesticide detection.

A multifunctional near-infrared fluorescent sensing material based on core-shell upconversion nanoparticles@magnetic nanoparticles and molecularly imprinted polymers for detection of deltamethrin

The construction of multifunctional sensors has attracted considerable attention due to their multifunctional properties, such as high sensitivity and rapid detection. Herein, near-infrared multifunctional fluorescent sensing materials based on core-shell upconversion nanoparticle@magnetic nanoparticle and molecularly imprinted polymers were synthesized for rapid detection of deltamethrin. The difunctional core-shell upconversion nanoparticle@magnetic nanoparticle was introduced as the optical signal and rapid separator. Firstly, the difunctional core-shell materials were prepared through solvothermal method. Then, molecularly imprinted polymers (MIPs) as recognition elements for deltamethrin were coated on the surface of upconversion nanoparticle@magnetic nanoparticle through polymerization. The structure and recognition characterizations of multifunctional fluorescent sensing materials were evaluated. Under optimal condition, the imprinting factor of sensing materials was 3.63, and the fluorescence intensity of sensing materials decreased linearly with increasing concentration of deltamethrin from 0.001 to 1 mg L^-1 with a detection limit of 0.749 μg L^-1, and a relative standard deviation of 3.10% was obtained with 5 mg L^-1 deltamethrin. The sensing materials showed a high selectivity and were successfully utilized for the detection of deltamethrin in grapes and cabbages; the results showed that the recoveries for two samples obtained were 95.6-102% and 91.8-105%.

Green synthesis of a deep-ultraviolet carbonized nanoprobe for ratiometric fluorescent detection of feroxacin and enrofloxacin in food and serum samples

A sensitive ratiometric fluorescent probe for EFC and FXC detection in milk and bovine serum samples based on the internal filtration effect.

Sensors/nanosensors based on upconversion materials for the determination of pharmaceuticals and biomolecules: An overview

Upconversion materials have been the focus of a large body of research in analytical and clinical fields in the last two decades owing to their ability to convert light between various spectral regions and their particular photophysical features. They emit efficient and sharp ultraviolet (UV) or visible luminescence after excitation with near-infrared (NIR) light. These features overcome some of the disadvantages reported for conventional fluorescent materials and provide opportunities for high sensitivity chemo-and bio-sensing. Here, we review studies that used upconversion materials as sensors for the determination of pharmaceuticals and biomolecules in the last two decades. The articles included in this review were retrieved from the SCOPUS database using the search phrases: "upconversion nanoparticles for determination of pharmaceutical compounds", and "upconversion nanoparticles for determination of biomolecules". Details of each developed upconversion nanoparticles based sensor along with their relevant analytical parameters are reported and carefully explained.

A time-resolved luminescence aptasensor of ofloxacin based on rolling circle amplification and magnetic separation

A novel sensitive, competitive, and time-resolved luminescence sensor for the detection of ofloxacin (OFL) was developed in this study. The sensor used OFL-specific aptamer as a recognition molecule and rolling circle amplification (RCA) as a signal amplification tool. In this way, the time-resolved luminescence can not only avoid background noise from sample, but also provide robust luminescence for detection. Besides, the separation and enrichment of target veterinary drug can be conducted assisted by magnetic treatment. Under optimal conditions, the logarithmic correlation between the concentration of OFL and the luminescence intensity was found to be linear in the range of 5 × 10^-11-5 × 10^-8 mol L^-1 (R² = 0.9988), with a detection limit (LOD) of 32.1 pmol L^-1. Furthermore, this method was applied to the determination of OFL in chicken and pork samples, exhibiting good recovery (72.5-100%) and repeatability (RSD < 10.0%). These results confirm that this novel established method has good application potential for the detection of OFL in food samples.

Fluorometric determination of acetamiprid using molecularly imprinted upconversion nanoparticles

This paper describes the fabrication of an imprinted fluorescent nanoprobe based on SiO₂-coated NaYF₄: Yb, Er upconversion nanoparticles (UCNP) encapsulated with a molecularly imprinted polymer (MIP) for determination of acetamiprid. The fluorescent MIP nanoprobe was prepared using UCNP as the material for fluorescence signal readout, acetamiprid as template molecule, methylacrylic acid (MAA) as functional monomer, and ethyleneglycol dimethacrylate (EGDMA) as cross-linking agent. The molecular imprinting layers were immobilized on the surface of the UCNP@SiO₂ by polymerization which occurred between the double bonds. UCNP@MIP shows a high selectivity towards acetamiprid with an imprinting factor (IF) of 7.84. When UCNP@MIP combines with acetamiprid, the fluorescence of the UCNP@MIP can be quenched due to the photo-induced electron transfer. Under optimum conditions, the fluorescence method shows a good linear relationship between the decreased fluorescence intensity (with excitation/emission peaks at 980/542 nm) and the variation of acetamiprid in the concentration range 20 to 800 ng mL^-1. The limit of detection (LOD) is 8.3 ng mL^-1. This fluorescence method was also successfully applied to detect acetamiprid in apple and strawberry samples. The recoveries range from 89.6 to 97.9%, with relative standard deviations between 1.6 and 2.9% (n = 5). Graphical abstractA simple fluorescence nanoprobe which integrates upconversion nanoparticles (UCNPs) and molecular imprinting polymer (MIP) was developed for the determination of acetamiprid. The limit of the detection was determined as 8.3 ng mL^-1. The selectivity was enhanced by molecular imprinting, and the sensitivity was improved by the high sensitivity of the fluorescence emitted from the UCNPs.

Application of molecularly imprinted polymers as artificial receptors for imaging

Medical diagnostics aims at specific localization of molecular targets as well as detection of abnormalities associated with numerous diseases. Molecularly imprinted polymers (MIPs) represent an approach of creating a synthetic material exhibiting selective recognition properties toward the desired template. The fabricated target-specific MIPs are usually well reproducible, economically efficient, and stable under critical conditions as compared to routinely used biorecognition elements such as fluorescent proteins, antibodies, enzymes, or aptamers and can even be created to those targets for which no antibodies are available. In this review, we summarize the methods of polymer fabrication. Further, we provide key for selection of the core material with imaging function depending on the imaging modality used. Finally, MIP-based imaging applications are highlighted and presented in a comprehensive form from different aspects. STATEMENT OF SIGNIFICANCE: In this review, we summarize the methods of polymer fabrication. Key applications of Molecularly imprinted polymers (MIPs) in imaging are highlighted and discussed with regard to the selection of the core material for imaging as well as commonly used imaging targets. MIPs represent an approach of creating a synthetic material exhibiting selective recognition properties toward the desired template. The fabricated target-specific MIPs are usually well reproducible, economically efficient, and stable under critical conditions as compared to routinely used biorecognition elements, e.g., antibodies, fluorescent proteins, enzymes, or aptamers, and can even be created to those targets for which no antibodies are available.

Rapid and sensitive detection of enrofloxacin hydrochloride based on surface enhanced Raman scattering-active flexible membrane assemblies of Ag nanoparticles

The abuse of antibiotics resulted in the pollution of river is more and more serious and it was necessary to exploit a sensitive detection method to improve the traditional analysis measurement. In this test, it is reported an Ag-based SERS sensing membrane synthesized by the technique of SERS detection and membrane separation. SERS analysis technique presented sensitive detection property, which could be applied into trace analysis. Membrane separation could effectively enrich the analytes to improve the sensitivity. The SERS membrane was synthesized by filtrating Ag nanoparticles (NPs) on the surface and investigating the amount of PVP and Ag NPs to the sensitivity. Meanwhile, the addition of Ag NPs effectively improved the hydrophilia to promote the detection effectivity in the water. By the investigations of optical analysis, the SERS membrane presented high sensitivity in the detection of antibiotics. Under the optimal condition, the SERS intensity presented good linear relationship with the concentration of antibiotics between 1.0 nmol L^-1 and 200 nmol L^-1. This method provided a sensitive detection approach and broadened the investigation field of antibiotics detection.

CdS quantum dots-based immunoassay combined with particle imprinted polymer technology and laser ablation ICP-MS as a versatile tool for protein detection

For the first time, the combination of molecularly imprinted polymer (MIP) technology with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is presented with focus on an optimization of the LA-ICP-MS parameters such as laser beam diameter, laser beam fluence, and scan speed using CdS quantum dots (QDs) as a template and dopamine as a functional monomer. A non-covalent imprinting approach was employed in this study due to the simplicity of preparation. Simple oxidative polymerization of the dopamine that creates the self-assembly monolayer seems to be an ideal choice. The QDs prepared by UV light irradiation synthesis were stabilized by using mercaptosuccinic acid. Formation of a complex of QD-antibody and QD-antibody-antigen was verified by using capillary electrophoresis with laser-induced fluorescence detection. QDs and antibody were connected together via an affinity peptide linker. LA-ICP-MS was employed as a proof-of-concept for detection method of two types of immunoassay: 1) antigen extracted from the sample by MIP and subsequently overlaid/immunoreacted by QD-labelled antibodies, 2) complex of antigen, antibody, and QD formed in the sample and subsequently extracted by MIP. The first approach provided higher sensitivity (MIP/NIP), however, the second demonstrated higher selectivity. A mixture of proteins with size in range 10–250 kDa was used as a model sample to demonstrate the capability of both approaches for detection of IgG in a complex sample.

Preparation of Monodisperse Enrofloxacin Molecularly Imprinted Polymer Microspheres and Their Recognition Characteristics

This study presents a new strategy for the detection of enrofloxacin (ENR) in food samples by the use of monodisperse ENR molecularly imprinted polymers (MIPs). Using enrofloxacin as template molecule, methacrylic acid as functional monomer, and ethylene diglycidyl ether as cross-linker, surface molecularly imprinted polymers (MIPs) were prepared on the surface of polymeric glycidyl methacrylate-ethylene glycol dimethacrylate (P_GMA-EDMA) microspheres. The surface morphology and imprinting behavior of P_GMA-EDMA@MIPs were investigated and optimized. Synthesized P_GMA-EDMA@MIPs showed good physical and chemical stability and specific recognition toward fluoroquinolones. The introduction of P_GMA-EDMA microspheres greatly increased the adsorption area of P_GMA-EDMA@MIPs and increased the adsorption capacity of target molecules. The core shell structure increased the adsorption rate, and adsorption equilibrium was achieved within 6 min, much higher than that of MIPs synthesized by traditional methods. Enrofloxacin in milk samples was detected by molecular imprinting solid phase extraction (MISPE) combined with high performance liquid chromatography (HPLC). Implementing this method resulted in a recovery rate of 94.6~109.6% with a relative standard deviation (RSD) of less than 3.2%. The limit of detection (LOD) of this method was identified as three times the signal-to-noise ratio (10 μg/L). In summary, this work proposed a sensitive, rapid, and convenient method for the determination of trace ENR in food samples.

Covalent organic framework-based electrochemical aptasensors for the ultrasensitive detection of antibiotics

We designed and synthesized a novel covalent organic framework (COF) by condensation polymerization of 1,3,6,8-tetrakis(4-formylphenyl)pyrene and melamine through imine bonds (represented by Py-M-COF). The basic characterizations revealed that the Py-M-COF not only exhibited an extended π-conjugation framework, a large specific surface area (495.5 m² g^-1), big pore cavities, and nanosheet-like structure but also possessed rich functional groups, such as C˭C, C˭N, C˭O, and NH₂. These features endowed the Py-M-COF with high charge carrier mobility, further improving the strong immobilization of DNA aptamer strands via π-π stacking interaction and electrostatic interaction. As such, the Py-M-COF-based electrochemical aptasensors are ultrasensitive in detecting different antibiotics, including enrofloxacin (ENR) and ampicillin (AMP), yielding extremely low detection limits of 6.07 and 0.04 fg mL^-1 (S/N = 3) toward ENR and AMP, respectively, along with other excellent sensing performances. This biosensing platform based on Py-M-COF has potential applications for the sensitive detection of antibiotics or other analytes by replacing the corresponding aptamers.

Aptamer based voltammetric determination of ampicillin using a single-stranded DNA binding protein and DNA functionalized gold nanoparticles

An aptamer based method is described for the electrochemical determination of ampicillin. It is based on the use of DNA aptamer, DNA functionalized gold nanoparticles (DNA-AuNPs), and single-stranded DNA binding protein (ssDNA-BP). When the aptamer hybridizes with the target DNA on the AuNPs, the ssDNA-BP is captured on the electrode surface via its specific interaction with ss-DNA. This results in a decreased electrochemical signal of the redox probe Fe(CN)₆^3- which is measured best at a voltage of 0.188 mV (vs. reference electrode). In the presence of ampicillin, the formation of aptamer-ampicillin conjugate blocks the further immobilization of DNA-AuNPs and ssDNA-BP, and this leads to an increased response. The method has a linear reposne that convers the 1 pM to 5 nM ampicillin concentration range, with a 0.38 pM detection limit (at an S/N ratio of 3). The assay is selective, stable and reproducible. It was applied to the determination of ampicillin in spiked milk samples where it gave recoveries ranging from 95.5 to 105.5%. Graphical abstract Schematic of a simple and sensitive electrochemical apta-biosensor for ampicillin detection. It is based on the use of gold nanoparticles (AuNPs), DNA aptamer, DNA functionalized AuNPs (DNA-AuNPs), and single-strand DNA binding protein (SSBP).