Self-polymerized polydopamine-imprinted layer-coated carbon dots as a fluorescent sensor for selective and sensitive detection of 17β-oestradiol

Blending polydopamine-derived imprinted polymers with rice straw-based fluorescent carbon dots for selective detection and adsorptive removal of ibuprofen

Dual-functioning probes capable of detecting and removing hazardous substances have recently received increased attention compared to exclusive sensory probes. Herein, a new composite is synthesized by blending polydopamine imprinted polymers with fluorescent carbon dots (PIP-FCDs) for the selective recognition and adsorption of Ibuprofen (IBF), which is a nonsteroidal anti-inflammatory drug and is excessively released in the pharmaceutical wastes. The PIP-FCDs consist of confined pockets for encasing IBF and generate fluorescence quenching signal when contact with the molecule. PIP-FCDs show high sensitivity (limit of detection = 1.58 × 10-5 μM) and selectivity towards IBF in the presence of other pharmaceutical drugs i.e., aspirin, ketoprofen, norfloxacin, and levofloxacin. The adsorption studies show an adsorption capacity of 209.8 mg g-1 with an extraction efficiency of around 99.9 %. Furthermore, PIP-FCDs are utilized to determine IBF levels in various aqueous pharmaceutical samples. This development provides a simple and dual-functioning probe for the detection and adsorption of IBF from various matrices.

Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer

This article introduces distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) and carbon dots (CDs) for simultaneous quantification of cytokine biomarkers, namely C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) in human biological samples for diagnosis of cytokine syndrome. Using fluorescent CDs and MIP technology, the dPAD exhibits high selectivity and sensitivity. Detection is based on fluorescence quenching of CDs achieved through the interaction of the target analytes with the MIP layer on the paper substrate. Quantitative analysis is easily accomplished by measuring the distance length of quenched fluorescence with a traditional ruler and naked eye readout enabling rapid diagnosis of cytokine syndrome and the underlying infection. Our sensor demonstrated linear ranges of 2.50-24.0 pg mL-1 (R2 = 0.9974), 0.25-3.20 pg mL-1 (R2 = 0.9985), and 1.50-16.0 pg mL-1 (R2 = 0.9966) with detection limits (LODs) of 2.50, 0.25, and 1.50 pg mL-1 for CRP, TNF-α, and IL-6, respectively. This sensor also demonstrated remarkable selectivity compared to a sensor employing a non-imprinted polymer (NIP), and precision with the highest relative standard deviation (RSD) of 5.14%. The sensor is more accessible compared to prior methods relying on expensive reagents and instruments and complex fabrication methods. Furthermore, the assay provided notable accuracy for monitoring these biomarkers in various human samples with recovery percentages ranging between 99.22% and 103.58%. By integrating microfluidic systems, nanosensing, and MIPs technology, our developed dPADs hold significant potential as a cost-effective and user-friendly analytical method for point-of-care diagnostics (POC) of cytokine-related disorders. This concept can be further extended to developing diagnostic devices for other biomarkers.

Distance-based paper analytical devices integrated with molecular imprinted polymers for Escherichia coli quantification

The development of distance-based paper analytical devices (dPADs) integrated with molecularly imprinted polymers (MIPs) to monitor Escherichia coli (E. coli) levels in food samples is presented. The fluidic workflow on the device is controlled using a designed hydrophilic bridge valve. Dopamine serves as a monomer for the formation of the E. coli-selective MIP layer on the dPADs. The detection principle relies on the inhibition of the E. coli toward copper (II) (Cu2+)-triggered oxidation of o-phenylenediamine (OPD) on the paper substrate. Quantitative detection is simply determined through visual observation of the residual yellow color of the OPD in the detection zone, which is proportional to E. coli concentration. The sensing exhibits a linear range from 25.0 to 1200.0 CFU mL-1 (R2 = 0.9992) and a detection limit (LOD) of 25.0 CFU mL-1 for E. coli detection. Additionally, the technique is highly selective with no interference even from the molecules that have shown to react with OPD to form oxidized OPD. The developed device demonstrates accuracy and precision for E. coli quantification in food samples with recovery percentages between 98.3 and 104.7% and the highest relative standard deviation (RSD) of 4.55%. T-test validation shows no significant difference in E. coli concentration measured between our method and a commercial assay. The proposed dPAD sensor has the potential for selective and affordable E. coli determination  in food samples without requiring sample preparation. Furthermore, this strategy can be extended to monitor other molecules for which MIP can be developed and integrated into paper-microfluidic platform.

Molecularly imprinted ratiometric fluorescence sensor for visual detection of 17β-estradiol in milk: A generalized strategy toward imprinted ratiometric fluorescence construction

17β-Estradiol (E2) is the typical endocrine disruptor of steroidal estrogens and is widely used in animal husbandry and dairy processing. In the environment, even lower concentrations of E2 can cause endocrine dysfunction in organisms. Herein, we have developed a novel molecularly imprinted ratiometric fluorescent sensor based on SiO2-coated CdTe quantum dots (CdTe@SiO2) and 7-hydroxycoumarin with a post-imprint mixing strategy. The sensor selectively detected E2 in aqueous environments due to its two fluorescent signals with a self-correction function. The sensor has been successfully used for spiking a wide range of real water and milk samples. The results showed that the sensor exhibited good linearity over the concentration range 0.011-50 μg/L, obtaining satisfactory recoveries of 92.4-110.6% with precisions (RSD) < 2.5%. Moreover, this sensor obtained an ultra-low detection limit of 3.3 ng/L and a higher imprinting factor of 13.66. By using estriol (E3), as a supporting model, it was confirmed that a simple and economical ratiometric fluorescent construction strategy was provided for other hydrophobic substances.

Remote Manipulation of TRPV1 Signaling by Near-Infrared Light-Triggered Nitric Oxide Nanogenerators for Specific Cancer Therapy

Specific activation of transient receptor potential vanilloid member 1 (TRPV1) channels provides a new avenue for cancer treatment by inducing excessive Ca2+ influx. However, controllable manipulation of TRPV1 signaling for clinical application has remained elusive due to the challenge in finding a mild and effective method of exerting external stimulus without adverse side effects in living systems. Herein, a TRPV1-targeting near-infrared (NIR) triggered nitric oxide (NO)-releasing nanoplatform (HCuS@PDA-TRPV1/BNN6) based on polydopamine (PDA) coated hollow copper sulfide nanoparticles (HCuS NPs) is developed for specific cancer therapy. Upon NIR irradiation, the NO donor BNN6 encapsulated in NIR-responsive nanovehicles can locally generate NO to activate TRPV1 channels and induce Ca2+ influx. This NIR controlled mode enables the nanoplatform to exert its therapeutic effects below the apoptotic threshold temperature (43°C), minimizing the photothermal damage to normal tissue. Integrating this special NO-mediated therapy with HCuS NPs mediated chemodynamic therapy, the designed nanoplatform exhibits a boosted anticancer activity with negligible systematic toxicity. Together, this study provides a promising strategy for site-specific cancer therapy by spatiotemporally controlled activation of surface ion channels, thus offering a solution to an unmet clinical need in cancer treatment.

Preparation of double-system imprinted polymer-coated multi-walled carbon nanotubes and their application in simultaneous determination of thyroid-disrupting chemicals in dust samples

Dust ingestion is a significant route of human exposure to thyroid-disrupting chemicals (TDCs), and simultaneous determination of multi-contaminants is a great challenge for environmental monitoring. In this study, molecularly imprinted polymer-coated multi-walled carbon nanotubes using thyroxine as the template were synthesized for highly selective TDCs capture. This polymer was prepared by integrating the atom transfer radical polymerization using 2-(3-indol-yl)ethylmethacrylamide as the monomer with the self-polymerization of dopamine. Construction of double-system imprinted cavities could significantly improve their selective recognition performance for TDCs and the coincidence rate reached 88.5 %. The prepared polymers were applied as the solid phase extraction adsorbent to simultaneously determine 7 groups of 35 TDCs. The proposed method showed wide linear range (0.25-1000 ng L-1), low limits of detection (0.02-0.23 ng L-1) and acceptable recoveries (81.8 %-103.5 %). The occurrence and distribution of TDCs were then studied in indoor dust samples (n = 65) collected from four cities in China. We found that tetrabromobisphenol A was the predominant compound and perfluorinated compounds were the most abundant TDCs. In addition, the distribution ratio of TDCs varied between regions. This study provides an efficient technology for direct exposure assessment of multi-contaminants.

A Review of Sensing Applications of Molecularly Imprinted Fluorescent Carbon Dots for Food and Biological Sample Analysis

Molecularly imprinted fluorescent carbon dots (MI-FCDs) find numerous applications in analytical chemistry due to their outstanding photoluminescent properties and having specific pockets for the recognition of target molecules. Despite significant advances, practical applications of MI-FCDs-based fluorescent sensors are still in their initial stages. Therefore, the topical developments in the synthesis, working, and application of MI-FCDs for sensing various target species (e.g., pharmaceuticals, biomolecules, pesticides, food additives, and miscellaneous species) in food and biological media have been highlighted. Moreover, a careful evaluation has been made to select the best methods based on their performance in terms of analytical parameters. To expand the horizons of this field, important challenges and future directions for developing MI-FCDs for practical use are also presented. This review will highlight important aspects of MI-FCDs-based fluorescent sensors for their applicability in food science, material science, environmental science, nanoscience, and biotechnology.

Fabrication of molecularly-imprinted gold nanoparticle-embedded Fe-MOFs for highly selective SERS detection of 17β-estradiol in milk

17β-Estradiol (17β-E2) could accumulate in humans through milk, thus causing diseases by interfering with the function of the endocrine system. However, its detection at a trace level in milk is still a challenge because of matrix interferences. In this work, a core-shell structured polydopamine molecular-imprinted gold nanoparticles (AuNP@MIP-PDA) were embedded into Fe metal-organic framework materials to form a well-defined hexagonal microspindle structure of AuNP@MIP-PDA@MIL-101(Fe). AuNP@MIP-PDA were successfully encapsulated within the MIL-101 crystals through the hydrophobic interaction between organic ligands and the aromatic groups of PDA, the chelating power of catechol groups, as well as the introduction of acetic acid. Combined with the SERS activity of AuNPs, the specific recognition sites from MIPs, and the adsorption and enrichment capability of MIL-101, the fabricated nanohybrids could be designed as highly selective SERS sensors for the detection. By effectively preventing the macromolecule adsorption and the preconcentration of 17β-E2 near the SERS-active surface, the SERS sensor could be directly applied in the selective detection of 17β-E2 in milk without tedious pretreatment. The method demonstrated an outstanding detection limit of 1.95 × 10^-16 mol L^-1, without the interference mainly originating from the two analogues, estrone and estriol. These promising results foresee the potential application of this novel MIP-based SERS sensor in food and environmental sensing.

Surface imprinting by using bi-functional monomers on spherical template magnetite for selective detection of levodopa in biological fluids

The present work introduces an innovative biosensing platform for greatly sensitive determination of levodopa medicine. Initially, spherical magnetic (SM) nanoparticles were prepared by hydrothermal fabrication approach and used as a pattern to make spherical magnetic molecular imprinted polymer (SMMIP). Afterward, levodopa-molecularly imprinted layer was grown on the surface of the spherical magnetic pattern by electropolymerization with dopamine and resorcinol as bi-functional monomers and levodopa as a template molecule, which enhanced the specific recognition of the sensing platform to levodopa. The presence of SM nanoparticles could not only accelerate the mass transfer, the electron transport rate, and improve specific surface area of the electrode but also facilitate the recognition of the polymer, in this way increasing the current response and improving the performance of the biosensor. The superior sensing efficiency of the presented biosensor was confirmed based on the low limit of detection of 10 nmol L^-1 which represented two linear ranges from 0.5 to 200 μmol L^-1 and 200-1000 μmol L^-1 for levodopa. More importantly, the practicability of the biosensor was proved by detecting levodopa in tablet, blood serum and plasma, implying that the sensing platform was suitable for monitoring levodopa in actual biological fluid and medicine.