Selective and sensitive determination of celastrol in traditional Chinese medicine based on molecularly imprinted polymers modified Mn-doped ZnS quantum dots optosensing materials

Synthesis of molecularly imprinted polymers based on nitrogen-doped carbon dots for specific detection of chlortetracycline by reversed phase microemulsion method

Among the tetracycline antibiotics, chlortetracycline (CTC) is the most frequently used antibiotic except for tetracycline (TC) for enhancing the ability of the organism to fight bacterial infections. The poor metabolism and degradability of CTC can cause serious health effects. Most studies have focused on the detection and analysis of TC, and research on CTC is relatively scarce. This is because the structures of CTC and TC and oxytetracycline (OTC) are extremely similar, and even indistinguishable. In this study, CTC was used as a template molecule and a molecularly imprinted layer was coated on the surface of highly fluorescent N-CDs using a reversed-phase microemulsion method to form N-CDs@MIPs. It was possible to specifically identify CTC without the influence of TC and OTC, which are extremely similar in structure. By comparing with the non-imprinted polymer (N-CDs@NIPs), it exhibited high sensitivity and selectivity with an imprinting factor of 2.02. And it was used in the determination of CTC in milk with recoveries and relative standard deviations of 96.7%-109.8% and 0.64%-3.27%, respectively, with high accuracy and precision. The specificity of the measurement is excellent compared with other assays, and it is a valid and reliable assay.

Applications of Molecular Imprinting Technology in the Study of Traditional Chinese Medicine

Traditional Chinese medicine (TCM) is one of the most internationally competitive industries. In the context of TCM modernization and internationalization, TCM-related research studies have entered a fast track of development. At the same time, research of TCM is also faced with challenges, such as matrix complexity, component diversity and low level of active components. As an interdisciplinary technology, molecular imprinting technology (MIT) has gained popularity in TCM study, owing to the produced molecularly imprinted polymers (MIPs) possessing the unique features of structure predictability, recognition specificity and application universality, as well as physical robustness, thermal stability, low cost and easy preparation. Herein, we comprehensively review the recent advances of MIT for TCM studies since 2017, focusing on two main aspects including extraction/separation and purification and detection of active components, and identification analysis of hazardous components. The fundamentals of MIT are briefly outlined and emerging preparation techniques for MIPs applied in TCM are highlighted, such as surface imprinting, nanoimprinting and multitemplate and multifunctional monomer imprinting. Then, applications of MIPs in common active components research including flavonoids, alkaloids, terpenoids, glycosides and polyphenols, etc. are respectively summarized, followed by screening and enantioseparation. Related identification detection of hazardous components from TCM itself, illegal addition, or pollution residues (e.g., heavy metals, pesticides) are discussed. Moreover, the applications of MIT in new formulation of TCM, chiral drug resolution and detection of growing environment are summarized. Finally, we propose some issues still to be solved and future research directions to be expected of MIT for TCM studies.

Random forest algorithm-enhanced dual-emission molecularly imprinted fluorescence sensing method for rapid detection of pretilachlor in fish and water samples

A sensitive and efficient fluorescence sensor based on dual-emission molecularly imprinted polymers (Dual-em-MIPs) was successfully developed using the random forest (RF) machine-learning algorithm for the rapid detection of pretilachlor. SiO₂ coatings on red-emitting CdSe/ZnS quantum dots (r-SiO₂@QDs) as intermediate light-emitting components are non-selective for pretilachlor, whereas molecularly imprinted layers coated with blue-emitting nitrogen-doped graphene quantum dots (N-GQD_S) are selective. Fluorescence images of the Dual-em-MIPs were acquired. The red (R), green (G), and blue (B) color values of the image were analyzed using an RF algorithm, and the classifier was trained using 103 fluorescent images for automatic analyses. Under optimized conditions, an excellent linear relationship between the sensor and pretilachlor was obtained in the range of 0.001-5.0 mg/L (R², 0.9958). Additionally, the satisfactory recoveries of Dual-em-MIPs ranged between 92.2 % and 107.6 % for the real samples, with a relative standard deviation (RSD) under 6.5 %. The satisfactory recoveries of the RF model based on the fluorescence sensor were 84.2-108.2 % with the RSD under 6.4 %. Overall, the proposed fluorescence sensor based on Dual-em-MIPs and machine learning methods was successfully used to determine pretilachlor in the environment and in aquatic products.

A strategy of utilizing Cu2+-mediating interaction to prepare magnetic imprinted polymers for the selective detection of celastrol in traditional Chinese medicines

In this work, a novel strategy to prepare molecularly imprinted polymers (MIPs) functionalized magnetic carbon nanotubes (MCNTs) via a facile sol-gel polymerization by adopting Cu²⁺-mediating interaction was presented for selective recognition of celastrol (Cel), in the traditional Chinese medicines (TCM). Firstly, template Cel, 3-aminopropyltriethoxysilane (APTES) as monomer and Cu²⁺ (co-monomer) were mixed to form a self-assembled pre-complex, in which Cu²⁺ could coordinate with Cel. Meanwhile, APTES plays a role of bridge between APTES and Cel. Secondly, carboxyl modified MCNTs as substrate was added into the pre-complex solution. After that, a multi-step sol-gel polymerization process was occurred in the presence of tetraethylorthosilicate as cross-linker and acetic acid as catalyst. Finally, MIPs layer was formed on the surface of the MCNTs (Cel-MIPs@MCNTs) after the removal of template with methanol/acetic. The morphology and structure of Cel-MIPs@MCNTs was investigated by various characterization techniques. The adsorption performance of Cel-MIPs@MCNTs to Cel was illustrated by kinetic, isothermal and selective binding experiments. The results displayed that the Cel-MIPs@MCNTs possessed fast kinetic equilibrium time (40 s), high adsorption capacity (13.35 μg mg^-1), good imprinting factor of 3.41, and high magnetic responsivity (44.38 emu·g^-1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A selective and sensitive method based on Cel-MIPs@MCNTs coupling with HPLC was developed for Cel determination including a wide linear range (0.15-200 μg mL^-1) with correlation coefficient of 0.9998, a low limit of detection (0.05 μg mL^-1). Furthermore, the applicability of Cel-MIPs@MCNTs was demonstrated to isolate and determine Cel in TCM samples with satisfactory recoveries ranged from 84.47% to 91.5% (RSD<5.35%). The results revealed that Cel-MIPs@MCNTs offer great potential as an adsorbent for selective and efficient isolation of Cel from complex TCM samples.

Novel synthesis of Mn: ZnSe@ZnS core-shell quantum dots based on photoinduced fluorescence enhancement

A novel Type-I Mn: ZnSe@ZnS core-shell quantum dots (QDs) was reported through a two-step procedure by using low-cost inorganic salts and naturalbiomacromolecule as raw materials. Based on a designed structure of L-cysteine-capped Mn: ZnSe QDs in aqueous media with the controllable surface, Mn: ZnSe@ZnS core-shell QDs were formed due to photoactive ions and defect curing under continuous constant light. The influences of experimental variables, including synthesis conditions of Mn: ZnSe QDs, different types and affecting factors of photo irradiation had been systematically investigated. Under the effect of photoinduced fluorescence enhancement, the photoluminescence (PL) intensity increases significantly by about 5-10 times after 1-3 h of UV irradiation. The position of the fluorescence peak was red-shifted by about 17 nm, emitting orange-red fluorescence. The photoluminescence quantum yield (PL QY) was markedly improved (up to 35%). The structure and morphology of Mn: ZnSe@ZnS core-shell QDs were also confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) in detail. The mechanism of photoinduced fluorescence enhancement was attributed to L-cysteine allowed to release S^2- to form a ZnS shell, and the passivated surface non-radiative relaxation centers of Mn: ZnSe@ZnS QDs was successfully synthesized with highuniform size, excellent photoluminescence performance, and good stability, all ofwhichmakethemgood potential candidates for white LEDs, and biological labels.

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.

Application of micro/nanomaterials in adsorption and sensing of active ingredients in traditional Chinese medicine

Traditional Chinese medicine (TCM) has been widely applied for the prevention and cure of various diseases for centuries. Ingredient with pharmacological activity is the key to the application of TCM. Hence, it is of significance to separate and detect active ingredients in TCM effectively. Micro/nanomaterial is the promising candidate for adsorption and sensing due to its unique physical and chemical properties. For years, many efforts have been made to develop functional micro/nanomaterials to realize the effective adsorption or sensing of bioactive compounds in TCM. In this review, we discussed recent progresses in the application of various functional micro/nanomaterials for adsorption or detection (electrochemical detection, fluorescent detection, and colorimetric detection) of active ingredients. Based on the kind of matrix materials, micro/nano-adsorbents or sensors can be classified into following categories: metal-based micro/nanomaterials, porous materials, carbon-based materials, graphene/graphite-liked micro/nanomaterials and hybrid micro/nanomaterials.

Interaction of LiYF4:Yb3+/Er3+/Ho3+/Tm3+@LiYF4:Yb3+ upconversion nanoparticles, molecularly imprinted polymers, and templates

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites. Three luminescent molecularly imprinted polymer (MIP) nanocomposites were prepared by in situ polymerization. The relationship between the functional monomers, templates, and upconversion nanoparticles was investigated. Two hydrophilic monomers (acrylic acid (AA) and acrylamide (AAm)) and one hydrophobic monomer (N-tert-butylacrylamide (TBAm)) were employed as functional monomers, while one amino acid (cysteine) and two proteins (albumin and hemoglobin) were employed as the templates to investigate the effect of their interaction with LiYF₄:Yb³⁺/Er³⁺/Ho³⁺/Tm³⁺@LiYF₄:Yb³⁺ core/shell UCNPs on the polymerization process, luminescence properties, and adsorption capacity. The results showed that the UCNPs were embedded in the polymeric matrix to form an irregular quasimicrospherical UCNPs@MIP with diameters ranging from several hundred nanometers to several micrometers depending on the functional monomer. The quenching effect was more pronounced for the adsorption of hemoglobin with UCNPs@MIP compared to cysteine and albumin. In addition, the adsorption capacities of the AA- and AAm-made UCNPs@MIP were greater than those of TBAm-made UCNPs@MIP. The rebinding of the templates onto UCNPs@MIP was very fast and approached equilibrium within 30 min, indicating that the synthesized UCNPs@MIP can be employed as fluorescent probes to offer rapid detection of molecules.

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites.