Molecularly Imprinting Polymers (MIP) Based on Nitrogen Doped Carbon Dots and MIL-101(Fe) for Doxorubicin Hydrochloride Delivery.

MIL-based molecularly imprinted polymer (MIP) nanocomposites were successfully synthesized through a simple and versatile stirring auxiliary encapsulation method. MIP as a carrier has been applied to the highly efficient selective recognition and sustained release of doxorubicin hydrochloride (DOX). The adsorption mechanism and release behavior of MIP@DOX in vitro were also discussed. Adsorption studies showed that MIP using DOX as template had specific selectivity to DOX, and its optimal drug loading efficiency reached 97.99%. The adsorption isotherm accorded with Freundlich models. The cumulative release curve showed that at the conditions of pH 5.5 and 7.4, the nanomaterials have a slow-release effect on the release of DOX. In addition, the cytotoxicity and bioactivity of MIP nanoparticles on HepG2 and HL-7702 cell lines measured by MTT assay also proved their low toxicity and biological activity. The cell activity of HepG2 and HL-7702 incubated with MIP for 24 h was 69.9% and 76.07%, respectively. These results collectively illustrated that the MIP nano-materials synthesized in this study can be efficiently employed to the drug delivery systems.

Development of an on-line immobilized α-glucosidase microreactor coupled to liquid chromatography for screening of α-glucosidase inhibitors.

In order to rapidly screen α-glucosidase (α-GLU) inhibitors from Chinese herbs extract, an online screening method was developed by using enzymatic microreactors in combination with HPLC. A type of dodecahedral and porous material (ZIF-90) was synthesized at room temperature and employed as supports to construct enzymatic microreactor. The amount of α-glucosidase immobilized on ZIF-90 was 58.65 µg per mg carrier under the optimized conditions. In the online screening process, the eluent of 30 s was selected for detection. For the application of this on-line screening system, three α-glucosidase inhibitors with known structure (2,4-dimethoxy-6,7-dihydroxyphenanthrene, batatasin I, 3,5-dimethoxy-2'-hydroxyaiaryl) were selectively extracted from Dioscorea opposita Thunb. Three compounds screened from honeysuckle leaves were isochlorogenic acid B, 1,5-dicaffeoylquinic acid and isochlorogenic acid C, respectively. Two compounds including (+)-catechin and (-)-epigallocatechin gallate were screened from Xinyang Maojian tea. Three unknown ingredients were also screened out from Radix Rehmanniae Praeparata. The nanomaterials in the microreactor can be conveniently replaced. The screening flow rate and elution time can be easily adjusted and controlled by microinjection pump. Considering the specificity of enzyme binding and convenience of online screening system, this method has great potential for fast real-time fishing of α-glucosidase inhibitors from Chinese herbal medicines.

Electrochemical Detection of Melamine by Using Reduced Graphene Oxide-Copper Nanoflowers Modified Glassy Carbon Electrode.

In this work, a robust and reliable electrochemical sensor was developed for sensitive detection of non-electroactive melamine (MEL) using a modified glassy carbon electrode with ascorbic acid (AA) as the active recognition element. To increase the current signal of AA, the working electrode was successively modified with l-arginine (l-Arg) and reduced graphene oxide-copper nanoflower composite. The voltammetry measurements denoted that the hydrogen bonding was formed between AA and MEL. Using the optimum conditions, the proposed enhanced sensor can detect MEL concentrations ranging from 10 × 10-9 to 9.0 × 10-8 M with a detection limit of 5.0 × 10-9 M that is proportional to the decrease of AA in the anodic peak current. Finally, the proposed sensor was successfully applied for the determination of MEL in commercial infant milk samples and good recovery values were obtained.

Reduced Graphene Oxide-Conjugated Urchin-Like NiCo2O4 Nanostructures for Individual Detection of o-Nitro and p-Amino Phenol.

This work introduced a facile synthesis method of reduced graphene oxide-conjugated urchin-like NiCo2O4 nanostructures via a simple, cost-effective, and environmental-friendly one-pot hydrothermal method. The as-prepared rGO-NiCo2O4 nanocomposites were used to fabricate 3-aminopropyltriethoxysilane-modified glassy carbon electrode (GCE/APTES/rGO-NiCo2O4) for ultrasensitive electrochemical detection of o-nitro (o-NP) and p-amino (p-AP) phenols. The structure and morphology of the nanocomposite were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical experiments revealed that the nanocomposite exhibited remarkable electrochemical performances. A linear relationship is observed with the differential pulse voltammetry experiment between the peak currents and the concentrations in the ranges of 5.0 × 10-9 to 5.0 × 10-7 M (R 2 = 0.996) and 1.0 × 10-6 to 2.5 × 10-5 M (R 2 = 0.992) for o-NP and of 1.0 × 10-8 to 5.0 × 10-7 M (R 2 = 0.996) and 1.0 × 10-6 to 1.0 × 10-4 M (R 2 = 0.987) for p-AP. The calculated detection limits (S/N = 3) are 5.0 × 10-9 M and 1.0 ×10-8 M for o-NP and p-AP, respectively. Furthermore, a very high recovery percentage is obtained with the proposed sensor after successful application in the determination of target analytes in tap water samples.

A glassy carbon electrode modified with a composite consisting of gold nanoparticle, reduced graphene oxide and poly(L-arginine) for simultaneous voltammetric determination of dopamine, serotonin and L-tryptophan.

A glassy carbon electrode (GCE) was modified with poly(L-arginine) (P-Arg), reduced graphene oxide (rGO) and gold nanoparticle (AuNP) to obtain an electrode for simultaneous determination of dopamine (DA), serotonin (5-HT) and L-tryptophan (L-Trp) in the presence of ascorbic acid (AA). The modified GCE was prepared via subsequent 'layer-by-layer' deposition using an electrochemical technique. The surface morphology of the modified electrode was studied by scanning electron microscopy, and electrochemical characterizations were carried out via cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode showed excellent electrocatalytic activity toward DA, 5-HT and L-Trp at pH 7.0. Figures of merit for the differential pulse voltammetric reponse are as follows: (a) Response to DA is linear in two intervals, viz. 1.0-50 nM and 1.0-50 µM DA concentration range, the typical working voltage is 202 mV (vs. Ag/AgCl), and the detection limit is 1 nM (at an S/N ratio of 3). For 5-HT, the respective data are 10 to 500 nM and 1.0 to 10 µM, 381 mV, and 30 nM. For L-Trp, the respective data are 10-70 nM and 10-100 µM, 719 mV, and 0.1 µM. The modified GCE is fairly selective. It was successfully applied to the simultaneous determination of DA, 5-HT, and L-Trp in spiked urine samples, and high recovery rates were found. Graphical abstract Schematic presentation of the voltammetric sensor based on a glassy carbon electrode modified with poly(L-arginine), reduced graphene oxide (rGO) and gold nanoparticle (GCE/P-Arg/ErGO/AuNP) for simultaneous determination of dopamine (DA), serotonin (5-HT) and L-tryptophan (L-Trp).