Hua Xiong

Label-free colorimetric detection of trace cholesterol based on molecularly imprinted photonic hydrogels

A novel colorimetric sensor for cholesterol assay was constructed by combining a molecular imprinting technique with photonic crystals. The molecularly imprinted photonic hydrogel (MIPH) film was prepared by a non-covalent, self-assembly approach using cholesterol as a template molecule, and exhibited a highly ordered three-dimensional macroporous structure characterized by scanning electron microscopy under the optimized imprinting conditions. Various factors affecting rebinding of cholesterol are discussed along with recognition specificity studies on its analogues of stigmasterol and ergosterol through estimation of UV-Vis and electrochemical impedance spectroscopy. The MIPH film generated a significantly readable optical signal directly self-reporting within less than 2 min upon binding cholesterol. The colorimetric measurement of cholesterol concentration strongly relies on the fact that the blue shift effect of the Bragg diffraction peak of the MIPH is gradually enlarged with the increase of cholesterol amounts. The detection level approached 10−13 g mL−1, which is comparable to that of fluorescence measurements. The simultaneous possession of high selectivity, high sensitivity, high stability, easy operation and being label-free enables this sensor to be potentially applicable for rapid on-site detection of trace cholesterol.

Enzymatic hydrolysis of rice dreg protein: Effects of enzyme type on the functional properties and antioxidant activities of recovered proteins

The effects of various proteases on the formation and characteristics of rice dreg protein hydrolysates (RDPHs) were investigated. Enzymatic hydrolysis of often under-utilised rice dreg protein (RDP) with different enzymes studied here was found to significantly improve protein content and solubility. RDPHs prepared by alkaline protease showed better protein recovery, producing higher protein content with much smaller peptides, while hydrolysates generated by Protamex showed the highest antioxidant activities with more than 80% solubility over a wide pH range. The results indicated that the type of protease greatly influenced the molecular weight and amino acid residue composition of RDPH. The enzyme type also determined the functional properties and antioxidant activity of the recovered proteins. It was found that an optimum allocation of alkaline protease in addition to the Neutrase enzyme could be an appropriate strategy to produce RDPH with desirable functionalities, antioxidant properties, and low salt content.

Application of targeted drug delivery system in Chinese medicine

Targeted drug delivery system of traditional Chinese medicine (TCM) refers to those using different carriers to make the effective parts or monomer extracted from TCM or natural medicine into agents which can directly concentrate on the target site. This system is an ideal delivery approach and has became a hot spot in the field of TCM pharmaceutical research since it can improve the pharmacological effects and reduce the adverse reactions. This paper reviews literatures on TCM targeted agents which were published in the past 10 years. In accordance with the different carriers, four types of agents, liposome, nanoparticle, microsphere, and emulsion are analyzed. Liposomes were studied most profoundly and a variety of new types of liposomes was developed on the basis of the traditional liposomes. Using natural or synthetic polymer materials to carry drugs, nanoparticles and microspheres can promote the drug through the blood-brain barrier and enhance its bioavailability. Emulsion has lymphatic affinity and the drug is coated in the internal phase, which can protect the drugs from hydrolysis. All these delivery agents are proved to be effective ways to improve the clinical efficacy of drugs, and each is discussed in detail with examples. At present, TCM targeted agents are still in the exploratory stage and many problems need to be solved. Especially, it is a huge challenge to research the targeted delivery systems for the effective parts of Chinese medicines and compound prescriptions, and the paper gives a particular discussion on this point. In the future, more attention should be paid to the research on the particle agents of TCM effective parts, and the development of new carrier materials in order to enhance the overall quality of TCM targeted agents.

Selective solid-phase extraction of Sudan I in chilli sauce by single-hole hollow molecularly imprinted polymers.

A new single-hole hollow molecularly imprinted polymer (SHH-MIP) was prepared by multistep seed swelling polymerization using Sudan I as template molecule and successfully applied to selective solid-phase extraction (SPE) of Sudan dyes in chilli sauce samples. The polymers possessed high specific surface area obtained by nitrogen adsorption and good thermal stability without decomposition lower than 380 °C by thermogravimetry analysis. Much higher binding capacity was exhibited than with irregular solid MIP prepared by bulk polymerization, because most of the binding sites were located in the surface of the polymers, facilitating template removal and mass transfer. Accordingly, the SHH-MIP was employed as SPE adsorbent for chilli sauce analysis and offered high recoveries for Sudan I in the range of 87.5-103.4% with the precision of 1.94-5.33% at three spiked levels. The SHH-MIP with high selectivity and high stability was demonstrated to be potentially applicable for high selective preconcentration and determination of trace Sudan dyes in complicated samples.

Rapid detection of melamine with 4-mercaptopyridine-modified gold nanoparticles by surface-enhanced Raman scattering

AbstractA surface-enhanced Raman scattering (SERS) strategy based on 4-mercaptopyridine (MPY)-modified gold nanoparticles (AuNPs) was developed for the rapid and sensitive detection of melamine in milk powder. The SERS measurement of melamine strongly relied on the “hotspot” effect, in which AuNPs immediately aggregated upon the addition of melamine, leading to significantly enhanced Raman intensity of the reporter molecule MPY and a color change for the solution from red to blue-gray. The limit of detection based on a signal to noise of 3 (S/Nu2009=u20093) was found to be as low as 0.1xa0ppb of melamine, with an excellent linearity of 0.5–100xa0ppb, demonstrating a higher sensitivity and a wider quantitation range than direct SERS sensing methods based on enhanced substrate. An impressive specificity for melamine detection over various common metal ions and excipients in dairy products, even at concentrations of 100-fold higher than melamine, was achieved. Good recoveries of 88.5% and 111.7% were obtained from milk samples spiked to 20 and 100xa0ppb levels, respectively. The proposed method is potentially applicable for the rapid in situ determination of melamine in complex matrices.n FigureAn indirect SERS strategy based on 4-mercaptopyridine (MPY) modified gold nanoparticles (AuNPs) for rapid and sensitive detection of melamine

A pH-responsive nano-carrier with mesoporous silica nanoparticles cores and poly(acrylic acid) shell-layers: Fabrication, characterization and properties for controlled release of salidroside

A novel pH-responsive nano-carrier MSNs-PAA, possessing mesoporous silica nanoparticles (MSNs) cores and poly(acrylic acid) (PAA) shell-layers, was developed for controlled release of salidroside. The vinyl double bonds modified MSNs were synthesized by using cetyltrimethylammonium bromide (CTAB) as templates, tetraethyl orthosilicate (TEOS) as silicon source, and 3-(trimethoxylsilyl) propyl methacrylate (MPS) as surface modification functionalities. The pH-responsive layers of PAA were grafted onto the vinyl double bonds of the MSNs via precipitation polymerization, producing the MSNs-PAA with a hollow cubic core and mesoporous shell with penetrating pore channels. The characteristic results also showed that PAA was successfully grafted onto the surface of the MSNs. The MSNs-PAA was investigated as carriers for loading and regulating the release of salidroside in different pH solutions for the first time. The results demonstrated that the PAA layers on the surface of MSNs-PAA exhibited opened and closed states at different pH values, and thus could regulate the uptake and release of salidroside. The application of such pH-responsive nano-carrier might offer a potential platform for controlled delivery and increasing the bioavailability of drugs.

Water-compatible temperature and magnetic dual-responsive molecularly imprinted polymers for recognition and extraction of bisphenol A

Versatile molecularly imprinted polymers (MIPs) have been widely applied to various sample matrices, however, molecular recognition in aqueous media is still difficult. Stimuli-responsive MIPs have received increasing attentions due to their unique feature that the molecular recognition is regulated by specific external stimuli. Herein, water-compatible temperature and magnetic dual-responsive MIPs (WC-TMMIPs) with hydrophilic brushes were prepared via reversible addition-fragmentation chain transfer precipitation polymerization for reversible and selective recognition and extraction of bisphenol A (BPA). Transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR) and vibrating sample magnetometry (VSM) as characterization methods were used to examine the successful synthesis of polymers, and the resultant WC-TMMIPs showed excellent thermosensitivity and simple rapid magnetic separation. Controlled adsorption and release of BPA by temperature regulation were investigated systematically, and the maximum adsorption and removal efficiency toward BPA in aqueous solutions were attained at 35 °C and 45 °C, respectively, as well as a good recoverability was exhibited with the precision less than 5% through five adsorption-desorption cycles. Phenolic structural analogs were tested and good recognition specificity for BPA was displayed. Accordingly, the WC-TMMIPs were employed as adsorbents for magnetic solid-phase extraction (MSPE) and packed SPE of BPA from seawater samples. Using the two modes followed by HPLC-UV determination, excellent linearity was attained in the range of 0.1-14.5 μM and 1.3-125 nM, with low detection limits of 0.02 μM and 0.18 nM, respectively. Satisfactory recoveries for spiked seawater samples were achieved ranging from 86.3-103.5% and 96.2-104.3% with RSD within 2.12-4.33%. The intelligent WC-TMMIPs combining water-compatibility, molecular recognition, magnetic separation, and temperature regulation proved potentially applicable for selective identification, controlled adsorption/release and high-efficiency enrichment/removal of trace targets in complicated aqueous media.

One-pot synthesis of magnetic molecularly imprinted microspheres by RAFT precipitation polymerization for the fast and selective removal of 17β-estradiol

A facile strategy was developed to prepare magnetic molecularly imprinted microspheres (MMIMs) for the selective recognition and effective removal of 17-beta-estradiol (17β-E2) by reversible addition-fragmentation chain transfer precipitation polymerization. One-pot synthesis was employed, which could simplify the imprinting process and shorten the experimental period. The resultant MMIMs displayed fast kinetics and high binding capacity, and the adsorption processes followed Langmuir–Freundlich isotherm and pseudo-second-order kinetic models. Excellent recognition selectivity toward 17β-E2 was attained over other phenolic estrogens such as 17-alpha-E2, estriol and estrone. The magnetic property of MMIMs provided fast and simple separation, and the recycling process for magnetic solid phase extraction (MSPE) was sustainable at least five times without obvious efficiency decrease. Furthermore, the MMIMs-MSPE presented satisfactory recoveries within 71.7–108.3% with the precisions of 1.1–6.0% for spiked 17β-E2 in water, soil and food samples. The developed MMIMs-based method proved to be a convenient and practical way in sample pretreatment and targeted pollutants removal.

Molecularly imprinted polymer on magnetic graphene oxide for fast and selective extraction of 17β-estradiol.

A novel nanosized substrate imprinted polymer (MIPs-GO-Fe3O4) was developed on a magnetic graphene oxide (GO-Fe3O4) surface for selective recognition and fast removal of 17β-estradiol (17β-E2). The characteristics of MIPs-GO-Fe3O4 were evaluated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy. and vibrating sample magnetometer (VSM). Results suggested that GO had a thin single-layer structure anchoring Fe3O4 nanoparticles and that the imprinted film was coated on the GO-Fe3O4 surface. MIPs-GO-Fe3O4 was sensitive to the magnetic field and could be easily separated using an external magnet. The adsorption results indicated that the kinetic value and binding capacity of MIPs-GO-Fe3O4 were 0.0062 g (mg·min)(-1) and 4.378 μmol g(-1), respectively. The Langmuir-Freundlich isotherm and pseudo-second-order kinetic models were the main adsorption mechanisms for MIPs-GO-Fe3O4. MIPs-GO-Fe3O4 showed excellent recognition selectivity, as well as enrichment and separation abilities for 17β-E2 in complex matrices. MIPs-GO-Fe3O4 was also used to analyze 17β-E2 in real food samples, and satisfactory recoveries such as 84.20% with relative standard deviation (RSD) of 4.67% at a spike of 0.5 μmol L(-1) were obtained. Thus, the MIPs-GO-Fe3O4-based method provided a convenient and practical platform for the separation, enrichment, and removal of 17β-E2 in food samples.

Molecularly Imprinted Photonic Hydrogels as Colorimetric Sensors for Rapid and Label-free Detection of Vanillin

A novel colorimetric sensor for the rapid and label-free detection of vanillin, based on the combination of photonic crystal and molecular imprinting technique, was developed. The sensing platform of molecularly imprinted photonic hydrogel (MIPH) was prepared by a noncovalent and self-assembly approach using vanillin as a template molecule. Morphology characterization by scanning electron microscope (SEM) showed that the MIPH possessed a highly ordered three-dimensional (3D) macroporous structure with nanocavities. The vanillin recognition events of the created nonocavities could be directly transferred into readable optical signals through a change in Bragg diffraction of the ordered macropores array of MIPH. The Bragg diffraction peak shifted from 451 to 486 nm when the concentration of the vanillin was increased from 10⁻¹² to 10⁻³ mol L⁻¹ within 60 s, whereas there were no obvious peak shifts for methyl and ethyl vanillin, indicating that the MIPH had high selectivity and rapid response for vanillin. The adsorption results showed that the hierarchical porous structure and homogeneous layers were formed in the MIPH with higher adsorption capacity. The application of such a label-free sensor with high selectivity, high sensitivity, high stability, and easy operation might offer a potential method for rapid real-time detection of trace vanillin.