The Effect of Drug Heterogeneous Distributions within Core-Sheath Nanostructures on Its Sustained Release Profiles.

The sustained release of a water-soluble drug is always a key and important issue in pharmaceutics. In this study, using cellulose acetate (CA) as a biomacromolecular matrix, core-sheath nanofibers were developed for providing a sustained release of a model drug-metformin hydrochloride (MET). The core-sheath nanofibers were fabricated using modified tri-axial electrospinning, in which a detachable homemade spinneret was explored. A process-nanostructure-performance relationship was demonstrated through a series of characterizations. The prepared nanofibers F2 could release 95% of the loaded MET through a time period of 23.4 h and had no initial burst effect. The successful sustained release performances of MET can be attributed to the following factors: (1) the reasonable application of insoluble CA as the filament-forming carrier, which determined that the drug was released through a diffusion manner; (2) the core-sheath nanostructure provided the possibility of both encapsulating the drug completely and realizing the heterogeneous distributions of MET in the nanofibers with a higher drug load core than the sheath; (3) the thickness of the sheath sections were able to be exploited for further manipulating a better drug extended release performance. The mechanisms for manipulating the drug sustained release behaviors are proposed. The present proof-of-concept protocols can pave a new way to develop many novel biomolecule-based nanostructures for extending the release of water-soluble drugs.

The key role of straight fluid jet in predicting the drug dissolution from electrospun nanofibers.

In nanopharmaceutics, a robust manipulation of the preparation process and an accurate prediction of the final product size are very important for developing novel nano drug delivery systems. In the present study, for the first time, a process parameter, i.e. the length of the straight fluid jet, L, is correlated with an experimental parameter, i.e. fluid flow rate, F; a nanofiber property, i.e. diameter, D; and the corresponding drug-sustained release profile. Using a mixed solution consisting of 15% (w/v) polyacrylonitrile and 3% (w/v) ketoprofen in acetone and N,N-dimethylformamide (2:8, v:v) as a spinnable working fluid, a series of medicated nanofibers were prepared under variable F and were characterized. The analysis results disclosed the quantitative relationships among different types of parameters. The process parameter L exhibited a better linear relationship with the nanofibers' diameter (D) than the processing parameter F. These results give a hint that process parameters can be exploited as useful tools for accurately predicting and tailoring the resultant nanofibers' D, and in turn their functional performances. The strategy proposed here presents a new approach to investigate the electrohydrodynamic process and manipulate the functions of nanoproducts through process-property-performance relationships.

Targeted delivery and controlled release of doxorubicin into cancer cells using a multifunctional graphene oxide.

We have synthesized a new multifunctional graphene oxide as a drug carrier targeting to hepatocarcinoma cells. Surface modified graphene oxide with polyethyleneimine (PEI) sequentially derivatised with fluorescein isothiocyanate (FI) and polyethylene glycol (PEG)-linked lactobionic acid (LA), and acetylation of remaining terminal amines of the PEI produced a new multifunctional graphene oxide drug carrier (GO/PEI.Ac-FI-PEG-LA). Doxorubicin (DOX), an anticancer drug, was encapsulated in GO/PEI.Ac-FI-PEG-LA to give GO/PEI.Ac-FI-PEG-LA/DOX, with a drug loading percentage of 85%. We showed that both GO/PEI.Ac-FI-PEG-LA and GO/PEI.Ac-FI-PEG-LA/DOX were water soluble and stable between pH 5.0 and 9.0. In vitro release studies indicated that the release rate of DOX from GO/PEI.Ac-FI-PEG-LA/DOX complexes were significantly higher at pH5.8 than that of the physiological pH. Another important feature of this carrier is its good cell viability in the tested concentration range (0-4µM), and the GO/PEI.Ac-FI-PEG-LA/DOX can specifically target cancer cells overexpressing asialoglycoprotein (ASGPR) receptors and exert growth inhibition effect to the cancer cells. The enhanced target specificity and the substantial improvement in pH responsive controlled release have made this new carrier a potential choice for non-covalent encapsulation of drugs in GO, and a delivery system for cancer therapy.

A thin-layer chromatography-bioautographic method for detecting dipeptidyl peptidase IV inhibitors in plants.

A thin-layer chromatography (TLC)-bioautographic method was developed with the aim to detect dipeptidyl peptidase IV (DPP IV) inhibitors from plant extracts. The basic principle of the method is that the enzyme (DPP IV) hydrolyzes substrate (Gly-Pro-p-nitroaniline) into p-nitroaniline (pNA), which diazotizes with sodium nitrite, and then reacts with N-(1-naphthyl) ethylenediamine dihydrochloride in turn to form a rose-red azo dye which provides a rose-red background on the TLC plates. The DPP IV inhibitors showed white spots on the background as they blocked enzymolysis of the substrate to produce pNA. The method was validated with respect to selectivity, sensitivity, linearity, precision, recovery, and stability after optimizing key parameters including plate type, time and temperature of incubation, concentration of substrate, enzyme and derivatization reagents, and absorption wavelength. The results showed good lineary within amounts over 0.01-0.1µg range for the positive control, diprotin A, with the coefficient of determination (r(2))=0.9668. The limits of detection (LOD) and quantification (LOQ) were 5 and 10ng, respectively. The recoveries ranged from 98.9% to 107.5%. The averages of the intra- and inter-plate reproducibility were in the range of 4.1-9.7% and 7.6-14.7%, respectively. Among the nine methanolic extracts of medicinal herbs screened for DPP IV inhibitors by the newly developed method, Peganum nigellastrum Bunge was found to have one white active spot, which was then isolated and identified as harmine. By spectrophotometric method, harmine hydrochloride was found to have DPP-IV inhibitory activity of 32.4% at 10mM comparing to that of 54.8% at 50µM for diprotin A.

Molecularly imprinted polymer based on MWCNT-QDs as fluorescent biomimetic sensor for specific recognition of target protein.

A novel molecularly imprinted optosensing material based on multi-walled carbon nanotube-quantum dots (MWCNT-QDs) has been designed and synthesized for its high selectivity, sensitivity and specificity in the recognition of a target protein bovine serum albumin (BSA). Molecularly imprinted polymer coated MWCNT-QDs using BSA as the template (BMIP-coated MWCNT-QDs) exhibits a fast mass-transfer speed with a response time of 25min. It is found that the BSA as a target protein can significantly quench the luminescence of BMIP-coated MWCNT-QDs in a concentration-dependent manner that is best described by a Stern-Volmer equation. The KSV for BSA is much higher than bovine hemoglobin and lysozyme, implying a highly selective recognition of the BMIP-coated MWCNT-QDs to BSA. Under optimal conditions, the relative fluorescence intensity of BMIP-coated MWCNT-QDs decreases linearly with the increasing target protein BSA in the concentration range of 5.0×10(-7)-35.0×10(-7)M with a detection limit of 80nM.

Bioactivity-guided fractionation of the volatile oil of Angelica sinensis radix designed to preserve the synergistic effects of the mixture followed by identification of the active principles.

In natural product research, it is a common experience that fractionation of biologically-active crude extracts can lead to the loss of their original activity. This is attributed to synergistic effects, where two or more components are required to be present together for full activity of the sample. Our previous study showed that a volatile oil of Angelica sinensis radix (VOAS) inhibited endothelial cell proliferation in culture. Here we have used a bioactivity-guided fractionation method to preserve any synergistic effects of VOAS combining countercurrent chromatography (CCC), the MTS cell viability assay and gas chromatography (GC). Using a two-phase CCC solvent system (heptane-ethyl acetate-methanol-water at a volume ratio of 27:23:27:23%), forty-five fractions were isolated, nine of which exhibited anti-endothelial properties. GC analysis showed two bioactive alkylphthalides, Z-ligustilide and n-butylidenephthalide (BP) were the major compounds detected in the bioactive fractions, and were absent in non-bioactive fractions. Our results indicate that Z-ligustilide and BP are the main constituents responsible for the anti-endothelial properties of VOAS. This rapid and reliable approach in preserving sample activity while isolating and identifying its active compounds suggests that this protocol can be a powerful tool for drug discovery from natural products.

Urinary (1)H-NMR metabonomics study on intervention effects of soya milk in Africans.

Metabonomics is an important tool in understanding the toxicological or therapeutic effects of interventions by analysing metabolic profiles and interpreting complex multi-dimensional spectroscopic/spectrometric data using multivariate data analysis. The objectives of this study were to evaluate the metabolic changes following a short-term 5 day soya milk intervention, and to investigate factors that influence soy-phytoestrogen metabolism focused on Africans based in either UK or Nigeria. (1)H-NMR metabonomics was applied to analyse urine samples collected at four phases I-IV (pre, days 3 and 5, and post) of the soy-intervention from African volunteers (n = 40 in total). Individual proton NMR spectra were visually and statistically assessed using multivariate analyses (MVA): principal component analysis (PCA) and (orthogonal-) partial-least square-discriminant analysis ((O-) PLS-DA). In addition, 22 endogenous metabolites were quantified using a Chenomx NMR suite. The results showed the levels of analysed endogenous metabolites (creatinine adjusted) present ranged from 4 µM to 12 mM with large inter-subject variances in acetate, acetone, lactate and trimethylamine. The MVA results showed high inter-individuality and sampling variances based on PCA score plots, and demonstrated soy metabolism to be significantly influenced by location and gender by both PLS-DA and O-PLS-DA.

¹H NMR study of monocrotaline and its metabolites in human blood.

Monocrotaline (MCT) is a naturally occurring hepatotoxic pyrrolizidine alkaloid found in plants. This investigation is aimed at furthering the understanding of the role of blood in mediating the transport of MCT and its reactive metabolites in humans. Reactions of monocrotaline and its metabolites, dehydromonocrotaline (DHM), retronecine (RET) and dehydroretronecine (DHR) with human blood plasma, red blood cells (RBCs), and whole blood were studied in vitro by proton nuclear magnetic resonance spectroscopy. In plasma MCT remained intact and weakly associated with plasma proteins, and DHM was rapidly hydrolyzed releasing necic and lactone acids, and the reactive pyrrolic metabolite. MCT and its metabolite DHM were internalized in RBCs to the extent of 46.0% and 48.9% respectively in 30 min. No polymerization of DHR was observed when incubated with plasma and RBCs. The data clearly showed that both human plasma and RBCs could be the carriers for the transportation of MCT and its metabolites, DHM, RET and DHR between organs and could stabilise the reactive MCT metabolite DHR.

Biological fingerprinting analysis of the traditional Chinese prescription Longdan Xiegan Decoction by on/off-line comprehensive two-dimensional biochromatography.

A comprehensive two-dimensional biochromatography method using a silica-bonded human serum albumin (HSA) column and a RP-HPLC column was developed for the biological fingerprinting analysis of bioactive components in a traditional Chinese medicine (TCM) prescription, Longdan Xiegan Decoction (LXD). The biochromatography with HSA-immobilized stationary phase was applied to study the interaction of multiple components in LXD with HSA in the first dimension, and fractions of HSA column were further separated by a silica monolithic ODS column (on-line)/an ODS column (off-line) coupled with a diode array detector and an atmospheric pressure chemical ionization mass spectrometer (APCI-MS). More than 100 compounds in LXD that interacted with the immobilized HSA were separated and analyzed. Among them 19 compounds were identified based on their retention values, UV spectra, molecular weights and mass spectra. The results show that the developed comprehensive two-dimensional biochromatography system reported here is capable of being used for biological fingerprinting analysis of natural products in complex matrices such as extracts of TCMs and their prescriptions.

Simultaneous determination of six isoflavonoids in commercial Radix Astragali by HPLC-UV.

A HPLC-UV method for the quantification of six major isoflavonoids, calycosin 7-O-beta-D-glucoside (1), formononetin 7-O-beta-D-glucoside (2), (6alphaR, 11alphaR) 3-hydroxy-9,10-dimethoxypterocarpan-3-O-beta-D-glucoside (3), 7,2'-dihydroxy-3',4'-dimethoxyisoflavan-7-O-beta-D-glucoside (4), calycosin (5) and formononetin (6), in Radix Astragali (Huangqi) was developed and validated. The method was proven to be sensitive, specific, accurate and precise, as well as effective and easy.