Biomedical subjects

Zhenghong Xu

Publications and source records attributed to Zhenghong Xu.

7 recordsLinked to original sources

PubMed2006

In vitro and in vivo evaluation of donepezil-sustained release microparticles for the treatment of Alzheimer's disease.

The purpose of this work is to prepare donepezil microparticles (DM) and evaluate its advantage as a sustained release delivery system with subcutaneous injection once a month. DM was prepared using poly (d,l-lactide-co-glycolide) (PLGA) by an oil-water emulsion solvent evaporation technique. DM showed the loading ratio 13.2+/-2.1% (w/w) and yield 54.8+/-0.8% with mean particle size about 75mum. In vitro release of DM showed that donepezil completely released within 28 days in water, but the cumulative release percentages up to day 30 were 98.4% and 49.1% for phosphate buffer saline (PBS, pH 5.8) and PBS (pH 7.4), respectively. The in vivo experiment demonstrated that DM (90mg/kg) produced a sustained release process in rats, and reached steady-state concentration at day 8 and maintained until day 27 with steady-state levels of donepezil between 130.3+/-7.8 and 121+/-9.8ng/ml, which was accordance with that of free donepezil by oral application route (3mg/kgday). DM (90mg/kg) by subcutaneous infusion in rats produced the same pharmacological role as free donepezil (3mg/kgday) by oral application route. These results implicated that DM as a sustained release delivery strategy could substitute for its oral formulation for therapy of AD and come true its administration once a month.

Alzheimer Disease↗

PubMed2006

Examination of depth-weighted optical signals during cardiac optical mapping: a simulation study.

Optical mapping has become a powerful tool to explore complex cardiac propagation. Many experiments and studies claimed that the fluorescence obtained from tissue surface is the averaged response of the transmembrane potential upon probing depth rather than only on the surface. With the electrical propagation model and the photon transport model, the effects of depth-weighted optical signals are examined both during a normal excitation wave and a spiral wave. Our results indicate that depth-weighted optical signals may infer cardiac activation dynamics, such as the mode and the direction of the propagation, the spatial distribution of depolarization or repolarization.

Action Potentials↗

PubMed2006

[Optical mapping of the membrane potential with voltage-sensitive dyes].

Optical mapping of the membrane potential with voltage-sensitive dyes is an advanced approach that involves in many theories such as molecular photonica, physiology and computer science. Compared with the conventional techniques of membrane patch-clamp and microelectrode, the optical mapping system can measure not only the changes of a single membrane potential from multiple sites simultaneously but also the conduction properties of the cell populations. So this technique provides an important method for studying the electrophysiology of the small cell, the tiny neurite and the cardiac arrhythmia, etc. Because this technique can also avoid the electromagnetic interferences, it uniquely provides an ideal means for studying the mechanisms such as cardiac defibrillation. In this paper the principles and the system structure of the optical mapping are introduced, its applications and future developments are also presented at the same time.

Animals↗

PubMed2005

A delivery strategy for rotenone microspheres in an animal model of Parkinson's disease.

In order to study the pathogenesis of Parkinson's disease (PD), and explore therapeutic drug or approaches, the accurate animal model of PD with inexpensive, biocompatible and convenient administration was necessary. The aim of the present work was to investigate a delivery strategy for rotenone microspheres in an animal model of PD. The rotenone microspheres were prepared by solvent evaporation technique. The rotenone microspheres showed high entrapment efficiency (97.4+/-2.2%) with particle size about 100 microm. In vitro release of rotenone microspheres demonstrated different profiles from medium with different pH or concentration of isopropyl alcohol. The most consistent medium with in vivo rotenone levels in rat plasma was PBS (pH 5.8) with 20% isopropyl alcohol, and the cumulated release amount of rotenone over 30 days was 95.4% in it. The rotenone microspheres (9 mg/kg) produced typical PD symptoms in rats, for example, the cataleptic behavior test demonstrated a obviously prolonged descent latency compared with control animals after administration, and the tyrosine hydroxylase (TH) immunohistochemistry tests showed typical histological evidence of selective degeneration of the nigrostriatal dopaminergic system (striatum and substantia nigra) in rotenone microspheres-treated rats. In addition, this delivery system for rotenone model showed many noticeable advantages such as inexpensive, biocompatible and expedient administration by direct subcutaneous injection. This information suggested that rotenone microspheres as a delivery strategy for setting up an ideal animal model of PD was feasible.

Animals↗

PubMed2005

Treatment of praziquantel wastewater using the integrated process of coagulation and gas membrane absorption.

Praziquantel is an anti-schistosoma drug, its wastewater contains numerous cyanide and other colloid pollutant. A novel integrated treatment process was proposed in this study, i.e., using coagulation to eliminate colloid pollutant and using gas membrane absorption (GMA) to remove cyanide. The optimization of coagulation condition, determination of cyanide removal rate, elimination of membrane fouling, and overall evaluation of the integrated process for the treatment of praziquantel wastewater were investigated in this study. Good results were achieved: turbidity reduced from 700 NTU to 10-40 NTU, 92% COD was removed, cyanide concentration dropped from 3500 mg/L to below 0.5 mg/L, recovery rate of cyanide reached to 98%, and operation cost could be entirely compensated from the gain of recovered cyanide. The results demonstrate that the novel integrated process offers a number of advantages over alkaline chlorination method in the treatment of praziquantel wastewater: cyanide can be reused rather than destroyed, no secondary pollutants are produced, the operation cost is low and the equipment etching is avoided.

Absorption↗

PubMed2004

In vitro and in vivo evaluation of actively targetable nanoparticles for paclitaxel delivery.

The aim of the present work was to assess the merits of an actively targetable nanoparticles (ATN), PEG-coated biodegradable polycyanoacrylate nanoparticles (PEG-nanoparticles) conjugated to transferrin, for paclitaxel delivery. PEG-nanoparticles loading paclitaxel were prepared by solvent evaporation technique in advance. ATN were prepared by coupling of transferrin to PEG-nanoparticles. The results showed that the average encapsulation efficiency of ATN was 93.4+/-3.6% with particle size (101.4+/-7.2 nm) and zeta-potential (-13.6+/-1.1 mV). The paclitaxel loaded ATN exhibited a low burst effect with about only 16.2% drug release within the first phase. Subsequently, paclitaxel release profiles displayed a sustained release phase. The amount of cumulated paclitaxel release over 30 days was 81.6%. ATN exhibited a markedly delayed blood clearance in mice, and the paclitaxel level from ATN remained much higher at 24 h compared with that of free drug from paclitaxel injection. The distribution profiles of ATN in S-180 solid tumor-bearing mice after intravenous administration showed the tumor accumulation of paclitaxel increase with time, and the paclitaxel concentration in tumor was about 4.8 and 2.1 times higher than those from paclitaxel injection and PEG-nanoparticles at 6 h after intravenous injection. For mice treated with 20 mg/kg x 5 of ATN, the decrease in body weight was limited within 4% of the initial weight at 5 days after the final administration, and tumor regression was significantly observed with complete tumor regression for five out of nine mice. The tumor burden with ATN-treated mice was much smaller compared with free paclitaxel or NTN-treated mice. In addition, the life span of tumor-bearing mice was significantly increased when they were treated with ATN, in particular, three mice survived over 60 days. Thus, PEG-coated biodegradable polycyanoacrylate nanoparticles conjugated to transferrin could be an effective carrier for paclitaxel delivery.

Animals↗

PubMed2004

Characterization and gene cloning of a novel beta-mannanase from alkaliphilic Bacillus sp. N16-5.

An alkaline beta-mannanase was purified to homogeneity from a culture broth of alkaliphilic Bacillus sp. N16-5. The enzyme had optimum activity at pH 9.5 and 70 degrees C. It was composed of a single polypeptide chain with a molecular weight of 55 kDa deduced from SDS-PAGE, and its isoelectric point was around pH 4.3. The enzyme efficiently hydrolyzed galactomannan and glucomannan, producing a series of oligosaccharides and monosaccharides. The beta-mannanase gene (manA) contained an open reading frame (ORF) of 1,479 bp, encoding a 32-amino acids signal peptide, and a mature protein of 461 amino acids, with a calculated molecular mass of 50,743 Da. Strain N16-5 ManA, deduced from the manA ORF, exhibited relatively high amino acid similarity to the members of the glycosyl hydrolase family 5. The eight conserved active-site amino acids in family 5 glycosyl hydrolase were found in the deduced amino acid sequence of strain N16-5 ManA.

Amino Acid Sequence↗