BACKGROUND:Chitosan is wel known as good biocompatibility and biodegradability;however, its extensive use in biomedical applications is restricted due to its poor transfection efficiency. OBJECTIVE:To prepare the polyethyleneimine-chitosan/DNA nanoparticles loading enhanced green fluorescent protein gene, and to detect their physicochemical properties and gene transfection efficiency towards chondrocytes in vitro.
METHODS:Low molecular weight polyethyleneimine was covalently linked to chitosan backbone to construct chitosan-graft-polyethyleneimine;then the chitosan-graft-polyethyleneimine was mixed with DNA nanoparticles, which loaded enhanced green fluorescent protein gene, by a complex coacervation method. The nanoparticle morphology was observed under a scanning electron microscopy. The sizes and zeta-potentials of the
nanoparticles were measured by a Marven-nano laser diffractometer. The binding capacity of plasmid DNA was evaluated by agarose gel electrophoresis analysis. The gene transfection experiments in vitro were performed towards rabbit’s chondrocytes. The gene transfection efficiency was measured with flow cytometry and under fluorescence microscope. How marked DNA entered into the nucleus of chondrocytes mediated by the nanoparticles was detected by laser scanning confocal microscopy.
RESULTS AND CONCLUSION:The prepared nanoparticles were mainly spherical, with an average size of (154.6±18.6) nm, and zeta-potential of (24.68±6.82) mV. The agarose gel electrophoresis analysis confirmed that the nanoparticles could effectively protect plasmid DNA from DNase Ⅰ-induced degradation. Gene transfection in vitro proved that the nanoparticles were efficient in transfecting rabbit’s chondrocytes and the expression of green fluorescent proteins was observed under fluorescent microscope, with a transfection efficiency of (23.80±1.74)%that was significantly higher than that of the naked plasmid DNA and chitosan/DNA nanoparticles (P<0.05). But no significant differences were observed between polyethyleneimine-chitosan/DNA nanoparticles and LipofectamineTM 2000. These findings indicate that the polyethyleneimine-chitosan/DNA nanoparticles can effectively protect plasmid DNA from nuclease degradation, and exhibit the favorable transfection ability towards articular chondrocytes.

BACKGROUND:Chitosanase is an enzyme for efficient and special hydrolysis of chitoan, and hence its effective and stable expression with enzymatic activity wil contribute to improving gene therapeutic effect.
OBJECTIVE: To construct a chitosanase gene for the efficient and specifical hydrolysis of chitosan, and to investigate its expression inEscherichia coli and the main influencing factors of enzymatic activity.
METHODS:According to the sequences of endo-chitosanase ofAspergilus sp. CJ22-326 provided in Genbank (EU302818), primers were designed and synthesized. The Asperguilus endo-chitosanase gene was amplified by successive extension PCR. And then the recombinant pET28a-His6-CSN was constructed and expressed in
Escherichia coli BL21. Finaly the recombinant His6-CSN fusion protein was analyzed by sodium dodecyl sulfate polyacrylamide gelelectrophoresis (SDS-PAGE), the western blot and dinitrosalicylic acid assay for detecting the enzyme activity of eluted His6-CSN fusion protein. The influence of different pH value and temperature on the enzyme activity of the recombinant chitosanase was investigated.
RESULTS AND CONCLUSION: SDS-PAGE showed that 29 kDa proteins were expressed and the western blot assay showed that His6-CSN expressed successfuly in the host. Dinitrosalicylic acid assay determined the
enzymatic activity of His6-CSN was significantly higher than that of lysozyme, but lower than that of chitosanase from Streptomyces griseus (P < 0.05). The recombinant chitosanase displayed the maximal activity at temperature of 50℃ and pH value of 6.0. There were a higher enzymatic activity remaining at pH value of 4.0-7.0 and
temperature of 30-50℃.

Objective To investigate the relationship between platelet-activating factor acetylhydrolase gene Arg92His(4, 275; G→A), Ile198Thr(7, 593; T→C) and Val279Phe(9, 994; G→T) mutation and cerebral artery athero-sclerosis stenosis. Methods Six hundred forty-twopatients with cerebral infarction underwent cerebral digital subtrac-tion angiography (DSA).The patients were then divided into cerebral artery atherosclerosis stenosis (CAAS) group(n=477) and control group(n=81) accroding to the site and severity of their cerebral artery stenosis. Furthermore, the CAAS group were divided into intracranial artery stenosis(ICAS) subgroup(n=251), extracranial artery stenosis(ECAS) subgroup (n=115) and extracranial-intracerebral artery stenosis(ECAS) subgroup(n=111). The distributions of genotype and allele frequencies of Arg92His,Ile198Thr and Val279Phe mutation of platelet-activating factor acetylhydrolase gene were ex-amined and comparied in different groups. Results There were significant differences in the distributions of genotype and allele of Arg92His mutation between ICAS subgroup and control group(42.6% vs. 30.3%;23.3% vs. 16.4%, P <0.05). These associations were not detected in ECAS and IECAS subgroups. There was no significant association be-tween Ile198Thr and Val279Phe and stenosis at any site(P>0.05). The distributions of genotype and allele of Arg92His, Ile198Thr and Val279Phe mutation were no significantly difference between CAAS group and control group (P >0.05). Conclusions Arg92His mutation may be associated with intracranial artery atherosclerotic stenosis.

Objective Toinvestigatetheriskfactorsforleukoaraiosis(LA)inpatientswithlarge arteryatherosclerosis(LAA).Methods Theclinicaldata(age,sex,hypertension,diabetes,smoking, serum lipid level,hyperhomocysteinemia,and numbers of stenosis or occluded cerebral arteries)of 312 patients with LAA classified by the modified stop stroke study trial of Org 10172 in acute stroke treatment (SSS-TOAST ) were analyzed retrospectively. The age-related white matter changes (age related white matter changes,ARWMC)scale was used to evaluate LA. All the 312 patients were divided into non-LA group(n=72)and LA group(n=240)according the T2 weighted magnetic resonance imaging (MRI) and fluid attenuated inversion recovery(FLAIR)sequence,and 3 groups according to the (age-related white matter changes,ARWMC)scores:mild LA,moderate LA,and severe LA groups. The patients with multiple risk factors were analyzed by the univariate and multivariate Logistic regression analyses. Results (1)Of the 312 patients with LA,227 were males (72. 8%). Their average age was 64 ± 11 years,and 240 of them (76. 9%)had LA. Multivariate Logistic regression analysis showed that age (OR,2. 911,95%CI 1. 647-5.146,P=0. 000),hypertension (OR,2. 583,95%CI 1. 373-4.857,P<0. 01),diabetes (OR,1. 882, 95%CI 1. 058-3. 348,P <0. 05),the numbers of stenosis or occlusion arteries (OR,1. 851,95%CI 1.018-3. 367,P<0. 05),and lacunar infarction (LI)(OR,1.493,95%CI 1. 202-1. 853,P<0. 01)were the risk factors for LA. (2)The comparison of the clinical data in patients with different severity in the LA group found that there were significant differences in age,hypertension,diabetes,the numbers of stenosis or occlusionarteries,andLIamongthe3groups(allP<0.05).Conclusion Age,hypertension,diabetes, the numbers of stenosis or occlusion arteries,and LI are the independent risk factors for patients with LAA,and it is associated with the severity of LA.