BACKGROUND:Silver nanoparticles (AgNPs) show strong antibacterial effect and are not easy to have drug resistance. But the antibacterial mechanisms of AgNPs have not been wel developed.
OBJECTIVE:To explain the antibacterial mechanisms of AgNPs.
METHODS:We investigated the influence of Ti, TiO2 and TiO2 containing AgNPs onEscherichia coliand Staphylococcus aureus by bacterial inhibition ring test. Escherichia coli was cultured in LB liquid medium with 0, 5, 10 mg/L AgNPs. We measured the absorbance value of bacterial culture. DNA gel electrophoresis was used to study the effect of AgNPs onEscherichia coliDNA. Then we researched the character of apoptosis on Escherichia coli by Annexin V and PI staining, using flow cytometry.
RESULTS AND CONCLUSION:The inhibiting effect of Ti and TiO2 onEscherichia coliandStaphylococcus aureus was not obvious. But the inhibition rings of TiO2 containing AgNPs to bacteria appeared. The absorbance value of Escherichia coliculture was reduced whenEscherichia coliwas co-cultured with AgNPs. And this decrease tendency was in direct proportion with AgNPs concentration. AgNPs reduced the amount of DNA of Escherichia coli and this tendency was directly proportional with AgNPs concentration. TheEscherichia coli apoptosis rate induced by AgNPs was increased and this tendency was positively correlated to the AgNPs concentration. These results indicate that AgNPs can induce bacterial apoptosis to influence the growth of bacteria.

Objective To study the association between the cerebral infarction and the angiotensin converting enzyme (ACE) gene rs4646994 and rs35397082 polymorphisms in Binhai area ,Tianjin .Methods Gene sequencing and DNA electrophoresis were used for the detection of the ACE gene single nucleotide polymorphisms (SNPs)(rs4646994 and rs35397082) .53 samples from pa‐tients with acute cerebral infarction and 53 samples from healthy volunteers were used in our study .Serum sample were collected from each group and tested by ACE ELISA .Results There were only deletion type of rs35397082 SNP in both of the control and cerebral infarction group .In the control group ,the number of insertion type of rs4646994 was 45(84 .91% ) ,deletion type was 8(15 . 09% ) and in the patients group ,the number of insertion was 47(88 .68% ) and the deletion was 6(11 .32% ) .There was no signifi‐cant difference between the patients group and the healthy donors (P>0 .05) .The concentration of ACE in control group was high‐er than the patients with acute cerebral infraction (P<0 .05) .Conclusion There is no significant association between the ACE gene polymorphisms(rs35397082 and rs4646994) and cerebral infarction in Binhai area ,Tianjin .The different concentration of ACE is not caused by these two SNPs .In this study ,these two SNPs are not the are not the risk factors of the cerebral infarction in Tianjin based on our study .

BACKGROUND:Bone marrow mesenchymal stem cel s have attracted widespread attention for the capabilities of self-renewal and muti-differentiation, which have been used in treatment of various diseases.
OBJECTIVE:To study the effect of three-dimensional spheroid culture system on the stemness and senescence of bone marrow mesenchymal stem cel s.
METHODS:Mesechyaml stem cel s were isolated from the bone marrow of C57/B6 mice, 3 weeks old, and cultured onto the culture plates coated with or without chitosan. After 5 days of culture, the cel phenotype and expression of stemness related markers CD44 and Sca-1 were analyzed by flow cytometry. PI and Annexin-V staining were used to detect cel apoptosis. Also,β-Gal staining was applied for identification of aging.
RESULTS AND CONCLUSION:The mouse mesenchymal stem cel s began to form spheroids on day 3. The stemness-related markers, including CD44 and Sca-1, expressed higher in spheroid mesenchymal stem cel s than the cel s under normal culturing. Compared with the normal culture group, the apoptosis and senescence of cel s from spheroid culture were lower. The results indicate that the formation of spheroids on chitosan films can increase the stemness, decrease the apoptosis and slow the senescence of mesenchymal stem cel s.