Résumé
@#Objective To explore the physical and chemical properties of electric charge modified liposomes and the immune enhancement effect as influenza vaccine adjuvants.Methods Four kinds of electric charge-modified liposomes were prepared with soybean lecithin,cholesterol,N-1-(2,3-dioleyloxy) propyl-N,N,N-trimethyllam-moniumchloride(DOTAP)and 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC)(DOTAP and DOPC mass ratio 1:4,2:3,3:2 and 4:1).The tetravalent influenza vaccine was mixed with the four liposomes according to the volume fraction of 1.4:1.0,which was prepared into cationic modified influenza vaccine liposome freeze-dried powder by freeze-thaw freeze-drying method.The liposome freeze-dried powder was redissolved with PBS,the particle size and Zeta potential were measured by laserparticle size analyzer,and the encapsulation efficiency of liposome was measured by Lowry method.231 female KM mice were randomly divided into negative control group(PBS),positive control group(tetravalent vaccine bulk),cationic liposome group(four electric charge modified influenza vaccine liposomes) and neutral liposome group(non-electric charge modified influenza vaccine liposomes),which were injected intraperitoneally at 7,14 and 28 d,0.2 mL per mouse.The cellular immune effect was evaluated by MTT assay and T lymphatic surface labeling,and the humoral immune effect was evaluated by hemagglutinin inhibition(HI) at 3,7,14,28,42 and 56 d of immunization.Results When the mass ratio of DOTAP to DOPC was 4:1,the particle size and Zeta potential of cationic modified liposomes reached the maximum,which were 529.65 nm and 12.05 mV respectively,and the encapsulation efficiency was also high,which was 81.82%.Stimulus index(SI) and CD4~+/CD8~+value of spleen cells of mice in the four cationic liposome groups were significantly higher than those in the negative control group(F=4.651～25.866,each P<0.05),among which,the two indexes in 4:1 cationic liposome group were higher than those in the other three groups;mice in this group produced early humoral immune effect 3 d after immunization,and the antibody titer reached the highest 42 d after immunization and maintained a high level during the whole immunization cycle.Conclusion Cationic liposomes with different electric charge modifications improved the immune effect of influenza vaccine,the immune enhancement effect was the best and the immune effect lasted the longest when the mass ratio of DOTAP to DOPC was 4:1.
Résumé
Electrical charge is an indicator of the cellular state of health. In cells, the cell membrane is a leaky dielectric. Capacitors are composed of two conducting sheets separated by a thin layer of insulating material known as a dielectric. Cells contain several forms of biological capacitors, which consist of an insulating material (the membrane) covered on both sides by collection of charged dissolved minerals, which serve the function similar to a conducting metal plate. This means that any condition, illness or change in dietary intake that affects the composition of the cell membranes and their associated minerals can affect and alter cellular capacitance. Healthy cells have a higher whole cell and cytoplasm conductivity and higher membrane capacitance than the malignant cells. The electric charge of cell membranes of mammals is negative at physiological pH. It is well-known that surface of cancer and tumor cells carry negative charge in excess to that of normal cells which is responsible for their increased mobility and invasiveness. The high negative surface charge on malignant cells and trophoblasts may mediate the lack of immune rejection of these cells. Thus, neutralizing or removing the tumor cell negative charge may allow negatively charged lymphocytes to approach and destroy them and thereby, the viability and survival of the cancer cells may be affected at least in vitro. The present study serves to - test this hypothesis on invasive human breast carcinoma cell line MDA-MB-231 (ER ) using specially designed and constructed combination of circuits. Preliminary results showed that out of the 8 designed circuits, sets 1, 2 and 7 were able to produce significant growth inhibition of MDA cells in vitro. The application of electrostatic field through specially designed circuits is unique and has never been reported previously. Our long-term goal is to develop a minimally invasive device that will selectively target and destroy both metastatic and non-metastatic cancer cells in humans. Better understanding of effect of decreasing surface charge density of tumor cells may lead to device effective treatment strategy of human tumors in future.
Résumé
The electric properties of the plasma membrane is an indicator of cell condition. The simple, and highly effective, normal-phase (NP) and reversed-phase (RP) high-performance liquid chromatography (HPLC) methods assess phospholipid and free unsaturated fatty acid content, respectively. Herein we focus on changes in phospholipid content [phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanoloamine (PE), phosphatidylcholine (PC)] and free unsaturated fatty acid content [arachidonic acid (AA), linoleic acid (LA), a-linolenic acid (ALA), palmitoleic acid (PA)] in the plasma membranes of non-metastatic colorectal cancer cells (pT3 stage, G2 grade). Surface charge density of normal and tumor large intestine tissue was measured by electrophoresis. The surface charge density as a function of pH, acidic (CTA) and basic (CTB-) functional group concentrations and their average association constants with hydrogen (KAH) or hydroxyl (KBOH-) ions were evaluated. Cancer transformation was accompanied by an increase in total phospholipids as well as and increase in CTA, CTB and KBOH whereas the content of free fatty acids and KAH decreased compared with unchanged tumor cells.