| The main objectives of the proposal are to design a novel polymeric micellar drug delivery systems with triggered release mechanism for targeting heterogeneous cancer cells.The anticancer drug thioridazine is hydrophobic entrapped in the block copolymer micelles to achieve the target tumor effect and increase the efficacy of reducing the toxicity of the drug,and connected the hyaluronic acid to the surface of micelles as specific receptors transparent to improve the carrier’s initiative targeting.Firstly,the pH-sensitive polymer PBAE was synthesized by Michael addition reaction which HDD and TDP were alternately connected with the 4-methylpiperidine capped Preparation.Secondly,the PBAE and PEG were connected.The obtained copolymers were characterized by FT-IR,1H-NMR and GPC.GPC result showed the molecular weight of PEG-PBAE was about 5 2 3 3 with narrow distribution and the GPC spectrum showed a good single peak.The determine pKa value of PEG-PBAE was about 6.7,and has a significant buffering capacity using acid-base titration.The particle size of the micelles increased following the pH value of environment changes by changing the pH of hydration media,showing the polymeric material having a certain pH sensitive properties.The CMC values of the copolymers were measured by the change of fluorescence spectrum of pyrene due to its selective partition into hydrophobic micellar core in the copolymer solution.The CMC was 2.49×10-3g/L,the value was lower enough than small molecule surfactant which could keep micelles stable and had a strong ability to resist dilution.Thioridazine(THZ)was chosen as a model drug,and HPLC method was developed and applied for the determination of the content of thioridazine in vitro analysis with encapsulation efficiency and drug loading index as reference.Single factor experiment was chosen to optimize the preparation process of THZ/HA modified PEG-PBAE micelles.Film dispersion was used to prepare PEG-PBAE micelles,then,HA was connected to surface of the micelles via amido bond and amount of HA was measured.The optimum experimental conditions were:a solvent of acetone,a film-forming temperature of 40℃,a film-forming time of 30 min,a hydration temperature of 45℃ and water phase of distilled water with 30 min.By this method,entrapment efficiency of micelles was(91.13±0.87)%and drug loading efficiency was(21.47±0.20)%.When HA was connected,entrapment efficiency and drug loading efficiency of the micelles decreased to(87.23±0.65)%and(20.72±0.15)%.By examining the kind and amount of cryoprotectant of freeze-dried,the final choice of 15%trehalose as cryoprotectant.The particle size we used the dynamic light scattering to measure was 130.8-153.5 nm with the Zeta potential of the micelles was-8.2～-5.2mV.The micelles were observed by transmission electron microscopy(TEM)which showed spherical and regular.Selecting dynamic dialysis method to examine the block copolymer micelles in vitro release in the PBS with 0.5%SDS as a solubilizer.The results showed that the micelles release faster in pH 5.0 than pH 7.4 in 48 hours which release more than 7 0%showing the pH-sensiti ve properties of material.Additionally,the difference of amount of HA had different speed of drug from the micelles.With the increase of amount of HA,the release rate slowed down.The vitro studies were performed on the human breast cancer MCF-7 cells,and we used MTT assay to study cytotoxicity of materials,free drug and pH triggered release of the drug-loaded micelles.The materials is substantially non-toxic,and the loaded THZ micelles showed cytotoxicity significantly,in addition,when the amount of HA was 47.72μg/mL,cytotoxicity was the strongest.In summary,the synthesized pH sensitive copolymers PEG-PBAE could deliver anti-cancer drugs thioridazine to induce tumor cell to death with a good anti-tumor effect. |
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