Preparation And Drug Controlled Release Of Thermo-sensitive Polymer (P(NIPAAm-DMAAm)-DSPE) Modified Paclitaxel-loaded Liposomes

Cancer is the second largest disease in the world,and paclitaxel plays an important role in the treatment of cancer.However,the strong fat solubility of paclitaxel limits its bioavailability in vivo.This subject encapsulates paclitaxel with liposome using thin film hydration method.Liposomal preparation could improve the bioavailability of paclitaxel and reduce its toxic side effects on normal tissues.The thermo-sensitive paclitaxel-loaded liposome was obtained by inserting thermo-sensitive copolymer on liposome membrane.Under temperature stimulation,paclitaxel was controlled release from liposomes.This subject screened the optimum phase transition temperature of thermo-sensitive polymer and the formulation process of temperature-sensitive liposome preparation,and carried out quality evaluation.In this paper,DSPE-Br was synthesized as initiator,and the polymerization of N-isopropylacrylamide(NIPAAm)and N,N-dimethylacrylamide(DMAAm)was initiated by bromine free radical to obtain the thermo-sensitive copolymer PNIPAAm-DSPE and P(NIPAAm-DMAAm)-DSPE using atom transfer radical polymerization.The structure and thermo-sensitive properties of copolymers were characterized.The results show that the copolymer monomer conversion rate is 54%~62%.By adjusting the monomer ratios,the lower critical solution temperature of obtained copolymer,which the ratio of NIPAAm and DMAAm is 51:8(mol/mol),in water was 46.9?,while in PBS it was 38.8?.The divergence in PBS and water is related to the competition of salt for water molecules.The factors,such as the ratio of lipid and cholesterol,hydration temperature and time,ultrasonic temperature and time,were investigated by single factor experiment and central composite design-response surface method.The prescription and process parameters were selected by particle size and encapsulation efficiency.The thermo-sensitive liposomes were prepared by alternating cold and heat and evaluated for quality.The results showed that the reproducible drug-loaded liposome formulation process were: the mass ratio of phospholipid to cholesterol is 4:1,the mass ratio of paclitaxel to phospholipid is 1:11.3,the hydration medium is 0.01 M pH 7.4 PBS,the volume of hydration solution is 2 mL corresponding to 20 mg HSPC phospholipid;rotary evaporation time is 15 min;hydration temperature sets at 65?;hydration time is 2 h;ultrasonic temperature is 60? and ultrasonic time is 40 min.The encapsulation efficiency of thermo-sensitive paclitaxel loaded liposomes is 80.84%,the drug loading is 7.82%,and the insertion amount of copolymer is 6.93%.the particle size is 110.4 nm.Liposomes are regular and exhibit negative charges.The drug release results showed that the thermo-sensitive liposome released fastly at 40 ? in the first 5 days,and then released smoothly.The cumulative release rate in the 10 th day reached 72.25%.The release feature was consistent with the Weibull model.The stability evaluation showed no significant change in particle size when the thermo-sensitive liposomes was stored at 4? for 30 days,and the encapsulation efficiency was still higher than 65%.This indicates that the prepared thermosensitive liposome has a certain long-circulating effect.Finally,the biocompatibility of copolymers,traditional liposomes and thermo-sensitive liposomes was evaluated.The results showed that the hemolysis rate of the copolymers and liposomes were less than 5%;the dynamic clotting time was close to the negative control;the plasma recalcification time was at least 60% higher than positive control.In the cytotoxicity evaluation,the relative activity of the cells was above 80%.There was no embryo toxicity at low concentrations,which confirmed that the copolymers and liposomes have good biocompatibility.In summary,this subject synthesized the temperature-sensitive polymer with a phase transition temperature slightly higher than the body temperature,and the optimal liposome formulation was screened.Thermo-sensitive paclitaxel liposome with high encapsulation efficiency,controllable drug release and good biological properties were obtained.