The Investigation Of Buserelin Acetate Sustained-release PLGA Nanoparticle For Injection

With the rapid development of biotechnology, protein and polypeptides, one of the major types in new drugs, has been widely used in the therapy of cancer, autoimmune disease etc. Nowadays, aqua and powder injection of proteins and peptides are the common routes of administration. However, these routes could not avoid the deficiencies of proteins and peptides caused by physical and chemical instabilities, and short half-life in vivo. Although enteric-coated tablets and capsules are applied to the delivery system, the bioavailability of proteins and peptides is still low. In pharmaceutics, these difficulties in administration of proteins and peptides remain a hot spot issue about how to develop the delivery system in pharmaceutical means to enhance their stabilities and improve their bioavailability.Buserelin acetate is a synthetic hypothalamic gonadotropin releasing hormone(GN-RH, LH-RH) analogue, which is a water-solubility polypeptide. It was completely absorbed after subcutaneous injection, with peak plasma concentrations occurring about 1 hour after a dose. It accumulates in liver and kidneys as well as in the anterior pituitary. The half-life after injection is stated to be about 80 minutes. It could urge the exudation of leuteinizing hormone (LH), follicle-stimulating hormone (FSH) and gonadal hormone. However the pharmacological effect of BA is 20-170 times of LHRH. Buserelin acetate was used in the treatment of malignant neoplasms of the prostate, endometriosis, and infertility etc. Subcutaneous injection of multiple dose is required when administrated.Nanoparticles can improve the bioavailability of protein and polypeptides, and release drugs continually and slowly. Avoiding direct connection with protease, drugs loaded on nanoparticles can be delivered to blood lymph and other targeting organs. In the present decades, nanoparticles has been considered as an effective carrier in the targeting delivery system. .Poly(lactic-co-glycolic acid) (PLGA) has the advantages in sustained-release, biodegradation, biocompatibility and no adverse reactions,. Its degradation productions—lactic acid and glycolic acid—can be good absorbed and involved in the metabolism. FDA has approved its application to be the carrier material of sustained-release drugs.In this reseach Buserelin Acetate, a water-solubility polypeptide drug, is selected as a model, and PLGA with good biodegradability and compatibility in vivo as the carrier material, then Buserelin Acetate PLGA nanoparticles(BA-PLGA-NP) was prepared by a double emulsion method. The optimized formulation of BA-PLGA-NP was conveniently obtainde by the single-factor investigation and the orthogonal methodology. Futhermore the analysis method of high performance liquid chromatography (HPLC) was established to quantified the entrapment efficiency and drug loading. Under optimum conditions, prepared nanoparticles entrapment efficiency was 63.37±0.29%, particle size was unimodal distribution, volume-weight mean particle diameter was 127 ~ 132nm, Zeta potential was -64.8 ~ -67.3 mV, The electron microscope photo proved that the BA-PLGA-NP was spherical shape.The BA-PLGA-NP lyophilized formulation was investigated by taking morphology and reconstitution as indexes. The powders of BA-PLGA-NP were perpared by lyophilization using 2% manicol as protector. We carride on the overall quality evaluation to the lyophilization injection, the results showed that the lyophilization didn't influence the quality index of the BA-PLGA-NP, such as entrapment efficiency, size, Zeta potential etc. The stability experiment indicated that the lyophilized BA-PLGA-NP was stable without obvious changes in morphology, entrapment efficiency, size, Zeta potential in 4℃or -20℃after storage of 3 months.The in vitro stability of Buserelin acetate in different release medium was studied, selected the phosphate buffer (pH7.4) which had a well environmental correlation with vivo as release medium. Investigation the in vitro release characteristics of drug were investigated by HPLC. The results showed that the cumulative release rate of drug was exceed 60% in 72h, indicating that BA-PLGA-NP had remained releasing characteristics.The pharmacokinetic parameters of BA-PLGA-NP and BA solution(BA-Sol) were investigated after intravenous adminstration to rats at a single dose of 50μg/ml. The results indicated that BA was absorbed after subcutaneous injection, with peak plasma concentrations occurring quickly. Comparatively, BA-PLGA-NP could prolong the half-time of BA-Sol in blood and AUC increased significantly, which were 7 times of BA-Sol Group.The present research points out that BA-PLGA-NP loaded by PLGA could release BA slowly, extend the cycle time in vivo, and enhance the bioavailability. The previous expectation has been accomplished. It is proved to be a new polypeptide pharmaceutical preparation with brilliant prospect.