Studies On The Insulin Liposome Dry Powder Inhalation

Developing non-injectable routes to deliver insulin has become the focus of pharmaceutical scientists since the morbility rate of diabetes increased year by year. Non-injectable drug delivery system includes oral,nasal,colon and transdermal and pulmonary delivery of insulin,among which pulmonary delivery seems to be the most promising one.Compared with other non-injectable routes,the lung consists of simple epithelium cells with large absorptive areas,which offers an effective way to deliver macromolecules;pulmonary delivery of peptides and protein drugs can also avoid first pass effect in the liver,as well as degradation due to the low local enzymatic activity.Among the drug formulations administered through lungs,dry powder inhalation(DPI)is the most popular one.Because it can be started by initiative breathe of the patients,thus avoid inconsistency of drug release and inhalation.Drug dose has a wide range in the form of capsules.It is also environmental friendly without using CFCs.An inhaled insulin Exubera^TMdeveloped by Pfizer/Sanofi-Aventis/Nektar,has already been approved by FDA in the early 2006,which becomes a milestone in the history of diabetes therapeutics.Though Exubera^TMis now on the market,it is short-acting insulin that needs to be inhaled frequently to maintain the insulin level in the body.To make sure the therapeutic effect,it is mainly administered before each meal,along with an injection of long-acting insulin per day for patients with IDDM. Its huge success cannot totally replace the injection method,though,long-acting insulin DPIs are needed to meet the clinical requirements.Liposome mainly consists of lecithin,which is the main ingredient of lung alveolar surfactant;hence it is the most proper formulation to control the drug release in the lung tissue.Thus,the purpose to achieve slow release and long acting of insulin can be accomplished in this thesis by encapsulation of insulin into liposomal carriers,followed by DPI preparation through spray drying method.The first part of this article describes the preparation and characteristic investigation of insulin liposome.Hydrogenated phopholipids and cholesterol were dissolved in diethyl ether as membrane materials,after the addition of drug solution, the suspension was ultrasounded and liposome formed during reverse phase evaporation.The entrapment efficiency was determined by Sephedex-G50 gel column with PBS buffer(pH 7.4)as eluant to separate free drug and liposome;the content of insulin was determined by HPLC(High performance liquid chromatography)method after destruction of liposome by sodium cholate and chloroform.Insulin liposome is globular and subsphaeroidal under TEM.The reproduction quality of three batches of product is fine with average size,zeta potential and entrapment efficiency as 289.2±13.80nm,-6.11±0.14mV,33.02±1.97%,respectively.The second part of this article selected the preparation method of DPI as spray drying and orthogonal experiment was utilized to prepare the optimized INS-LIP-DPI, which can meet the requirement of both deposition on the alveolar epithelium and controlled release in the local site.According to the results,mass ratio of lipid:lactose was chosen as 1:4 to maintain the bioactivity and entrapment efficiency of insulin. The factors influencing spray drying method in the preparation design of INS-LIP-DPI included air flow,pumping speed,inlet temperature,aspirator of spray drying instrument,as well as the concentration of the suspension.The preparation parameters were optimized by orthogonal experiment design with four characteristic indices such as mean diameter of the powder,fine particle fraction,moisture content, retention of entrapment efficiency.The ultimate technology and formulation are determined as air flow 800L/h,pumping speed 5ml/min,inlet temperature 100℃, aspirator 90%,concentration 2%respectively.The average diameter of DPI particles was 3.22±0.24μm,bulk density was 0.71±0.10g/cm³,angle of repose was 38.42±2.30°,moisture content was 1.28±0.02%,product yield was 70.45±5.31%, MMAD was 3.06±0.45μm,fine particle fraction was 21.78±2.17%,emptying rate was 97.66±1.12%,atomizing property ranked 3,i.e.very easy to be atomized.After redispersion of DPI,insulin liposome was still globular and subsphaeroidal,with a little adherence under TEM.The entrapment efficiency could maintain 65.65±2.59% of the initial value of original liposomes.The final average size,zeta potential and entrapment efficiency were 376.6±21.57nm,-5.45±0.28mV,20.03±1.89%, respectively.The third part of this article researches the pharmacodynamics of diabetic rats after giving INS-LIP-DPI through lungs,however,according to experimental situation,the preparations were intratracheally instilled.Streptozocin was used to produce diabetic rat models.8IU/kg INS solution,INS+blank rehydrated liposomes, and rehydrated INS-LIP-DPI were evaluated in the animals.And their relative pharmacological bioavailability(f%)were compared.Subcutaneous injection of 2IU/kg INS solution was used as control group.The values of f%were 20.50%, 29.03%and 36.34%respectively.Rehydrated INS-LIP-DPI was approved to show longer and more significant hypoglycemic effect on diabetic rats.