Muco-adhesive multivesicular liposomes as an effective carrier for transmucosal insulin delivery

Considering limitations of conventional insulin therapies, the present study characterizes usefulness of novel mucoadhesive multivesicular liposomes as a mucoadhesive sustained release carrier of insulin via nasal and ocular routes, thus attempts to develop non-invasive carrier system for the controlled release of bioactives. Multivesicular liposomes (MVLs) of 26-34 microm were prepared with a high protein loading (58-62%) and were coated with chitosan and carbopol. These mucoadhesive carriers were characterized by zeta potential studies, in vitro mucoadhesion test and insulin protective ability against nasal aminopeptidase. In vitro, mucoadhesive carriers released insulin for a period of 7-9 days compared to 24 h of conventional liposomes. After intranasal administration to STZ induced diabetic rats, the mucoadhesive MVLs (chitosan coated MVLs) effectively reduced plasma glucose level up to 2 days (35% reduction), compared to non-coated MVLs (32% at 12 h) and conventional liposomes (34% at 8 h). Although the differences are statistically insignificant, chitosan coated formulation has shown a better hypoglycemic profile as the effects were prolonged compared to carbopol coated formulation. When compared to ocular route, chitosan formulation after nasal administration has shown better therapeutic profile as the hypoglycemic effects were prolonged until 72 h. The effectiveness of this chitosan coated MVLs was further demonstrated by the significant quantities of ELISA detectable insulin levels after nasal (334.6 microIu/ml) and ocular (186.3 microIu/ml) administration. These results demonstrate that mucoadhesive carrier is a viable option for a sustained release transmucosal insulin carrier, and open an avenue to develop a non-invasive carrier platform for the controlled release of bioactives.     

Novel Mucosal Insulin Delivery Systems Based on Fusogenic Liposomes

Purpose Fusogenic liposomes (FLs) are unique delivery vehicles capable of introducing their contents directly into the cytoplasm with the aid of envelope glycoproteins of Sendai virus (SeV). The objective of this study was to evaluate the potential of FL to improve the mucosal absorption of insulin from rat intestinal membranes. Method The FLs containing insulin were prepared by fusing insulin-loaded liposomes with inactivated SeV particles and were administered directly into the ileal, the colonic, and the rectal loops (10 IU/kg). Results The FL successfully enhanced the insulin absorption and induced a significant hypoglycemic effect following the colonic and the rectal administration without detectable mucosal damage. This enhancing effect of insulin absorption was further improved by increasing the amount of insulin loaded in the FL and by coencapsulating insulin-degrading enzyme inhibitor. In contrast, the insulin absorption was not increased by the ileal administration of FL because the mucous/glycocalyx layers overlaid on the ileal epithelium impede the fusion of FL to the intestinal mucosa. Conclusion Our results indicated that FL is a useful carrier for improving the absorption of poorly absorbable drugs, such as insulin, via the intestinal tract.     

Muco-adhesive multivesicular liposomes as an effective carrier for transmucosal insulin delivery

Considering limitations of conventional insulin therapies, the present study characterizes usefulness of novel mucoadhesive multivesicular liposomes as a mucoadhesive sustained release carrier of insulin via nasal and ocular routes, thus attempts to develop non-invasive carrier system for the controlled release of bioactives. Multivesicular liposomes (MVLs) of 26–34 μm were prepared with a high protein loading (58–62%) and were coated with chitosan and carbopol. These mucoadhesive carriers were characterized by zeta potential studies, in vitro mucoadhesion test and insulin protective ability against nasal aminopeptidase. In vitro, mucoadhesive carriers released insulin for a period of 7–9 days compared to 24 h of conventional liposomes. After intranasal administration to STZ induced diabetic rats, the mucoadhesive MVLs (chitosan coated MVLs) effectively reduced plasma glucose level up to 2 days (35% reduction), compared to non-coated MVLs (32% at 12 h) and conventional liposomes (34% at 8 h). Although the differences are statistically insignificant, chitosan coated formulation has shown a better hypoglycemic profile as the effects were prolonged compared to carbopol coated formulation. When compared to ocular route, chitosan formulation after nasal administration has shown better therapeutic profile as the hypoglycemic effects were prolonged until 72 h. The effectiveness of this chitosan coated MVLs was further demonstrated by the significant quantities of ELISA detectable insulin levels after nasal (334.6 μIu/ml) and ocular (186.3 μIu/ml) administration. These results demonstrate that mucoadhesive carrier is a viable option for a sustained release transmucosal insulin carrier, and open an avenue to develop a non-invasive carrier platform for the controlled release of bioactives.     

Preparation and characterization of directly compactible layer-by-layer nanocoated cellulose

Iontophoresis is a promising technique for enhancing transdermal administration of charged drugs. However, conventional iontophoresis is not sufficient for effective delivery of large, hydrophilic, or electrically neutral molecules. In this study, we utilized charged liposomes as carriers, focused on a transfollicular route for delivery of the liposomes, and optimized iontophoretic conditions and lipid composition for this method in both in vitro and in vivo conditions. As a result, we identified the optimum condition (lipid composition: DOTAP/EPC/Chol=2:2:1, current supply: 0.45mA/cm(2), duration: 1h) for effective iontophoretic delivery of aqueous solution, which cannot be transferred into the skin without charged liposomes. We also examined the pharmacological effects of iontophoresis of liposomes encapsulating insulin (INS-lipo) using a rat model of type I diabetes. Interestingly, iontophoresis of INS-lipo onto a diabetes rat skin resulted in a gradual decrease in blood glucose levels, with levels reaching 20% of initial values at 18h after administration. These lower blood glucose levels were maintained for up to 24h. Significant amount of insulin were also detected in plasma 18h after iontophoresis of INS-lipo. We succeeded in developing a non-invasive and persistent transfollicular drug delivery system that used a combination of liposomes and iontophoresis.     

Hypoglycemic efficacy of chitosan-coated insulin liposomes after oral administration in mice

INTRODUCTION In the past two decades the potential usefulnessof liposomes as drug carriers for improving enteral ab-sorption of poorly absorbed drugs including peptidedrugs such as insulin has attracted considerable interest.These phospholipid vesicles are capable of encapsulat-ing both hydrophobic and hydrophilic drugs; they arebiodegradable and are not toxic in vivo. The drugsencapsulated in liposomes are sufficiently protectedfrom enzymatic attack and immune recognition[1]. Li-po…     

Rectal administration of insulin

According to recent statistics for the time span 1951-1970, the mortality ratio of diabetics to non-diabetics was 335% (46). For those diabetics who were younger than 15 years when entering the study, the mortality ratio was 1127%, with a mean life expectancy of another 32 years, as compared to 59 years for non-diabetics. Among the major causes of disablement and early death are ischemic heart disease, retinopathy, nephropathy, peripheral vascular disease and neuropathy. In spite of newer, more potent and highly purified insulins, development of human insulin, change of once-daily injection to twice-daily insulin therapy (47), and the introduction of portable insulin infusion pumps, diabetes is still a high-risk disease, far from being controlled. Considering that the present mode of insulin administration is by the subcutaneous route by which the insulin is presented to the body in a nonphysiological manner, because the insulin is peripherally administered to the systemic circulation instead of portally, new therapeutic ways for insulin administration are worth study. During the past years, considerable interest has arisen in the rectal route of administration. Based on a physiological-kinetic model presented in this paper, utilization of the first-pass effect inherent to the rectal anatomy offers a physiological insulin input via the rectal route of administration. A review on the present state of rectal insulin administration is given, and experimental data from our laboratories are presented. The usefulness of sorption promoters on rectal insulin absorption is discussed. The "effectiveness" of rectal insulin preparations is suggested to be evaluated by four criteria: the pharmacological availability via the area under the % glucose reduction-time profile, the maximum glucose concentration reduction, Cmax, the time to reach the maximum reduction, tmax, and the mean residence time for glucose reduction, MRT.     

Absorption and efficiency of insulin after oral administration of insulin-loaded nanocapsules in diabetic rats

Poly(isobutylcyanoacrylate) nanocapsules have been shown to decrease the blood glucose level after oral administration to streptozotocin-induced diabetic fasted rats after 2 days [Diabetes 37 (1988) 246]. Yet, the absorption of insulin in the blood of rats has not been characterised. The aim of this work was to evaluate the biological activity of insulin given orally as nanocapsules. Humalog-loaded nanocapsules (50 IU/kg) were administered by gavage to streptozotocin-induced diabetic rats. Thirty minutes to 1 h after oral administration, significant levels of human insulin were detected in rat plasma. However, the concentrations were very heterogenous from one rat to another and no decrease of glycemia could be observed. In addition, parenteral injection of insulin in solution showed that high levels of the protein are necessary to decrease blood glucose concentration in diabetic rats. These concentrations were not reached after oral administration. The same dose of insulin decreased glycemia by 50% in normal rats and by only 25% in diabetics. This suggested that an insulino-resistance was developed by streptozotocin-induced diabetic rats.     

State of insulin self-association does not affect its absorption from the pulmonary route.

This study is designed to compare and contrast the pulmonary absorption profiles of monomeric and hexameric insulin in the presence or absence of ethylene diamine tetraacetic acid (EDTA) or n-tetradecyl-beta-d-maltoside (TDM). The pulmonary absorption of two forms of insulin was studied by monitoring the changes in plasma insulin and glucose levels after intratracheal administration of monomeric or hexameric insulin into anesthetized rodents. EDTA or TDM was added to the formulation in order to evaluate if either of these agents has effects on the rate and extent of pulmonary absorption of monomeric and hexameric insulin. The biochemical changes that may occur after acute administration of TDM-based formulation have also been investigated by estimating lung injury markers in bronchoalveolar lavage fluid. A dose-dependent increase in the plasma insulin and decrease in plasma glucose levels was observed when increasing concentrations of hexameric or monomeric insulin were administered via the pulmonary route. Pulmonary administration of monomeric and hexameric insulin produced comparable absorption profiles in the presence or absence of EDTA or TDM. The bronchoalveolar lavage fluid analysis did not show differences in the levels of injury markers produced in TDM-treated rats and that produced in saline-treated rats, indicating no evidence for adverse effects of TDM in these short-term studies. Overall, in terms of rapidity of action and efficacy to reduce blood sugar, monomeric insulin did not provide advantages over hexameric insulin when administered via the pulmonary route.     

Population Pharmacokinetic–Pharmacodynamic Modeling of Subcutaneous and Pulmonary Insulin in Rats

Purpose: To develop a population pharmacokinetic–pharmacodynamic (PKPD) model for insulin in rats. Methods: Rats were administered insulin either subcutaneously (s.c) (0.26,1.3,2.6 U/kg) or by pulmonary route (spray-instillation (s.i)) (0.26,1.3,2.6,13,26 U/kg). Insulin (0.26,1.3,2.6 U/kg) combined with different combinations of hydroxy methyl amino propionic acid (HMAP: 5,10,16,25 mg/kg) was also administered by spray-instillation. Plasma insulin and glucose concentrations at pre-determined time points were measured. Population pharmacokinetic–pharmacodynamic modeling was performed using NONMEM. Results: Insulin exhibited dose-disproportional PK across formulations and routes of administration. The kinetic model suggested monoexponential disposition with simultaneous first order (64%-dimeric form of insulin) – zero order (36%-hexameric form of insulin) absorption. Maximum relative bioavailability (relative to s.c – 0.26 U/kg) of spray-instilled insulin was 46%. Addition of HMAP increased the relative bioavailability of insulin administered via spray-instilled route by 40%. The insulin–glucose relationship was characterized using an indirect response model, wherein, insulin stimulation of glucose uptake into muscle cells was assumed. The basal zero order production rate of glucose (k_{G, prod}) was estimated as 0.98 mg/dl/min. The SC₅₀ was fixed at 80 μ U/ml based on literature reports and the S_max was estimated to be 6. Conclusions: The proposed PKPD model satisfactorily describes insulin disposition and glucose concentrations across range of doses with and without HMAP.     

Enteral Absorption of Insulin in Rats from Mucoadhesive Chitosan-Coated Liposomes

Purpose. The mucoadhesiveness of polymer-coated liposomes was evaluated to develop a novel drug carrier system for oral administration of poorly absorbed drugs such as peptide drugs. Methods. Multilamellar liposomes consisting of dipalmitoylphosphatidylcholine (DPPC) and dicetyl phosphate (DCP) (DPPC:DCP = 8:2 in molar ratio) were coated with chitosan (CS), polyvinyl alcohol having a long alkyl chain (PVA-R) and poly (acrylic acid) bearing a cholesteryl group. The adhesiveness of the resultant polymer-coated liposomes to the rat intestine was measured in vitro by a particle counting method with a Coulter counter. The CS-coated liposomes containing insulin were administered to normal rats and the blood glucose level was monitored. Results. The existence of polymer layers on the surface of liposomes was confirmed by measuring the zeta potential of liposomes. The CS-coated liposomes showed the highest mucoadhesiveness and the degree of adhesion was dependent on the amount of CS on the surface of the liposomes. The blood glucose level of rats was found to be significantly decreased after administration of the CS-coated liposomes containing insulin. The lowered glucose level was maintained for more than 12h after administration of the liposomal insulin, which suggested mucoadhesion of the CS-coated liposomes in the intestinal tract of the rats.     

Population pharmacokinetic model of human insulin following different routes of administration

Multiple-compartment disposition of insulin has been demonstrated following intravenous administration; however, because of slow absorption and flip-flop kinetics, meal-time insulin pharmacokinetics have been described by a 1-compartment model. Technosphere insulin (TI) is an inhaled human insulin with rapid absorption and a distinct second compartment in its pharmacokinetics. The aim of this analysis was to develop a pharmacokinetic model for insulin administered via the intravenous, subcutaneous, and inhalation routes. A 2-compartment pharmacokinetic model with 1 (inhaled) or 2 sequential (subcutaneous) first-order absorption processes and first-order elimination was developed using data from 2 studies with a total of 651 concentrations from 16 healthy volunteers. Insulin was administered intravenously (5 U), subcutaneously (10 U), and via inhalation (25, 50, and 100 U). The data were modeled simultaneously with NONMEM VI, using ADVAN6 subroutine with FO. Typical values were clearance, 43.4 L/h; volume of distribution in the central compartment, 5.0 L; intercompartmental clearance, 23.9 L/h; volume of distribution in the peripheral compartment 30.7 L; TI first-order absorption rate constant, 2.35 h?1; and first-order absorption rate constants associated with subcutaneously administered insulin, 0.63 and 1.04 h?1, respectively. Absorption rate after subcutaneous dosing was found to decrease with increasing body mass index. Insulin pharmacokinetics were found to be consistent with 2-compartment disposition, regardless of route of administration, with insulin curve differences attributable to absorption differences.     

荆豆凝集素修饰脂质体对小鼠口服吸收胰岛素的促进作用

目的研究荆豆凝集素(UEA1)修饰的胰岛素脂质体在小鼠胃肠道的吸收作用。方法采用碳二亚胺偶联法制备荆豆凝集素修饰的磷脂酰乙醇胺(PE)，将PE-UEA1参入胰岛素脂质体中制成凝集素修饰脂质体，并证实UEA1凝集活性不受影响。分别对正常小鼠及糖尿病模型小鼠灌胃给予350 u·kg^-1胰岛素的修饰脂质体溶液，用葡萄糖酶试剂盒测定小鼠血糖，并与同剂量普通胰岛素脂质体比较。结果对于正常小鼠，荆豆凝集素修饰脂质体在4 h使血糖降至初始水平的(84±15)%，8 h降至(78±11)%，12 h为(90±12)%。胰岛素普通脂质体几乎没有降糖作用，与生理盐水对照组相当。对于糖尿病模型小鼠，荆豆凝集素修饰脂质体在4 h使血糖降至初始水平的(73±7)%，8 h降至(74±9)%，12 h为(86±9)%。结论荆豆凝集素修饰的脂质体可能通过与M细胞表面特异性受体的结合促进大分子药物的胃肠吸收。     

Nasal route and drug delivery systems

Nasal drug administration has been used as an alternative route for the systemic availability of drugs restricted to intravenous administration. This is due to the large surface area, porous endothelial membrane, high total blood flow, the avoidance of first-pass metabolism, and ready accessibility. The nasal administration of drugs, including numerous compound, peptide and protein drugs, for systemic medication has been widely investigated in recent years. Drugs are cleared rapidly from the nasal cavity after intranasal administration, resulting in rapid systemic drug absorption. Several approaches are here discussed for increasing the residence time of drug formulations in the nasal cavity, resulting in improved nasal drug absorption. The article highlights the importance and advantages of the drug delivery systems applied via the nasal route, which have bioadhesive properties. Bioadhesive, or more appropriately, mucoadhesive systems have been prepared for both oral and peroral administration in the past. The nasal mucosa presents an ideal site for bioadhesive drug delivery systems. In this review we discuss the effects of microspheres and other bioadhesive drug delivery systems on nasal drug absorption. Drug delivery systems, such as microspheres, liposomes and gels have been demonstrated to have good bioadhesive characteristics and that swell easily when in contact with the nasal mucosa. These drug delivery systems have the ability to control the rate of drug clearance from the nasal cavity as well as protect the drug from enzymatic degradation in nasal secretions. The mechanisms and effectiveness of these drug delivery systems are described in order to guide the development of specific and effective therapies for the future development of peptide preparations and other drugs that otherwise should be administered parenterally. As a consequence, bioavailability and residence time of the drugs that are administered via the nasal route can be increased by bioadhesive drug delivery systems. Although the majority of this work involving the use of microspheres, liposomes and gels is limited to the delivery of macromolecules (e.g., insulin and growth hormone), the general principles involved could be applied to other drug candidates. It must be emphasized that many drugs can be absorbed well if the contact time between formulation and the nasal mucosa is optimized.     

小鼠口服多糖包覆胰岛素脂质体的降血糖作用小鼠口服多糖包覆胰岛素脂质体的降血糖作用

目的 研究壳聚糖和海藻酸钠两种多糖包覆胰岛素脂质体的小鼠po降血糖作用。方法 用逆相蒸发法制备胰岛素脂质体;用透射电镜和激光粒度仪测定它们的形态和粒径;用HPLC法和超速离心法测定包封率;用胃蛋白酶和胰蛋白酶溶液试验多糖包覆脂质体对胰岛素的保护作用;用酶-苯酚法测定小鼠po多糖包覆胰岛素脂质体后降血糖作用。结果小鼠po 0.1%壳聚糖和0.1%海藻酸钠包覆的胰岛素脂质体具有较好的降血糖作用。结论壳聚糖或海藻酸钠包覆的脂质体能减少胃蛋白酶或胰蛋白酶对胰岛素的降解并促进胰岛素po吸收。     

Improved nasal bioavailability of elcatonin by insoluble powder formulation

In this study, phosphatidylethanol formed by phospholipase D catalysed transphosphatidylation of phosphatidylcholine was employed as a component for preparation of liposomal carrier for oral delivery of insulin. Thermotropic behaviour of liposomes from mixtures of dipalmitoyl phosphatidylcholine and dipalmitoyl phosphatidylethanol, and their resistance to pancreatic phospholipase A(2) catalysed hydrolysis were studied. Three kinds of liposomes with insulin were prepared to examine the pharmacological availability of liposomes with phosphatidylethanol: (i) dipalmitoyl phosphatidylcholine/dipalmitoyl phosphatidylethanol (1:1 w/w) liposomes; (ii) dipalmitoyl phosphatidylcholine/dipalmitoyl phosphatidylethanol/palmitoyl-stearoyl sucrose (1:1:0.2) liposomes; and (iii) liposomes composed of natural phosphatidylcholine and phosphatidylinositol (1:1). The resultant liposomes were orally administrated to rats with blood glucose concentration of 270 mg/100 ml in a dose of 12 IU/kg body weight. Blood samples were collected 0.5, 1.5, 3, 5, and 24 h after treatment. Oral administration of all liposomal species resulted in hyperinsulinemia. Hyperinsulinemia induced by liposomes containing dipalmitoyl phosphatidylethanol was attended by a decrease of blood glucose concentration. No correlation between insulin level and glucose concentration in the rat blood after oral administration of phosphatidylinositol-containing liposomes was observed.     

Investigation of lectin-modified insulin liposomes as carriers for oral administration

The aim of this study was to design and characterize lectin-modified liposomes containing insulin and to evaluate the potential of these modified colloidal carriers for oral administration of peptide and protein drugs. Wheat germ agglutinin (WGA), tomato lectin (TL), or Ulex europaeus agglutinin 1 (UEA1) were conjugated by coupling their amino groups to carbodiimide-activated carboxylic groups of N-glutaryl-phosphatidylethanolamine (N-glut-PE). Insulin liposomes dispersions were prepared by the reverse-phase evaporation technique and modified with the lectin-N-glut-PE conjugates. Lectin-modified liposomes were characterized according to particles size, zeta potential and entrapment efficiency. The hypoglycemic effect indicated by pharmacological bioavailability of insulin liposomes modified with WGA, TL and UEA1 were 21.40, 16.71 and 8.38% in diabetic mice as comparison with abdominal cavity injection of insulin, respectively. After oral administration of the insulin liposomes modified with WGA, TL and UEA1 to rats, the relative pharmacological bioavailabilities were 8.47, 7.29 and 4.85%, the relative bioavailability were 9.12, 7.89 and 5.37% in comparison with subcutaneous injection of insulin, respectively. In the two cases, no remarkable hypoglycemic effects were observed with the conventional insulin liposomes. These results confirmed that lectin-modified liposomes promote the oral absorption of insulin due to the specific-site combination on GI cell membrane.     

西红柿凝集素修饰脂质体对小鼠口服吸收胰岛素的促进作用西红柿凝集素修饰脂质体对小鼠口服吸收胰岛素的促进作用

目的研究西红柿凝集素修饰的胰岛素脂质体在小鼠胃肠道吸收作用。方法采用碳二亚胺交联法制备西红柿凝集素(TL)修饰的磷脂酰乙醇胺(PE),将TL-PE掺入胰岛素脂质体中制成凝集素修饰脂质体并证实TL凝集活性不受影响。分别对正常小鼠及糖尿病模型小鼠灌胃给予350 u·kg^-1胰岛素的修饰脂质体溶液,用葡萄糖酶试剂盒测定小鼠血糖,并与同剂量普通胰岛素脂质体比较。结果正常小鼠中,西红柿凝集素修饰脂质体在4 h血糖降至初始水平的(85±5)%,8 h降至(54±11)%,12 h为(57±6)%。胰岛素普通脂质体几乎没有降糖作用,与生理盐水对照组相当。糖尿病模型小鼠中,西红柿凝集素修饰脂质体在4 h血糖降至初始水平的(38±13)%,8 h降至(50±15)%,12 h为(50±16)%。结论西红柿凝集素修饰的脂质体可能通过与细胞表面特异性受体的结合作用促进大分子药物的胃肠吸收。     

Alternative routes of administration as an approach to improve insulin therapy: update on dermal, oral, nasal and pulmonary insulin delivery

For the past 75 years subcutaneous injections have been the only route of delivery of insulin therapy to diabetic patients. During this time, numerous attempts have been made to explore alternative routes for systemic insulin administration. However, thus far, no feasible other way of non-invasive insulin delivery has been developed. Dermal insulin application does not result in a reproducible and sufficient transfer of insulin across the highly efficient skin barrier. The dream of an "insulin tablet" has also not become a reality, the main problem being digestion and a lack of a specific peptide carrier system in the gut. Nasal insulin application was considered for a number of years as a potential method, because of the rapid absorption of insulin across the nasal mucosa. However, relative bioavailability was low and required use of absorption enhancers and more importantly, the metabolic effect lasted too short to be of clinical usefulness. To date the most promising alternative route of insulin administration, is the pulmonary delivery of insulin by inhalation which will likely lead to a practically usable system within the next few years. For maximal rate of absorption insulin must be applied deep into the lung, i.e., into the alveoli. A considerable number of inhalers (in combination with appropriate insulin formulations), which are ask to generate insulin particles with an appropriate size for pulmonary delivery, are currently in the clinical phase of development. The pharmaco dynamic effects of insulin formulations administered via the lung are comparable to, or even faster than, those of s.c. injected regular insulin or rapid-acting insulin analogues. The relative biopotency of inhaled insulin in most cases is approximately 10%, i.e., the dose of insulin administered must be 10-fold higher than with s.c. application. The published results of clinical trials thus far, indicate that metabolic control is comparable to that of s.c. insulin therapy. As of to date no serious side effects have been reported from these human trials. In summary, it appear that after several decades of research, for the first time a feasible alternative route for insulin administration is within reach.     

胰岛素肠溶微球口服的实验研究

目的 :研制一种可供口服的胰岛素肠溶微球。方法 :采用相分离法制备胰岛素丙烯酸树脂微球 ;建立放射性免疫法测定微球包封率 ;利用体外实验法考察微球的抗酸及肠溶能力 ;将不同处方的微球给大鼠灌胃 ,测定其血糖变化。结果 :制得微球粒径分布在 2～ 7μm ;包封率 95 .17% ;在人工胃液中 2h有少于 14%的胰岛素释放 ;在人工肠液中 1h内胰岛素的释放度达 96 % ;微球可使大鼠产生明显的降血糖效果。结论 :胰岛素口服肠溶微球是一类具有发展前景的制剂。     

M cells prefer archaeosomes: an in vitro/in vivo snapshot upon oral gavage in rats

The archaeolipids (lipids extracted from archaebacterias) are non saponificable molecules that form self sealed mono or bilayers (archaeosomes-ARC). Different to liposomes with bilayers made of conventional glycerophospholipids, the bilayer of ARC posses a higher structural resistance to physico chemical and enzymatic degradation and surface hydrophobicity. In this work we have compared the binding capacity of ARC exclusively made of archaeols containing a minor fraction of sulphoglycophospholipids, with that of liposomes in gel phase on M-like cells in vitro. The biodistribution of the radiopharmaceutical (99m)Tc-DTPA loaded in ARC vs that of liposomes upon oral administration to Wistar rats was also determined. The fluorescence of M-like cells upon 1 and 2h incubation with ARC loaded with the hydrophobic dye Rhodamine-PE (Rh-PE) and the hydrophilic dye pyranine (HPTS) dissolved in the aqueous space, was 4 folds higher than upon incubation with equally labeled liposomes. Besides, 15% of Rh-PE and 13 % of HPTS from ARC and not from liposomes, were found in the bottom wells, a place that is equivalent to the basolateral pocket from M cells. This fact suggested the occurrence of transcytosis of ARC. Finally, 4 h upon oral administration, ARC were responsible for the 22.3 % (3.5 folds higher than liposomes) shuttling of (99m)Tc-DTPA to the blood circulation. This important amount of radioactive marker in blood could be a consequence of an extensive uptake of ARC by M cells in vivo, probably favored by their surface hydrophobicity. Taken together, these results suggested that ARC, proven their adjuvant capacity when administered by parenteral route and high biocompatibility, could be a suitable new type of nanoparticulate material that could be used as adjuvants by the oral route.