Yukako Ito

Self-dissolving microneedles for the percutaneous absorption of EPO in mice

Erythropoietin (EPO) loaded microneedles were prepared using thread-forming polymer as a base for the percutaneous administration of EPO. The used polymers were dextrin, chondroitin sulfate and albumin. Under room temperature, EPO solution was added to high concentration of polymer solution and microneedles were prepared by forming thread with polypropylene tips. The mean weight of microneedle was 0.59 ± 0.01 mg and length and basal diameter were 3.24 ± 0.16 and 0.55 ± 0.03 mm, respectively. Four microneedles were percutaneously (pc) administered to mice at the EPO dose levels of 100 IU/kg. After administration, blood samples were collected for 24 h and serum EPO levels were measured. Dextrin EPO microneedles were administered both pc and subcutaneously (sc) to mice. Serum EPO levels vs. time profiles showed Cmax of 138.6 ± 16.1 and 146.5 ± 8.0 mIU/ml, respectively. Tmax were 7.5 h. The values of bioavailability (BA) of EPO were 82.1 and 99.4%, respectively. By decreasing the dose from 100 to 50 and 25 IU/kg, dose-dependent serum EPO levels vs. time profiles were not clearly obtained. When chondroitin sulfate and albumin were used as the microneedle base, the serum EPO levels vs. time profiles showed almost the same pattern. Cmax of chondroitin sulfate and albumin microneedles were 96.3 ± 8.8 and 132.2 ± 18.9 mIU/ml, respectively. AUCs were 835.1 and 1098.7 mIU h/ml. Tmax were 8 and 6.8 h. These results suggest the usefulness of microneedles for the percutaneous administration of EPO.

Two-layered dissolving microneedles formulated with intermediate-acting insulin.

Two-layered dissolving microneedles (DMs) containing intermediate-acting insulin, protamine sulfate insulin (PSI), were prepared. Then a pharmacodynamic study was performed to evaluate the prolonged hypoglycemic effects in rats. The DMs were approximately 497±5 μm long, with 303±3 μm diameter at their base. The length of the insulin loaded space was 182±4 μm. PSI contents in DMs were 0.51±0.02 IU. A three-month stability study showed that 99.9±1.4% of PSI was recovered at 4 °C. As the temperature increased to 40 °C, recovery decreased to 97.5±2.0%. PSI was released within 5 min from DMs. Hypoglycemic effects of PSI DMs were evaluated in rats where subcutaneous injection preparations were used as references. Total area above the plasma glucose level (% of the pre-dose level) vs. time curve as an index of hypoglycemic effect was 144.0±16.0% h and 243.3±8.5% h for PSI DMs at 1.46 and 3.28 IU/kg. The relative pharmacologic availability of PSI from DMs were 100.2±9.8% and 91.4±4.1%. No significant difference of hypoglycemic curves was found between DMs and injection solutions, which suggests the usefulness of two-layered DMs of PSI for the displacement therapy of sc injection preparation.

Antigen-loaded dissolving microneedle array as a novel tool for percutaneous vaccination.

Antigen-loaded dissolving microneedle array (dMNA) patches were investigated as novel systems for vaccine delivery into the skin, where immuno-competent dendritic cells are densely distributed. We fabricated micron-scale needles arrayed on patches, using chondroitin sulfate mixed with a model antigen, ovalbumin. Insertion of dMNA effectively delivered substantial amounts of ovalbumin into the skin within 3 min and induced robust antigen-specific antibody responses in the sera of mice. The antibody dose-response relationship showed that the efficiency of dMNA patch immunization was comparable to that of conventional intradermal injections. Thus, Antigen-loaded dMNA patches are a promising antigen-delivery system for percutaneous vaccination.

Technology to Obtain Sustained Release Characteristics of Drugs after Delivered to the Colon

AbstractTo determine the necessary technology by which sustained drug release is obtained after drug is delivered to the colon, two kinds of microcapsules were prepared and were filled in a pressure-controlled colon delivery capsule (PCDC). As a model drug 5-aminosalicylic acid (5-ASA) was used, because the target site of 5-ASA is the entire large intestine. 5-ASA was microencapsulated using a water-insoluble polymer, ethylcellulose (EC) or with pH-sensitive polymers, Eudragit™ L-100 or S-100 and encased in PCDC. The particle size of these microcapsules was around 800 μm and the loading efficiencies of 5-ASA were approximately 90%. In vitro dissolution tests were performed with the prepared microcapsules. The release rate of 5-ASA from the microcapsules was significantly prolonged as compared to 5-ASA powder, although there were no significant differences in the release rates between these microcapsules. By incorporating the 5-ASA microcapsules into PCDC, sustained release PCDCs for colon delivery were pr...

Incidence of low bioavailability of leuprolide acetate after percutaneous administration to rats by dissolving microneedles

Two-layered dissolving microneedles of which acral portion contained leuprolide acetate (LA) as solid dispersion were prepared with sodium chondroitin sulfate as the base and the systemic absorption efficiency of LA was studied in rats after administration to their abdominal skin. A patch contained 100 dissolving microneedles of which length and basement diameter were 469.8±4.7 μm and 284.5±9.8 μm, where LA content was 14.3±1.6 μg. In vitro dissolution experiment showed that LA was released from dissolving microneedle patch within 3 min. LA was stable in the patch, % recoveries for 3 months were 102.2±1.9-95.3±1.9%. One and half-patch of LA dissolving microneedles were administered to the rat skin and plasma LA concentrations were measured by LC-MS/MS. Plasma LA concentrations increased immediately after administration, and reached to the maximum level at 15 min, where C(max) were 6.0±0.7 and 16.4±0.9 μg/ml, respectively. The AUC were 5.8±0.8 and 14.5±0.4 μg h/ml and BA were 33.8±4.3% and 31.7±0.8%. When LA solution was subcutaneously (s.c.) injected to rats, 50 μg/kg, the BA was 32.0±2.1%. Relative BA of LA from dissolving microneedles against s.c. solution was 105.6±13.5%. The degradation rate of LA in the rat skin tissue homogenate was very fast where the half-life was 16.3±5.7 min. The degradation of LA in the skin tissue was the cause of the low BA of LA after percutaneous administration to rats.

Percutaneous absorption of interferon-α by self-dissolving micropiles

To ascertain the pharmaceutical usefulness of self-dissolving micropiles (SDMPs) containing interferon (IFN), two types of SDMPs were prepared using chondroitin sulfate and dextran as the base. After percutaneous administration of 5000 IU/kg IFN-α2b SDMP to rats, serum IFN levels were measured for 6 h. The peak serum IFN level, maximum drug concentration (Cmax), and the time when serum IFN level reaches to Cmax, time to reach maximum concentration (Tmax), were 8.2 ± 0.5 IU/ml and 1.2 ± 0.1 h, respectively, for chondroitin SDMP. For dextran SDMP, Cmax and Tmax were 3.1 ± 0.4 IU/ml and 3.3 ± 0.3 h, respectively. AUC of chondroitin SDMP was 1.5 times greater than that of dextran SDMP. Bioavailabilities (BAs) of IFN were 378.3% for chondroitin SDMP and 255.9% for dextran SDMP that were larger than 100%. The BA of IFN from subcutaneous (s.c.) injection solution was 320.9%. The relative BAs of IFN SDMPs against s.c. injection solution were 117.8% for chondroitin SDMP and 79.9% dextran SDMP. An in vitro release experiment suggested the faster release rate of IFN from chondroitin SDMP, 57.3% at 5 min, than dextran SDMP, 32.6% at 5 min. Chondroitin SDMP containing IFN showed good stability for 3 months and no damage to the administered rat skin.

Two-layered dissolving microneedles for percutaneous delivery of sumatriptan in rats

A novel transdermal delivery of sumatriptan (ST) was attempted by application of dissolving microneedle (DM) technology. Dextran DM (d-DM) and hyaluronate DM (h-DM) were prepared by adding ST solution to dextran solution or hyaluronic acid solution. One DM chip, 1.0 × 1.0 cm, contains 100 microneedle arrays in a 10 × 10 matrix. The mean lengths of DMs were 496.6 ± 2.9 μm for h-DM and 494.5 ± 1.3 μm for d-DM. The diameters of the array basement were 295.9 ± 3.9 μm (d-DM) and 291.7 ± 3.0 μm (h-DM), where ST contents were 31.6 ± 4.5 μg and 24.1 ± 0.9 μg. These results suggest that ST was stable in h-DM. Each DM was administered to rat abdominal skin. The maximum plasma ST concentrations, Cmax, and the areas under the plasma ST concentration versus time curves (AUC) were 44.6 ± 4.9 ng/ml and 24.6 ± 3.9 ng · h/ml for h-DM and 38.4 ± 2.7 ng/ml and 14.1 ± 1.5 ng · h/ml for d-DM. The bioavailabilities of ST from DMs were calculated as 100.7 ± 18.8% for h-DM and 93.6 ± 10.2% for d-DM. Good dose dependency was observed on Cmax and AUC. The stability study of ST in DM was performed for 3 months under four different conditions, −80, 4, 23, and 50°C. At the end of incubation period, they were, respectively, 100.0 ± 0.3%, 97.8 ± 0.2%, 98.8 ± 0.2%, and 100.7 ± 0.1%. These suggest the usefulness of DM as a noninvaisive transdermal delivery system of ST to migraine therapy.

Effect of Lipophilicity on the Bioavailability of Drugs After Percutaneous Administration by Dissolving Microneedles

To elucidate drug lipophilicity effects on the bioavailability (BA) of drugs from skin after administration by dissolving microneedles, nine compounds with different lipophilicity indexes (log p value) were formulated into two-layered dissolving microneedles and administered percutaneously to rat skin: desmopressin (DDAVP), sumatriptan (ST), fluorescein (FL), granisetron (GRN), pindolol (PDL), pravastatin (PRV), rhodamine 123 (Rho), rifampicin (RFP), and salmeterol (SLM). Plasma drug concentrations were measured using liquid chromatography-tandem mass spectrometry and spectrofluorometry. In vivo dissolution and diffusion in both horizontal and vertical directions of FL and RH in the skin were studied using fluorescence microscopy. Respective BAs were 95.1 ± 7.9% (DDAVP), 84.2 ± 2.7% (ST), 82.3 ± 7.2% (FL), 82.7 ± 6.7% (GRN), 71.6 ± 3.8% (PDL), 63.6 ± 7.5% (PRV), 53.7 ± 8.3% (Rho), 46.2 ± 6.1% (RFP), and 38.4 ± 2.7% (SM). BA decreased as the lipophilicity index, log p value, of the drug increased from-1.95 to 1.73. The respective remaining percentages in skin tissue were 1.4 ± 0.7% (DDAVP), 0.9 ± 0.1% (ST), 1.0 ± 0.2% (FL), 3.4 ± 1.2% (GRN), 14.5 ± 3.7% (PDL), 23.4 ± 5.2% (PRV), 32.2 ± 6.0% (Rho), 40.7 ± 4.9% (RFP), and 40.6 ± 5.1% (SLM), dependent on log p. Fluorescence microscopy showed no FL or Rho in skin tissue within 4 and 24 h after administration, respectively. The BA of drugs delivered by dissolving microneedles depends on the drug solubility in the skin epidermis and dermis.

Pharmacokinetic and Pharmacodynamic Evaluation of Insulin Dissolving Microneedles in Dogs

BACKGROUND This study tested the hypothesis that dissolving microneedles are a useful transdermal drug delivery system (TDDS) for insulin. METHODS Insulin was loaded on a patch (1.0 cm2) that had 100 dissolving microneedles with chondroitin sulfate by microfabrication technology. Pharmacodynamic evaluation was performed by applying two or four patches to the shaved abdominal skin of dogs, and blood samples were collected for 360 min to measure plasma glucose and insulin levels. In diffusion experiment, microneedles containing fluorescein isothiocyanate-insulin and/or Evans blue were administered to the rat skin, and the diffusion rates of tracers were recorded. RESULTS The mean length, diameter of basement, and drug-loaded space from the top of the microneedles were 492.6 +/- 2.4, 290.0 +/- 3.6, and 316.0 +/- 7.3 microm, respectively. The insulin content was 1.67 +/- 0.17 IU per patch. The time when the minimum plasma glucose level was obtained was 50.0 +/- 8.7 min for two-patch and 82.5 +/- 14.4 min for four-patch studies. A dose-dependent hypoglycemic effect was observed. By comparing the cumulative percentage change in the plasma glucose level between insulin microneedles and solution, the relative physiological availabilities were calculated to be 71.1 +/- 17.8% (for two patches) and 59.3 +/- 4.4% (for four patches). Bioavailabilities of insulin from microneedles were 72.1 +/- 11.6% (for two patches) and 72.4 +/- 8.3% (for four patches). High diffusion rates of fluorescein isothiocyanate-insulin and Evans blue were observed at the administered skin site and correlated well with the high absorption rate of insulin into the systemic circulation. Insulin was stable in dissolving microneedles for 1 month at 4 degrees C; the recovered percentage was 99.2 +/- 13.9%. CONCLUSIONS Dissolving microneedles were demonstrated to be a useful TDDS as an immediate-acting insulin preparation.

Sustained-release self-dissolving micropiles for percutaneous absorption of insulin in mice.

Microparticles-adsorbed insulin and zinc insulin (Penfil®N) were molded to self-dissolving micropiles (SDMPs) with chondroitin sulfate as the base for the percutaneous administration of insulin. Porous silicon dioxide (Sylysia® 320, 440 and 730) and porous calcium silicate (Florite®RE) were used as microparticles. As a reference, insulin loaded SDMPs were prepared. SDMPs were percutaneously administered to mice at the insulin dose level of 2.5 IU/kg. After the insertion of SDMPs to mouse skin, blood samples were collected for 8 h and plasma glucose levels were measured. There were not significant differences on minimum plasma glucose levels between the test preparations. However, Tmins, the time when the minimum glucose level appeared were 1.5 ± 0.2 h (Sylysia 320), 1.3 ± 0.2 h (Sylysia 440), 1.6 ± 0.4 h (Sylysia 730), 2.1 ± 0.3 h (Florite) and 1.7 ± 0.3 h (zinc insulin) which were greater than insulin SDMP, 0.8 ± 0.1 h. In addition, greater hypoglycemic effects were observed with SDMPs containing adsorbent-insulin and/or zinc insulin than insulin SDMP. The mean AACs (area above the plasma glucose level vs. time curve) of SDMPs containing adsorbent-insulin and zinc insulin were 357.8% h for Florite®RE, 333.1% h for Sylysia 320, 308.1% h for Sylysia 440, 328.1% h for Sylysia 730, and 374.7% h for zinc insulin, respectively, which were about two folds higher than that of insulin SDMN, 161.2% h. Those results suggest the usefulness of SDMPs composed of adsorbent-insulin as a long-acting percutaneous insulin preparation.