Issei Takeuchi

Estradiol-loaded PLGA nanoparticles for improving low bone mineral density of cancellous bone caused by osteoporosis: Application of enhanced charged nanoparticles with iontophoresis

Postmenopausal osteoporosis among older women, which occurs by an ovarian hormone deficiency, is one of the major public health problems. 17 β-estradiol (E2) is used to prevent and treat this disease as a drug of hormone replacement therapy. In oral administration, E2 is significantly affected by first-pass hepatic metabolism, and high dose administration must be needed to obtain drug efficacy. Therefore, alternative administration route is needed, and we have focused on the transdermal drug delivery system. In this study, we have prepared E2-loaded poly(DL-lactide-co-glycolide) (PLGA) nanoparticles for osteoporosis by using a combination of an antisolvent diffusion method with preferential solvation. The average particle diameter of the nanoparticles was 110.0±41.0nm and the surface charge number density was 82 times higher than that of conventional E2-loaded PLGA nanoparticles. Therapeutic evaluation of E2-loaded PLGA nanoparticles was carried out using ovariectomized female rats. Therapeutic efficacy was evaluated to measure bone mineral density of cancellous bone using an X-ray CT system. When the E2-loaded PLGA nanoparticles were administrated once a week, bone mineral density was significantly higher than that of the non-treated group at 60days after the start of treatment. Also, in the group administered this nanoparticle twice a week, the bone mineral density increased significantly at 45days after the start of treatment. From these results, it was revealed that E2-loaded PLGA nanoparticles with iontophoresis were useful to recover bone mineral density of cancellous bone, and it was also suggested that they extend the dosing interval of E2.

Estimation of crystallinity of trehalose dihydrate microspheres by usage of terahertz time‐domain spectroscopy

Crystalline state of pharmaceutical materials is of great importance in the preparation of pharmaceutics because their physicochemical properties affect bioavailability, quality of products, therapeutic level, and manufacturing process. In this study, we have estimated the crystallinity of trehalose dihydrate microspheres by measuring terahertz (THz) spectroscopy. The commercially available trehalose dihydrate takes in general a crystalline state, but trehalose dihydrate microspheres prepared by using spray-drying method are in an amorphous state. We have prepared amorphous anhydrous trehalose by using melt-quenched method from crystalline trehalose dihydrate. We have measured the absorbance of trehalose dihydrate containing amorphous anhydrous trehalose (0%, 25%, 50%, 75%, and 100%) using THz time-domain spectroscopy (THz-TDS) to prepare calibration curves. Using the calibration curves, we have estimated the crystallinity of trehalose dihydrate microspheres prepared by using spray-drying method. Our results suggest that THz-TDS is well suited to distinguish crystallinity differences in pharmaceutical compounds.

Transdermal delivery of estradiol-loaded PLGA nanoparticles using iontophoresis for treatment of osteoporosis.

BACKGROUND Estradiol is one of the therapeutic agents for osteoporosis. We have reported transdermal permeability of estradiol-loaded nanoparticles, and permeability effect of estradiol was enhanced by using nanoparticle system and iontophoresis [Colloids and Surfaces B: Biointerfaces97 (2012), 84-89]. OBJECTIVE This study was conducted in vivo to evaluate therapeutic efficacy of the estradiol-loaded PLGA nanoparticles for osteoporosis. METHODS Prior to the in vivo study, we have determined the surface charge density of the particles and found they have negatively charged polyelectrolyte layers on the surfaces. Ovariectomized female Sprague-Dawley rats were used as an animal model of osteoporosis. They were separated into three groups by administration route of estradiol-loaded PLGA nanoparticles, passive diffusion group, iontophoresis group and control. After treatment, we have measured bone mineral density of spine using an X-ray computed tomography system. RESULTS Bone mineral density after iontophoresis was significantly higher than that of passive diffusion and control group. By usage of iontophoresis, the nanoparticles were permeated through follicles and migrated into capillary vessel around follicles, and the loaded drug reached effective blood concentration in plasma of rat. CONCLUSIONS From this study, we found that the combination with charged nanoparticle system and iontophoresis is useful to osteoporosis treatment.

Biodistribution and excretion of colloidal gold nanoparticles after intravenous injection: Effects of particle size

BACKGROUND Inorganic gold nanoparticles (NPs) have a huge potential in targeted drug delivery. Simple preparation and surface modification procedure with their special physicochemical properties of gold NPs attract their use such as tumor targeting and the detection of cancerous cell. OBJECTIVE Various studies were reported, however, details of biodistribution profile of gold NPs were not enough evaluated. We have studied biodistribution profile of gold NPs having various particle sizes (20, 50 and 100 nm). METHODS Gold concentrations in brain, heart, lungs, liver, stomach, pancreas, spleen, kidneys, blood, urine, and feces were measured at 5 minutes, 0.25, 0.5, 1, 2, 3, 6, 12, 18 and 24 hours after administration of gold NPs using inductively coupled plasma atomic emission spectrometry. RESULTS In lungs and brain, especially 20-nm gold NPs were accumulated after 2-3 hours of dose administration, and they were kept for 24 hours, whereas they showed relatively low accumulation in heart, stomach and pancreas. After 12 hours, 3.3-14.4% of the injected gold were observed in fecal matter and urine. CONCLUSIONS From this study, the application of gold NPs for targeted delivery to lungs and brain and the excretion route of the gold NPs from the body were suggested.

Nondestructive Analysis of Structure and Components of Tablet Coated with Film by the Usage of Terahertz Time-Domain Reflection Spectroscopy

Nondestructive analysis of tablet is of great importance from the aspect of productivity and safety. In terahertz (THz) region, however, the analysis of core of coated tablet has not been progressed. In this study, we have measured a flat-surface push-pull osmotic pump tablet, having no orifice, having bilayer core and a coating film layer. The bilayer core was made from the drug layer and the push layer, and acetaminophen was contained in the drug layer as a model drug. To study its structure and components, we have obtained reflection spectra from the drug layer side and the push layer side measurements using THz time-domain reflection spectroscopy (THz-TDRS). From these results, detection of the peak of acetaminophen in the spectrum from the drug layer side measurements was confirmed. We have made ridges approximated toward the peak using a general method of linear regression analysis in both spectra. Two-sample t-test was applied to their gradients, and significant difference between the drug layer and the push layer was shown. These results suggested that THz-TDRS is applicable to the analysis of structure and component of a coated tablet.

Iontophoretic transdermal delivery using chitosan-coated PLGA nanoparticles for positively charged drugs

Recently, poly(dl-lactide-co-glycolide) (PLGA) nanoparticles prepared using a combination of an antisolvent diffusion method with preferential solvation was shown to be beneficial for the iontophoretic transdermal delivery of therapeutic agents. Also, this preparation method can contain a hydrophilic drug. However, since PLGA nanoparticles were negatively charged, it was difficult to apply iontophoresis for positively charged hydrophilic drugs. In this study, we prepared positively charged PLGA nanoparticles containing donepezil hydrochloride (DP). DP was used as a positively charged hydrophilic drug model. The PLGA nanoparticles were coated with chitosan hydroxypropyltrimonium chloride. The average particle diameter of the nanoparticles was 117.7±60.6nm and the surface charge number density changed from negative to positive. Ex vivo skin accumulation study was carried out using abdominal rat skin and a Franz-type diffusion cell with/without iontophoresis. When iontophoresis was applied, the DP concentration in the rat skin of chitosan-coated PLGA nanoparticles was 2.2 times higher than that of non-coated PLGA nanoparticles. This indicated that chitosan-coated PLGA nanoparticles were suitable for iontophoresis. To investigate the transdermal delivery route of the nanoparticles, we prepared chitosan-coated PLGA nanoparticles containing DP, coumarin-6, and rhodamine 6G. Coumarin-6 and rhodamine 6G were used as a trace marker of the PLGA nanoparticles and positively charged hydrophilic drug model, respectively. From the results of ex vivo accumulation test of this fluorescent nanoparticles, it was suggested that positively charged hydrophilic drugs reached the hair follicles as a nanoparticle, and then they were released from the nanoparticles.

Skin permeability and transdermal delivery route of 50-nm indomethacin-loaded PLGA nanoparticles

Recently, nano-seized systems for transdermal delivery have attracted attention. To efficiently deliver drugs to hair follicles, we focused on poly(DL-lactide-co-glycolide) (PLGA) nanoparticles prepared using a combination of an antisolvent diffusion method with preferential solvation. The PLGA nanoparticles prepared using this method are suitable for iontophoresis because of their high surface charge number density. It has been reported that PLGA nanoparticles were delivered to hair follicles by applying iontophoresis, however research on PLGA nanoparticles with a size of less than 100nm was lacking. In this study, we prepared 50-nm and 100-nm PLGA nanoparticles. Indomethacin was used as a hydrophobic drug model and the nanoparticles were evaluated their skin permeability using the abdominal skin of a rat. Two hours after administration, the skin permeation indomethacin amounts of 50-nm and 100-nm PLGA nanoparticles with iontophoresis were significantly higher than those of passively diffused nanoparticles and indomethacin solution. Moreover, when iontophoresis was applied, the indomethacin concentration in the rat skin of 50-nm PLGA nanoparticles was 1.7 times higher than that of 100-nm PLGA nanoparticles. We also prepared coumarin-6-loaded 50-nm and 100-nm PLGA nanoparticles having surface characteristics equivalent to those of indomethacin-loaded PLGA nanoparticles to investigate transdermal delivery route of indomethacin-loaded PLGA nanoparticles. The 50-nm nanoparticles reached a deeper portion of the hair follicle when applying iontophoresis. Therefore, it was shown that this nanoparticle was useful for targeting to hair follicles.

Estimation of Crystallinity of Nifedipine–Polyvinylpyrrolidone Solid Dispersion by Usage of Terahertz Time-Domain Spectroscopy and of X-Ray Powder Diffractometer

Crystalline state of pharmaceutical materials is of great importance in preparation of pharmaceutics, because their physicochemical properties affect bioavailability, quality of products, therapeutic level and manufacturing process. In this study, we have estimated time-dependent changes of nifedipine in nifedipine-polyvinylpyrrolidone (PVP) solid dispersion by measuring terahertz time-domain spectroscopy (THz-TDS) and by X-ray powder diffractometry (XRPD), and compared their correlativity. Crystallinity of nifedipine-PVP solid dispersion was changed by storing the amorphous sample at 25°C-75°C and relative humidity of over 80% for 0.25-24.00 h. To compare the results of two types of measurements, we have used a general method of linear regression analysis. Crystallinities estimated using THz-TDS were plotted on the x-axis and that of XRPD were on the y-axis. From the result of the calculation, the correlativity of them was confirmed. THz-TDS has the capability of becoming the replacement of XRPD.

Hydrophobic boron compound-loaded poly(l-lactide-co-glycolide) nanoparticles for boron neutron capture therapy

Poly(DL-lactide-co-glycolide) (PLGA) has been widely used and studied because of its biocompatibility and biodegradability. Recently, the usefulness of nanoparticles using poly(L-lactide-co-glycolide) (PLLGA) having a higher glass transition temperature than PLGA was suggested. In this study, we investigated the availability of boron compound-loaded PLGA and PLLGA nanoparticles for boron neutron capture therapy (BNCT) by conducting biodistribution study using tumor-bearing mice. o-Carborane, a hydrophobic boron compound, was used as a boron carrier, and o-carborane-albumin conjugate was used as a control. We prepared PLGA and PLLGA nanoparticles with diameters of 100nm and 150nm. In 100-nm PLLGA nanoparticles, the boron concentration in the tumor reached 113.9±15.8μg/g of tissue at 8h after administration. This result indicated that 100-nm PLLGA nanoparticles were able to achieve an intratumoral 10B concentration of 20μg/g without replacing the 11B with 10B. In addition, by nanoparticulation using PLGA7510 and PLLGA7510, intratumoral boron concentration was 1.7-3.2 and 3.5-4.2 times higher than that of the o-carborane-albumin conjugate, respectively. The tumor/blood ratios of boron concentration reached over 5 at 8-12h after injection. Boron atoms in nanoparticles were excreted mainly in the urine, and characteristic accumulation was not observed in other organs. These results suggested that 100-nm PLLGA nanoparticles were particularly useful for BNCT.

Push-pull controlled drug-release systems: Effect of molecular weight of polyethylene oxide on drug-release

First, an elementary osmotic pump (EOP) with a simple structure was prepared using polyethylene oxide (PEO) and NaCl as an excipient, and the influence of the molecular weight (Mw) of PEO on drug release was investigated. In the dissolution test of EOP, it was observed that the gelated core tablet was pushed out through the orifice. The dissolution profile of EOP was sigmoidal, and despite the short time, a zero-order release region was observed. The gel swelling rate in the zero-order region was independent of the Mw of PEO. It was also found that higher the Mw of PEO, the larger the saturated swelling amount. Next, a push-pull pump (PPP) with almost identical formulation to that of EOP was prepared, and its drug release characteristics were investigated. PPPs were prepared by varying the combination of Mws of PEO in both layers, and their dissolution profiles were compared. It was found that PPP using a low-Mw PEO for the drug layer and PEO with a high-Mw in the push layer showed the longest dissolution profile of the linear region. The obtained findings suggested that the properties of PEO and its hydrogel play a crucial role in the drug release of PPP.