Keishiro Tomoda

Biodistribution of colloidal gold nanoparticles after intravenous administration: Effect of particle size

Purpose of the present research work was to evaluate the biological distribution of differently size gold nanoparticles (NP) up on intravenous administration in mice. Another objective was to study effect of particle size on biological distribution of gold NP to enable their diverse applications in nanotechnology. Gold NP of different particle sizes, mainly 15, 50, 100 and 200 nm, were synthesized by modifying citrate ion concentration. Synthesized gold nanoparticles were characterized by SEM and their size distribution was studied by particle size analyzer. Gold NP was suspended in sodium alginate solution (0.5%, w/v) and administered to mice (1g/kg, intravenously) [n=3]. After 24h of administration of gold NP, blood was collected under light ether anesthesia, mice were sacrificed by cervical dislocation and various tissues/organs were removed. The tissues were then washed with saline, homogenized and lysed with aqua regia. The determination of gold in samples was carried out quantitatively by inductively coupled plasma mass spectrometry (ICP-MS). SEM study revealed spherical morphology of gold NP with narrow particle size distribution. Biodistribution study revealed gold NPs of all sizes were mainly accumulated in organs like liver, lung and spleen. The accumulation of gold NP in various tissues was found to be depending on particle size. 15 nm gold NP revealed higher amount of gold and number of particles in all the tissues including blood, liver, lung, spleen, kidney, brain, heart, stomach. Interestingly, 15 and 50 nm gold NP were able to pass blood-brain barrier as evident from gold concentration in brain. Two-hundred nanometers gold NP showed very minute presence in organs including blood, brain, stomach and pancreas. The results revealed that tissue distribution of gold nanoparticles is size-dependent with the smallest 15 nm nanoparticles showing the most widespread organ distribution.

Enhanced transdermal delivery of indomethacin-loaded PLGA nanoparticles by iontophoresis

Nanoparticles effectively deliver therapeutic agent by penetrating into the skin. Indomethacin (IM) and coumarin-6 were loaded in PLGA nanoparticles with an average diameter of 100 nm. IM and coumarin-6 were chosen as a model drug and as a fluorescent marker, respectively. The surfaces of the nanoparticles were negatively charged. Permeability of IM-loaded PLGA nanoparticles through rat skin was studied. Higher amount of IM was delivered through skin when IM was loaded in nanoparticles than IM was free molecules. Also, iontophoresis was applied to enhance the permeability of nanoparticles. When iontophoresis with 3 V/cm was applied, permeability of IM was much higher than that obtained by simple diffusion of nanoparticles through skin. The combination of charged nanoparticle system with iontophoresis is useful for effective transdermal delivery of therapeutic agents.

Enhanced transdermal delivery of indomethacin using combination of PLGA nanoparticles and iontophoresis in vivo

Nanoparticles effectively deliver therapeutic agent by penetrating into the rat skin in vivo. Indomethacin (IM) and coumarin-6 were loaded in PLGA nanoparticles with an average diameter of 100 nm. Indomethacin (IM) and coumarin-6 were chosen as a model drug and as a fluorescent marker, respectively. The surfaces of the nanoparticles were negatively charged. Permeability of IM-loaded PLGA nanoparticles through rat skin was studied in vivo. Higher amount of IM was delivered through skin when IM was loaded in nanoparticles than IM was free molecules. Also, iontophoresis was applied to enhance the permeability of nanoparticles. When iontophoresis was applied at 0.05 mA/cm(2), permeability of IM was much higher than that obtained by simple diffusion of nanoparticles through skin. The combination of charged nanoparticle system with iontophoresis is useful for effective transdermal systemic delivery of therapeutic agents.

Preparation and properties of inhalable nanocomposite particles for treatment of lung cancer.

Nanoparticles have widely been studied in drug delivery research for targeting and controlled release. The aim of this article is application of nanoparticles as an inhalable agent for treatment of lung cancer. To deposit effectively deep the particles in the lungs, the PLGA nanoparticles loaded with the anticancer drug 6-{[2-(dimethylamino)ethyl]amino}-3-hydroxyl-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103) were prepared in the form of nanocomposite particles. The nanocomposite particles consist of the complex of drug-loaded nanoparticles and excipients. In this study, the anticancer effects of the nanocomposite particles against the lung cancer cell line A549. Also, the concentration of TAS-103 in blood and lungs were determined after administration of the nanocomposite particles by inhalation to rats. TAS-103-loaded PLGA nanoparticles were prepared with 5% and 10% of loading ratio by spray drying method with trehalose as an excipient. The 5% drug-loaded nanocomposite particles were more suitable for inhalable agent because of the sustained release of TAS-103 and higher FPF value. Cytotoxicity of nanocomposite particles against A549 cells was higher than that of free drug. When the nanocomposite particles were administered in rats by inhalation, drug concentration in lung was much higher than that in plasma. Furthermore, drug concentration in lungs administered by inhalation of nanocomposite particles was much higher than that after intravenous administration of free drug. From these results, the nanocomposite particle systems could be promising for treatment of lung cancer.

Enhanced transdermal permeability of estradiol using combination of PLGA nanoparticles system and iontophoresis

Estradiol is a therapeutic agent for treatment of perimenopausal symptoms and osteoporosis. Conventional oral or intravenous administration of estradiol has many problems, such as, metabolization in gastrointestinal tract and liver, pain by using an injection needle, rapid increase of drug levels in blood and fast clearance with unwanted side effects including thrombosis, endometriosis and uterus carcinoma. The use of nanocarriers for transdermal delivery has been studied because of their ability to deliver therapeutic agents for long time with a controlled ratio, escaping from the first pass effect by liver. In this study, permeability of estradiol-loaded PLGA nanoparticles through rat skin was studied. Higher amount of estradiol was delivered through skin when estradiol was loaded in nanoparticles than estradiol was free molecules. Also, iontophoresis was applied to enhance the permeability of nanoparticles. When iontophoresis was applied, permeability of estradiol-loaded PLGA nanoparticles was much higher than that obtained by simple diffusion of them through skin, since they have negative surface charges. They were found to penetrate through follicles mainly. Also, enhanced permeability effect of estradiol by using nanoparticle system and iontophoresis were observed in vivo. The combination of charged nanoparticle system with iontophoresis is useful for effective transdermal delivery of therapeutic agents.

Hydroxyapatite particles as drug carriers for proteins

Recently, much attention has been paid to hydroxyapatite (HA) particles as protein drug carriers. HA is biological substance like tooth and bone, and HA has biodegradable and biocompatible property. Also HA has high affinity for versatile substances, such as proteins. The aim of this study was to prepare HA particles and to evaluate the effects of various experimental conditions on particles properties (i.e. shape and amount of protein adsorption to HA). HA particles were prepared by three methods including solvent diffusion methods, the method using sintering porous HA microgranules, and homogeneous precipitation method. Complicated spiky crystals were prepared by solvent diffusion method, whereas spherical amorphous agglomerates were prepared by sintering of porous HA granules. Spherical particles were obtained by homogeneous precipitation method and were well dispersed. The spherical particles were composed of minute spiky crystals. The temperature and time duration of the producing process and the amount of additives, such as urea and EDTANa(2), strongly affected the particle shape and size. When the production process is kept under low temperature, tiny crystals were not mutually sintered and also their aggregation was not deposited. Also, inhomogeneous crystal growth occurred when the reaction time was long. Addition of enough amount of EDTANa(2) to reaction solution made the small and spherical HA particles. Bovine serum albumin (BSA) or lysozyme hydrochloride (LSZ)-adsorbed HA particles were prepared. The affinity of HA particles and release profile of proteins from the particles were evaluated. X-ray powder diffraction measurements suggested that the surface area ratio of a plane against total surface area of HA crystal became smaller by decreasing EDTANa(2) concentration. The surface of plane a is positively charged but that of plane c is negatively charged. HA particle size decreased as EDTANa(2) concentration increased. The amounts of BSA and LSZ adsorbing onto HA particle surface were different, since BSA was negatively charged and LSZ was positively charged in the solution. Therefore BSA seems to adsorb onto plane c, whereas LSZ adsorb onto plane a. The differences of the ratio of surface a plane against the total surface area of HA particles and particles size influenced the amount of protein adsorption. The sustained release of BSA and LSZ from HA particles were observed for two weeks.

Preparation and properties of inhalable nanocomposite particles: Effects of the size, weight ratio of the primary nanoparticles in nanocomposite particles and temperature at a spray-dryer inlet upon properties of nanocomposite particles

Nanoparticles are expected to be applicable to inhalation as carrier but there exist disadvantages because of their size. Their deposition dose to the lung will be small. To overcome this problem and utilize nanoparticles for inhalation, we have prepared nanocomposite particles as drug carriers targeting lungs. The nanocomposite particles are prepared as drug-loaded nanoparticles-additive complex to reach deep in the lungs and to be decomposed into nanoparticles when they deposit into lung. In this study, we examined the effect of preparation condition--inlet temperature, size of primary nanoparticles and weight ratio of primary nanoparticles--on the property of nanocomposite particles. When the size of primary nanoparticles was 400 nm and inlet temperature was 90 degrees C, only the nanocomposite particles containing between 45 and 55% of primary nanoparticles could be decomposed into nanoparticles in water. On the other hand, when the inlet temperature was 80 degrees C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameter of the nanocomposite particles was between 1.5 and 2.5 microm, independent of the weight ratio of primary nanoparticles. When the size of primary nanoparticles was 200 nm and inlet temperature was 70 degrees C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameters of them were almost 2.0 microm independent of the weight ratio of primary nanoparticles. When the nanocomposite particles containing nanoparticles with the size of 200 nm are prepared at 80 degrees C, no decomposition into nanoparticles was observed in water. Fine particle values, FPF, of the nanocomposite particles were not affected by the weight ratio of primary nanoparticles when they were prepared at optimum inlet temperature.

Electrophoretic Mobility of Colloidal Gold Particles in Electrolyte Solutions

The electrophoretic mobility of five different-sized spherical colloidal gold particles has been measured in aqueous potassium chloride (KCl) and sodium phosphate electrolyte solutions over the concentration range 0.005-0.154 M solutions. The measured mobilities are independent of electrolyte type and dependent on electrolyte concentration. Interpretation of the mobilities using the simplified electrokinetic formula of Ohshima (J Colloid Interface Sci. 2001, 239, 587-590) indicates that the magnitude of the effective electrokinetic charge density and total charge of particle remains apparently constant with electrolyte concentration. The effective electrokinetic surface charge is negative in KCl and sodium phosphate solutions. The zeta-potential shows a maximum absolute value in both electrolyte solutions (negative).

Preparation and properties of carrageenan microspheres containing allopurinol and local anesthetic agents for the treatment of oral mucositis

For the treatment of oral mucositis, carrageenan microspheres containing allopurinol and local anesthetic agents, such as lidocaine hydrochloride, dibucaine hydrochloride and tetracaine hydrochloride were prepared using a spray-drying method. As base materials, kappa-carrageenan and iota-carrageenan were evaluated, since carrageenan mitigates bitter taste of lidocaine hydrochloride, dibucaine hydrochloride and tetracaine hydrochloride. The microspheres were spherical and their average diameters were about 10 microm. The drug loading efficiency was more than 70%. Allopurinol and local anesthetic agents became amorphous by the spray drying. Allopurinol and the local anesthetic agents were released from the microspheres for at least 400 min when iota-carrageenan was used as a base material. On the other hand, the release was prolonged to 600 min when kappa-carrageenan was used. The microspheres were spread and made membranes at the air/water interfaces immediately after dropped on the water surfaces. The properties of the microspheres such as dispersing efficacy and membrane production on the water surfaces suggest that the microspheres can uniformly cover inner surfaces of oral cavity to prevent and treat oral mucositis.

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.