Yoshiharu Machida

Biodegradation and distribution of water-soluble chitosan in mice

Randomly 50% deacetylated chitin, called Chi, was examined on the biodegradability, body distribution and urinary excretion after the intraperitoneal (ip) administration to mice. These characteristics were investigated using fluorescein isothiocyanate (FITC)-labeled Chi (FTC-Chi). The in vitro biodegradability was investigated by incubation with lysozyme and murine plasma and urine. The degradation of Chi or FTC-Chi was accelerated by lysozyme, plasma and urine. The molecular weight was checked by gel-chromatography. The degradation product showed a fairly small molecular weight and contained no FTC-Chi of a large one. The body distribution and urinary excretion of FTC-Chi were investigated at 1, 14 and 24 h after the ip injection to mice. FTC-Chi moved fast to the kidney and urine, and was scarcely distributed to the liver, spleen, abdominal dropsy and plasma. Most of FTC-Chi was excreted into urine after 14 h, and the molecular weight of the excreted FTC-Chi was as small as that of the product obtained by the long in vitro incubation. Therefore, Chi is considered to be highly biodegradable and easily excreted in urine, and further it is suggested to have no problem on accumulation in the body; however, at the same time, Chi is found not to operate as a polymer support showing long retention in the body.

Application of chitin and chitosan derivatives in the pharmaceutical field

Chitin and chitosan derivatives are used as excipients and drug carriers in the pharmaceutical field. Their derivatization contributed to expansion of application and decrease toxicity. Chitosan is used as an excipient in oral dosage form. Chitosan tablet can exhibit a sustained drug release compared to commercial products. Films prepared using chitin or chitosan have been developed as wound dressings, oral mucoadhesive and water-resisting adhesive by virtue of their release characteristics and adhesion. Intratumoral administration of gadopentetic acid-chitosan complex nanoparticles (approximately 430 nm in diameter) has been more effective for gadolinium neutron-capture therapy compared with a group treated with the solution. Compared to intragastrical feeding with diphtheria toxoid (DT) in PBS, a strong enhancement of the systemic (IgG) and local (IgA) immune responses against DT has been observed in mice fed with DT loaded chitosan microparticles (approximately 4.7 microm in size). When DNA-loaded chitosan microspheres (1.15 - 1.28 microm) were intramuscularly administrated into mice, high beta-galactosidase and luciferase productions were obtained even after a long post-transfection period (12 weeks). N-Succinyl-chitosan (Suc-Chi) has been studied for cancer chemotherapy as a drug carrier and the conjugates of mitomycin C with Suc-Chi exhibited good antitumor activities against various tumors. Furthermore, trimethyl-chitosan and monocarboxymethyl-chitosan has been shown to be effective as intestinal absorption enhancers due to their physiological properties. Chitosan-thioglycolic acid conjugates has been found to be a promising candidate as scaffold material in tissue engineering due to their physicochemical properties. This review summarizes the application of chitin and chitosan derivatives for hospital preparations and drug carriers.

Characteristics of polyion complexes of chitosan with sodium alginate and sodium polyacrylate

Abstract With a view to the application of chitosan (CS) for drug delivery formulations, formation of interpolymer complexes of CS with sodium alginate (AL) and sodium polyacrylate (AC) was investigated, employing viscosity measurement, Fourier-transform infrared (FT-IR) spectroscopy and elementary analysis. The effect of the molecular weight of AL or AC on complexation with CS was analyzed by gel-permeation chromatography. The binding ratio of a unit molecule of CS with AL was found to be approximately 1:1. This ratio was relatively constant in media of various pH values. On the other hand, the unit molecular binding ratio of CS with AC was greatly affected by the pH values of the media, showing a change from 1:4 to 1:1.7 with increase in pH values from 3.7 to 4.7. Results obtained from gel-permeation chromatography suggested that the lower molecules of AL bind with CS more selectively on complex formation, although the selectivity was unclear in the case of the CS-AC system. Based on the results of FT-IR spectra and elementary analysis, the binding ratio of each component in the solid complexes was very close to that observed in viscosity measurements.

N-succinyl-chitosan as a drug carrier: water-insoluble and water-soluble conjugates.

N-succinyl-chitosan (Suc-Chi) has favourable properties as a drug carrier such as biocompatibility, low toxicity and long-term retention in the body. It was long retained in the systemic circulation after intravenous administration, and the plasma half-lives of Suc-Chi (MW: 3.4 x 10(5); succinylation degree: 0.81 mol/sugar unit; deacetylation degree: 1.0 mol/sugar unit) were ca. 100.3h in normal mice and 43 h in Sarcoma 180-bearing mice. The biodistribution of Suc-Chi into other tissues was trace apart from the prostate and lymph nodes. The maximum tolerable dose for the intraperitoneal injection of Suc-Chi to mice was greater than 2 g/kg. The water-insoluble and water-soluble conjugates could be prepared using a water-soluble carbodiimide and mitomycin C (MMC) or using an activated ester of glutaric MMC. In vitro release characteristics of these conjugates showed similar patterns, i.e. a pH-dependent manner, except that water-insoluble conjugates showed a slightly slower release of MMC than water-soluble ones. The conjugates of MMC with Suc-Chi showed good antitumour activities against various tumours such as murine leukaemias (L1210 and P388), B16 melanoma, Sarcoma 180 solid tumour, a murine liver metastatic tumour (M5076) and a murine hepatic cell carcinoma (MH134). This review summarizes the utilization of Suc-Chi as a drug carrier for macromolecular conjugates of MMC and the therapeutic efficacy of the conjugates against various tumours.

In vitro and in vivo nasal mucoadhesion of some water-soluble polymers

Abstract In this study the adhesion of water-soluble neutral polymers, i.e. hydroxypropylcellulose (HPC), xanthan gum (XG), tamarind gum (TG) and polyvinyl alcohol (PVA), to nasal mucosa was evaluated in vivo and in vitro. The polymers mixed with a dye were applied to the nasal cavity of rabbits in powder form, and residue of the dye was observed through a thin fiberscope. XG showed the longest residence of the dye in the cavity, followed by TG, HPC and PVA in this order. These polymers should thus prove useful as bases for mucoadhesive powder formulations. At a ratio of 2:8, a mixture of PVA and XG showed nearly the same residence time as those of HPC and TG, suggesting that it is feasible to control the residence time by mixing two or more polymers differing in adhesiveness. The order of adhesion of these polymers to agar plates in two in vitro methods agreed with that of their mucoadhesion in vivo. These in vitro methods may thus be of use for predicting the nasal mucoadhesion of powder formulations of neutral polymers.

Hypoglycemic effect of novel oral microspheres of insulin with protease inhibitor in normal and diabetic rats

Abstract The effectiveness of an oral administration of insulin microspheres (IMS) containing a protease inhibitor was evaluated in normal and diabetic rats. The dosage form is based on the incorporation of insulin with protease inhibitor into polyacrylic polymer (Eudragit L100). These preparations were administered orally with a 20 U/kg insulin dose by force-feeding to rats. Insulin absorption was evaluated by its hypoglycemic effect. IMS without protease inhibitor and with trypsin inhibitor (TI) or chymostatin (CS) produced no marked hypoglycemic response in both groups of rats. A significant continuous hypoglycemic effect was obtained after oral administration of IMS containing aprotinin (AP) or Bowman-Birk inhibitor (BBI) in both normal and diabetic rats when compared with controls. To calculate the relative efficacy, log dose/effect curves for i.v. insulin were obtained in both groups of rats. The efficacy of oral administration, relative to i.v., was assessed by measuring the cumulative percentage of change in serum glucose levels during the experimental period. The efficacy order of four protease inhibitors incorporated into IMS was AP ⩾ BBI > CS=Tl. The results suggest that the use of protease inhibitors as pharmaceutical adjuvants for IMS has the advantage of enhancing the efficacy of insulin.

Biological characteristics of lactosaminated N-succinyl-chitosan as a liver-specific drug carrier in mice

Lactosaminated N-succinyl-chitosan (Lac-Suc) was prepared by reductive amination of N-succinyl-chitosan (Suc) and lactose using sodium cyanoborohydride. Six-day reaction using lactose (12.8-fold (w/w)) yielded Lac-Suc with lactosamination degree of 30% (mol/sugar unit). Fluorescein thiocarbamyl-Lac-Suc (Lac-Suc-FTC) was prepared by labeling Lac-Suc with fluorescein isothiocyanate. Lac-Suc-FTC was injected intravenously at a dose of either 1 (high dose) or 0.2 (low dose) mg/mouse. At both doses, Lac-Suc-FTC initially underwent fast hepatic clearance, showed maximum liver localization at 8 h, and the amounts localized there were maintained even at 48 h post-injection. Very slow excretion into feces and urine was observed. The ratio of liver AUC(0--48 h) to plasma AUC(0--48 h) at low dose was three times higher than that at high dose. On the other hand, the Suc derivative, Gal-Suc, obtained by reductive amination of Suc/galactose showed very little distribution to the liver similarly to Suc itself. Further, since the liver uptake of Lac-Suc-FTC was inhibited by asialofetuin, it was suggested that the liver distribution of Lac-Suc should be concerned with asialoglycoprotein receptor. Thus, Lac-Suc was found available as a carrier exhibiting a high affinity to and long retention in the liver.

Buccal delivery systems using hydrogels

Abstract Buccal or oral mucosal routes have various advantages for the administration of drugs which undergo severe first-pass metabolism. Hydrogel seemed an appropriate material for the buccal delivery systems because of its mucoadhesiveness, sustained-release property, good feel in the mouth, and safety. In this review, recent reports on buccal delivery systems using hydrogels developed for topical and systemic drug delivery are introduced after a description of the basic concepts of buccal administration.

Effect of ethanol on skin permeation of nonionized and ionized diclofenac

Abstract The effect of ethanol on the skin permeation of diclofenac (DF) was investigated using excised hairless rat abdominal skin in vitro. The steady-state flux of DF increased with increase in the pH of DF-suspended donor solution; this phenomenon demonstrated a close correspondence with enhancement in the solubility of DF in the donor solution. In constrast, the steady-state permeability coefficient ( P ) of DF was inversely proportional to the change in pH of the donor solution, suggesting that the pattern of skin permeation of DF apparently obeyed the pH-partition theory, although the contribution of the ionized form of DF cannot be taken as being negligible. In order to determine the contribution of either the nonionized or ionized form on the skin permeation of DF, the permeability coefficients for each form (nonionized and ionized molecules) were calculated using the P values and the degree of ionization of DF in the donor solution. Addition of ethanol in the donor solution led to a marked decrease in the P value of nonionized DF, whereas the P value of ionized DF was not greatly affected by ethanol. A large amount of ethanol might increase the extent of permeation of DF through the lipid pathway by affecting the dense barrier structure of the skin. The flux of the ionized form of DF was particularly enhanced due to the increase in solubility as a result of the addition of ethanol, since the partition coefficient (skin/donor solution) of the ionized form was not greatly decreased compared with that of the nonionized form.

Sustained release ketoprofen microparticles with ethylcellulose and carboxymethylethylcellulose.

Microparticulate systems for sustained release of ketoprofen were prepared and evaluated by monitoring drug release in the JP XIII second fluid, pH 6.8. All the microparticulate dosage forms were prepared using ketoprofen in the form of calcium salt (KP-Ca). Simple ethylcellulose microparticles of KP-Ca (EC-MP) exhibited the fairly rapid release in the first phase with slower release in the late period. Most of the drug was released from EC-MP showing high drug content. For polymer-coated microparticles of ketoprofen, Eudragit microparticles of KP-Ca (ER-MP) were first prepared, and then coated with ethylcellulose or with a mixture of carboxymethylethylcellulose and ethylcellulose to produce ethylcellulose-coated (EC-coat) and the mixture-coated microparticles (CMEC/EC-coat), respectively. Some polymer-coated microparticles showed drug release at nearly zero-order rate. Especially, CMEC/EC-coat prepared at a CMEC:EC ratio of 1:1 (w/w), named formation I, could supply the drug constantly and efficiently for about half a day except for an initial rapid release. When formation I was administered intraduodenally to rats, the plasma concentration of ketoprofen could be maintained at a nearly constant level. Kinetic analysis demonstrated that formation I showed a nearly zero-order release rate in vivo consistent with that observed in vitro.