Evaluation of glycosylated docetaxel-encapsulated liposomes prepared by remote loading under solubility gradient.

Docetaxel comprises one of the most effective anti-cancer drugs despite of serious side effects. Liposomes encapsulation is practically feasible to deliver the drug. However, due to the significant hydrophobicity, docetaxel will be integrated into the lipid bilayer resulting in poor encapsulation capacity. Here, we evaluated a remote loading strategy using a solubility gradient made between the two solvents for 7-glucosyloxyacetyldocetaxel, which has enhanced water solubility of docetaxel with a coupled glucose moiety. Therefore, 7-glucosyloxyacetyldocetaxel was more effectively encapsulated into liposomes with 71.0% of encapsulation efficiency than docetaxel. While 7-glucosyloxyacetyldocetaxel exhibited 90.9% of tubulin stabilisation activity of docetaxel, 7-glucosyloxyacetyldocetaxel encapsulated in liposomes significantly inhibited the growth of tumour in vivo with side effects less than unencapsulated drug. Collectively, the encapsulation of 7-glucosyloxyacetyldocetaxel into liposomes by remote loading under the solubility gradient is considered to be a promising application to prepare practical drug delivery system.

Microbacterium saccharophilum sp. nov., isolated from a sucrose-refining factory.

A Gram-stain-positive, non-motile, non-spore-forming, rod-shaped bacterium, designated strain K-1(T), was isolated from soil at a sucrose refinery in Japan. The strain grew at 9-37 °C (optimum, 30 °C) and at pH 6-11 (optimum, pH 7.0). Phylogenetic analysis based on the full-length 16S rRNA gene sequence of strain K-1(T) revealed that it was a member of the genus Microbacterium. High 16S rRNA gene sequence similarities were found between strains K-1(T) and both Microbacterium pumilum NBRC 101279(T) (99.7 %) and Microbacterium deminutum NRRL B-24453(T) (99.5 %). However, the DNA-DNA hybridization values between strain K-1(T) and M. pumilum NBRC 101279(T) and M. deminutum NRRL B-24453(T) were only 12 % and 10 %, respectively. The DNA G+C content of strain K-1(T) was 73 mol%. The major fatty acids of strain K-1(T) were anteiso-C15 : 0 and anteiso-C17 : 0, and the major menaquinones were MK-12 and MK-13. The diamino acid in the cell-wall peptidoglycan was lysine. On the basis of these results, strain K-1(T) is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium saccharophilum sp. nov. is proposed. The type strain is K-1(T) (= NBRC 108778(T) = NCIMB 14782(T)).

The aqueous solubility and thermal stability of α-lipoic acid are enhanced by cyclodextrin.

We investigated the effects of various cyclodextrins (CDs) on the aqueous solubility and thermal stability of α-lipoic acid, a compound with low water solubility. α-CD, ß-CD, and γ-CD had little effect on the aqueous solubility of α-lipoic acid. In contrast, 6-O-α-maltosyl-CDs increased it in a concentration-dependent manner, 6-O-α-maltosyl-ß-CD enhancing solubility the most. The thermal stability of α-lipoic acid in the solid state was improved by the addition of G2-ß-CD(®), a commercial product of 6-O-α-maltosyl-ß-CD. The thermal stability of α-lipoic acid was also improved by the addition of ß-CD. Analysis by differential scanning calorimetry showed that G2-ß-CD(®), a mixture of maltosyl-ß-CDs, and ß-CD efficiently formed complexes with α-lipoic acid. These results suggest that the sizes and shapes of these ß-CD compounds are compatible with complexation with α-lipoic acid. Moreover, both the formation of an aqueous complex with G2-ß-CD(®) and an insoluble complex with ß-CD increased the thermal stability of α-lipoic acid.

Enhancement of water-solubility and bioactivity of paclitaxel using modified cyclodextrins.

We investigated the aqueous solubility of paclitaxel using 11 kinds of cyclodextrins (CDs) and the bioactivity of the paclitaxel-CD inclusion complex. 2,6-Dimethyl beta-cyclodextrin was the most effective and its solubility was 2.3 mM in a 0.1 M 2,6-dimethyl beta-cyclodextrin aqueous solution. The inclusion complex of paclitaxel and 2,6-dimethyl beta-cyclodextrin had a 1.23-fold polymerization activity as paclitaxel in a tubulin assay.

Efficient drug delivery of Paclitaxel glycoside: a novel solubility gradient encapsulation into liposomes coupled with immunoliposomes preparation.

Although the encapsulation of paclitaxel into liposomes has been extensively studied, its significant hydrophobic and uncharged character has generated substantial difficulties concerning its efficient encapsulation into the inner water core of liposomes. We found that a more hydrophilic paclitaxel molecule, 7-glucosyloxyacetylpaclitaxel, retained tubulin polymerization stabilization activity. The hydrophilic nature of 7-glucosyloxyacetylpaclitaxel allowed its efficient encapsulation into the inner water core of liposomes, which was successfully accomplished using a remote loading method with a solubility gradient between 40% ethylene glycol and Cremophor EL/ethanol in PBS. Trastuzumab was then conjugated onto the surface of liposomes as immunoliposomes to selectively target human epidermal growth factor receptor-2 (HER2)-overexpressing cancer cells. In vitro cytotoxicity assays revealed that the immunoliposomes enhanced the toxicity of 7-glucosyloxyacetylpaclitaxel in HER2-overexpressing cancer cells and showed more rapid suppression of cell growth. The immunoliposomes strongly inhibited the tumor growth of HT-29 cells xenografted in nude mice. Notably, mice survived when treated with the immunoliposomes formulation, even when administered at a lethal dose of 7-glucosyloxyacetylpaclitaxel in vivo. This data successfully demonstrates immunoliposomes as a promising candidate for the efficient delivery of paclitaxel glycoside.

In vivo antitumor activity of novel water-soluble taxoids.

The antitumor activity of newly developed taxoids possessing a sugar moiety (glucose, galactose or mannose) to improve water solubility was evaluated. Galactose-bound taxoid (10-alpha-GAG-DT) proved superior to all other taxoids in both water solubility and antitumor activity. Therapeutic efficacy of 10-alpha-GAG-DT in terms of in vivo antitumor activity was found to be approximately equivalent to that of docetaxel, which is known to be superior to that of paclitaxel. The observation that the sugar moiety was gradually hydrolyzed in serum to release docetaxel indicates that 10-alpha-GAG-DT acts as a prodrug.