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

Intracellular Signal-Responsive Gene Carrier for Cell-Specific Gene Expression

We designed a peptide-polymer conjugate (CPCCtat) as a novel gene carrier that could control gene expression responding to the intracellular caspase-3 signal. This carrier consists of an uncharged main polymer chain and a cationic peptide side chain, which includes the substrate sequence of caspase-3 and the protein transduction domain sequence of HIV-1 Tat. In the present study, CPCCtat formed a tight complex with DNA through an electrostatic interaction, and in this state the gene expression was totally suppressed. In contrast, the complex disintegrated in the presence of caspase-3 due to cleavage of the cationic portion from CPCCtat. This event led to an activation of gene expression. Our results also indicate that the complex can be delivered into living cells due to the cell-permeable peptide side chain of CPCCtat. This intracellular signal-responsive system with CPCCtat will be useful for the cell-specific gene expression system.

Controlled release of plasmid DNA from cationized gelatin hydrogels based on hydrogel degradation

This paper shows achievement of the in vivo controlled release of a plasmid DNA from a biodegradable hydrogel and the consequent regulation of gene expression period. Cationization of gelatin was preformed through introduction of ethylenediamine and the gelatin prepared was crosslinked by various concentrations of glutaraldehyde to obtain cationized gelatin (CG) hydrogels as the carrier of plasmid DNA. In vivo release of plasmid DNA from the CG hydrogels was compared with the in vivo degradation of hydrogels. When CG hydrogels incorporating 125I-labeled plasmid DNA were implanted into the femoral muscle of mice, the plasmid DNA radioactivity remaining decreased with time and the retention period prolonged with a decrease in the water content of hydrogels used. The higher the water content of 125I-labeled CG hydrogels, the faster the hydrogel radioactivity remaining decreased with time. The time profile of plasmid DNA remaining in the hydrogels was in good accordance with that of hydrogel radioactivity, irrespective of the water content. Intramuscular implantation of plasmid DNA-incorporated CG hydrogels enhanced significantly expression of the plasmid DNA around the implanted site. The retention period of gene expression became longer as the hydrogel water content decreased. Fluorescent microscopic study revealed that the plasmid DNA-CG complex was detected around the hydrogel implanted even after 7-day implantation in marked contrast to the injection of plasmid DNA solution. It was concluded that in our hydrogel system, active plasmid DNA was released accompanied with the in vivo degradation of hydrogel, resulting in extended gene expression. The time profile of plasmid DNA release and the consequent gene expression was controllable by changing the water content of hydrogels.

Efficacy of lactosaminated and intact N-succinylchitosan-mitomycin C conjugates against M5076 liver metastatic cancer

In this study,lactosaminated N-succinyl-chitosan (Lac-Suc) was investigated for its liver targeting ability in the early metastatic stage of liver cancer, and subsequently Lac-Suc-mitomycin C conjugate (Lac-Suc-MMC) and highly-succinylated N-succinyl-chitosan (Suc(II))-MMC conjugate (Suc(II)-MMC) were examined for efficacy against the liver metastasis. Mice into which M5076 cells were inoculated intravenously were used as liver metastatic models. Fluorescently labelled Lac-Suc (Lac-Suc-FTC) was intravenously administered at a daily dose of 0.2 mg/mouse for 4 days or at a single dose of 0.8 mg/mouse at 3 days post-inoculation. At a dose of 0.2 mg/mouse for 4 days, liver accumulation of Lac-Suc-FTC was increased after all except the fourth injection, indicating that the capacity of accumulation might be limited to around 110 microg per mouse with repeated daily administration at 0.2 mg/mouse. As to the efficacy of intravenous administration at 7 days post-inoculation, Lac-Suc-MMC was less effective at a dose of 1 mg kg(-1) for 4 days than a single dose of 4 mg kg(-1). This result was not in accordance with that expected from the biodistribution study. On the other hand, with intravenous administration at 3 days post-inoculation, Suc(II)-MMC was more effective on repeated administration, and it showed higher efficacy than Lac-Suc-MMC at both 1 mg kg(-1) for 4 days and 4 mg kg(-1) as a single dose. Further, with intravenous administration at 3 days post-inoculation, Suc(II)-MMC exhibited a much higher survival effect at a dose of 4 mg kg(-1) for 4 days.

Preparation and characterisation of fluorescent chitosans using 9-anthraldehyde as fluorophore

Chitosans with chemical composition ranging from a fraction of N-acetylated units (F(A)) of 0.01 to 0.61 were used to prepare fluorescence labelled chitosans by reductive amination with 9-anthraldehyde. Fluorescent chitosans with a low theoretical degree of substitution (DS, 0.001-1%) were prepared, and the actual DS of the products were determined by UV and (1)H NMR spectroscopy. The fluorescence excitation and emission spectra of the chitosan with F(A) of 0.09 and DS 1% showed an excitation maximum at 254 nm and an emission maximum at 413 nm. The intrinsic viscosities ([eta]) of the fluorescent chitosans were compared to those of the original chitosans, showing that the derivatisation procedure lead only to a negligible decrease in [eta]. The conformation of these fluorescent chitosans with very low DS-values is not altered and they can conveniently be directly quantified by UV or fluorescence spectroscopy.

Lactosaminated and intact N-succinyl-chitosans as drug carriers in liver metastasis

The biodistributions of fluorescently labeled N-succinyl-chitosan (Suc-FTC) and lactosaminated N-succinyl-chitosan (Lac-Suc-FTC) after i.v. administration to mice intravenously inoculated with M5076 cells were investigated at 3 and 12 days post-inoculation. At both time points, Lac-Suc-FTC was specifically localized to the liver. However, the area under the concentration-time curve in the liver decreased gradually by progress of the liver metastasis. At 3 days post-inoculation, Suc-FTC showed good retention in the systemic circulation and was little distributed to the liver. However, at 12 days post-inoculation, Suc-FTC was eliminated relatively fast from the systemic circulation and gradually accumulated in the liver. The antitumor effects of mitomycin C (MMC), Lac-Suc-MMC conjugate (Lac-Suc-MMC) and highly succinylated Suc (Suc(II))-MMC conjugate (Suc(II)-MMC) were examined on single i.v. administration for both metastatic stages. For administration at 3 days post-inoculation, Lac-Suc-MMC alone tended to elongate significantly the lifespan at a lower dose (0.4 mg eq. MMC/kg), and MMC, Suc(II)-MMC and Lac-Suc-MMC increased significantly the lifespan at a higher dose (10 mg eq. MMC/kg). However, at 12 days post-inoculation (late stage of metastasis), neither MMC nor the conjugates were effective even at the higher dose (10 mg eq. MMC/kg). Both carriers, Suc showing systemic long-circulation and Lac-Suc with an ability of liver-specific localization, are thought to be drug carriers with potentialities for therapeutics at early stage of metastasis.