Synthesis and characterization of some modified polysaccharides containing drug moieties

Facile preparation of chitosan-dopamine-inulin aldehyde hydrogel for drug delivery application

Chitosan-based hydrogels are a suitable and versatile system for the design of localized and controlled drug delivery systems. In the current study, a hydrogel based on chitosan (CS), Dopamine (DA), and Inulin aldehyde (IA) was fabricated without the further use of catalyst or initiators. The effect of the IA contents as a crosslinking agent on the properties of the prepared hydrogel was studied. The crosslinking reaction between CS and IA was verified by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Various characteristics of the CS/DA/IA hydrogels were further assessed utilizing swelling experiment, in vitro drug release, in vitro cytotoxicity assay. The drug-loaded hydrogels represented the sustained release of Indomethacin according to the in vitro drug release test in acidic (pH = 4), basic (pH = 10) medium as well as physiological condition (pH = 7). Finally, the CS/DA/IA hydrogels exhibited appropriate cytocompatibility against the L-929 fibroblast cell line according to the direct contact MTT assay.

Influence of Oxidation Degree on the Physicochemical Properties of Oxidized Inulin

This paper reports the oxidation of inulin using varying ratios of sodium periodate and the characterization of the inulin polyaldehyde. The physicochemical properties of the inulin polyaldehyde (oxidized inulin) were characterized using different techniques including 1D NMR spectroscopy, ¹³C Nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetric (DSC), ultraviolet-visible spectroscopy (UV), and scanning electron microscopy (SEM). The aldehyde peak was not very visible in the FTIR, because the aldehyde functional group exists in a masked form (hemiacetal). The thermal stability of the oxidized inulin decreased with the increasing oxidation degree. The smooth spherical shape of raw inulin was destructed due to the oxidation, as confirmed by the SEM result. The ¹HNMR results show some new peaks from 4.8 to 5.0 as well as around 5.63 ppm. However, no aldehyde peak was found around 9.7 ppm. This can be attributed to the hemiacetal. The reaction of oxidized inulin with tert-butyl carbazate produced a carbazone conjugate. There was clear evidence of decreased peak intensity for the proton belonging to the hemiacetal group. This clearly shows that not all of the hemiacetal group can be reverted by carbazate. In conclusion, this work provides vital information as regards changes in the physicochemical properties of the oxidized inulin, which has direct implications when considering the further utilization of this biomaterial.

Synthesis and Characterization of pH-Sensitive Inulin Conjugate of Isoniazid for Monocyte-Targeted Delivery

The use of particles for monocyte-mediated delivery could be a more efficient strategy and approach to achieve intracellular targeting and delivery of antitubercular drugs to host macrophages. In this study, the potential of inulin microparticles to serve as a drug vehicle in the treatment of chronic tuberculosis using a monocytes-mediated drug targeting approach was evaluated. Isoniazid (INH) was conjugated to inulin via hydrazone linkage in order to obtain a pH-sensitive inulin-INH conjugate. The conjugate was then characterized using proton nuclear magnetic resonance (¹HNMR), Fourier transform infrared spectroscopy (FTIR) as well as in vitro, cellular uptake and intracellular Mycobacterium tuberculosis (Mtb) antibacterial efficacy. The acid-labile hydrazone linkage conferred pH sensitivity to the inulin-INH conjugate with ~95, 77 and 65% of the drug released after 5 h at pH 4.5, 5.2, and 6.0 respectively. Cellular uptake studies confirm that RAW 264.7 monocytic cells efficiently internalized the inulin conjugates into endocytic compartments through endocytosis. The intracellular efficacy studies demonstrate that the inulin conjugates possess a dose-dependent targeting effect against Mtb-infected monocytes. This was through efficient internalization and cleavage of the hydrazone bond by the acidic environment of the lysosome, which subsequently released the isoniazid intracellularly to the Mtb reservoir. These results clearly suggest that inulin conjugates can serve as a pH-sensitive intracellular drug delivery system for TB treatment.

Preparation and Characterization of Oxidized Inulin Hydrogel for Controlled Drug Delivery

Inulin-based hydrogels are useful carriers for the delivery of drugs in the colon-targeted system and in other biomedical applications. In this project, inulin hydrogels were fabricated by crosslinking oxidized inulin with adipic acid dihydrazide (AAD) without the use of a catalyst or initiator. The physicochemical properties of the obtained hydrogels were further characterized using different techniques, such as swelling experiments, in vitro drug release, degradation, and biocompatibility tests. The crosslinking was confirmed with Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). In vitro releases of 5-fluorouracil (5FU) from the various inulin hydrogels was enhanced in acidic conditions (pH 5) compared with physiological pH (pH 7.4). In addition, blank gels did not show any appreciable cytotoxicity, whereas 5FU-loaded hydrogels demonstrated efficacy against HCT116 colon cancer cells, which further confirms the potential use of these delivery platforms for direct targeting of 5-FU to the colon.

Effect of the Chemical Modification of Dextran on the Degradation by Dextranase

Dextran was modified using three different methods: a) partial periodate oxidation and subsequent reduction of the aldehyde groups, b) suc cinoylation and c) chloroformate activation with subsequent reaction with 2- hydroxypropylamine, ethylenediamine and tris(2-aminoethyl)amine. Degrada tion of these dextran derivatives by dextranases was investigated. It was observed that the rate of degradation decreased with increasing degree of chemical modification of the parent polysaccharide. The nature of modification had no significant influence on the rate of degradation.

Macromolecular Drug Conjugates II. Metronidazole-Dextran Prodrugs

The antimicrobial drug metronidazole was attached to dextran. Two methods of dextran-metronidazole synthesis were studied: (1) the reaction of metronidazole with chloroacetylated derivatives of crosslinked dextran microparticles in basic aprotic solvents, and (2) the reaction of metronidazole chloroacetic acid ester with crosslinked dextran microparticles in basic media. The release of metronidazole from the two types of macromolecular prodrugs was compared.

A facile one-pot synthesis of a fluorescent agarose-O-naphthylacetyl adduct with slow release properties

A microwave assisted facile synthesis of a fluorescent 6-O-naphthylacetyl agarose (NA-agarose) employing carbodiimide chemistry (dicyclohexylcarbodiimide/4-dimethylaminopyridine) has been described. NA-agarose was characterized by TGA, GPC, UV spectrophotometry, fluorescence spectroscopy, FT-IR, (1)H and (13)C NMR spectra, exhibiting that in NA-agarose the naphthylacetyl group was attached to the backbone of the agarose polymer. The hydrolysis of NA-agarose in heterogeneous aqueous phase showed that the 1-naphthyl acetic acid (NAA), a plant growth regulator, got released in a controlled manner, the release rate being dependent on the hydrophilicity of the polymer adduct as well as on pH and temperature. The fluorescence emission (λmax 332 nm) of NA-agarose (1×10(-3) M) in ethylene glycol was significantly higher (ca. 82%) than that of the molar equivalent of NAA content in the product i.e. 0.08 mg in 1×10(-3) M solution. The resulting polymer would be of potential utility as a sustained release plant growth regulator and sensory applications.

Synthesis and inverse emulsion polymerization of aminated acrylamidodextran

A chemically modified form of dextran was prepared, having a polymerizable moiety (acrylamide) and a reactive functional group (primary amine). Dextran was activated with 4-nitrophenyl-chloroformate (24 mol per polysaccharide, 9.8 mol per 100 glucose residues); 9.8% glucose residues were converted to aliphatic carbonates and 5.2% were converted to cyclic carbonates. The activated dextran was coupled with trityldiaminoethane (8 mol per 100 glucose residues), reactivated with 4-nitrophenylchloroformate, then coupled with acryloamidodiaminohexane (6.8 mol per 100 glucose residues). The trityl group was removed by hydrolysis with trifluoroacetic acid to yield the required aminated acryloamidodextran. The modified dextran was shown to be polymerizable by inverse emulsion polymerization. Submicron particles were successfully prepared, containing functional amine groups suitable for preparing drug conjugates or for modifying the surface properties of this biomaterial.