Carboxymethyl derivative of scleroglucan: a novel thermosensitive hydrogel forming polysaccharide for drug delivery applications

A carboxymethyl derivative of scleroglucan (Scl-CM) with a derivatization degree of 65 +/- A 5% was synthesized. The rheological behaviour of this novel polymer was studied and compared with that of the starting polymer. We observed that the charged moieties carried on the chains could prevent the triple helix formation of Scl. Scl-CM aqueous solutions behave like true polymer solutions up to 1% w/v, whereas above this concentration a weak gel behaviour was observed. CaCl(2) addition to aqueous Scl-CM solutions led to a physical gel formation; the hydrogel strength was related to polymer and CaCl(2) concentrations. Temperature sweeps, registered at 1 Hz on hydrogels differing in CaCl(2) concentration, evidenced a gel -> sol transition in the range of 30-40A degrees C, depending on the molar ratio between carboxylic groups and Ca(+2). In order to verify a possible use of these hydrogels as drug delivery systems, acyclovir was loaded into the network. Rheological analysis evidenced that the loaded drug can affect the hydrogel elastic modulus. The release of acyclovir in phosphate buffer was evaluated at different temperatures in order to assess the suitability of this novel drug delivery system in topical applications

Solid lipid nanoparticles incorporated in dextran hydrogels: A new drug delivery system for oral formulations

Solid lipid nanoparticles (SLN) containing or not (S)-(+)-2-(4-isobutylphenyl)propionic acid (ibuprofen) were prepared with Preciol ATO 5 as lipid phase by the hot homogenization technique and characterized through particle size analyses and zeta potential measurements. DSC experiments carried out on the freeze-dried samples of loaded SLN showed a shift of the melting endotherm of the lipid phase, with the maximum at a temperature value higher then that of the"empty" SLN. H-1 NMR of the nanosuspension allowed to calculate the encapsulation efficiency of the particles that was 52 +/- 3%. By adding dextran methacrylate (DEX-MA) to the aqueous phase and submitting the mixture to UV irradiation, systems of SLN (drug-loaded and unloaded) incorporated into a dextran hydrogel were prepared. Finally, dissolution studies of ibuprofen from the freeze-dried samples were performed. The comparison among the release profiles of ibuprofen from SLN, DEX-MA hydrogel and SLN/DEX-MA-hydrogel allows to affirm that this last system, retaining about 60% of the drug after 2 h in acid medium and releasing it slowly in neutral solution, is suitable for modified delivery oral formulations. (c) 2006 Elsevier B.V. All rights reserved

Influence of the formulation components on the properties of the system SLN-dextran hydrogel for the modified release of drugs

A system composed by solid lipid nanoparticles (SLN) entrapped into a chemical hydrogel of dextran was recently proposed for the controlled release of lipophilic drugs in oral formulations. This study reports now an extension of such study focused on the investigation of how the nature and the amount of the formulation components are able to modify the properties of the system. In particular the concentration of the two surfactants used for the nanosuspension stabilization, the nature of the lipid phase used for the nanoparticles preparation, as well as the concentration and the derivatization degree of the polymer employed for the gel preparation were investigated. The effects of these variables on the physicochemical properties of the nanoparticles and/or on the release profiles of the model drug (S)-(+)- 2-(4- isobutylphenyl)-propionic acid (ibuprofen) were reported and discussed. Rheological experiments on samples of SLN, dextran hydrogel, and SLN-dextran hydrogel were also performed