Physical gels of a carboxymethyl derivative of scleroglucan: Synthesis and characterization

Carboxymethyl Scleroglucan Synthesized via O-Alkylation Reaction with Different Degrees of Substitution: Rheology and Thermal Stability

This paper presents the methodology for synthesizing and characterizing two carboxymethyl EOR-grade Scleroglucans (CMS-A and CMS-B). An O-Alkylation reaction was used to insert a hydrophilic group (monochloroacetic acid-MCAA) into the biopolymer's anhydroglucose subunits (AGUs). The effect of the degree of the carboxymethyl substitution on the rheology and thermal stability of the Scleroglucan (SG) was also evaluated. Simultaneous thermal analysis (STA/TGA-DSC), differential scanning calorimetry (DSC), X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy, and Energy Dispersive Spectroscopy (SEM/EDS) were employed to characterize both CMS products. FTIR analysis revealed characteristic peaks corresponding to the carboxymethyl functional groups, confirming the modification. Also, SEM analysis provided insights into the structural changes in the polysaccharide after the O-Alkylation reaction. TGA results showed that the carboxymethylation of SG lowered its dehydroxylation temperature but increased its thermal stability above 300 °C. The CMS products and SG exhibited a pseudoplastic behavior; however, lower shear viscosities and relaxation times were observed for the CMS products due to the breakage of the SG triple helix for the chemical modification. Despite the viscosity results, the modified Scleroglucans are promising candidates for developing new engineering materials for EOR processes.

Physical carboxymethylscleroglucan/calcium ion hydrogels as modified drug delivery systems in topical formulations

A carboxymethyl derivative of scleroglucan (Scl-CM) with a 65±5% carboxylic group degree of derivatization (DD) was recently synthesized and characterized. Aqueous solutions of the polymer underwent to a sharp transition toward a gel like behaviour in the presence of divalent ions such as Ca⁺². Physical hydrogels with different Scl-CM/Ca⁺² ratios were prepared and characterized for their rheological behaviour. Their potential as drug delivery systems was also evaluated. To this end three non steroidal anti-inflammatory drugs (NSAIDs) were loaded into the hydrogels obtained with 2% w/v solution of Scl-CM and 0.05 and 0.1 M CaCl₂. The release rate of the drugs was critically related to the salt concentration. By an appropriate combination of the hydrogels prepared using different amounts of salt, it was possible to obtain a system able to release diclofenac with zero-order kinetics. Primary skin irritation tests showed a good biocompatibility of the new polymer, as well as of its hydrogels. These results suggest a potential of the new hydrogels for the development of modified delivery systems in topical formulations.

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 +/- 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 30-40 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.