Rheological characterisation of hydroxypropylcellulose based networks for drug delivery

The rheological properties of water-soluble le cellulose ether networks were studied to assess their suitability as drug delivery platforms. The type of substituent on the cellulose backbone, the polymer concentration and molecular weight had a significant effect upon the formulation, demonstrated by the oscillatory frequency dependence of the storage and loss moduli and the intrinsic viscosity. HPC demonstrated a unique behaviour within aqueous solutions therefore the effect of commonly used pharmaceutical solvents on the conformation of HPC in solution was investigated. Diol solvents decreased the critical concentration of HPC and increased its thermal stability in solution. Ethanol, DMSO and Ethylene glycol co-solvent systems on the contrary increased the critical concentration of HPC. In a related study HPC-solvent gel systems were investigated as potential drug delivery systems. All HPC-solvent systems provided gel networks with rheological properties dependant upon polymer concentration. Diol solvents increased the elastic nature of the HPC formulations which may aid in the retention of the device and its resistance to erosion. In vitro dissolution studies highlighted the HPC- 50water:50pentanediol formulation had the ability to provide zero-order release kinetics. Additional manipulation of the rheological and drug release properties can be obtained using mixed polymer systems. Therefore the rheological and drug release properties of HPC and l-Carrageenan systems were investigated. Rheological synergy was observed in all formulations. The formulations possessed suitable rheological behaviour to allow for easy application and retention at the site of application. All binary formulations were also capable of retarding the release of metronidazole. In a related study HPC and t-Carrageenan polymeric blends were investigated as potential hydrophilic matrices. A link between the rheological results and the drug release mechanisms was established. In vitro dissolution studies demonstrated that the optimized formulation HPC 30: Carrageenan 70 could provide zero order release kinetics.EThOS - Electronic Theses Online ServiceGBUnited Kingdo