Placeholder image for staff profiles

Professor Anthony Clough


Emeritus Professor of Physics
+44 (0)1483 682733
06 BC 04

Academic and research departments

Department of Physics.

My publications

Publications

Smith Richard, Booth John, Massingham G., Clough Anthony (2004) A study of water diffusion, in both radial and axial directions, into biodegradable monolithic depots using ion beam analysis,Polymer 45 (14) pp. 4893-4908 Elsevier
Water diffusion into cylindrical biodegradable monolithic depots fabricated from extruded mixtures of poly(dl-lactide) and a peptidic drug, goserelin, containing 20, 30 and 40% drug by weight has been studied using an ion beam analysis technique. A series of depots were immersed in a phosphate buffered saline/heavy water solution at 37 °C for times ranging from 1 h to 7 days. One-dimensional radial profiles showing the diffusion of water into the depots were produced at points along the length of the sample and, for some short immersion times, axial profiles were obtained for the cylinder ends. The changes in weight, radius, drug release and water uptake of the depots with time were also studied. Using the water uptake measurements the one-dimensional radial profiles were normalised. From appropriate one-dimensional profiles at the shorter times Fickian diffusion coefficients were obtained for initial water diffusion. The average radial diffusion coefficients were (1.07±0.22)×10?8 cm2 s?1 for the 20% drug-loaded depots, (1.54±0.27)×10?8 cm2 s?1 for the 30% drug-loaded depots and (2.00±0.83)×10?8 cm2 s?1 for the 40% drug-loaded depots?in the ratio of the drug loadings i.e. 2:3:4, implying the water associated with drug during its uptake into the monoliths. The axial diffusion coefficients were found to be of the same order of magnitude as the radial diffusion coefficients, in accord with this hypothesis. At longer times there is a subsequent non-Fickian increase in the water concentration profile. In the case of depots loaded with 40% by weight of goserelin, the substantial fraction of the hydrophilic drug released at times greater than one day is accompanied by a decrease in radius and a decrease in water concentration near the depot surface.
Smith Richard, Massingham Gary, Clough Anthony (2003) Investigation of drug-release polymers using nuclear reaction analysis and particle induced X-ray emission,Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 505 (1-2) pp. 582-585 Elsevier
The diffusion of water into the developmental drug-release polymer addition cured silicone has been investigated using {sup 3}He ion scanning micro-beam techniques developed at the University of Surrey. Polymer samples loaded with 15% by weight of the drug chlorohexidine diacetate were immersed in a water based phosphate buffered saline solution for times of 1 hour, 1 day, 1 week and 1 month. The results showed that as the water diffused into the polymer it associated with the drug allowing its release by diffusion through the network formed by water filled pores. Future improvements to the techniques are discussed including the use of an array of CdZnTe detectors.