3 He ion-beam analysis of water uptake and drug delivery

Drug release kinetics and transport mechanisms of non-degradable and degradable polymeric delivery systems

“…In addition to crosslink density, water uptake is another important impact factor which may affect the degree of swelling and solute transport within the PDMS network. Riggs et al studied the water uptake kinetics of silicone elastomers using 3 He ion-beam analysis and their study demonstrated that water uptake was initially linear with time and then linear with t 1/2 which indicated a Fickian profile [39]. Malcolm et al investigated the metronidazole release kinetics from crosslinked silicone elastomers and all of the silicone systems evaluated were shown to obey simple matrix-type t 1/2 kinetics due to the fact that most of the drug within the systems existed in the solid state [25].…”

Thin Film Depth Profiling

“…The ability of ion beam analysis to capture an entire concentration profile in a single measurement makes these techniques ideal for studying one dimensional diffusion problems. When diffusion occurs over ranges that exceed the conveniently accessible range of ion beams (a few microns) it is equally possible to quantify diffusion by scanning a micro-focussed ion beam across the fracture surface [3]. Any material provided it can be frozen or vitrified for the duration of an experiment can be studied in this way.…”

“…In this chapter the examples are all of analyses which can be carried out using a 1.7 MV Tandem accelerator (for example), so that there is no discussion of MEIS or LEIS examples. We have also deliberately not included any examples of ERD since heavy ion ERD uses (typically) much larger accelerators and completely different instrumentation, and the light ion (helium) ERD frequently carried out on these small accelerators for hydrogen profiling is interpreted in a way very similar to RBS (or EBS).. We also do not discuss analyses carried out on sample cross-sections (as in, for example, Jenneson et al 1998 [2], or Riggs et al [3]) since this is the trivial case of using a sequence of (essentially) bulk analyses to build up a depth profile.…”

Computational Methods for the Development of Polymeric Biomaterials

“…Fick's diffusion law, a power law and the Weibull equation [59] are generally used to model the water uptake of polymers. Also, empirical models such as Riggs' error function [60,61] or the Peleg equation [62] have been used to explain water-uptake behavior. Ebube et al [63] built an ANN model for water uptake by polymer blends of hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), polyvinylpyrrolidone (PVP), sodium alginate and carregeenan, using the composition of the blend as descriptor.…”