Physicochemical and drug diffusion analysis of rifampicin containing polyethylene glycol-poly(epsilon-caprolactone) networks designed for medical device applications

This study reports the physicochemical and drug diffusion properties of rifampicin containing poly(epsilon-caprolactone) (PCL)/polyethylene glycol (PEG) networks, designed as bioactive biomaterials. Uniquely, the effects of the states of both rifampicin and PEG and the interplay between these components on these properties are described. PCL matrices containing rifampicin (1-5%, w/w) and PEG 200 (0-15%, w/w) were prepared by casting from an organic solvent (dichloromethane). The films were subsequently characterized in terms of their thermal/thermorheological, surface and tensile properties, biodegradation and drug diffusion/release properties. Incorporation of PEG and/or rifampicin significantly affected the tensile and surface properties of PCL, lowering the ultimate tensile strength, % elongation at break, Young modulus and storage and loss moduli. Both in the absence and presence of PEG, solubilisation of rifampicin within the crystalline domains of PCL was observed. PEG was present as a dispersed liquid phase. The release of rifampicin (3% loading) was unaffected by the presence of PEG. Similarly the release of rifampicin (5%) was unaffected by low concentrations of PEG (5-10%) however, at higher loadings, the release rate of rifampicin was enhanced by the presence of PEG. Rifampicin release (10% loading) was enhanced by the presence of PEG in a concentration dependent fashion. These observations were accredited to enhanced porosity of the matrix. In all cases, diffusion-controlled release of rifampicin occurred which was unaffected by polymer degradation. This study has uniquely illustrated the effect of hydrophilic pore formers on the physicochemical properties of PCL. Interestingly, enhanced diffusion controlled release was only observed from biomaterials containing high loadings of PEG and rifampicin (5, 10%), concentrations that were shown to affect the mechanical properties of the biomaterials. Care should therefore be shown when adopting this strategy to enhance release of bioactive agents from biomaterials. (C) 2011 Elsevier B.V. All rights reserved.

The level playing field: the impact of assessment practice on professional development

Context: The effects of assessment practice on students’ learning are unclear, particularly regarding professional development. Corralling in objective structured clinical examinations (OSCEs) is designed to reduce illicit passing of examination information. Candidates completing an examination are kept secluded until the next cohort of examinees has begun. We used the introduction of corralling as a context in which to explore social influences on examination misconduct, with the aims of improving understanding of the hidden effects of assessment, and evaluating the acceptability of corralling from the student perspective.

Methods: A questionnaire was administered to students corralled post-OSCE for the first time. Eleven semi-structured interviews were subsequently conducted. Questionnaire data were analysed for descriptive statistics and thematic analysis of interview transcripts was carried out.

Results: The questionnaire response rate was 95.4% (251/263). Before corralling, 80.9% (203/251) of students were aware of the sharing of information among peers and 78.5% (197/251) agreed that such misconduct was unprofessional. The majority were in favour of corralling (90.8%, 228/251). Four themes emerged from the semi-structured interviews: the student network versus the individual; assessment-driven culture; the deferring of professionalism, and the ‘level playing field’. Students saw interaction within the student network, on a background of assessment-driven culture, as the key driver in examination misconduct. Conforming to the rules of the social network was prioritised over individual agency, although the mismatch between the rules of the network and the dominant professional discourse caused some conflict for individuals. Deferred professionalism (described as the practice of taking on the norms of professional behaviour only when qualified) was a rationalisation used to minimise this conflict. Corralling provided a ‘level playing field’ in which the influences of the network were minimised.

Conclusions: Examination misconduct is thus a complex social construction with implications for individual learners in terms of professional development. Corralling is one mechanism for addressing misconduct that is acceptable to students, but assessment processes have important hidden effects which educators should acknowledge.