ABSTRACT
Drug-eluting systems are currently used in cardiac leads in order to reduce inflammation and fibrosis at the lead-tissue interface. Drug release from these drug delivery systems can be modulated by the manufacturing processes used to create the drug systems and assemble them onto the cardiac lead. In this study, scanning electron microscopy, atomic force microscopy and Raman microscopy are employed to explore the material characteristics of a polydimethylsiloxane-dexamethasone acetate drug collar used on cardiac leads when varying the strain during collar assembly on the lead. A novel test fixture was created in order to investigate these drug collars under simulated stresses. Measurements of the collar while fitted to a rod revealed microcracks that are hypothesized to affect the drug release performance, resulting in increased drug elution. It was found that the strain that occurs during assembly of the collar onto the lead is a key factor in the formation of these microcracks. Results also suggest that cracks tend to form in areas of high drug particle density, and propagate between drug particles.
Subject(s)
Dexamethasone/analogs & derivatives , Dimethylpolysiloxanes/chemistry , Drug-Eluting Stents , Electrodes, Implanted , Nylons/chemistry , Compressive Strength , Dexamethasone/administration & dosage , Dexamethasone/chemistry , Diffusion , Elastic Modulus , Hardness , Materials Testing , Stress, Mechanical , Surface Properties , Tensile StrengthABSTRACT
Argument about the ethical possibility of the therapeutic use of embryonic stem cells depends critically on the evaluation of the moral status of the very early embryo. Some assert that at the blastocyst stage it is only potentially human, not yet possessing the full ethical status of personhood, while others assert that from its formation the embryo possesses all the moral rights of a human person. It is shown that a decision on this issue is closely related to how human nature is to be understood. The idea of a person as a dual combination of body and spirit correlates naturally with the assertion of absolute personhood from conception, while an idea of human psychosomatic unity encourages a development picture in which the embryo only grows gradually into personhood. The latter view is seen to be encouraged by new advances in science which emphasise the importance of the concept of information in the discussion of complex systems. Other ethical issues related to human genetics are also briefly reviewed.
Subject(s)
Ethics, Medical , Ethics, Research , Personhood , Cloning, Organism/ethics , Embryo Research/ethics , Genetic Engineering/ethics , Genetic Testing/ethics , Humans , Morals , Prenatal Diagnosis/ethics , ReligionABSTRACT
New ethical questions have arisen from our ability to intervene in the structure of the genome. Responsible use of this technique requires ethical evaluation in which experts, potential beneficiaries and the general public should all participate. The examples of genetically modified food and of human genetics help to illustrate the issues involved.
