This chapter describes the incorporation of man-made materials into a variety of medical devices. There is an emphasis on the properties of materials that “copy” or at least reflect those of natural tissue. This relatively new technology is often called biomimicry and is an important aspect of medical treatment. Following a précis of material physical properties that are potentially applicable to such devices, the chapter systematically, but concisely, reviews particular classes of materials in terms of their use in medicine. Materials such as alloys of nickel and titanium are capable of shape memory transformations, where the mechanism of the effect is based on thermal energy acquired by the alloy through heating provides the energy necessary for the atoms to return to their original positions, so the sample regains its original shape. Such materials are employed in medical devices such as vascular stents, surgical tools, and cardiac catheters. Various ceramics such as zirconia and hydroxyapatite are used widely in implant technology such as hip and joint replacement. A major criterion for this type of material is their apparent biocompatibility in terms of interaction with tissue. In a similar vein, a variety of polymeric materials have been employed not just for tissue replacement but also as scaffolds for growth of cells and as an agent for drug release. There has also been interest in combining polymeric materials with nanoparticles in attempts to take advantage of the properties of these entities. One area that has attracted considerable research with respect to materials in medicine is neuroscience. In particular, quantum dots and other nanoparticle-based optical probes are employed successfully for reporting neurotransmitter concentrations and dynamic molecular processes with respect to neurons and glia cells. Nanotubes and nanowires have found utility for highly local electrical measurements, sensing of neurochemicals, for the delivery of photons to specific locations, and for the local release or collection of chemicals with regard to neural tissue. From a neuroregeneration perspective, carbon nanotubes can perform as a scaffold for the repair of injured nerves. Finally, a significant number of studies have appeared on the use of electronic devices such as field-effect transistors, often incorporating materials such as graphene, for the detection of neurotransmitters and other biochemicals. The chapter finishes with a look at the vexing problem of the material–biological fluid interaction which is crucial as it pertains to implant biocompatibility. There are known deleterious medical effects associated with this issue, such as micro-clot formation, that are thought to be initially instigated by surface protein adsorption. One possibility to ameliorate the problem with dramatic enhancement of biocompatibility through ultra-thin adlayer formation on a polymer substrate is described.

A thickness-shear mode acoustic wave biosensor operated within a flow-through system was used to examine the response of mouse retinal tissue to radiation. Control experiments conducted with respect to exposure of the bare gold electrodes of the device under various conditions of light intensity and bathing solution yielded reversible changes in resonant frequency (Fs) and motional resistance (Rm). The magnitude of transient changes was proportional to light intensity, but independent of solution type. These alterations in acoustic parameters were ascribed to acoustic coupling phenomena at the electrode-to-liquid interface. Pre-differentiated retina from mouse samples deposited on the thickness shear mode (TSM) electrode exposed to a high light intensity condition also exhibited reversible changes in both Fs and Rm, compared to control experiments involving a coating used to attach the tissue to the electrode. In this case, the radiation-instigated reversible responses for both acoustic parameters exhibited a reduction in magnitude. The changes are ascribed to the alteration in viscoelasticity of the retinal matrix on the TSM electrode surface. The precise biophysical mechanism responsible for the changes in Fs and Rm remains a challenge, given the complex make up of retinal tissue.

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