Plenary Speaker

Printing, Spinning and Weaving our Way into a New World of Delivery Systems
Gordon Wallace
Australia
 
Using techniques more usually associated with the textile industry: printing, spinning and weaving, we are developing novel approaches to the creation of drug delivery systems suitable for bionic devices.

Bionic devices seek to establish a more effective integration of biological and electronic systems, in order that devices such as the bionic ear, the bionic eye or interconnects to neural driven prosthetic limbs can continue to improve in performance. Another field of endeavor has become known as regenerative bionics and uses the interface to electronic systems to facilitate tissue (e.g. nerve and muscle) repair. Obviously, the judicious use of bioactives (such as drugs or growth factors) integrated within such devices and with temporal as well as spatial control to determine availability facilitates the integration of these inherently incompatible domains (biology and electronics).

Selected polymer compositions have proven to be excellent hosts for the carriage and delivery of bioactive moieties. In order to obtain spatial and/or temporal control over the accessibility of the bioactives the ability to arrange the polymer-bioactive formulation in three dimensions is required. Polymer formulations can be modified to ensure they possess the physical characteristics (viscosity and surface tension) that make them amenable to processing into micro-patterns (ink-jet printing), nano-fibres (electrospinning) or long lengths of micro-dimension fibres (wet-spinning) that can be twisted into yarn or knitted into structures. These fabrication capabilities mean that simple polymer chemistries can be built into unique structures to produce the required drug release profiles.

The introduction of electrically conductive polymers provides a further exciting dimension in that electrical stimulation can be used to enhance the effect of the bioactive molecule. Our most recent advances in coupling novel controlled release devices with electrical stimulation protocols to influence nerve and muscle cell growth will be presented here. We have demonstrated that the integration and controlled release of the neurotrophins NT₃ and BDNF have a dramatic effect on neurite outgrowth from cochlea explants. In more recent work, we have shown a significant synergistic effect on neurite outgrowth combining electrical stimulation and the simultaneous release of two (NT₃, BDNF) growth factors.

In parallel studies, we have used electrospinning and wet-spinning techniques to create unique microdimensional fibres that function as directional cues for both nerve and muscle re-growth. The use of wet spinning to produce highly advanced bionic conduits is an excellent example whereby a processing system of the old world can provide a unique delivery platform for the 21^st century. An additional dimension can be added to such fibre structures using the traditional methods of knitting and weaving. We have also devised strategies that utilize printing including ink-jet printing to create novel drug delivery platforms. The ability to print domains with micrometre resolution enables bioactive molecules to be placed discreetly throughout the structure intended for implantation.