Peripheral nerve injuries are difficult to treat because axon regeneration is limited and functional recovery is often unsatisfactory in patients. Brief electrical stimulation of injured nerves is emerging as a new promising therapy that can relieve pain or induce better axon regeneration and functional recovery than untreated nerves. In this study, we report an innovative wireless and biocompatible stimulator that is also a scaffold for injured nerves when an autograft is applied to bridge a gap in rat sciatic nerves. We have named this device “graft-antenna” to highlight the double functionality of the implant. The scaffold is made of chitosan and incorporates a gold loop antenna (diameter ~1.3 mm, thickness ~70 nm) powered wirelessly by a transcranial magnetic stimulator (TMS). The device is bonded to tissue non-invasively and without sutures, exploiting the photo-adhesion properties of the chitosan scaffold. The stimulator did not migrate after implantation on healthy sciatic nerves in rats and was able to trigger a steady compound muscle action potential for 12 weeks (CMAP ~1.3 mV). No CMAP was elicited by the TMS when the wireless stimulator was not implanted on nerves. Axon regeneration was facilitated in sciatic nerves that were grafted with the graft-antenna and stimulated for 1 hour, once a week (magnetic field magnitude~0.72 T, pulse duration ~350 μs, repetition rate=1 pulse/sec). Eight weeks post-operatively, myelinated axon count, CMAP and nerve conduction velocity were statistically higher in the graft-antenna group (n=5) than in nerves grafted with the chitosan scaffold without antenna.
Low fat composition in newborns exposes them to an immediate risk of increased mortality and morbidity, inhibited physical and cognitive development and to diabetes and obesity diseases in later life. Information about nutritional and dietary status of newborns can be accessed by measuring the amount of fat composition in the body. The functions of subcutaneous fat involve energy storage, thermo-insulation and a physical buffer. Current technologies for newborn body fat monitoring are: a device based on air displacement plethesmography (PeaPod), dual-energy Xray, and underwater weighting. However they are bulky, expensive, immobile, and require technical expertise. We propose an alternative portable measurement system of in-vitro for subcutaneous fat that uses diffuse near-infrared light reflectance measurement system. We also introduce an in-vitro three-layered tissue model mimicking the subcutaneous fat layer in newborns together with a preliminary study to measure fat using dual-wavelength nearinfrared light. Based on the output data from these measurements, we have proposed a suitable transmission and scattering model. This model estimated the amount of reflected light collected by a photodetector after incident light is scattered in several fat layers. Our portable sensor is low cost and does not require training hence it is suitable for mass use in the developing world. It consists of a single LED and two photodetectors (900 nm and 1000 nm). The photodetectors wavelengths were chosen to be sensitive to fat as it exhibits a peak in the wavelength at 930 nm and to water at which exhibits a peak at 980 nm; the latter is used, to remove hydration bias. Results on a porcine tissue model demonstrate differentiation as low as 2 mm fat which is a relevant screening thickness to indicate low percentage body fat.