Foreign body response investigated with an implanted biosensor

One of the principal challenges facing the long-term implantation of biosensors into humans is that over time the normal physiological response of the body creates a fibrotic capsule of scar-like tissue surrounding the implanted device (the foreign body response). This growing collagenous capsule increasingly isolates the sensor device from its local environment, causing a time dependent degradation of the sensor signal. We utilize this degradation or change to the signal as an indicator of the physiological responses to the implantation of the device. We have chosen a micro-electrode array as the sensor device. We thus track the foreign body response electronically as the basis for this novel assay, which determines in comparable terms, an ongoing measurement of foreign body response (FBR) capsule character. This technique has the potential to become an important analytical method for comparing biomaterials and surface treatments aimed at reducing the foreign body response.;The assay method analyzes a chronological series of electrical impedance spectroscopy (EIS) data to track the changes of the electrical signal behavior. We have performed biosensor trials in vitro, ex ova and in vivo.;In vitro, the device was placed into a saline reservoir into which selected proteins were introduced that adsorb onto the electrode surface. Three proteins were studied and each was found to affect the EIS results differently.;The foreign body response to the implanted electrodes was investigated ex ova using the chick chorio-allantoic membrane (CAM) model. Electrodes were coated with decorin protein and tetraglyme polymer. Both are coatings designed to effect wound healing. Changes in the behavior of the FBR were observed when comparing clean electrode surfaces to coated surfaces.;The electrode array was implanted into the temporalis muscle of a mature rat. Some of these in vivo implants utilized electrodes coated with tetraglyme polymer. Changes in the in vivo behavior of the electrical signal comparing clean to coated electrodes were similar to the ex ova investigations.;Enactment and verification of this novel method to assay the chronological physiological behavior of the foreign body response demonstrates proof that our biosensor can be used to track the foreign body response.