Developing active biomaterials for implantable devices: platforms to investigate capacitive charge based control of biofouling

Abstract

Implantable devices, in particular biosensors, have clear utility within medicine, but face a hurdle to long-term function due to adsorption of biomolecules (biofouling) and subsequent immune re- sponse to implants, the foreign body response (FBR). Strategies to control this immune reaction have included material selection, drug release and, more recently, engineered surface properties.

The increasing use of embedded electronics within many classes of implanted devices presents an opportunity to exploit electromagnetic phenomena at the device surface to mitigate biofouling and FBR. Such active biomaterials would allow dynamic modification of the apparent material properties of an implanted device.

A hypothesis was developed that biological interaction with a biomaterial surface can be altered by capacitive charging. A platform was constructed to test this and related hypotheses around cell and protein surface interactions in vitro and adapted into a second platform for initial characterisa- tion work on an early in vivo model using chick eggs. These platforms were designed to be easy to fabricate and to provide multiple electrical connections into a substrate in contact with biological solutions or tissue.

Electrodes were fabricated from fluoropolymer coated tantalum pentoxide, a high-κ dielectric, and compared against adjacent, identically coated, silicon dioxide regions. Cells from the MDA- MB-231 cancer cell line were cultured on these regions under electrical stimulation. A voltage de- pendent reduction of cell attachment and spreading was detected on capacitively charged surfaces compared to uncharged controls. The tentative results, suggest capacitively charged surfaces hold promise as active biomaterials. A second cell type MCF-7 did not reproduce the effect, implying a more coherent understanding is required of the mechanisms behind cell surface interactions on these surfaces.

Multiple independent bioelectrochemical cell-surface interactions were observed using the plat- form and several quantification techniques were successfully employed. It is therefore argued that the platform may have wide applicability as a future research tool.