Theranostics in the Gut
As a part of the body that is considered external, the gastrointestinal (GI) tract should allow easy access, but it remained relatively obscure, particularly the small intestine, until video capsule endoscopy (VCE) emerged in the past 20 years, uniquely able to view the entire length routinely. Additionally, drawing on contemporary topics including miniaturisation of electronics, wireless communications and efficient electrical power delivery, VCE provides a model for future devices. However, research in therapeutic capsule endoscopy (TCE) has been limited and poorly integrated with diagnostics. This chapter reviews relevant progress, highlighting ultrasound (US) as particularly promising for GI TCE. A description of the GI tract at different length scales is given, including the common, multi-layered structure maintained from mouth to anus and its variation down to cellular and sub-cellular level. Recent developments in multimodal capsule endoscopy are described, including US for imaging within tissue, and targeted drug delivery (TDD) is highlighted for TCE, particularly with US-mediation, because of the potential perforation associated with simpler ablation techniques. This is exemplified by a proof-of-concept theranostic device with the potential to treat conditions such as inflammatory bowel disease and colon cancer. Finally, with significant development ahead, relevant areas are highlighted, including further capsule development and nanotechnology.