Introduction of agent with medical device

The disclosure is directed to apparatus and techniques that deliver an antibiotic or loosening agent to a patient by diffusion. An element of the medical device deployed proximate to the living cells includes a diffusible material, which comprises a lumen. An agent introduced into the lumen diffuses through the diffusible material to the living cells or tissues. The invention can be applied to medical devices that are placed partially inside a patient, as well as those that are fully implanted. Some embodiments support moving the internal element of a medical device proximate to targeted cells, such as a tumor, and administering an antibiotic agent to the targeted cells by diffusion. The disclosure also encompasses a testing system that helps test and develop apparatus and techniques for delivering an agent by diffusion.