Design and characterization of drug delivery devices with embedded sensors

Implantable drug delivery devices are an emerging technology and a promising alternative for controlled drug release applications. Their development has progressed considerably in recent years and affects the work of many research centers all over the world. Nowadays, efforts are converging in the realization of continuously tunable drug delivery systems able to operate independently of constant external activation. In many of these systems, drug release is controlled via concentration-based diffusion through nanofluidic membranes that regulate the delivery of drug compounds from an implantable reservoir. Such systems are suitable for many different applications in the biomedical field, especially in the management of chronic diseases where continuous ad hoc monitoring and rapid adjustment of drug doses are needed. Furthermore, they allow localized delivery with the possibility of lower drug concentrations. In the following chapters, we discuss the design and development of implantable devices for drug delivery with embedded strain sensors to measure the osmotic pressure on which the drug flow release depends. This project revolves about the nanofluidic membrane developed by Dr. Alessandro Grattoni at the Houston Methodist Research Institute. The initial phase of activity focuses on the analysis of different types of sensors to select the best instrument to measure reservoir pressures of our systems. After a careful evaluation, the choice fell on the use of strain gauges of which a brief theoretical review is proposed. The following step concerns the FEM structural analysis of different design solution to characterize the main properties of our implantable devices and realize samples to perform tests. The thesis proceeds with the presentation and set up of the data acquirement system used for in vitro tests and the explanation of the assembled test bench to pressurize the prototypes. We tested several capsule samples, some provided by Dr. Grattoni Laboratory and others developed by us. In the end, the core experimental activity of the thesis is presented with the description of the in vitro tests and the analysis of the acquired data. In particular, we focused on the correlation between pressure and strain to validate the measurement method and check its accuracy, by comparing with the results obtained with theoretical computations.