Microdevices For Drug Delivery-1

Advances in microelectromechanical systems and miniaturization technologies have enabled the creation of biomedical microdevices designed to aid in the diagnosis, monitoring and treatment of various chronic and nonchronic illnesses. The ability to create very precisely defined micrometer and nanometer features allows for the production of a new generation of biomedical devices that can be implanted using minimally invasive procedures.

Biomedical microdevices are of two types
1. Passive delivery microdevices.
2. Active delivery microdevices.

Active and passive delivery devices represent the next generation of drug delivery modalities that can be incorporate and store drugs in multiple reservoirs and locally release these drugs at the area of interest without the risk of potentially toxic systemic delivery. The devices can deliver multiple drugs in precisely defined doses at precisely dictated times and have the ability to store liquid and solid-phase drug formulations.

The choice of the type of device depends on the nature of the illness as well as the specific treatments and environmental requirements, including implantation site, device dimensions, duration of treatment, biocompatibility, delivery time constants, desired pharmacokinetic profiles, dose and payload. Because unwanted reactions between therapeutic compounds and devices have been observed, the risk of such reactions must be an integral part of the design considerations. The selection of materials and their chemical and biological compatibilities are crucial for successful performance of the device.

Delivery devices designed for long term therapy must last as long as possible in order to minimize the number of implantations or revision surgeries. The design should incorporate biodegradable materials so as to avoid the need for extraction surgery. Delivery devices for short term therapy must be designed either for easy extraction after implantation or with biodegradable and bioresorbable materials.

References:

1. Staples J, Richards T, Scheidt A.C, Cima R, Langer M.J, “Microchips as controlled drug delivery devices”. Angew.ChemInt.Ed.Engl.39, 2396-2407(2000).
2. Santini J.T, Jr.Cima, M.J and Langer RA “Controlled release microchip”. Nature 397, 335-339(1999).
3. Li, Y.et.al. In vivo release from a drug delivery MEMS device’s. Control. Release 100, 211-219(2004).

In the coming episodes I’m going to present in detail about the passive and active devices for rapid and slow controlled delivery of therapeutic agents.