Microfabricated Drug Delivery Systems

Strategies to provide reasonable oral bioavailability of peptide and protein drugs have been developed (36). Although delivery systems such as immunotoxins and liposomes improve selectivity of a few cancer drugs, the previous technology has not been suitable for the vast majority of such molecules. 

Drug delivery concepts have been presented that are based on microfabrication. Possible applications include micromachined silicon membranes to create implantable biocapsules for the immimoisola-tion of pancreatic islet cells, as a possible treatment for diabetes and sustained release of injectable drugs needed over long time periods. 

Asymmetrical, drug-loaded microfabricated particles with specific ligands linked to the surface are proposed for improving oral bioavailability of peptide- and protein based drugs (36). 

Thermal inkjet spray freeze-drying was used to produce inhalable particles of terbutaline sulfate (37). Scanning electron micrograph images proved that the particles are spherical, highly porous and suitable for aerosolization from a capsule-based dry-powder device. There is no need for additional experiments. 

The particle size is dependent on the concentration of the jetted solution and also on the distance between the printhead and the surface of the liquid nitrogen. 

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Tao, S.L. and T.A. Desai, Microfabricated drug delivery systems from particles to pores. Adv. Drug Delivery Rev, 2003,55 315-28. 

Numerous microfabrication techniques have been used to produce a wide range of implantable and oral drug delivery systems using materials ranging from silicon, glass, silicone elastomer, and plastics. Fabrication techniques have rapidly evolved to produce nanoscale objects and therapeutic systems using polymeric materials as the substrate due to their biodegradable nature. There are a number of different synthetic polymer systems that have been developed for this type of application, and the most common ones are listed below ... 

More complex structures, additional length scales, property prediction (e.g., microelectronics devices, microfabrication, polymers, drug delivery systems,... 

Yuzhakov et al. [93] describe the production of an intracutaneous microneedle array and provide an account of its use (microfabrication technology). Various embodiments of this invention can include a microneedle array as part of a closed loop system smart patch to control drug delivery based on feedback information from analysis of body fluids. Dual purpose hollow microneedle systems for transdermal delivery and extraction which can be coupled with electrotransport methods are also described by Trautman et al. [91] and Allen et al. [100]. These mechanical microdevices which interface with electronics in order to achieve a programmed or controlled drug release are referred to as microelectromechanical systems (MEMS) devices. 

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