Chitosan: an integrative biomaterial for lab-on-a-chip devices.

Chitosan is a naturally derived polymer with applications in a variety of industrial and biomedical fields. Recently, it has emerged as a promising material for biological functionalization of microelectromechanical systems (bioMEMS). Due to its unique chemical properties and film forming ability, chitosan serves as a matrix for the assembly of biomolecules, cells, nanoparticles, and other substances. The addition of these components to bioMEMS devices enables them to perform functions such as specific biorecognition, enzymatic catalysis, and controlled drug release. The chitosan film can be integrated in the device by several methods compatible with standard microfabrication technology, including solution casting, spin casting, electrodeposition, and nanoimprinting. This article surveys the usage of chitosan in bioMEMS to date. We discuss the common methods for fabrication, modification, and characterization of chitosan films, and we review a number of demonstrated chitosan-based microdevices. We also highlight the advantages of chitosan over some other functionalization materials for micro-scale devices.

A cantilever sensor with an integrated optical readout for detection of enzymatically produced homocysteine.

Microcantilever sensors have been recognized as a promising sensor platform for various chemical and biological applications. One of their major limitations is that the measurement of cantilever displacement typically involves elaborate off-chip setups with free-space optics. An improved device, known as the optical cantilever, has been proposed recently to eliminate the external optics. The response of the optical cantilever is measured on-chip through integrated waveguides. However, this method has been previously demonstrated only for devices operating in air, whereas most chemical and biological samples are in solution state. We present the first optical cantilever capable of operation in liquid. We test it with the detection of homocysteine with a minimal concentration of 10 muM. The minimal measurable cantilever displacement and surface stress are 5 nm and 1 mN/m, respectively. The presented device will be used in studies of a homocysteine-producing bacterial pathway for the purpose of drug discovery. It can also be extended to various other chemical- or biological-sensing applications by selecting an appropriate surface coating.