The ability to anchor cells in predefined patterns on a surface has become very important for the development of cell-based
sensors, tissue-engineering applications, and the understanding of basic cell functions. Currently, the most widely
used technique to generate micrometer or sub-micrometer-sized patterns for various biological applications is
microcontact printing (&mgr;CP). However, the fidelity of the final pattern may be compromised by deformation of the
PDMS stamps used during printing. A novel technique for accurately patterning and positioning biological cells is
presented, which can overcome this obstacle. We have fabricated a chip on a silicon wafer using standard
photolithographic and deposition processes consisting of gold patterns on top of PECVD silicon dioxide. A hydrophobic
self-assembled monolayer (SAM) derived from 1-hexadecanethiol (HDT) was coated on the gold surface to prevent cell
growth, and a hydrophilic SAM derived from (3-trimethoxysilyl propyl)-diethylenetriamine (DETA) was coated on the
exposed PECVD silicon dioxide surface to promote cell growth. Immortalized mouse hypothalamic neurons (GT1-7)
were cultured in vitro on the chip, and patterned cells were fluorescently stained and visualized by fluorescence
microscopy. By our method, hydrophobic and hydrophilic regions can be reliably generated and easily visualized under
a microscope prior to cell culturing. Cell growth was precisely controlled and limited to specific areas. The achieved
resolution was 2 microns, and it could be improved with high resolution photolithographic methods.
In this paper, we describe the development of a culture-based biochip for detecting mycobacteria in environmental samples. The biochips use the paraffinophilic nature of mycobacteria to rapidly detect and differentiate them from non-target micro-organisms. New methods of depositing and patterning paraffin were developed to fabricate prototype biochips. Biochips were experimentally tested to demonstrate rapid detection of mycobacteria in environmental samples collected from a municipal sewage treatment plant. Our successful demonstration of the culture-based biochip technology presents an alternative approach for developing new technology to track microorganisms in complex environmental samples.