Abstract
The growing interest in DNA biochips for rapid detection of diseases, infections, genetic contaminations, and hereditary illnesses necessitates the understanding of how DNA macromolecules may be immobilized on surfaces with high density, reproducibility and precision. These are the reasons why this project is focusing on developing a micro-contact printing process for DNA biochip applications. The aim of this research project is to use a soft-lithography technique also called Micro-Contact-Printing to arrange DNA oligonucleotides on surfaces in order to develop DNA biochip applications. The idea of the method consists of using an elastomeric stamp to transfer molecular ink onto surfaces. This method has been demonstrated as a more cost effective technique than the commonly used spotting technology and allows an increased surface density.
Extract
[...] also added – after many experiments – that contamination could increase the affinity between stamp and DNA and consequently increase the resolution. We will explore this way using ToF-SIMS for different printing times. 5 Soxhlet extractor is used for the extraction of lipid from solid materials but also allow extracting compounds from polymers. Page 8 B. Approach and experiments The aim of this study is to develop a protocol of micro contact printing to produce DNA biochips with high density, reproducibility and precision. Today many studies use micro contact printing but only a few are specialized on µCP of DNA. [...]
[...] a new stamp was used for each printing This experiment also shows how rapidly contamination is recreated on stamp surfaces. Time of printing 0s Contact angle same stamp – 16,3 Contact angle – five different stamps – 15,6 15s 30s 1min 26,7 64, 2 70,8 27,1 65,6 72 2 min 73,4 75 Table contact angle value after different times of contact printing 14 Secondary Ion Mass Spectrometry Page 20 Graph below shows the rapid evolution of the contamination on the glass surfaces and shows that the surface contact angle has increased by a factor of four after printing compared with the starting surface. [...]
[...] The idea is to transfer ink to a substrate by inking and pressing a stamp on the substrate surface. For DNA biochips, the ink is a molecular ink such as oligonucleotides and the stamp used is an elastomeric stamp. The success of this process depends on three important points. o The activation of substrate by surface functionalization– attaching reactive chemical groups on the surface such as thiol, amino, carboxyl or hydroxyl groups. o The effectiveness of surface functionalization of oligonucleotides4 with same chemicals functions as above. [...]
[...] 3. Contact Printing of Micro Arrays with Variable Pixel Size and Density Using a New Micromachined PDMS Tip Array Stamp. Jung Moo Hong, Fatih M. Ozkeskin, and Jun Zou. Texas, USA : s.n. 4. C. Thibault, C. Séverac, A.F Mingotaud, C. Vieu and M. Mauzac. Poly(dimethylsiloxane) Contamination in Microcontact Printing and Its Influence on Patterning Oligonucleotides. Langmuir Vol. 23. [...]
[...] The covalent binding technique used in this work consists of chemical binding between substrate and DNA strands. It is the subject of active research due to good resistance of the biochips to temperature, aqueous solution and rinsing. This technique has also a good commercial aspect because biochips can be reused. The last important step in DNA biochip technology is reading of the hybridization, which depends on the tagging method that has been used. Today two tagging methods are used. A direct method may be employed where no markers are involved and the detection is made by mass detection, Surface Plasmon Resonance (SPR) detection, or electrical detection (12)(13). [...]
