SearchBiochip Group Pages:
Start
Scientific Projects
Scientific Instrumentation
People & Publications
Collaborations
Financial Support
Biochip group
Scientific Projects
A new 3D surface chemistry improving microarray technology
Since the first presentation in 1995 microarrays have been a growing field of interest, mainly because of their enormous potential in genomic and proteomic research.
However, one chip is typically used for a single analytical problem and then disposed. besides what? Besides that, one of the key problems in the development of biochips for a given analytical problem is the determination of suitable chip parameters such as probe affinities and optimized hybridization conditions like buffer concentrations and temperature. Major drawbacks are lack of robustness, loss of sensitivity and specificity compared to conventional methods, the consumable costs and costs for the development time preventing their use in routine application and diagnostics.
Therefore, we developed a novel three dimensional surface chemistry consisting of a water soluble polymer. With this polymer probes for protein or DNA analysis can be immobilized on matrices such as plastic or glass by using UV photo cross linkage (254 / 365nm) (Figure 1).
Fig. 1: 3D Technology.
This model illustrates the differences between a two dimensional (2D) and a three dimensional (3D) surface. The immobilization of the probes takes place with a 5´-modification (15 mer thymine-tail) or with the special probe sequence. In the three dimensional manner the probes can be immobilized on the surface of the substrate and the polymer network. The polymer network itself consists of three statistically disposed components (DMAA, MABP and VPA). The labelled PCR amplicon (green indicated) hybridises on the immobilized probe. PMMA can also be used as good as glass substrates.
Development of technical platforms for microarray applications
The importance of micro arrays in science and medicine is still increasing due to the benefits of this technology.
For a simple usable microarray production and read-out technology, we develop a system using fluorescence excitation by an evanescent field.
Monochromatic light is coupled into a glass or plastic substrate, on which the microarray is printed. The substrate acts as a waveguide with an evanescent wave travelling along the surface.
Labeled analyte molecules bound to the surface are excited by the evanescent field. The intensity of the fluorescence is detected by a CCD chip (Figure 2).
Fig. 2: Principle of detecting only bonded analyte molecules, like DNA, by excitation via evanescent field.
Chips can be placed in a reader system consisting of a laser, a flow cell chamber and a CCD camera (Figure 3).
Figure 3: Technical details of the reader. Monochromatic light (4) is coupled into the plastic microarray substrate (1), that total internal reflection occurs. An evanescent field travels along the surface allowing fluorescence excitation. The substrate serves as a waveguide, which allows detection of the interaction between the immobilized probes (2) and the labelled DNA in the flow cell (3). A CCD-camera (7) with its filter (8) detects the fluorescence intensities. (5) Cooling system with a peltier element behind (6) regulating the temperature of the hybridization solution.
Using our newly developed 3D-printing technology with an increased probe density gives us the possibility to study hybridization kinetic, to detect gene mutations (e.g. SNP, Single Nucleotide Polymorphism) or to use on-chip PCR and on-chip NASBA (Nucleic Acid Sequence Based Amplification) as well as conventional DNA- and protein microarrays.
Biochip technology platforms for mircoarray applications
We develop microarray technology platforms for DNA biochip analysis (for example subtyping of human papilloma virus [HPV]), protein analysis (competitive assays for different clinical parameters like microglobulin-2β, HbA1C or cytokines), on-chip-PCR and on-chip-NASBA (Nucleic Acid Sequence Based Amplification) analyzing genomic DNA and gene expression simultaneously (Figure 4).
