Project Description
In modern medicine, fast detection and highly specific identification of diseases is a crucial and fundamental task. Time-consuming and expensive tests needed for a reliable diagnosis present a major challenge to present-day diagnostics. We propose an advanced procedure for the simultaneous detection of various infectious diseases in a fast and inexpensive manner using only a few drops of a patient's blood serum. Our approach is based on a novel technique called “Microarray Xeroxing”, which allows for the generation of antigens directly from a DNA-template via a “copying step.” Subsequently, interactions between the copied antigens and antibodies present in a patient’s blood sample will be detected label-free using an optical measurement method called iRIf (imaging Reflectometric Interference). Our project, named the “DiaCHIP”, is based on the specific interactions between antibodies and their respective antigens. Pathogen specific antigens of known diseases that are to be diagnosed are immobilized in distinct spots on the template side of our chip. Since purifying the antigens for every disease is tedious and expensive work, the antigens will instead be expressed in-vitro via cell-free protein expression from DNA strands coding for the specific antigens. This is realized by placing the microarray with the coding DNA strands on top of the glass slide. This sandwich is subsequently flooded with cell-free expression lysate, leading to expression of the antigens. By simple diffusion, the proteins are transferred from the DNA spot of the template side to the glass slide. They adhere to the glass slide via specific interactions, since the expressed proteins are fused to a tag (e.g. a His Tag) whilst the glass surface bears the respective catchers for the tags (e.g. Ni-NTA-modified surface). Once the cell-free expression is completed, the lysate is removed and replaced by the patient's blood serum. All reactions and the exchange of liquids take place in a microfluidic system. If antibodies against any of the antigens are present in the blood sample, they will attach to the antigens. This interaction results in a local increase of optical thickness at this antigen spot which is detected via iRIf technology. This optical detection method offers label-free and real-time detection of binding events. Once the measurement is completed, the same DNA microarray can be reused various times on different glass slides.
One of the main advantages of the “DiaCHIP” is the circumvention of the difficult and expensive production of protein chips. Our approach relies on a simple copying process of a template DNA microarray containing the genomic sequences coding for the various antigens into a protein microarray. Since DNA microarrays are a well-established technology, their production and storage is much easier than that of protein chips. In addition, protein chips denature quite easily, which is troublesome for long-term storage and shipping. In our setup, the protein chips are synthesized on-demand inside the measurement chamber, which minimizes degradation of the proteins and thus allows for a constant quality of the chip and a more reliable diagnosis.
The DiaCHIP is an innovative diagnostic device, which we anticipate will be used in many distinct application areas, whereby medical professionals as well as pharmacists will likely be the main users of our device. Concerning diagnostics in general, our DiaCHIP can be used to simultaneously detect antibodies for numerous diseases, requiring only a few drops of blood, thus allowing fast detection of an acute disease. We are developing a next generation diagnostic technology and hope to contribute positively to public health – saving lives through earlier and more precise diagnostics. With the DiaCHIP we make simultaneous disease diagnostics accessible to everyone: cheap, fast, and in real-time.
