Team:Freiburg/Testpage

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The DiaCHIP - A Versatile Detection System

DiaCHIP_Sabi

Project Motivation

Serological tests are a key element in modern medicine. Especially for detection and identification of infectious diseases, performing several blood tests is inevitable. Testing for more than one disease at a time or diagnosing a patient with diffuse symptoms usually requires more than one serological test. Every single test that is performed increases the time of waiting for a result as well as the bill. In case of dangerous infectious diseases every minute until the onset of the appropriate treatment is important for survival. What if there was a possibility to combine all this testing in one single chip which is affordable for everyone?

Detecting Antigen-Antibody Interactions

The DiaCHIP is an innovative tool to screen for a broad range of antibodies present in serum. Antibodies serve as indicator for an immune response towards an infectious disease or a successful vaccination. They also play an important role in the diagnosis of autoimmune diseases. Identifying diseases by detecting disease associated antibodies in a patient's serum is an established method in modern diagnostics.
Based on the very same principle, the DiaCHIP enables to simultaneously screen for multiple diseases at a time, thereby reducing time and costs of a diagnosis. Especially the ability to differentiate between life threatening diseases and mild infections within a short time bears the potential to save lifes.

The Concept

The key feature of the DiaCHIP concept is the combination of on-demand protein synthesis of disease related antigens and a novel method for label-free detection - all this packed into one device. The idea is to overcome challenges commonly found in protein array production and preservation. In addition, results can be obtained in a time- and cost-efficient manner; with a device simple enough to be rebuilt by future iGEM teams.

Step by Step Overview

  • The DiaCHIP - System Overview

    The core of our new diagnostic device consists of two slides that form a microfluidic chamber. Therein, an antigen array can be generated on demand on the bottom slide. By flushing the chamber with a blood sample, antibodies present in the sample bind to corresponding antigens. This interaction is detected in real-time using the optical detection method iRIf.

    Step by Step Overview

  • Outlook

    Our results provide a proof of concept that the functional priciple of the DiaCHIP is suitable for antibody detection in complex samples. Although further improvements have to be done in terms of reliablitiy and quantification, various additional applications are conceivable. Representing a way to reduce time and cost required for testing a single patient, the DiaCHIP holds the potential to enhance and enlighten future diagnostics.

    DiaCHIP in the
    Future

  • Optical Detection: iRIf

    One disadvantage of currently available serological tests is the need for secondary labels that allow the detection of disease markers. Making use of an optical method based on the interference of light, the DiaCHIP can detect specific binding events on a protein microarray without further labeling. Read more about this innovative tool and the physics behind it.

    iRIf Principle and Physics

  • Surface Chemistry

    The production of a customized protein microarray in the DiaCHIP is based on selective immobilization of antigens on a glass slide. Therefore, a specific surface chemistry was established to reduce the proportion of unspecific binding of non-target proteins to a minimum. Read more about the different layer compositions we tested on our way to high specificity.

    Establishing a Specific Surface

  • Protein Purification

    Protein expression in the DiaCHIP is mediated by cell-free expression. As this is an advanced method dependent on the optimization of many parameters, we got back to conventional protein purification in E. coli for being able to compare the results of both techniques.
    Read more about the overexpression and purification of several antigenic peptides.

    Purification of Antigens

  • Cell-Free Expression

    A key feature of the DiaCHIP is the capability to produce protein arrays on demand via cell-free expression. To reduce the cost of a DiaCHIP measurement, we produced a cell-free expression system based on an E. coli lysate ourselves. This system is also capable of expressing immobilized DNA sequences. See how this sensitive system was established and optimized.

    Cell-free Antigen Expression

  • DNA Engineering

    Genetic fusion of different antigens and tags is a basic requirement of our project. In order to enable several people to work in parallel we designed a cloning strategy easy to follow and additionally easy to expand for further needs. Read more about combining different cloning methods to reduce efforts in DNA Engineering and the design of an expression vector meeting iGEM requirements.

    DNA
    Engineering

  • Diagnostics Today

    Currently used serological tests are available for a broad range of infectious diseases. However, they meet limitations that restrict an early onset of appropriate treatments which could be life-saving. The necessity of performing several tests to check for more than one disease at once is not only time-consuming but also costly. The DiaCHIP tackles these issues by providing a fast and affordable method for simultaneous testing.

    Limitations and Solutions