The System:

DLS Solutions designed and implemented the software for a real-time SPR Imaging system for measuring protein binding in an array of samples. The system can measure affinity properties for up to 400 samples simultaneously. By processing this number of samples in parallel, the analyst can evaluate a diverse collection of potential binders, increasing the likelihood of identifying candidates with the desired functional characteristics. This product, developed by a small company, was sold to the world leader in SPR instrumentation. It is now a cornerstone of their product portfolio.

Implementation Details:

The SPR data is collected by capturing CCD images of the analysis plate and measuring the change in intensity of each sample spot as the angle of a light source changes. Approximately 10 CCD frames are captured and analyzed per second. Each image is 1500x1000 pixels, 16 bits per pixel. Intensities for each spot are assembled into curves and fit to a theoretical SPR curve profile. The data of interest is the angle at which the light intensity is at a minimum. This angle changes as the protein binding events occur. The instrument control software simultaneously runs a fluidics control program (the user method) passing reagents and wash solutions over the sample candidates as the image data is captured and analyzed.

For time-to-market reasons, the instrument hardware was designed without an embedded system. Therefore all instrument control and data acquisition is performed by the Windows XP CPU. An image capture card and a National Instruments motion control card are installed in the Windows PC. The motion control card is used for control of the light angle and autoloader motors and for digital IOs for valves, etc. Pumps are controlled via RS-232. To achieve the required data analysis performance, we implemented a pipelined architecture such that during one image capture, the previous image is DMA'ed into RAM, and the next previous frame is being analyzed. Completed SPR curve sets are fitted and measured asynchronously and results are displayed in the UI as soon as they are available. Analysis for 400 sample spots, with 400 background spots and arbitrarily shaped ROIs, is always completed before the next light source angle sweep is started.

General Technology:

• Visual Studio 6.0
• Windows 2000/XP
• Visio-based UML Analysis and Design
• Gigasoft ProEssential (scientific graphing package)
• Proprietary Image Processing (using Intel Performance Primitives)
• Gigasoft ProEssential (scientific graphing package)
• CCD Camera (Roper Scientific)
• National Instruments Motion Control