Principle of Operation
MFI integrates digital microscopy, micro-fluidics and image processing into a single instrument for automatic analysis of particles or cells suspended in liquids. MFI operates by capturing images from the sample as it passes through the flow cell's sensing zone. Every particle in each image is analyzed to create a database of particle count, size, transparency and morphology (or shape). For immediate visual verification, images are displayed on the system monitor in real-time. MFI can also produce Trend Charts to monitor dynamic processes.
While the operating principles of MFI are straight forward, there are many technical issues in obtaining accurate and consistent performance across multiple samples and instruments, particularly for challenging sample types. ProteinSimple continues to enjoy working with its collaborators and customers to investigate these issues and to incorporate the solutions in our products. Examples include obtaining sample introduction, user friendly "data mining" software and high and consistent sensitivity, accurate and consistent measurements, high sampling efficiency, small sample volumes, convenient and robust sample introduction, user friendly "data mining" software and validatable methods for using MFI.
Traditional particle counters relied exclusively on particle size and/or particle concentration measurements by light scattering, light obscuration, size exclusion chromatography or other indirect methods which often miss subvisible particles (see comparison figure below). Additional particle morphology or shape analyses required filtering and inspection by manual microscopy which can often compromise the particles or interest.
MFI goes beyond simply counting and sizing particles. With MFI, particle morphology can now be measured "in situ". Measuring particle shape in addition to size and concentration provides many advantages in terms of understanding the source of the particles, their physical structure and the isolation of different sub-populations which may be of interest.
MFI offers a comprehensive morphology detection options which can be customized with the most popular and useful being:
- Equivalent circular (or spherical) diameter – ECD
- Maximum feret diameter
- Aspect ratio
- Edge particles
For detailed information on morphology detection options please visit the particle size and morphology page on the MFI web site
The MFI View Analysis Suite software also provides users with the ability to create derivative parameters. A derivative parameter is formed using two of the existing morphological parameters and a mathematical operator (e.g. aspect ratio ÷ perimeter).
The figure below is representative of visible and subvisible particles detected by MFI.