Gel electrophoresis uses electrical charge to separate macromolecules, such as DNA, RNA and proteins, by size or charge within a matrix. The matrix, or gel, is typically made of agarose or polyacrylamide.
Samples are loaded into wells at the edge of a gel along with a ladder— a premade mixture of molecules with a known distribution of size or charge. When current is applied to the gel, smaller or more negatively charged molecules migrate farther from the wells than do the larger or more positively charged molecules. The molecules are visualized as bands in the gel.
Using the ladder as reference, the distance a molecule travels in the gel allows the size of nucleic acid fragments or proteins to be determined. Based on band intensity, the concentration of the sample can also be estimated. These properties may provide evidence for the presence of specific genetic mutations or traits, or the protein composition of a solution.
Gel imaging is used to measure the defining properties of a sample, and automated gel-imaging systems can do so with minimal human input. Software and hardware improvements, such as higher-resolution cameras and automatic configuration of camera settings, have streamlined the image-acquisition process.
A typical gel-imaging system consists of a gel-loading and -imaging area, a light source, and an image-capturing device. Imagers are often paired with advanced software that drives automation and increases the depth of analysis for end-users. Manufacturers have increasingly focused on creating fully integrated systems that increase automation and provide systems capable of running independently of a desktop computer.
Bio-Rad Laboratories’ ChemiDoc Touch system is able to automatically adjust imaging parameters to optimally capture images from samples using chemiluminescence, fluorescence or colorimetry/densitometry. LI-COR’s Odyssey Sa system is fully compatible with an automated microplate-stacking system to maximize throughput. Stacks of up to 50 gels can be automatically imaged and analyzed, with little input from the end-user.
Manufacturers of gel-imaging systems have also responded to increased demands for traceability by integrating software improvements, such as decoding common bar code symbologies for sample tracking and preparing images for ELNs for electronic record keeping. As record-keeping standards become increasingly stringent, these improvements are necessary for laboratories that utilize gel electrophoresis.
Excluding aftermarket and service, the market for gel-imaging systems represents just under half of the total market for gel-electrophoresis instruments. As gel electrophoresis is a well-understood technique that provides valuable genetic insight, gel-imaging systems are in high demand. Existing users may be motivated to upgrade or consolidate their systems to meet higher output necessitated by the growing number of regulations worldwide.
Gel-Imaging Systems at a Glance:
• GE Healthcare
• Bio-Rad Laboratories
• Government Research