Gel Imaging and Documentation Systems

While some gel imaging and documentation systems are meant solely for visualizing gels, it is increasingly common for “gel docs” to support other applications, such as chemiluminescent and fluorescent western blot imaging. Here, we look at the advantages of using a gel doc and suggest some features to consider when choosing a gel doc for your lab.

What is a gel doc?

The term gel doc was originally coined to describe an instrument for imaging nucleic acids or proteins suspended in gels, typically after separation by gel electrophoresis. To achieve this, gel docs use UV, blue or white transillumination light to visualize common nucleic acid stains, such as ethidium bromide and SYBR™ Safe, or proteins that have been stained with silver or Coomassie Blue. However, gel docs have evolved to offer multifunctional capabilities.

“As well as a transillumination light source, many modern gel docs are also equipped with overhead lighting, which allows for performing other applications besides imaging DNA or protein gels,” reports April Wang, Application Scientist at Analytik Jena. “Depending on the system in question, these could include multiplexed imaging of fluorescent western blots, analysis of antibody microarrays, and counting of bacterial colonies.”

Early methods for gel and blot imaging

Before the advent of gel docs, researchers used a variety of methods to capture gel and blot images. “One approach, still in use today, was to expose stained gels or chemiluminescent blots to X-ray film,” explains Deanna Woo, Global Product Manager, Protein Quantitation, Bio-Rad Laboratories. “However, this process was relatively labor-intensive, requiring development in darkrooms and the use of hazardous chemicals. Another option was to place gels on a UV transilluminator for image capture with a Polaroid camera, yet this offered only limited resolution and no way of quantifying your target band. Researchers could also use densitometry to generate a digital readout of band intensity, but this was not compatible with chemiluminescent or fluorescent detection.” Gel docs were developed as more efficient, accurate, and versatile alternatives to traditional methods.

Advantages of using a gel doc

According to Tram Tran, Associate Marketing Manager at Azure Biosystems, gel docs offer many advantages for scientific research. “First, data quality is improved through higher resolution imaging,” she says. “Second, digitization simplifies data storage and sharing, and supports quantitative analysis. Using a gel doc also saves time and can reduce overhead cost, as well as offers access to more applications, including newer methods such as in-cell westerns and total protein normalization.”

“Another important advantage of using a gel doc is the ease of creating optimal imaging conditions,” says Wang. “Modern gel docs are designed to have everything integrated, including properly configured emission filters and a controlled dark environment, allowing for cleaner gel images. Additionally, the acquisition software that accompanies these systems is typically designed to drive all of the hardware components, enhancing safety and providing greater consistency between captures.”

Key considerations for product selection

When choosing a gel doc for your lab, there are multiple factors to consider. These include the applications you wish to run, both now and in the future. “Choosing a gel doc that can be upgraded to, for example, chemiluminescent or near-infrared (NIR) fluorescent imaging means that your investment will continue to support you as your needs change,” advises Tran. She also recommends checking the footprint of the gel doc, including whether it requires an external laptop. “While some gel docs have a built-in computer system, others operate using an external laptop, which can be clunky and takes up more bench space,” she says.

Camera resolution and sensitivity are also important. Wang explains that two types of camera sensors are commonly used in current bioimaging systems: Charged Coupled Device (CCD) and Complementary Metal-Oxide-Semiconductor (CMOS) sensors. “Cooled CCD and CMOS cameras are generally preferred for chemiluminescent western blotting, NIR imaging, and in vivo applications due to their high sensitivity and low noise,” she reports. “On the other hand, uncooled CMOS cameras are more commonly used for gel documentation and other applications involving digital cameras. However, the performance of CMOS sensors has been rapidly improving, with cooled scientific CMOS sensors now providing results comparable to high-end CCD cameras in certain applications.”

Woo suggests looking for imagers with a user-friendly interface and software that simplifies image acquisition and analysis. “Using a gel doc should not be a challenge,” she says. “Features such as automated exposure settings and pre-set protocols reduce the learning curve and help to minimize the variability associated with manual methods. This leads to more consistent and reproducible results, which are crucial for scientific accuracy and validation.”

Lastly, you will want to consider the overall cost of the gel doc, including not only the initial investment but also any ongoing maintenance. “Make sure that the value provided by the system in terms of its features, performance, customer support, and how it currently fits into your workflow makes sense with your research,” cautions Woo.

Five factors to consider when choosing a gel doc

• Which applications you plan to run
• Camera resolution and sensitivity
• Ease of use
• Instrument footprint
• Overall cost of the system

Available options

A broad array of gel docs is available to meet different needs. “Bio-Rad’s gel docs include the GelDoc Go, which is solely a gel documentation system, and the ChemiDoc Imaging System Family, which also enables western blot membrane imaging and analysis,” reports Woo. “All of the ChemiDoc systems allow for both colorimetric and chemiluminescent detection, with the ChemiDoc Go additionally providing detection of StarBright Blue 520 and 700 and the ChemiDoc MP offering detection of full spectrum fluorescence.”

“Analytik Jena’s UVP GelStudio imaging series is equipped with UV, blue, and white transillumination light, as well as UV, blue, green, and red LED overhead lighting, providing flexibility for various dyes and applications,” says Wang. “The VisionWorks software installed on these systems allows for one-touch capture and uses real samples to train the machine learning algorithm that is used for analysis, ensuring more accurate results.”

“The Azure Imaging Systems start with our basic gel doc, the Azure 200,” explains Tran. “This can be upgraded to detect chemiluminescence, visible fluorescence, or NIR fluorescence, as well as to a system combining all of these detection modes. We also offer the Sapphire FL Biomolecular Imager, which reaches into the UV spectrum and allows for imaging complex samples like phosphor screens, tissues, and even live animals.”