Caitlin Smith has a B.A. in biology from Reed College, a Ph.D. in neuroscience from Yale University, and completed postdoctoral work at the Vollum Institute.
Gel documentation systems might not warrant the ooohs and aaahs of, say, a synchrotron. But gel documentation systems, also called gel imaging systems, are relied upon by vastly more researchers and play a pivotal role in more research projects than the noble synchrotron. As a means of recording and analyzing the results of every day DNA or protein gels, their ubiquity ranks up there with pH meters on the lab bench. “Gel documentation systems have progressed immensely in terms of functionality, reliability, ease of use and affordability since their inception, and today’s advanced equipment offerings exemplify this development,” says Kathy Buckman-Polk, marketing services manager at UVP. “Many of today’s imagers provide affordability, consistency in operation and simplicity, allowing researchers to spend less time worrying about gel documentation and more time focused on research.”
Why use imaging systems to document and analyze gels instead of traditional methods like film? The main reason is that imaging systems put many more tools in your hands. For example, when imaging chemiluminescent signals from a gel, a gel documentation system will give you a greater dynamic range for crisper images, faster exposure times and greater efficiency, compared with film, according to Maggie Pochyla, U.S. market manager for Syngene. Other tools include indicators of signal saturation, and automated features that are gradually making gel documentation systems more user-friendly for people with no imaging experience. In addition, gel imaging systems provide digital images that can be analyzed and quantified with analysis software.
But for many researchers who are comfortable using film or other methods of documentation, the number of parameters to optimize in an imaging system, to end up with the best data possible, can be overwhelming if not a downright impossible task not worth their valuable time. So it is lucky that gel documentation systems continue to evolve to the benefit of the user—and the user’s work. Here are some examples of today’s instruments and their features.
Ease of use
Many factors enter into the ultimate decision to commit yourself, and perhaps everyone in your lab, to one type of gel documentation system. UVP’s product manager for bioimaging systems, Mike Capps, says one of the most important points for researchers to consider when choosing a system is whether it is easy to use. He also recommends trying the instrument first. “Since the researchers will likely use their imager on a daily basis for years to come, we encourage potential customers to demo a system, much like test driving a car, until they find the one that’s right for them,” he says. “Factoring in costs, feature sets and ease of use, finding an imaging system that the user is comfortable using on a regular basis is vital for ensuring the best results day in and day out.” UVP’s new touch screen gel imager, the GelDoc-It®TS2, is designed to speed the workflow by being easy and efficient to use. It also allows wireless connectivity and different formats for saving data easily. Another gel documentation system designed for ease of use is the Thermo Scientific myECL Imager, which is self-contained to avoid the need for a darkroom and has a small footprint. Researchers looking for easy-to-use, economical solutions that still offer advanced features like CCD camera imaging and integrated software for acquisition and analysis might be interested in Aurogene's SmartGel System.
Ease of use extends to a gel imaging system’s analysis software, as well. “The software should not be a barrier to getting results and should allow researchers to analyze their results where it’s convenient for them, whether that be in the lab or at their desk,” says Kate Smith, senior product manager in Bio-Rad's lab separations division. “Gel imaging users report that their greatest frustration is the level of difficulty associated with using the systems that are currently available, which typically require manual adjustment of filters, lenses or lights. The traditional response from gel documentation providers has been to develop systems with more specifications rather than to consider what's really important to customers, which is ease of use.”
Automation
The ultimate form of ease of use is automation, which is where many gel documentation systems are headed today. For example, Syngene offers a new line of smaller, more compact gel documentation systems called PXi. Along with Syngene’s gel imagers comes the devices’ acquisition software, GeneSys. This is the brain that runs the automated tasks for you. After telling GeneSys what kind of sample you are imaging, GeneSys sets up optimal imaging conditions for the sample automatically. “Before this program, users needed to know exactly how to image their sample—including exposure time, light settings, filter settings, camera settings—in order to get the best image,” says Maggie Pochyla, U.S. market manager for Syngene. “GeneSys eliminates that need and automatically captures an image perfectly, even if the user is unaware of what lights, filters and exposure time to use.” Such a system is especially useful in labs with younger students.
Another important point is how the gel imager interfaces with its software, says Pochyla. Ideally, the software should help, not hinder—which makes the automation valuable. “The image acquisition and analysis software should be intuitive and easy to use so that even if [users have] no prior imaging experience, they can easily operate the software and system,” she says. Syngene’s G:BOX and PXi gel documentation systems include automation of the camera and hardware controls. Another advantage of being able to automate these parameters is that they can be saved to use for future use.
Another system using automation to ease the workflow is Bio-Rad’s Gel Doc EZ. It completely automates the process of imaging, requiring the researcher merely to push a button. The system’s different trays (which hold the gels) are specific to particular applications, so the acquisition software, Image Lab, automatically recognizes what kind of imaging you need, based on the tray you insert into the imager. In addition to automation, Smith at Bio-Rad points out that flexibility and ease of use are especially important in labs with many users. “Researchers should consider this when making their decision about which system to choose,” she says. “The Gel Doc EZ allows the use of multiple application-specific trays, including a UV tray for imaging fluorescent stains such as ethidium bromide, a white tray for imaging colorimetric stains such as Coomassie blue and a blue tray for imaging green fluorescent dyes.” Another fully automated imaging system for gel documentation is offered by ProteinSimple. That company’s AlphaImager HP system is designed for fluorescent and colorimetric signals, with the option of expanding its capabilities to chemiluminescence detection, as well.
More imaging tools
A gel documentation system contains too many parts for a comprehensive review here, but an integral part that bears mentioning is the camera that captures the signals. Pochyla believes camera quality is one of the most important considerations when choosing a gel documentation system. This necessitates some forethought concerning the types of sample you use now or may use in the future. For example, “imaging chemiluminescent samples requires a cooled CCD camera and a wide aperture lens, so users must consider their imaging application first before purchasing a system,” Pochyla says. “Camera specifications such as the lens f/stop, pixel size and pixel array all contribute to the sensitivity and performance of the camera when imaging chemiluminescent and fluorescent samples.” If camera specifications sound like a foreign language to you, a fully automated imaging system that enables a wide range of parameters may be the ticket.
A robotic camera is integrated into the MF-ChemiBIS gel imaging system from DNR Bio-Imaging Systems. Software controls the camera via motors, which move it up and down to substitute for the more conventional zoom lens. According to DNR, its robotic camera is faster, more sensitive and has a wider field of view, compared with a stationary camera with a zoom lens. This can be advantageous when acquiring data from gels with faint signals, because the camera can be moved very close to the sample.
Often a manufacturer will offer a range of gel documentation systems to serve a variety of researchers. For example, UVItec offers its highest-performance instruments, the Platinum HD2 and FireReader systems at one end of the spectrum and its most basic UVIsave HD2 system at the other. Similarly, LI-COR has created a sibling for its Odyssey Classic Infrared Imaging system, designed for Western blots. LI-COR’s new Odyssey Fc is an economical gel documentation system for DNA and protein gels, as well as Western blotting. Jeff Harford, LI-COR senior product marketing manager, says that in developing the Odyssey Fc, the company aimed to maintain the sensitivity of the Odyssey Classic system while simultaneously simplifying the system to make the work of traditional, everyday lab techniques easier. LI-COR particularly focused on simplifying the acquisition of nice images. “With traditional imaging systems, you set [parameters such as] exposure and sensitivity on the system and then find that bands are blown out or saturated,” Harford says, which requires you to adjust the parameters and then image again. “This not only takes time, but it complicates the process of just getting answers. So our team of designers came out with the FieldBrite XT optical design, which provides over six logs of dynamic range. This means you can now get a perfect image on the first try and be able to then analyze the data obtained. This has provided a big step forward in allowing the researcher to have a versatile lab tool that is sensitive, simple to use and eliminates all the guesswork of older technology.”
Harford says that even though researchers may document gels in different ways, they all have the same woes about their systems. “One of the things I hear frequently is that researchers are tired of systems that are very complicated to use and that consistently break down,” he says. “The last thing a researcher wants to do is invest in a system that is not reliable or cannot be easily operated.”
Gel documentation systems have advanced in many ways, but according to Alex Waluszko, UVP’s vice president of marketing and sales, they can be easier and simpler still. “Moving forward, I anticipate that gel imaging will continue to develop in simplicity, efficiency and effectiveness, while simultaneously remaining affordable to the end user,” he says. The gel imagers of the near future may even win over even staunch devotees of film.
The image at the top of the page is Thermo Scientific's myECL Imager.