Original source: Physics World
A portable fluorometer designed to detect fluorescence emitted from labelled cancer cells has been successfully validated by researchers at the University of Saskatchewan. The device — constructed of inexpensive, off-the-shelf products — is targeted at researchers in hospitals and laboratories for use as an alternative to expensive fluorescence imaging microscopes (Biomed. Opt. Express 10.1364/BOE.10.000399).
Principal developer Mohammad Wajih Alam and colleagues developed the device to promote the use and availability of fluorometers to medical and research labs throughout the world, especially in regions where resources are limited. They believe their fluorometer will overcome the prohibitive purchase and maintenance costs of conventional fluorescence detection instruments and the need for trained staff to operate the sophisticated imaging equipment. They hope that their design will foster clinical and biomedical research into fluorescence-based detection of multiple types of cancer.
The team designed the system so that it can be easily assembled using readily available, economical equipment. The fluorometer consists of a flashlight, a photodiode that responds in the range 400–1100 nm, an emission filter, a microcontroller and an LCD screen. The photodiode, which is immediately below the emission filter, is placed inside a custom-built 3D-printed sample chamber that houses the detection circuitry.
Visible light from the flashlight excites the sample, in this study, a breast cancer cell line engineered to express green fluorescent protein (GFP). As soon as a fluorescent signal is generated, the emitted signal is detected by the photodiode. The emission filter, chosen to match the emission wavelength of the GFP, ensures that only the emitted fluorescence from the sample reaches the photodiode. The microcontroller controls the detected signal, converting the analogue signal generated by the photodiode to digital, and communicating it to the display.
To validate the fluorometer, the researchers tested the system using cultured cells seeded on coverslips and mounted on glass slides. They first measured the fluorescent signal from a control cell sample (breast cancer cells without GFP), repeating the process 10 times to obtain an average base measurement. They then measured breast cancer cells expressing GFP in the same way. The system compares the average values from the samples, and if the difference is greater than 700 mV, the LCD screen displays a “Cancercell found” message.
As the confluency of cultured cells can affect readings, the researchers evaluated cell samples with confluency of between 30% and 95%. They determined that their fluorometer required a minimum of 60% confluency to differentiate between control and cancer cells. Using cultured samples with confluency greater than 60%, the device identified all control cells, and correctly detected nine out of 10 cancer cells.
“Our fluorometer detected fluorescence emitted from human breast cancer cells genetically engineered to express the green fluorescence protein. These cells served as a biologically appropriate and technically convenient clinical proxy of patient tissue for the fluorescence-based selective-detection of breast cancer cells,” wrote the authors.
“We are trying to expand the use of this device, which we designed to detect fluorescence emitted from cancer cells cultured in vitro, to see if our already compact prototype system can be further miniaturized,” Alam tells Physics World. “We are also currently working towards investigating other types of cancer with our fluorometer.”
“This device can work as an alternative to expensive commercial microscopes where the resources are limited. It can be used in remote places where diagnosis is not possible due to resource constraints,” Alam adds. “Our fluorometer is not a substitute for an MRI scanner, nor is it intended to be. But it does exhibit immense potential for future applicability in the selective detection of fluorescently-labelled breast cancer cells.”