Fluorescent Sensors Boosted With New Technique to Help with Better Observation of Drug Effects and Medical Diagnosis

MIT engineers recently developed a technique to overcome the problems encountered when using fluorescent sensors for scientific and medical examinations.

As specified in a Phys.org report, fluorescent sensors provide a unique glimpse inside living cells, which can be employed for labeling and imaging an array of molecules.

Nevertheless, they usually can just be treated in cells grown in a lab dish or tissues near the body's surface since their signal is lost when implanted quite deeply.

To overcome this limitation, engineers at MIT used a novel photonic technique they had developed to excite any fluorescent sensor; they could improve the fluorescent signal dramatically.

Embedding Fluorescent Sensors and Still Receive a Strong Signal

Using this method, the researchers showed they could embed sensors as deep as 5.5 centimeters in tissue and still receive a strong signal.

In the study published in the Nature Nanotechnology journal, the authors said this kind of technology could enable fluorescent sensors to be used for tracking specific molecules inside the brain or other tissues deep within the body, either for monitoring the effects of drugs or medical diagnosis.

According to the Carbon P. Dubbs Professor of Chemical Engineering at MIT, Volodymyr Koman, "If you have a fluorescent sensor" that analyzes biochemical information in cell culture or thin tissue layers, this technology enables translation of all of those fluorescent dyes "and probes into thick tissue."

Scientists are using many different kinds of fluorescent sensors, including quantum dots, fluorescent proteins, and carbon nanotubes, to label molecules inside cells.

'Autofluorescence'

Essentially, the fluorescence of these sensors can be seen by shining laser light on them. Nonetheless, this does not work in thick, dense tissue. It does not work either, deep within tissue, as tissue itself emits some fluorescent light.

This light, called "autofluorescence," is drowning out the signal from the sensor. Commenting on the said light, Koman explained that all tissues autofluoressce, which becomes a limiting factor.

As the signal from the sensor turns weaker and weaker, it becomes overtaken by the tissue autofluorescence. To address this limitation, the MIT research team devised an approach to modulate the frequency of fluorescent light emitted by the sensor for it to be more easily distinguished from the tissue fluorescence.

Their approach, called "wavelength-induced frequency filtering" or WIFF, uses three lasers to create a laser beam using an oscillating wavelength.

An Approach that Works at Any Wavelength

On top of detecting TMZ activity, the study investigators demonstrated that they could employ WIFF to improve the signal from a wide range of other sensors, which include carbon-nanotube-based sensors that the lab of Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the senior author of the study, has developed before to detect hydrogen peroxide, ascorbic acid, and ascorbic acid.

Strano said the approach works at any wavelength, and it can be employed for any fluorescent sensor. A similar AMU Biochemical Society report noted that since there's so much more signal now, one can embed a sensor at depths into tissue that was impossible before.

For this study, the researchers used three lasers together to develop the oscillating laser beam, although, in future work, they are hoping to use a tunable laser to create the signal and improve the technique even further.

Related information about fluorescence is shown on Reactions' YouTube video below:

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