Detect single molecules using a smartphone-based microscope to diagnose disease

Biomarkers play a central role in diagnosing disease and assessing its course. Markers currently in use include genes, proteins, hormones, lipids, and other classes of molecules. Biomarkers are found in blood, cerebrospinal fluid, urine, and various types of tissues, but most of them have one thing in common. It occurs at very low concentrations and is technically difficult to detect and quantify.

Many detection procedures use molecular probes, such as antibodies or short nucleic acid sequences, designed to bind to specific biomarkers. When the probe recognizes and binds to its target, a chemical or physical reaction produces a fluorescent signal. Such a method works well if it is sensitive enough to recognize the relevant biomarker in a high proportion of all patients who carry it into the blood.

In addition, the biomarker itself or its signal must be amplified before actually using such a fluorescence-based test. The ultimate goal is to be able to perform medical screening directly on patients without sending samples to remote laboratories for analysis.

Molecular Antenna Amplifies Fluorescent Signals Philip Tinnefeld, chair of physical chemistry at LMU, has developed a strategy to determine the levels of biomarkers present at low concentrations. He succeeded in binding the DNA probe to small particles of gold or silver. A pair of particles (“dimer”) acts as a nanoantenna that amplifies the fluorescent signal.

The trick works as follows: The interaction between the nanoparticles and the incident light wave intensifies the local electromagnetic field, which in turn leads to a significant increase in fluorescence amplitude. In this way, bacteria that contain antibiotic resistance genes or even viruses can be specifically detected.

“DNA-based nanoantennas have been studied for the past few years,” said Kateryna Trophymchuk, co-lead author of the study. “But there are challenges in manufacturing these nanostructures.” Philip Tinnefeld’s research group more accurately constructs the components of the nanoantenna and produces DNA molecules that act as capture probes at the site of signal amplification. I succeeded in placing it. Together, these changes allow the fluorescent signal to be amplified more effectively.

In addition, more molecules can be captured in the associated microvolume, which is on the order of zepto liters (zepto liters are equal to 10-21 per liter).

Advanced positioning control is made possible by structure-based DNA nanotechnology Properties of DNA To guide the assembly of all kinds of nanoscale objects-very many. “One sample can basically make billions of these nanoantennas at the same time, using the procedure of pipetting several solutions together,” says Trohymchuk.

Viktorija Glembockyte, co-lead author of the magazine, said of routine diagnostics on smartphones, “Our technology may be used for diagnostic testing even in areas where access to electricity and laboratory equipment is restricted. A smartphone-based portable microscope that operates with a traditional USB power pack can be used to directly detect small fragments of DNA in serum and monitor the assay. “

New smartphones usually have pretty good cameras. Apart from that, all you need is a laser and a lens. Two easily available and inexpensive components. LMU researchers used this basic recipe to prototype.

They further demonstrated that this setting can detect DNA fragments specific for bacterial antibiotic resistance genes. However, this assay can be easily modified to detect the full range of interesting target types such as viruses. Tinefeld is optimistic. “Last year, we always needed new and innovative diagnostic methods, and perhaps our technology could contribute to the development of cheap and reliable diagnostic tests that can be run at home.”