The University of Barcelona is leading an international project that aims to develop a chip-sized super-resolution microscope capable of observing the inside of living cells in real time. The team, coordinated by Dr. Ángel Diéguez is made up by the UB and other academic and business institutions such as the Brunswick Technical University (Germany), the University of Rome Tor Vergata (Italy), the Medical University of Vienna, the Austrian Institute of Technology, the Swiss Foundation for Research in Microtechnology and the Barcelona company Expert Ymaging.
The initiative, named ChipScope, is financed for its four-year duration with 3.75 million euros from the European Commission’s Future and Emerging Technologies (FET Open) call for projects. FET Open supports incipient research efforts for them to develop groundbreaking technologies. The ChipScope project, which began last January 2017 and will be prolonged until December 2020, aims to overcome the limits of physics for conventional optical microscopy through a completely new approach that will make optical super-resolution available to the entire scientific community.
Breaking through the laws of physics with miniature microscopes
The diffraction limit now refers to the minimum distance of some 200 nanometers (nm) (about 500 times thinner than a human hair) that must separate two elements in order to distinguish them with a conventional microscope. With this limit, it is impossible to see molecules such as proteins and DNA, or the internal structures of cells, which present even smaller dimensions, with traditional optical microscopes. “This kind of observation beyond the so-called diffraction limit is only possible through complex and costly electron microscopes that also destroy the sample,” says Ángel Diéguez, member of the Research Group on Instrumentation Systems and Communication (SIC) and coordinator of the project.
In this regard, the nanoscope, a technology that earned its developers the Nobel Prize for Chemistry in 2014, enables the study of structures two thousand times thinner than a human hair. Today, nanoscopes can be used to observe synaptic vesicles or the nuclear pores of cells, to cite just two examples. As opposed to this method, the goal of ChipScope is to develop a new type of miniature microscope with which researchers can monitor objects below the diffraction limit without altering or compromising their viability. “The idea is for resolution to depend more on the light source than the optical detection system. In other words, instead of a single light source, as the highest-resolution microscopes now have, we will use hundreds of miniature light sources,” states Diéguez, whose team is a fore-runner in the development of miniature integrated circuits.
Image: University of Barcelona
To develop this chip-sized super-resolution microscope, researchers must overcome certain technical challenges. Perhaps the most daunting of them is to manufacture the world’s smallest LED’s, which have a size of approximately 50 nanometers, and will be the light source for the technology. These nanoLED light sources will be regularly spaced at nanometric distances, and switched on one after the other, individually and at high speed. The research team is certain that the nanoLED light sources being switched on separately will let them know what information is coming from each position of the object or structure to be studied. Then, a high-sensitivity photodetector will be able to discern the signals, so that an image of the object can be transferred in real time. According to the researchers in this international project, “The core idea of ChipScope is to use spatially resolved illumination instead of spatially resolved detection for achieving microscopy functionality with superresolution.”
“The theoretical basis for the project had already been conceived in the 1960’s, but to materialize these ideas, microchips, LEDs and the capacity to build those things at nanometric scale, and then space them at regular intervals, was necessary.” says Daniel Prades, member of the Research Group on Micro and Nanotechnology and Nanoscopies for Electronic and Electrophotonic Devices (MIND), which also forms part of the project. In the project presented to the European Union, the scientific team asserted that, “Making optical superresolution ubiquitously available is expected to lead to foundational breakthroughs in virtually every field of research and technology that makes use of optical microscopes.” Once the initial prototypes are developed, researchers hope to make the first observations in samples from patients with idiopathic pulmonary fibrosis, a chronic pathology that causes symptoms such as shortness of breath, chest pain and cough, and whose cause is still unknown. According to an article published in Archivos de Bronconeumología, the disease, technically known as chronic fibrosing interstitial pneumonia, especially affects persons over 50 and causes half a million deaths annually.