Label-free nanoscopy of living cells through nanoscale refractive index profiler

Every object scatters light. The amount and direction of scattering of light is given by the refractive index of the object, which is a signature of the object. The cells in our body have many nanoscale sub-cellular structures, each having a specific refractive index. If we can estimate the refractive index at every point in the 3D volume of the cell with nanometer precision and high sensitivity, we can identify the sub-cellular structures without using the currently popular but toxic fluorescent dyes. This will make it possible to image cells and their functions in their natural state for a long time. NanoRIP will make this possible. We have been able to debunk the myth that use of high refractive index photonic substrates invariably improves resolution. We have also established several works at the junction of physics, mathematics, engineering that are fundamental in filling the gaps between fluorescence resolution and scattering resolution. These works pave the path towards scattering super-resolution so that we can address the problem of nanometer scale. We have also been able to conduct a first-ever study of non-linear full wave solvers for intensity only microscopy data. It shows the key limitations imposed by the microscope as an instrument and points to some suitable microscope design modifications. We have participated in popular science and public outreach through Digital Life Norway, the Arctic Optica Student chapter, the website and LinkedIn. We have participated in innovation event Nordic Life science days, and also been visible in national news. We also participated in Digital Life Norway's innovation pilot.

Imaging live cells with resolution <100 nm is important for designing treatment of various diseases. Fluorescent nanoscopy provides resolution, but fluorescent labeling is invasive and toxic to cells. Raman imaging uses no labels but is highly phototoxic. Label-free nanoscopy in linear optics is minimally invasive and toxic, but faces a resolution barrier of 100 nm (lateral) and 150 nm (axial). nanoRIP breaks this resolution barrier, provides 3D resolution of 70 nm by reconstructing the 3D refractive index (RI) profile of cells, and sets a new paradigm in nanoscopy. nanoRIP exploits the information-rich multiple scattering (MS) between the cell organelles, which non-linearly encodes the RI of organelles into the light back-scattered by them. MS contributes a minuscule component to the back-scattered light. The resolution barrier results from the inability to sense and decode this component. nanoRIP mitigates this challenge using a novel approach where innovatively designed instrument and algorithm work in tandem for exploitation of MS. The novel microscope removes all the ambient light to sense this component and its polarization. The novel algorithm decodes MS from this component through a physics solver with robust priors. nanoRIP enables imaging of complex spatiotemporal interplay of cell organelles in living cells at nanometer scale for long durations (~hrs). It will lead to new insights into sub-cellular processes underlying several diseases and lead to new avenues of treatments. For proof-of-concept, nanoRIP will study the lipid processes in the muscle cells of heart that can lead to heart failure. nanoRIP will place Norway as a leader in label-free nanoscopy. nanoRIP will serve biologists in Norway as a national technology platform.