Biology subjects

Kueppers, M.

Publications and source records attributed to Kueppers, M..

3 recordsLinked to original sources

bioRxiv2025

Interferometric Image Scanning Microscopy for label-free imaging at 120 nm resolution inside live cells

Light microscopy remains indispensable in life sciences for visualizing cellular structures and dynamics in live specimens. Yet, conventional fluorescence imaging can suffer from phototoxicity, limited labeling efficiency, or perturbation of biological function. Label-free techniques such as interferometric scattering microscopy (iSCAT) offer a powerful alternative by detecting nanoscale structures based on their light scattering, without the need for dyes or genetic tags. iSCAT has enabled high-sensitivity detection of single proteins and viruses on clean surfaces. More recently, its application to live cells has been extended by using confocal illumination and detection, allowing suppression of out-of-focus light, yielding subcellular structures with high contrast. This development laid the foundation for biologically relevant label-free imaging. Here, we introduce interferometric image scanning microscopy (iISM). This next-generation technique combines interferometric detection with image scanning microscopy to achieve about 120 nm lateral resolution while operating at tenfold lower incident illumination power per diffraction limited spot, significantly reducing photodamage while enhancing signal-to-noise and contrast. Using iISM, we are able to visualize intracellular organelles such as the endoplasmic reticulum, actin cytoskeleton, mitochondria, and vesicles in live cells at essentially unlimited observation times. Importantly, iISM can be readily combined with confocal fluorescence microscopy, enabling correlation of label-free dynamics and structural information with molecular specificity. Our approach opens new avenues for studying dynamic biological processes, such as host-pathogen interactions, intracellular trafficking, or cytoskeletal rearrangements, under label-free, near-native conditions. iISM thus offers a powerful new tool for high-resolution, low-impact imaging of live cells, paving the way for new biological insights.

biophysics↗

bioRxiv2024

Measuring concentration of nanoparticles in polydisperse mixtures using interferometric nanoparticle tracking analysis (iNTA)

Quantitative measurements of nanoparticle concentration in liquid suspensions are in high demand, for example, in the medical and food industries. Conventional methods remain unsatisfactory, especially for polydisperse samples with overlapping size ranges. Recently, we introduced interferometric nanoparticle tracking analysis (iNTA) as a new method for high-precision measurement of nanoparticle size and refractive index. Here, we show that by counting the number of trajectories that cross the focal plane, iNTA can measure concentrations of subpopulations in a polydisperse mixture in a quantitative manner and without the need for a calibration sample. We evaluate our method on both monodisperse samples and mixtures of known concentrations. Furthermore, we assess the concentration of SARS-CoV-2 in supernatant samples obtained from infected cells.

biophysics↗

bioRxiv2021

GraviKit: an easy-to-implement microscope add-on for observation of gravitation dependent processes

One of the most important environmental cues for living organisms is gravity and many developmental processes depend on it. However, when it comes to light microscopy, a majority of studies on these processes work with their objects of interest placed perpendicular to their natural orientation. One reason for that is probably that light microscopes with the required horizontal beampath are either costly or require advanced technical skills. To circumvent these obstacles and make imaging of gravity-dependent processes with a horizontal beampath possible for any lab we developed GraviKit. It converts a standard inverted research microscope into an imaging device with a horizontal beampath with a stage that rotates the sample around the optical axis. Like this, the direction of gravity can be freely chosen during an imaging experiment. The system is easy to implement and suitable for multi-user environments.

developmental biology↗