STED confocal microscope (renewal)

• Subject Area: Basic Research in Biology and Medicine
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 583687990

With the present application we seek to upgrade and refurbish an existing confocal microscope that is approaching the end of its useful service life with a Stimulated Emission Depletion (STED) unit. Following the upgrade, the microscope will i) provide additional "work-horse" imaging capacity and instrument redundancy for the state-of-the-art confocal system that will be installed in the facility at the end of the year, and ii) provide the capability for superresolution microscopy, an imaging modality for which there is a clear but as yet insufficiently met need within the biomedical community. The resolving power of conventional microscopes is limited by diffraction, which prevents focusing of the excitation light to an arbitrarily small focal volume. For most biological samples, the practically achievable resolution lies at roughly half the excitation wavelength, i.e. 200-300 nm for the usual dyes. Crucially, many interesting biological processes and structures exist just below this length scale. Thus, studying these directly requires an imaging modality that can circumvent this physical limit. Examples include the colocalization of proteins within individual organelles, the molecular organization of cytoskeletal structures and junctions, the internal organization of mitochondria, or the interaction of virus particles with antimicrobial peptides. All these are difficult to study with diffraction-limited conventional confocal microscopy, but become tractable when the resolution drops below 50 nm. While there are several approaches that can achieve super-resolution in optical microscopy, for use in a facility setting we favor the Stimulated Emission Depletion (STED) approach. In a STED microscope, fluorophores are first excited in a standard, diffraction-limited focal volume. Next, a second laser depletes the excited state everywhere except in a non-diffraction limited central spot. This smaller, remaining excited area is then used to scan the object with super-resolution. STED units can in principle be fitted to any microscope that could also be equipped with a confocal scanning unit. It is thus also possible to retrofit existing confocal systems with STED units, upgrading these microscopes to super-resolution capability. With the present application we therefore seek to acquire a STED unit that can be fitted to the base microscope of an existing core facility confocal. The upgraded microscope will offer standard confocal imaging and will, in STED mode, achieve < 40 nm lateral, two-dimensional resolution in real biological samples. The proposed upgraded microscope will extend the lifetime of the existing microscope for at least one more funding cycle. It will allow us to reuse most of the components, thus furthering the sustainability aims of the DFG and of the University. At the same time, it will equip the core facility with a long-awaited imaging modality covering an as yet unmet scientific need within the biomedical community.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Stimulated Emission Depletion (STED) Superresolutions-Modul für ein existierendes Konfokalmikroskop
• Instrumentation Group: 5090 Spezialmikroskope
• Applicant Institution: Universität Ulm
• Leader: Professor Dr. Gilbert Weidinger