Cells use molecules to exchange information. A very prominent example is signaling between neurons, inflammation or stress signaling in plants. However, it is up to date difficult to quantify these processes with high spatial, temporal and chemical resolution. Our goal is to develop optical tools that access this information and understand how it is processed. I will present two topics that showcase recent insights from my group:
We use nanomaterials that fluoresce in the near infrared (NIR) tissue transparency window, which offers ultra-low background and high tissue penetration. For example, we have developed multiple NIR fluorescent sensors based on single-walled carbon nanotubes (SWCNTs). They are chemically modified to render them selective for important biomolecules (dopamine, serotonin, ROS) or motifs characteristic for specific cells or pathogens (siderophores, spike protein). I will showcase the potential of these fluorescent sensors in different biomedical scenarios. Fast parallel imaging of many of those sensors provides NIR images (>900 nm) of signaling molecules around single cells. This technique was used to image dopamine release from neurons as well as serotonin and ROS release from human blood platelets. Moreover, such sensors can also be used to identify pathogens such as bacteria based on their chemical fingerprint. They further enable remote imaging of plant stress and pathogen-related responses in plants. Additionally, I will show concepts such as spectral multiplexing, fluorescence lifetime imaging and NIR detection with lowcost optical setups that further push the limits. These results illustrate that near infrared fluorescent sensors are powerful tools for quantitative chemical imaging.
Immune cells constantly process extracellular information to decide which effector functions are used. For example, neutrophilic granulocytes can release their own DNA as neutrophil extracellular traps (NETs) to capture and eliminate pathogens (NETosis) but dysregulated NETosis has been implicated in many diseases. During NETosis, neutrophils undergo dynamic and dramatic alterations of their cellular as well as subcellular morphology. I will show that entropic chromatin swelling is the major physical driving force that causes cell morphology changes and the rupture of both nuclear envelope and plasma membrane. Through its material properties, chromatin thus directly orchestrates this complex biological process. Furthermore, adhesion, light and certain signaling molecules affect NETosis, which shows well-orchestrated computation of extracellular signals by these cells.
