Research group  leaders at the BBZ:  Prof. Dr. Mareike Zink  

Research group
leaders at the BBZ:
Prof. Dr. Mareike Zink

Research Topics

Mechanical Properties of the Retina
Mechanical spectroscopy: tissue & protein mechanics at the molecular level
Quantitative analysis of contractile cell forces
Interaction of cells with ferromagnetic shape memory alloys

Mechanical Properties of the Retina

TiO2 nanotube arrays (upper right and lower left) with tuneable surface morphology offer ideal conditions for culturing adult retinal explants (upper left) and adult brain slices (lower right). Even after two weeks the neuronal tissue struc

The mechanical properties of neuronal tissue determine their function and the interaction of cells. Even adult tissue such as the human retina is still under mechanical tension, which can cause severe problems during surgery. Moreover, changes in cell and tissue elasticity during eye diseases, such as macular degeneration, can result in tissue rupture and blindness. Aim or our research is a better understanding of the global mechanical properties of retinal tissue and how local heterogeneities might influence the entire tissue elasticity. To this end, we employ nanotube array substrates, whose interaction properties with individual cells and the overall tissue can be tuned by the tube parameters. We showed for the first time that adult retinal tissue can be successfully cultured longer than 14 days with no indications of degeneration. These substrates are used to strain retinal tissues and investigate their mechanical response to external stresses. Together with the application of different drugs, our research will pave the way for new therapeutic approaches of eye diseases from a materials science perspective.

Television feature of MDR (Mitteldeutscher Rundfunk) from 8.3.2017
(only in german)

Link to radio feature of MDR (Mitteldeutsche Rundfunk ) from 8.3.2017

Mechanical spectroscopy: tissue & protein mechanics at molecular level

We employ freely oscillating cantilevers composed of nanostructured TiO2 scaffolds to study the frequency-dependent mechanical response of adult mammalian retina explants at the nanoscale. Within a self-designed mechanical spectroscopy setup, the reed with a retina explant on top is excited to perform free damped oscillations. The detected oscillation parameters represent a fingerprint of the frequency-dependent mechanical tissue properties that are derived in combination with sandwich beam analysis and finite element calculations. We found that the Young’s modulus of the retina is of the order of a few GPa, much higher than values obtained from experiments in which tissue response is investigated on micrometer length scales. In our study, polymers and proteins on the photoreceptor side of the retina in contact with the nanostructured reed are stretched and compressed during vibration of the underlying scaffold and the acting intramolecular forces are probed at the protein level. In fact, the Young’s moduli of proteins from serum – a major component of the used tissue culture medium – are about 16 times higher compared to the modulus of the TiO2 nanostructure when probed at the nanoscale (38 GPa vs. 2 GPa). To this end, our mechanical spectroscopy approach offers new perspectives in probing mechanical response of individual proteins within the tissue for studying tissue mechanics, diseases and the effect of drugs.

*Mechanical Spectroscopy of retina tissue:
Free damped oscillation of the TiO2 nanotube scaffold with the tissue explant placed on top (left). The scaffold which acts as a vibrating reed is fixed at one end. A lever presses the flexible end down to excite the reed to oscillate freely. A laser beam is reflected on a silicon plate attached to the reed’s bottom to a position sensing detector (PSD) which records the oscillation (the magnification showing the first 14 oscillations) as a voltage change during time (right).

Quantitative analysis of contractile cell forces

Cells require adhesion to survive, proliferate and migrate, as well as for wound healing and many other functions. The strength of contractile cell forces on an underlying surface is a highly relevant quantity to measure the affinity of cells to a rigid surface with and without coating. By employing a self-designed setup, we show that these forces create surface stresses that are sufficient to induce measurable bending of macroscopic cantilevers. In detail, a metal cantilever with and without coatings is employed as substrate for NIH 3T3 fibroblast cells. Prior to measurements, cells are seeded onto the cantilever and adhered, which results in a stress acting onto the cantilever. The resulting cantilever bending is determined with a laser beam reflected on the cantilever’s bottom and monitored with a position sensitive detector (PSD). Subsequently, trypsin is added to the cells to detach them. Consequently, contractile cell forces are not acting on the cantilever anymore and it relaxes to its initial without cells. For quantitative analysis, we perform finite element simulations on the beam bending to back up the calculation of contractile forces from cantilever bending under non-homogenous surface stress. Our investigations show that contractile forces are a measure of bioactivity of the underlying cantilever material.
Currently, we are investigating contractile forces of cancerous and metastatic cells. Here active contractions are supposed to play a major role in overcoming tumor boundaries and migration towards the lymph and blood vessels. However, a quantitative analysis of the acting forces is lacking so far.

Interaction of cells with ferromagnetic shape memory alloys

NIH 3T3 mouse fibroblast cells on RGD-coated Fe70Pd30 ferromagnetic shape memory alloys thin film.

Recent decades have seen a huge turn in implantology and biomaterial development towards regenerative medicine. The approach in orthopedic surgery is no longer to just replace damaged tissue by a passive implant that evokes the least possible interference with biological tissue, but rather to provide active stimulation and actuation. Ferromagnetic shape memory alloys (FSMAs) have received great attention recently as an exciting class of smart functional materials with great potential for medical applications. In comparison to conventional shape memory alloys, FSMA bear the significant potential for miniaturized devices for single cell actuation which is capable of yielding magnetically controllable shear strains and/or volume dilations of several percent, thus perfectly matching the requirements of cell investigations. However, biocompatibility of this material remains to be confirmed. We investigate biocompatibility and adhesive properties of different cell types, such as fibroblast, osteoblast and epithelial cells, on vapor-deposited single crystalline Fe70Pd30 thin films and roughness graded polycrystalline splat-quenched samples, synthesized by the group of Prof. Mayr, IOM Leipzig. In fact, proliferation, adhesion and morphology are assessed on substrates coated with different adhesive agents, such as fibronectin, laminin and poly-L-lysine, as well as RGD peptides. Additionally, the cytoskeletal arrangements, as well as focal contacts of the cells are examined using confocal laser scanning microscopy. FSMA films with roughness graded surfaces are employed to furthermore investigate possible influences of substrate morphology on cell adhesion and viability. We show that these three cell types obtain the ability to spread and proliferate well on Fe70Pd30 FSMA substrates, demonstrating good biocompatibility and bioactivity of the films for future application in medical devices.


last update: 16.10.2017 

Contact

Prof. Dr. Mareike Zink
Universität Leipzig
Fakultät für Physik und Geowissenschaften
Soft Matter Physics Division
Linnéstr. 5
04103 Leipzig

Phone: +49 341 97-32573
Fax: +49 341 97-32479
E-Mail

Logo EFRE
Logo EFRE
pages