JPK reports on the use of tip assisted optics to characterise biomolecular hydrogels at CIC biomaGUNE
CIC biomaGUNE is a non-profit research organisation created in 2006 to promote scientific research and technological innovation in the Basque Country.
Dr Ralf Richter leads Laboratory 3 in the Biosurfaces Research Unit applying a number of techniques for surface nanostructure characterisation and biofunctionalisation to guide the assembly of molecules down to the nanometer-scale.
For this characterisation, his group has developed a toolbox of biophysical in-situ techniques including a quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), reflection interference contrast microscopy (RICM), ellipsometry and fluorescence methods.
The current research work is centered on biomolecular hydrogels, a broad class of materials that are produced in the human body or by other bioorganisms.
They are assembled from proteins and glycans. They are typically very soft and contain a lot of water. Even though biomolecular hydrogels play crucial roles in many fundamental biological processes, we lack understanding about how they function.
Of particular interest for the group’s research are cellular coats that are rich in the polysaccharide hyaluronan which are important in processes such as fertilisation, osteoarthritis and inflammation.
Dr Richter’s group develops methods to re-create these specialized natural hydrogels through the controlled assembly from their molecular components in vitro.
Functionalised surfaces are used to guide the self-assembly process. The resulting model films have the advantage that they can be better controlled and studied in much greater detail than the original materials.
By doing so, the hope is to understand the fundamental mechanisms behind the assembly and functions of biomolecular hydrogels.
While AFM is used to obtain nanoscale topographic information about the self-assembled architecture of the materials created, AFM is also used to quantify the mechanical properties of these hydrogels.
Dr Richter explains: “We employ colloidal probe AFM. When analysing polymer films, a fundamental problem in colloidal probe AFM experiments is to determine the distance at closest approach between the probe and the substrate on which the film is deposited.
“In a study published earlier this year (Attili & Richter, Langmuir, 2012, 28:3206) we have overcome this problem by combining optical interferometry (RICM) and AFM in situ.
“With the combined setup, forces and absolute distances between substrate and probe can be measured at the same time. Thanks to its tip-assisted optics (TAO) module and the integration of high-resolution optical microscopy, the combination of RICM and AFM can be readily setup with the JPK NanoWizard system.”