21. April 2015
Lu Shin Wong, University of Manchester, Invited Talk at the Biomaterials Seminar Glasgow: New Materials for Cell & Molecular Biology by Scanning Probe Microscopy
Wouldn't it be nice to know how cells interact with materials, what chemical surface features could be used to control stem cell differentiation?
Controlling at the nanoscale the exact composition and structure of the interface where materials stop and the environment starts is what Lu's talk was all about. Dip Pen Nanolithography was initially developed as an application of atomic force microscopy to write at the nanoscale. As technology has moved on it is now possible to print large areas with nanometer resolution using to good effect a modification of dip pen nanolithography applying the materials of micro-contact printing. The main tool that Lu's group uses is a 'potato-stamp', made of a soft polymer - with thousands of nanometric pyramids. The arrangement, and the shape of the pyramids define the printed features (shape, spacing and arrangement of printed spots). This process allows to print effectively over large areas (square cms) with high throughput. A lot of thought and development went into the 'inks' that are applied to the surfaces, to allow writing onto different materials, and to allow defined chemical modifications at the exposed parts of the inks. To have contrast between the written and the background a backfilling technique with self assembling monolayers of polyethylene glycol is used. As the parameter space for pattern, chemistry, and cells is substantial gradients are a good way to minimise the time to screen for the best possible throughput. To achieve a spot size gradient his group "simply" tilted the stamp when printing - as the soft material gets squashed, when pressed in, the pyramids that hit the surface first will leave a larger spot behind. The optimised patterns were then tested for effectiveness in supporting mesenchymal stem cell differentiation. The nano-patterned substrates were better at supporting osteogenic differentiation than larger, or uniformly coated ones. The limits for the spotsize is the tip of the cantilever and the contact angles of the liquid that suspends the ink (90nm), to overcome this a gold-micelle ink was developed that allowed to write gold (Au) nanoparticles as small as 4nm. The nanoparticle ink could be tuned to enable the group to create single molecule arrays. This not only works for adhesion moieties but also for functional enzymes.
In the last part Lu talked about current, unpublished work on dynamic hydrogels to study durotaxis, here he started off with earlier work on cells responses to local differences in substrate stiffness (e.g. see Joe Swift's talk).
More about Lu Shin Wong: http://www.manchester.ac.uk/research/l.s.wong/
Lu Shin Wong, University of Manchester, Invited Talk at the Biomaterials Seminar Glasgow: New Materials for Cell & Molecular Biology by Scanning Probe Microscopy
Wouldn't it be nice to know how cells interact with materials, what chemical surface features could be used to control stem cell differentiation?
Controlling at the nanoscale the exact composition and structure of the interface where materials stop and the environment starts is what Lu's talk was all about. Dip Pen Nanolithography was initially developed as an application of atomic force microscopy to write at the nanoscale. As technology has moved on it is now possible to print large areas with nanometer resolution using to good effect a modification of dip pen nanolithography applying the materials of micro-contact printing. The main tool that Lu's group uses is a 'potato-stamp', made of a soft polymer - with thousands of nanometric pyramids. The arrangement, and the shape of the pyramids define the printed features (shape, spacing and arrangement of printed spots). This process allows to print effectively over large areas (square cms) with high throughput. A lot of thought and development went into the 'inks' that are applied to the surfaces, to allow writing onto different materials, and to allow defined chemical modifications at the exposed parts of the inks. To have contrast between the written and the background a backfilling technique with self assembling monolayers of polyethylene glycol is used. As the parameter space for pattern, chemistry, and cells is substantial gradients are a good way to minimise the time to screen for the best possible throughput. To achieve a spot size gradient his group "simply" tilted the stamp when printing - as the soft material gets squashed, when pressed in, the pyramids that hit the surface first will leave a larger spot behind. The optimised patterns were then tested for effectiveness in supporting mesenchymal stem cell differentiation. The nano-patterned substrates were better at supporting osteogenic differentiation than larger, or uniformly coated ones. The limits for the spotsize is the tip of the cantilever and the contact angles of the liquid that suspends the ink (90nm), to overcome this a gold-micelle ink was developed that allowed to write gold (Au) nanoparticles as small as 4nm. The nanoparticle ink could be tuned to enable the group to create single molecule arrays. This not only works for adhesion moieties but also for functional enzymes.
In the last part Lu talked about current, unpublished work on dynamic hydrogels to study durotaxis, here he started off with earlier work on cells responses to local differences in substrate stiffness (e.g. see Joe Swift's talk).
More about Lu Shin Wong: http://www.manchester.ac.uk/research/l.s.wong/