More and more materials are developed for regenerative medicine purposes. However, understanding exactly how cells interact with biomaterials is still work in progress. One of the materials properties important in cell-material interaction is surface structure, and to study this, we developed the TopoChip (below). The TopoChip is a high-throughput platform to screen bio-active surface topographies for their effect on cellular processes.
In order to fit the application of interest, we can produce TopoChips from a wide of materials via a streamlined cleanroom production line. Furthermore, we have already shown the bio-active capacity of our defined surface topographies for many cell types and for diverse cellular processes. Using the TopoChip platform, we can identify ideal surface topographies for almost any application of interest, typically within weeks of experimental work. Completely from the in silico design, via in vitro screening and validation, all the way towards in vivo testing!
The TopoChip. Primitive shapes (circles, triangles, and rectangles) are used to design topographical features. Arrays of a unique topographical feature build a 290 × 290 μm square TopoUnit. The TopoChip contains 2176 unique surface topographies in duplicate and 4 unpatterned units.
Where the TopoChip is ideal for imaging based high-throughput screening, it lacks the possibility to retrieve biological material from the individual TopoUnits. Therefore we proposed to isolate TopoUnits and at the same time enlarge the topographically enhanced surface area in a tissue culture standard 96-well plate, the TopoWellPlate (below). With the TopoWellPlate, we are able to gather biological material from cell populations exposed to a single defined surface topography. So, both the cell lysates and metabolized cell culture medium can be used in the wealth of standardized molecular assays available.
The TopoWellPlate. Primitive shapes are used to create topographical features which are used to fill a TopoUnit. On the first generation of the TopoWellPlate, 87 different surface topographies are included that induced a broad spectrum of cell and nuclear morphologies.
In order to manipulate cells different than using strong confinements we created the NanoTopoChip on which nanometer-scale topographical features are used (below, left). Using the nano-topographies, we interact with cells on the level of their focal adhesion receptors which can create striking differences in cell morphology as well! (below, right) Numerous morphological reactions have been observed so far, ranging from cytoskeleton polymerization to extreme filopodia stretching and podosome formation.
The NanoTopoChip. Left) SEM images of nanometer-scale topographical features as found on the NanoTopoChip. Right) Fluorescence micrographs of U2OS cells cultured on two different surface topographies. Dramatic changes in cell morphology are observed in, for example, cytoskeleton organization (F-actin in gray, DNA in blue).
To allow identification of our 2176 unique topographies, we apply our own designed nomenclature. The topographies are duplicated on the TopoChip which gives rise to 4356 TopoUnits (including 3 flat surfaces) ordered in 66 rows and 66 columns. When we position the flat surface located at the edge of the TopoChip in the bottom right corner, the first 33 rows and 66 columns contain all unique topographical structures. This ordering allows us to use 4 digits, e.g. 0345, of which the first 2 designate the row and the last 2 the column. Our topographical surfaces can be imprinted on various materials, e.g. polystyrene (PS) or poly-lactic-acid (PLA). This is also taken into account into the nomenclature, whereby we denote the abbreviation of the material before the numbering. Furthermore, when a coating is applied to the imprinted material, we add an extra abbreviation after the abbreviation of the ground material. Let’s say a surface from the 3rd row and 45th column was imprinted on PLA and sputter coated with titanium, then the correct nomenclature would be: T2-PLA-Ti-0345. Here the T2 stands for the version of the TopoChip design.
Since this new nomenclature has only recently been developed, our previous publications do not implement this yet. For example, in our latest Biomaterials TopoChip publication by Hulshof et al. entitled "Mining for osteogenic surface topographies: In silico design to in vivo osseo-integration", we identified a number of interesting hit surfaces that correlated with cellular alkaline phosphatase (ALP) levels. These hit surfaces were simply denoted by numbers. Using the new nomenclature, they are now identified as follows:
ALP Top Hits:
ALP Low Hits:
Beijer et al., Adv Biosyst, 2017
Hulshof et al., Acta Biomater, 2017
Hulshof et al., Biomaterials, 2017