Spider Silk Nanostructuring and its Applications for Tissue Engineering
Time: Fri 2021-03-26 13.00
Location: zoom link for online defense (English)
Subject area: Electrical Engineering
Doctoral student: Linnea Gustafsson , Mikro- och nanosystemteknik
Opponent: Professor David Kaplan, Tufts University, Massachusetts, USA
Supervisor: Professor Wouter van der Wijngaart, Mikro- och nanosystemteknik, Signaler, sensorer och system
This thesis introduces new ways to produce micro-and nanostructures of recombinant spider silk and explores ways to characterize their topography, mechanical properties, cell compatibility, and permeability. The suitability of the formed structures for applications within tissue engineering, primarily in vitro tissue modeling, is also investigated.
One big challenge in drug development is that many drug candidates fail to pass in vivo studies in humans. This is largely because the currently used animal models fail to emulate the full human condition. Therefore, researchers aim to develop in vitro models of various tissues using human cells. These new systems will allow studies of biological responses and mechanisms related to human health and disease. To accurately represent what happens in the body, the materials used for cell culture should as closely as possible mimic their in vivo counterparts. Many of the materials used today are made out of plastic and lack physiologically relevant properties, and do not replicate the micro-and nano dimensions present in the native cell environment.
Spider silk has been suggested as a suitable replacement material for cell culture. The usage of spider silk for medical purposes is not new; it was used already in ancient Greece and Rome to staunch wounds. However, the spider's limited production has haltered the applicability. Lately, new doors have opened up through recombinant production of the base constituent of silk: the spider silk protein (spidroin). Recombinant spidroin production is not only scalable but also allows for facile integration of additional biofunctionality. With this building material at hand, it is possible to produce other formats than spider silk fibers, i.e., coatings, films, membranes, hydrogels, porous scaffolds, and microparticles.
With the work presented in this thesis, the list is extended through the introduction of new methods to produce nanomembranes and uniformly shaped micro-and nanostructures by manipulating the liquid:air interface. Micropatterned mm-sized films, microfilms, nanochains, and nanowires were produced by manipulating a droplet of soluble spidroin solution on a superhydrophobic surface. Alterations in the concentration of spidroins, the motion of the droplet, and the dimensions of the pillars allow for precise control of the silk formation. The formed silk structures retained their shape upon release from the surface, and the culture of mammalian cells showed good compatibility with the silk structures. Nanofibrillar spider silk membranes mimicking the dimensions of basal membranes (280 nm thick) were formed by letting spidroins self-assemble at the liquid:air interface of a standing solution. The assembly time, initial spidroin concentration, and beaker size are directly related to the membrane's thickness and size. The thereby obtained membranes were stable, had an internal nanofibrillar structure, could stretch over 200%, and were permeable to human plasma proteins. An in vitro blood vessel model was established by growing human endothelial cells and smooth muscle cells on opposing sides of the membrane, showing the potential of using the membranes for further in vitro modeling