Controlled Microchannelling in Dense Collagen Scaffolds by Soluble Phosphate Glass Fibers

Abstract

A problem with tissue engineering scaffolds is maintaining seeded cell viability and function due to limitations of oxygen and nutrient transfer. An approach to maintain suitable oxygen concentrations throughout the scaffold would be to controllably incorporate microchannelling within these scaffolds. This study investigated the incorporation of unidirectionally aligned soluble phosphate based glass fibers (PGF) into dense collagen scaffolds. PGF are degradable, and their degradation can be controlled through their chemistry and dimensions. Plastic compression was used to produce composite scaffolds at three different weight percentage while maintaining greater than 80% resident cell viability. PGF-collagen scaffold composition was quantified through thermogravimetric analysis as well as being morphologically and mechanically characterized. PGF degradation was measured through ion chromatography, and channel formation was verified with ultrasound imaging and SEM. The free movement of coated microbubble agents confirmed the channels to be continuous in nature and of 30-40 microm diameter. These microchannels in dense native collagen matrices could play an important role in hypoxia/perfusion limitations and also in the transportation of nutrients and potentially forming blood vessels through dense implants.

Rheological characterization of the nucleus pulposus and dense collagen scaffolds intended for functional replacement

“…21 Our technique of plastic compression differs from earlier studies, because we use cell culture inserts with 3 mm pores to reduce the liquid content instead of nylon and stainless steel meshes. [7][8][9][10]21 Furthermore, the dimensions of our scaffolds are much larger than reported earlier and the compression times therefore longer. The latter reduces the attractivity to enrich scaffolds with cells, which should not easily survive in such large constructs.…”

“…The latter reduces the attractivity to enrich scaffolds with cells, which should not easily survive in such large constructs. 10 To our knowledge, a detailed rheological characterization of dense collagen I scaffolds, as in the current study, has not been reported previously in literature. With our dense collagen scaffolds, we are able to approach the viscoelastic properties of the NP, in particular its elasticity.…”

“…Plastic compression of collagen solutions leads to significant densification and viscoelastic properties that closely approach those of skeletal tissue and has already been investigated for its potential in cartilage and bone engineering. [7][8][9][10] In the current study, we characterize the viscoelastic properties of the NP by rheology, 11,12 and screen dense collagen type I scaffolds to determine which collagen density matches to these properties. Our overall scope is to develop a collagen scaffold that could be used in in situ therapy in patients with a herniated NP.…”

Engineering stable topography in dense bio-mimetic 3D collagen scaffolds

“…largely irreversible) deformation as fl uid is forced out of the collagen fi bril network, and predictably the same plastic (non-elastic) deformation should occur at the micron scale around structures pressed into the surface. This process also leaves stable micro-channels running through the bulk of the material where embedded phosphate glass fi bres dissolve (Nazhat et al, 2007). However, the fl uid fl ow out of such gels and eventual collagen distribution during PC are by no means homogeneous (Hadjipanayi et al, 2011), and this study clearly shows that topographic patterning can be signifi cantly infl uenced by these local factors.…”

Cell encapsulation using biopolymer gels for regenerative medicine

“…A concern when increasing the collagen content of the hydrogel is that diffusion of nutrients and waste products through the scaffold would not be sufficient to maintain cell viability over extended periods of time. To address this problem Nazhat et al (2007) incorporated micro-channels into the gels using soluble phosphate glass fibres and after 24 h the cell viability of encapsulated fibroblasts was seen to be greater than 80%.…”