Sep 16, 2013
Nanotubes help turn stem cells into cartilage
Researchers at the George Washington University in the US have employed carbon nanotubes to modify polymeric scaffolds, add nanoscale surface roughness to these structures, and modulate their mechanical properties. The idea is that these nanotubes can be incorporated into existing polymer networks so that the scaffolds’ properties match the characteristics of the human tissue extracellular matrix (ECM), which makes up cartilage.
Joint injuries, especially those affecting cartilage, are notoriously hard to treat because cartilage cannot heal itself. For the past decade researchers have been looking at ways to regulate and control stem cell growth to help repair joints and cartilage. However, current stem cell based cartilage regeneration is still in its infancy because it is difficult to entice stem cells to remain in a desired tissue site and survive. It is also difficult to control their so-called chondrogenic differentiation.
Labs around the world have recently begun looking at innovative nanomaterials to create complex, biomimetic composites and structures called "scaffolds" that can support and direct how stem cells form, and eventually develop fully formed tissue. The idea is that these nanomaterials can mimic the physical and chemical characteristics of human tissue extracellular matrix (ECM), which provides a structural as well as functional framework for cell growth.
In their most recent study, the team, led by Lijie Grace Zhang and Michael Keidar used H2 purified multiwalled carbon nanotubes (MWCNTs) coated with poly-L-lysine in a biocompatible poly-L-lactic acid (PLLA) polymer to electrospin CNT doped microfibres for use in cartilage regeneration. The researchers found that scaffolds made from these fibres had mechanical properties that were virtually similar to native articulate cartilage.
More importantly, cell studies with human bone marrow derived stem cells showed that biomimetic nano/micro scaffolds made with H2 treated MWCNTs not only outperformed unpurified MWCNT scaffolds, but also greatly outperformed plain PLLA scaffolds. Stem cells not only grew better on H2 CNT scaffolds, but also regenerated more cartilage in two weeks. This means that CNT-modified polymer scaffolds could usher in a new era in cartilage tissue engineering, and foster a whole new class of nanocomposite materials for tissue regeneration and stem cell therapies.
More information can be found in the journal Nanotechnology 24 365102.
About the author
Benjamin Holmes is currently a PhD student in the Bioengineering Lab for Nanomedicine and Tissue Engineering at George Washington University. His research interests include nano- and micro-fabrication techniques, novel nanocomposite materials and 3D printing for stem cell based bone, cartilage and vascular regeneration. Dr Lijie Grace Zhang is the director of the Nanomedicine and Tissue Engineering lab at GWU. Her research areas include nanobiomaterials; bone, cartilage, osteochondral and neural tissue engineering; 3D bioprinting, stem cells and drug delivery. The CNT evaluations were performed in Dr Michael Keidar’s Micropropulsion and Nanotechnology Laboratory. His lab is actively investigating how to produce both carbon nanotubes and graphene and studying the properties of these materials.