Artificial biocomposites of silk fibroin and amyloid fibrils

Researchers have combined two widely-studied fibrous protein assemblies – silk fibroin fibrils and amyloid fibrils – into a novel composite material. By varying the weight ratio of the two components, mechanical properties could be tuned: more amyloid fibril increased tensile modulus whereas more silk fibroin promotes tougher composites. The amyloid component could be enzymatically removed to generate a porous silk membrane.  Inorganic components were also added and a shape memory effect observed.  

Modulating Materials by Orthogonally Oriented β-Strands: Composites of Amyloid and Silk Fibroin Fibrils; S. Ling et al; Advanced Materials; DOI: 10.1002/adma.201400730

http://onlinelibrary.wiley.com/doi/10.1002/adma.201400730/abstract

A shear stress threshold for angiogenesis

In vitro experiments using microfabricated microfluidic devices have revealed a threshold of shear stress from fluid flow above which endothelial cell monolayers sprout new blood vessels.  The shear stress also sustained the sprout and prevented vessel retraction.  Further experiments revealed that matrix metalloproteinase 1 expression increased dramatically at the shear threshold.  These findings offer a basic mechanism for regulating vessel densities in tissue modulated by other mechanical, geometric,and biochemical factors.

Fluid shear stress threshold regulates angiogenic sprouting; P.A.Galie et al; PNAS; doi:10.1073/pnas.1310842111

http://www.pnas.org/content/early/2014/05/16/1310842111.abstract

Mechanically functional engineered cartilage

Researchers have mimicked mesenchymal condensation using a cellular self-assembly method to successfully generate centimetre-sized anatomically-shaped cartilage from human mesenchymal stem cells.  The engineered tissue was stratified with physiologically relevant values of Young’s modulus and co-efficient of friction.  In vitro data suggested the method could be used to repair cartilage defects.

Large, stratified and mechanically functional human cartilage grown in vitro by mesenchymal condensation, S. Bhumiritana et al, PNAS, doi/10.1073/pnas.1324050111

http://www.pnas.org/content/early/2014/04/25/1324050111.full