Latest Derby Group publication:
Inkjet printing and cell seeding thermoreversible photocurable gel structures
Manuela Di Biase, Rachel E. Saunders, Nicola Tirelli and Brian Derby
Soft Matter, 2011, 7, 2639-2646, DOI: 10.1039/C0SM00996B
We have developed a biocompatible fluid suitable for inkjet delivery that gels by a tandem mechanism of a rapid physical gelation followed by a photoactivated chemical cross-linking. We prepared 20 vol% aqueous solutions of acrylate functionalised Pluronic F127, a poly(ethylene glycol-b-propylene glycol-b-ethylene glycol) (PEO–PPO), with triethanolamine and eosin Y as a photocurable cross-linker combination; poly(ethylene glycol) diacrylate was also added to the solution to improve the sol–gel transition. This fluid has a viscosity <20 mPa s at 5 °C and is suitable for inkjet printing. We used a piezoelectric drop-on-demand inkjet printer at this temperature to print single and multilayer structures on a substrate held at room temperature. The dimensions of the resulting structures are consistent with models developed for the interaction of overlapping drops. After photocrosslinking the resulting gel structures, which are stable in an aqueous environment, were successfully seeded with fibroblast cells also delivered by an inkjet printer.
Our review paper ‘Characterizing the Elastic Properties of Tissues’ was published this week in Materials Today (Volume 14, Issue 3 pp. 96-105 (March 2011):
Our work using nanoindentation to characterise the micromechanical properties of blood vessels has been published in this month’s special issue of Journal of Materials Research: Indentation Methods in Advanced Materials Research. The reference and abstract are below:
“Nanoindentation of histological specimens: Mapping the elastic properties of soft tissues”. R. Akhtar, N. Schwarzer, M.J. Sherratt, R.E.B. Watson, H.K. Graham, A.W. Trafford, P.M. Mummery, B. Derby, J. Mat. Res. 24, 638-646 (2009).
Although alterations in the gross mechanical properties of dynamic and compliant tissues have a major impact on human health and morbidity, there are no well-established techniques to characterize the micromechanical properties of tissues such as blood vessels and lungs. We have used nanoindentation to spatially map the micromechanical properties of 5 µm thick sections of ferret aorta and vena cava and to relate these mechanical properties to the histological distribution of fluorescent elastic fibers. To decouple the effect of the glass substrate on our analysis of the nanoindentation data, we have used the extended Oliver and Pharr method. The elastic modulus of the aorta decreased progressively from 35 MPa in the adventitial (outermost) layer to 8 MPa at the intimal (innermost) layer. In contrast, the vena cava was relatively stiff, with an elastic modulus >30 MPa in both the extracellular matrix-rich adventitial and intimal regions of the vessel. The central, highly cellularized, medial layer of the vena cava, however, had an invariant elastic modulus of ~20 MPa. In extracellular matrix-rich regions of the tissue, the elastic modulus, as determined by nanoindentation, was inversely correlated with elastic fiber density. Thus, we show it is possible to distinguish and spatially resolve differences in the micromechanical properties of large arteries and veins, which are related to the tissue microstructure.