No abstract

Inkjet printing offers controlled placement of both biological and synthetic materials. The precision, control and small working volumes associated with inkjet printing are advantageous where biological materials such as proteins, enzymes and cells can incur high costs. This review is primarily technology focused and divides bioprinting into three categories of interest: proteins, cells and scaffolds and demonstrates that the logistical hurdles and material formulation requirements remain a common denominator to the advancement of the field into commercial applications and three-dimensional (3-D) constructs. A variety of cell types printed using thermal, piezoelectric and electrostatic actuation mechanisms yield 80-95% cell viability. Transient membrane damage is reported for cells printed using a thermal printer. Protein deposition by thermal and piezoelectric printing results in reversible deformation leading to an increased need for the addition of ink modifiers. The fluid characteristics and the drop substrate interactions are identified as crucial with regards to future applications. The current approaches to scaffold matrix selection with regards to the complex criterion require fluid and solid phases and a controlled phase change while maintaining the criterion for printing vary from chemical gelation, physical gelation mechanisms (e.g. thermo reversible gels) and tandem gelation.

No abstract

Solitons in laser physics.

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, poly(ethylene glycol-bl-propylene glycol-bl-ethylene glycol) (PEO-PPO) with triethanolamine and eosin-Y as a photocurable cross-linker; in order to minimise phase separation a small amount of polyethylene glycol diacrylate were added to the solution. This fluid has a viscosity < 20 mPas at 5 ºC 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 gels, which are stable in an aqueous environment, were successfully seeded with fibroblast cells also delivered by an inkjet printer.