Tissue engineering is a field devoted to the design and creation of replacementtissues with the ultimate goal of one day providing replacement organs. Traditionalstrategies to accomplish this through the bulk seeding of cells onto a singlemonolithic porous bio-scaffold are unable to realise a precise architecture, thusthe inability to mimic the cells natural micro-environment found within the body.Bio-printing approaches are the current state of the art with the ability toaccurately mimic the complex 3D hierarchical structure of tissue. However, afunctional construct also requires high strength to provide adequate support inload bearing applications such as bone and cartilage tissue engineering, and tomaintain the open geometry of a large intricate channel network, which is crucialfor the transport of nutrients and wastes. Typical approaches utilise materialswhich have processing parameters more amendable for cell incorporation, thusthey can be simultaneously deposited with scaffolding material. However, theresulting construct is typically of low strength.This thesis explores the automation of a printing and “tissue assembly” processwith the ability to incorporate delicate cell aggregates or spheroids within a highstrength bio-scaffold requiring harsh processing parameters, at precise locations.The 3D printed bio-scaffold has a lattice architecture which enables a frictional fitto be formed between the particle and scaffold, thus preventing egress. To achievethis the pore must be expanded before the delivery of a single 1mm particle.Novel subsystems were developed to automate this process and provide the abilityto achieve scalable, flexible, complex constructs with accurate architecture.A system architecture employing the benefits of modularity was devised. Themain subsystems developed were the singulation device, to ensure the separationof a single particle; the injection device, to deliver and seed particles into thescaffold, and the control system, to facilitate the operation of the devices.Three generations of singulation devices have been developed ranging frommechanical to fluid manipulation methods alone. The first prototype utilisedmechanical methods, with simple control methods. However the inability tocorrectly position the lead particle within the singulation chamber, resulted indamage to the test alginate particles. In the second prototype a fully fluidics baseddevice utilised two trapping sites to capture the leading particles. Singulationsuccess rates of up to 88% was achieved. Higher rates were limited by the trappedparticle’s interaction with the lagging particles during capture. In a similarconcept to the second prototype, the third prototype utilised only a single trappedparticle, and achieved much higher throughput, and 100% singulation accuracy.The injection device, utilised a conical expanding rod within a thin outersheath. It was able to expand the pore, with minimal damage to the scaffold,providing an unobstructed path for the delivery of the particle into the pore.A decentralised control system was devised to integrate the process operationfor the electro-mechanical devices. Separate microcontrollers were able to sense,interact and communicate with one another, and the master control PC, to executespecific tasks to automate the process.The development of systems to automate the process has addressed theability to accurately incorporate delicate cells with a high strength bio-scaffold,and will enable the realisation and investigation of intricate complex constructs,unachievable with current manual processes. Thus features found within thebody may be more closely mimicked and functionalised, which may provide thenecessary signals, micro-environment and infrastructure to correctly regulate theformation of complex functional tissue, supported by the adequate mass transportof nutrients and wastes. This may one day lead to 3D printing or assembly ofviable replacement tissue, accurate in vitro model systems for laboratory testing,or even whole organs.
展开▼
