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Agent-basedmodels (ABMs) provide a flexible multilayer platformfor incorporating various modeling techniques into a single hybridmodel for designing optimal biomaterial scaffolds for angiogenesisin tissue engineering applications. Scaffold geometrical variablesare considered as design variables. The growth-factor concentrationprofile is the only process variable considered in this study. Theproduct variables used to illustrate the combined effects of scaffolddesign variables and process variables on the outcome of angiogenesisinclude the density and depth of capillary invasion within the scaffold.The scaffold design process and the ABM developed to simulate angiogenesisare described in this article. The performance of the ABM and thevascularization of the polymer scaffolds are evaluated by simulationstudies. The effects of pore size, pore size distribution, and interconnectivityon the total blood vessel length, invasion depth, and total numberof sprouts formed during the vascularization process are reported.The integration of the simulation of angiogenesis with ABMs and scaffolddesign techniques provides an iterative process for designing optimalscaffold structures. Such an approach facilitates faster design ofoptimized scaffolds with significantly less cost and enables betterunderstanding of the mechanisms of angiogenesis of polymer scaffoldsfor tissue engineering applications. [ABSTRACT FROM AUTHOR]

Alginate hydrogels have been used for a broad variety of medical applications. The ability to assemble alginate gels at neutral pH and mild temperatures makes alginate a promising choice for the encapsulation and delivery of cells and proteins. This chapter covers the basics of cell encapsulation and protein delivery using two different variations of alginate microbeads, single layered and multilayer systems. The first section describes a method for encapsulating cells within alginate microbeads coated with a permselective polymer layer. The second section describes a multilayer alginate microbead system that allows simultaneous encapsulation of cells and delivery of growth factors. The primary goal of the systems described is for encapsulation of islets as a treatment for type I diabetes. However, these microbeads can be used for a broad variety of applications in tissue engineering, cell encapsulation, and regenerative medicine.

Mesenchymal stem cells (MSC) have shown promise in tissue engineering applications due to their potential for differentiating into mesenchymal tissues such as osteocytes, chondrocytes, and adipocytes and releasing proteins to promote tissue regeneration. One application involves seeding MSCs in biomaterial scaffolds to promote osteogenesis in the repair of bone defects following implantation. However, predicting in vivo survival and differentiation of MSCs in biomaterials is challenging. Rapid and stable vascularization of scaffolds is required to supply nutrients and oxygen that MSCs need to survive as well as to go through osteogenic differentiation. The objective of this study is to develop an agent-based model and simulator that can be used to investigate the effects of using gradient growth factors on survival and differentiation of MSCs seeded in scaffolds. An agent-based model is developed to simulate the MSC behavior. The effect of vascular endothelial growth factor (VEGF) and bone morphogenic protein-2 (BMP-2) on both survival and osteogenic differentiation is studied. Results showed that the survival ratio of MSCs can be enhanced by increasing VEGF concentration. BMP-2 caused a slight increase on survival ratio. Osteogenesis strongly depends on the VEGF concentration as well because of its effect on vascularization. BMP-2 increased the osteogenic differentiation of MSCs.