Electronic Theses and Dissertations


Allison Fetz



Date of Award


Document Type


Degree Name

Doctor of Philosophy


Biomedical Engineering

Committee Chair

Gary Bowlin

Committee Member

Marko Radic

Committee Member

Marie van der Merwe

Committee Member

Richard Smith


The neutrophil has long been acknowledged as an abundant responder to an implanted biomaterial, but its importance as a dynamic effector cell has only recently been realized. The neutrophil response is especially important for in situ tissue regeneration where acellular biomaterials must be populated by endogenous cells and guide the growth of new tissues. More specifically, the release of neutrophil extracellular traps (NETs), or extracellular chromatin structures decorated with toxic nuclear and granular components, can cause collateral tissue damage, uncontrolled inflammation, and fibrosis, thereby preventing functional tissue regeneration. Therefore, the purpose of this work was to investigate the role of neutrophils and their release of NETs in the potential for electrospun biomaterial-guided in situ tissue regeneration. We evaluate the hypothesis that NETs are released in response to electrospun biomaterials, governed by biomaterial design features, and further postulate that the release of NETs is intimately related to biomaterial surface-adsorbed proteins and outside-in signaling, which can be regulated by the local delivery of pharmacological additives. Using in vitro assays with primary human neutrophils and in vivo subcutaneous implant models, we found that both electrospun fiber size and composition regulate the in vitro and in vivo release of NETs. Additionally, we show that the up-regulation of NETs on an implanted biomaterial nucleates tissue fibrosis, demonstrating that NET release is a significant, physiological preconditioning event in guided tissue regeneration. Moreover, through the characterization and quantification of protein adsorption on the biomaterial surfaces, we found that IgG, ligation of fragment crystallizable domain receptor IIIb, and signaling through transforming growth factor beta-activated kinase 1 is involved in electrospun biomaterial-induced NET release. Finally, using drugs that inhibit two different molecular pathway targets, we showed that biomaterial-induced NETs can be regulated through the local delivery of active drugs in vitro and in vivo, improving tissue integration and promoting a pro-healing neutrophil phenotype. Together, the findings of this dissertation illustrate that the release of NETs is a significant preconditioning event on an electrospun biomaterial. Therefore, designing immunomodulatory biomaterials to regulate NET release and the neutrophil response may enhance in situ tissue regeneration and the clinical application of electrospun biomaterials.


Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest