Date of Award

2017

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Biomedical Engineering (PhD)

Administrative Home Department

Department of Biomedical Engineering

Advisor 1

Bruce P. Lee

Committee Member 1

Jingfeng Jiang

Committee Member 2

Megan C. Frost

Committee Member 3

Qingli Dai

Abstract

The structure of catechol is found in mussel adhesive proteins and contributed to both wet-resistant adhesion and cohesive curing of these proteins. A synthetic nano-silicate, Laponite was incorporated into catechol-containing hydrogels and the hydrogel network-bound catechol formed strong reversible interfacial interaction with Laponite. The contribution of incorporated catechol-Laponite reversible interfacial interactions to the mechanics of hydrogels constructed by different strategies was studied. In the first strategy, Laponite and catechol were introduced into the double network hydrogel (DN) via the free radical co-polymerization of a catechol-containing monomer, backbone monomer, and crosslinker. The introduction of catechol-Laponite interactions significantly improved the compressive strength and toughness of DN without compromising the compliance of the hydrogel and enabled the DN’s ability to recover its mechanical properties during successive loading cycles. In the second strategy, Laponite was combined with an catechol-modified 4-armed poly(ethylene glycol)-based adhesive, which cured in the present of an oxidative catalyst, sodium periodate, to form an injectable naoncomposite tissue adhesive hydrogel. The addition of up to 2 wt% Laponite significantly reduced the cure time, enhanced the bulk mechanical and adhesive properties of the adhesive due to strong catechol-Laponite interfacial binding. Additionally, subcutaneous implantation result showed that incorporation of Laponite effectively promote cell infiltration into the nanocomposite hydrogel, providing a simple way to improve the bioactivity of a bio-inert, synthetic poly(ethylene glycol)-based adhesive. On the basis of the second strategy, higher concentration of Laponite was combined with catechol-modified 6- and 8-armed PEG-based adhesive to form a nanocomposite hydrogel without introducing additional oxidative catalyst in the third strategy. This hydrogel underwent unique dynamic crosslinking process. At early stage it recovered to its original stiffness immediately after failure induced by shear strain up to 1000% interactions and could be reshaped to adhere to the contour of tissue due to the catechol-Laponite interactions and loosely chemically crosslinked network structure, respectively. The hydrogel gradually transformed to a densely chemically crosslinked network meanwhile fixed its shape as tissue sealant. This dissertation provided an insight of exploiting mussel-inspired chemistry in designing a hydrogel with specific materials property.

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