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Madison, WI, United States

King W.J.,550 Engineering Drive | Murphy W.L.,550 Engineering Drive | Murphy W.L.,1300 University Avenue
Polymer Chemistry | Year: 2011

Hydrogels that respond to their environment have been extensively used as controlled drug delivery devices. An emerging trend is to form these "dynamic" hydrogels from polymers that undergo conformational changes. Indeed, nanometer scale polymer conformational changes have translated to macroscopic changes in hydrogel properties and controlled the release of encapsulated drugs. This review will focus on the mechanisms that control protein release from dynamic hydrogels. Specifically, we will highlight emerging mechanisms to form dynamic hydrogels, whose functional nature is derived from nature-inspired polymer conformational changes. Pertinent results from the literature will be examined to illustrate how these nanometer scale polymer conformational changes influence therapeutic protein release from dynamic hydrogels. © The Royal Society of Chemistry 2011.

Slane L.C.,550 Engineering Drive | Thelen D.G.,550 Engineering Drive | Thelen D.G.,1513 University Ave | Thelen D.G.,1300 University Ave
Medical Engineering and Physics | Year: 2015

The purpose of this study was to investigate middle-age effects on Achilles displacement patterns under passive stretch and eccentric loading. Healthy young (24.1±1.4 years, n=9) and middle-aged (49.0±3.1 years, n=9) adults were positioned prone and the ankle was cyclically dorsiflexed (0.5Hz, 25° range) during passive stretch and active lengthening. Achilles displacements were tracked in cine ultrasound using 2D speckle tracking. Displacements were found to be non-uniform, with mid and deep portions of the tendon displacing more than superficial portions. However, the degree of non-uniformity was significantly reduced in middle-aged adults, suggesting a potential age-related reduction in inter-fascicle sliding or a shift in loading sharing between plantarflexors. Eccentric loading reduced displacement magnitudes, likely reflecting distal tendon stretch induced via active muscle contractions. Changes in tendon displacement with active loading were greater in middle-aged adults, which could reflect greater tendon compliance. The observed age-related changes in Achilles tendon behavior may have implications for both plantarflexor performance and injury risk. © 2015 IPEM.

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