Shape memory is an effect in which polymer chains
temporarily entangle holding the material in a set shape until the polymer is
heated above a specific rubber-glass transition temperature at which point the
polymer chains can move and the material naturally forms back into its original
shape. Recently, researchers at Johns Hopkins University purchased PLA (PolyVivo
AP004) from PolySciTech (www.polyscitech.com)
and used it to create a gold nanoparticle loaded microparticle which changes
from elongated shapes into spherical shapes when heated gently by exposure to
light. This research holds promise to create materials with tunable macrophage
uptake for a variety of biomedical applications. Read more: Guo, Qiongyu, Corey
J. Bishop, Randall A. Meyer, David R. Wilson, Lauren Olasov, Daphne E.
Schlesinger, Patrick T. Mather, James B. Spicer, Jennifer H. Elisseeff, and
Jordan J. Green. "Entanglement-Based Thermoplastic Shape Memory Polymeric
Particles with Photothermal Actuation for Biomedical Applications." ACS
Applied Materials & Interfaces (2018). https://pubs.acs.org/doi/abs/10.1021/acsami.8b01582
“Abstract: Triggering shape memory functionality under
clinical hyperthermia temperatures could enable the control and actuation of
shape memory systems in clinical practice. For this purpose, we developed
light-inducible shape memory microparticles composed of a poly (D,L-lactic
acid) (PDLLA) matrix encapsulating gold nanoparticles (Au@PDLLA hybrid
microparticles). This shape memory polymeric system for the first time
demonstrates the capability of maintaining an anisotropic shape at body
temperature with triggered shape memory effect back to a spherical shape at a
narrow temperature range above body temperature with a proper shape recovery
speed (37 ˚C < T < 45 ˚C). We applied a modified film-stretching
processing method with carefully controlled stretching temperature to enable
shape memory and anisotropy in these micron-sized particles. Accordingly, we
achieved purely entanglement-based shape memory response without chemical
crosslinks in the miniaturized shape memory system. Furthermore, these shape
memory microparticles exhibited light-induced spatiotemporal control of their
shape recovery using a laser to trigger photothermal heating of doped gold
nanoparticles. This shape memory system is composed of biocompatible components
and exhibits spatiotemporal controllability of its properties, demonstrating
potential for various biomedical applications, such as tuning macrophage
phagocytosis as demonstrated in this study.”
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