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Marija Vukomanović,* Lea Gazvoda, Mario Kurtjak, Marjeta Maček-Kržmanc,
Matjaž Spreitzer, Qiao Tang, Jiang Wu, Hao Ye, Xiangzhong Chen, Michele Mattera,
Josep Puigmartí-Luis, and Salvador Vidal Pane
Poly-L-lactide (PLLA) offers a unique possibility for processing into biocompatible,
biodegradable, and implantable piezoelectric structures. With such
properties, PLLA has potential to be used as an advanced tool for mimicking
biophysical processes that naturally occur during the self-repair of wounds
and damaged tissues, including electrostimulated regeneration. The piezoelectricity
of PLLA strongly depends on the possibility of controlling its
crystallinity and molecular orientation. Here, it is shown that modifying PLLA
with a small amount (1 wt%) of crystalline filler particles with a high aspect
ratio, which act as nucleating agents during drawing-induced crystallization,
promotes the formation of highly crystalline and oriented PLLA structures.
This increases their piezoelectricity, and the filler-modified PLLA films provide
a 20-fold larger voltage output than nonmodified PLLA during ultrasound
(US)-assisted activation. With 99% PLLA content, the ability of the films to
produce reactive oxygen species (ROS) and increase the local temperature
during interactions with US is shown to be very low. US-assisted piezostimulation
of adherent cells directly attach to their surface (such as skin keratinocytes),
stimulate cytoskeleton formation, and as a result cells elongate and
orient themselves in a specific direction that align with the direction of PLLA
film drawing and PLLA dipole orientation.
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