Piezoelectric poly-L-lactide (PLLA) films are highly applicable for designing soft electronics in biomedicine. However, due to a lack of reactive side-chain groups, PLLA is characterized by a chemically inert and hydrophobic surface. Although compatible with biological environments, this polymer has very poor interactions with cells. This work is the first report on piezoelectric PLLA films with hydrophilic surfaces. We performed a systematic study that correlated processing parameters (drawing ratio, drawing temperature, drawing rate) with postprocessing steps (annealing and etching) to produce active, hydrophilic, piezoelectric PLLA surfaces. During processing, the optimal drawing ratio, temperature and rate increase the crystallinity and crystallite size and provide chain orientation. Postprocessing annealing and etching afford further improvements in structural properties and optimized surface characteristics. Consequently, the resulting PLLA films possess piezoelectric properties in combination with hydrophilic surfaces and specifically patterned topography. Using this approach, we designed active PLLA films with high potential for strong interactions with cells in further biomedical applications, including exploring the effect of piezoelectricity on cell proliferation. This study provides novel insight into designing synthetic piezoelectric polymers with significantly improved interactions with cells and tissues, which are particularly important for their application in biomedicine.
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The authors are grateful to David Fabijan and Damjan Vengust, Advanced Materials Department, Jozef Stefan Institute, for the piezoelectric and Raman spectroscopy measurements, respectively. We also acknowledge the CENN Nanocenter for the use of the NTEGRA Spectra I confocal Raman spectrometer. The work has been funded by the Slovenian Research Agency (ARRS) (grants J2-8169 and PR-08338).
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Udovč, L., Spreitzer, M. & Vukomanović, M. Towards hydrophilic piezoelectric poly-L-lactide films: optimal processing, post-heat treatment and alkaline etching. Polym J 52, 299–311 (2020). https://doi.org/10.1038/s41428-019-0281-5