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Description
Introduction
Biodegradable and piezoelectric poly(L-lactide) (PLLA) is gaining attention for biomedical applications, especially in the field of tissue regeneration, based on piezoelectrically-induced electrical cell stimulation. (1,2) However, PLLA possess weaker piezoelectric properties than non-biodegradable poly(vinylidene fluoride) PVDF. (3) Enhancing PLLA’s piezoelectricity can be achieved by incorporating biocompatible piezoelectric ceramics barium titanate (BTO) nanoparticles (NPs). (4) However, the high stiffness of ceramic BTO nanoparticle limits stress transfer efficiency and thus piezoelectric effect. This might be overcome by polydopamine (PDA) coating of the BTO NPs (cBTO), what has been shown to increase the piezoelectric response of PVDF nanocomposites. (5) Since for piezoelectric PLLA-based nanocomposites it remains unexplored, this study investigates the piezoelectric improvement of PLLA/cBTO nanocomposite scaffolds due to cBTO NPs.
Materials and Methods
PLLA/cBTO nanocomposite scaffolds with 5 wt.% cBTO NPs of a size of about 50 nm (cat#745952) were electrospun with a drum collector and subsequently post-annealed. PDA-coating on BTO NPs and nanocomposite were examined by XPS and TGA. The fiber morphology was examined by SEM. The degree of crystallinity was determined by DSC and the crystal orientation was assessed by WAXS. Piezoelectric properties of a were examined by PFM and an impact system. Cytocompatibility was assessed via fibroblast metabolic activity.
Results and Discussion
Piezoelectric Enhancement of PLLA/cBTO Nanocomposite Scaffolds: The PFM measurement confirmed piezoelectric behaviour of nanocomposite fibers, depicted in (Figure 1). Moreover, the piezoelectric impact test showed that post-spun annealed PLLA/cBTO nanocomposite scaffolds exhibited the highest voltage output, 2.2 times higher than pristine PLLA and 1.6 times higher than PLLA/BTO scaffolds. PDA coating on BTO NPs improved matrix-particle adhesion, optimizing force transfer and reducing interface defects and thus increasing the piezoelectric response. The improvement in piezoelectricity of PLLA by 120 % due to cBTO NPs is a breakthrough for biomedical applications, particularly tissue regeneration, energy harvesting, ultrasonic transducers, and implantable sensors. The enhanced voltage output (3.2 V) surpasses that of previous PLLA scaffolds used for cartilage regeneration. (1)
Piezoelectric Chain Morphology: High chain orientation, crystal orientation, and a high degree of crystallinity are key factors to induce piezoelectric properties of PLLA matrix. DSC analysis confirmed that all post-spun annealed scaffolds had a similar high degree of crystallinity and 2D WAXS pattern confirmed similar high crystal orientation in all scaffolds.
Conclusions
The present work introduced a new approach to enhancing the piezoelectric properties of PLLA by cBTO NPs. The incorporation of cBTO NPs led to a significant increase in piezoelectric response of PLLA/cBTO nanocomposite scaffold maintaining great cytocompatibility.
References:
(1) Liu Y. et al, 2022, 10.1126/scitranslmed.abi7282
(2) Das R. et al, 2023, 10.1016/j.biomaterials.2023.122270
(3) Smith M. et al, 2021,10.1080/09506608.2021.1915935
(4) Dai X. et al, 2022, 10.2147/IJN.S378422
(5) Su Y. et al, 2021, 10.1016/j.nanoen.2021.106321
Acknowledgments and Disclosure
The authors are thankful for the following funds: Basque Government, Department of Education, University and Research (consolidated research groups GIC IT1766-22 and IT1503-22); Spanish Government MICINN (PID2019-106236GB-I00/AEI/10.13039/501100011033); ELKARTEK program; PID2022-138572OB-C42 by MCIN/AEI/10.13039/501100011033/FEDER; Horizon Europe Framework Programme (HORIZON-TMA-MSCA-SE); Project BIOIMP_ACE_MAS_6_E Interreg VI-A Spain-Portugal Programme (POCTEP) 2021-2027.
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