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Abstract

In the field of biomedical materials, conventional approaches to tissue engineering and wound healing face limitations that encourage the exploration of innovative treatments. This work presents multifaceted exploration of piezoelectric polylactic acid (PLA) films intended for biomedical applications, from the optimization of the conditions for efficient film preparation to the investigation of the degradation processes, the development of nanotextured (NT) PLA films, and presents the evaluated performance for wound healing as an applicative view of use.
The study firstly presents the polymer physical, chemical and piezoelectric properties and behavior at different temperatures to successfully optimize the preparation of piezoelectric polymer film by uniaxial tensile stretching. As part of this study, piezoelectric measurements of the whole film were directly correlated to the newly formed properties of the polymer, such as crystallinity and orientation, and more importantly, how additional modifications (annealing and surface etching, topography) affect piezoelectricity through modified method of measurements. The surface was additionally alkali etched due to poor hydrophilic properties, which noticeably improves the surface. Accelerated degradation using proteinase K reveals that enhanced surface hydrophilicity alters the degradation process from bulk to surface-oriented erosion, maintaining mechanical stability and, consequently, piezoelectric properties for extended durations.
The study also introduces a template-assisted method for preparing NT PLA films. The nano-sized topography significantly enhances piezoelectric properties, offering promising biological responses. A new method for assessing piezoelectric properties which employed the decomposition of an organic dye as a measure was proposed, which enables a complete evaluation of piezoelectric properties by considering materials with complex surface texture.
The antibacterial effects of piezoelectric PLA films on both Gram negative and Gram positive bacteria were explored. Notably, the research identifies (piezo)electric stimulation, activated externally via ultrasound (US), to lead to bactericidal effects for bacteria in contact with piezoelectric NT film. The study also dismisses concerns of toxicity to non-adherent (red blood cells) or adherent cells (epithelia skin cells), establishing the films as promising candidates for antibacterial agents or wound healing applications.
Cellular (keratinocytes) and immune response (macrophages) to piezoelectric and non-piezoelectric PLA films were also investigated. Mechanical stimulation through US activates (piezo)electric stimulation on cells and reveals improved cell attachment, enhanced actin filament production, improved cell-to-cell connections, and indicates towards improved cell differentiation. The immune response, evaluated through monocyte differentiation into macrophages, suggests minimal immune reaction towards the PLA polymer films, with different polarization responses observed for different film types.
In conclusion, this comprehensive exploration establishes the potential of piezoelectric PLA films in biomedical applications. The findings offer valuable insights into the material's degradation, antibacterial properties, and cellular responses, providing a foundation for future advancements in electro-stimulated regeneration and wound healing technologies.