9 Piezopolymers can be of natural (e.g., collagen or silk) or synthetic origin, e.g., poly( l-lactic acid) (PLLA), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-trifluoro ethylene) (P(VDF-TrFE)). Piezoelectric inorganic materials (e.g., lead zirconate titanate (PZT), barium titanate (BT), boron nitride (BN), zinc oxide (ZnO), and hydroxyapatite (HA)) are more versatile compared to organic alternatives as they usually possess an extremely high piezoelectric coefficient and favorable mechanical properties ( Figure 1). Various piezoelectric biomaterials have been explored for different biomedical applications ( Table 1). ![]() 7 These materials can also transform electrical stimuli to mechanical stresses via geometric deformation, known as reverse piezoelectricity. ![]() 6 Such piezoelectric biomaterials offer numerous advantages over conventional biomaterials as they can easily transduce electricity to living systems in response to processes such as cell migration, body movements or external stimulation (e.g., ultrasound (US), vibration, etc.). Nevertheless, the complexity and inconvenience to patients associated with electrotherapy have triggered the development of piezoelectric biomaterials possessing a built-in capacity for electric signaling. 5 To this end, external devices or electrodes are employed to supply low level electric currents across the skin. 4 Due to the importance of bioelectricity, electrotherapy has been developed for accelerated wound healing, deep brain stimulation, tissue regeneration, improved musculoskeletal conditions and recovery of bone fractures. 3 In addition, EFs also affect cell division, intracellular communication, neuronal activities, mechanotransduction, ion transport, as well as bone and epithelial healing. 2 Endogenous electric fields may influence cellular processes such as chemotaxis, migration, proliferation and differentiation of cells. 1 In the embryonic phase, developmental defects may arise due to minor deviations from the steady-state potential of the embryo. This phenomenon leads to loss of the center of symmetry and induces accumulation of charge through an ordered dipole distribution.īioelectricity is an integral part of living systems where endogenous electric fields (EFs) play a vital role in early embryonic development to tissue regeneration. Transient deformation of crystalline materials (highly ordered crystal lattices) occurs under mechanical stress leading to an atomic position shift within unit cells. In Greek, “piezo” means “pressure.” Accordingly, piezoelectricity can be translated as “pressure-induced electricity.” Piezoelectricity in the physiological environment originates from structural anisotropy or transient deformations developing a net dipole moment greater than zero. Finally, recent studies on nano- piezoceramics and piezopolymers are presented, with specific focus on barium titanate, zinc oxide, and polyvinylidene fluoride.īiomaterials exhibiting piezoelectric properties (piezoelectric biomaterials) are a specific class of smart materials which display electromechanical behavior by transforming mechanical energy into electric polarization without the application of an external voltage. Subsequently, relevant properties and postfabrication strategies of nanostructured piezoelectric biomaterials are discussed aiming to maximize piezoresponse. After a brief introduction to piezoelectricity, an overview is provided on the major classes of piezoelectric biomaterials as well as a description of the origin of biopiezoelectricity in different tissues and macromolecules. Herein, the major focus is to highlight the wide range of applications of piezoelectric nano-biomaterials in drug delivery, theranostics, and tissue regeneration. Piezoelectric properties, high surface energy, targeting properties, and intricate cell–material interactions render piezoelectric nanomaterials highly attractive for application in therapeutics as well as regenerative medicine. ![]() Due to the growing interest in nanomaterials, piezoelectric nano-biomaterials have been widely investigated, leading to remarkable advancements throughout the last two decades. Among various classes of biomaterials, the majority of non-centrosymmetric crystalline materials exhibit piezoelectric properties, i.e., the accumulation of charge in response to applied mechanical stress or deformation.
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