Tailoring Bacteria Response by Piezoelectric Stimulation

Abstract

Bacteria are simple organisms with a remarkable capacity for survival by adapting to different environments, which is a result of their long evolutionary history. Taking into consideration these adapting mechanisms, this work now investigates the effect of electrically active microenvironments on bacteria and on how this stimulation may trigger bacteria growth inhibition or proliferation. Electrical microenvironments are generated via stimulation of a piezoelectric polymer with a mechanical cue, thus developing an electrical response and a variation on the surface charge of the polymeric material. Specifically, Grampositive Staphylococcus epidermidis and Gram-negative Escherichia coli were grown overnight under static and dynamic conditions on piezoelectric poly(vinylidene) fluoride (PVDF) films to further study bacteria behavior under: (i) the effect of the material surface charge in static conditions, (ii) the mechanical effect, and (iii) the piezoelectric effect, the last two performed under dynamic conditions. Bacteria viability in planktonic and biofilm forms was measured, and the microorganism morphology was characterized. Whereas E. coli responds little to any of the stimuli application, S. epidermidis growth can be regulated through the material surface charge and by the applied frequency. Positively charged PVDF induces bacterial growth inhibition in planktonic and adhered cells in static conditions, whereas antifouling properties are obtained when a mechanical or piezoelectric effect at 4 Hz stimuli is applied. By increasing the stimuli to 40 Hz, however, the adhesion of bacteria is promoted. In conclusion, the behavior of certain bacteria species is tailored through the application of piezoelectric materials, which provide sufficient mechanoelectrical stimuli for growth or inhibition of bacteria, allowing for the design of suitable anti-and promicrobial strategies. Such strategies are only found in studies related to mammalian cells, whereas in bacterial cells this type of stimuli are still unknown. Thus, this work provides one of the first insights on the effect of piezoelectric stimuli on bacterial cells.

Composite Ferroelectric Membranes Based on Vinylidene Fluoride-Tetrafluoroethylene Copolymer and Polyvinylpyrrolidone for Wound Healing

“…Second, it is known that PVDF-based piezoelectric polymer membranes are capable of negatively affecting the Staphylococcus culture when under a dynamic load of the membrane, even in the absence of antibacterial agents [49]. Since in membranes containing 15 wt % of PVP the predominant conformation of VDF-TeFE macromolecules was the electrically active trans conformation ( Figure 2) and crystallites with characteristic ferroelectric properties predominate in the crystal structure (Figure 3), it can be assumed that the decrease in the concentration of pathogens in the wound and improved tissue regeneration is due to the piezoelectric properties of the formed membranes.…”

Biofilm and swarming emergent behaviours controlled through the aid of biophysical understanding and tools

“…Tuning frequency and amplitude of surface waves can control biofilm formation [85][86][87][88][89][90]92] Shear flows High shear flows lead to more compact biofilm formation and changes in its mechanical properties [48,92,93,103] Biofilms, sessile microbial communities embedded in EPS, also emerge on surfaces, but the conditions favourable for biofilm formation are distinct from those for swarming. Biofilms are prominent on solid-liquid, solid-air and liquid-air phase boundaries, and are recalcitrant to almost all types of biological and biochemical stresses.…”

Electroactive Smart Materials: Novel Tools for Tailoring Bacteria Behavior and Fight Antimicrobial Resistance

“…On the other hand, the proliferation effect of bacteria has been observed at the surface of electrically polarized hydroxyapatite (Ueshima et al, 2002). Recent findings reported that bacterial cells behavior, which grow upon piezoelectric polymers, may be tailored according to the surface charge of the material and on the application of weak electrical field, promoted by a piezoelectric polymer under mechanical stimuli, demonstrating a different behavior between Gram-positive and Gram-negative cells (Carvalho et al, 2019). The Gram-positive bacteria seems not adhere to positively charged surface, as opposed to the negatively charged surface.…”

“…The Gram-positive bacteria seems not adhere to positively charged surface, as opposed to the negatively charged surface. In the presence of an electrical stimuli, this strain shows a different behavior: the lower frequency promotes the antifouling and the higher stimulates the bacteria adhesion (Figure 6) (Carvalho et al, 2019).…”

“…Electroactive microenvironments created by a mechanical bioreactor on a piezoelectric scaffold, inducing different responses on bacterial cells including proliferation or growth inhibition/antifouling properties, depending on the frequency applied, thus proving a new concept of bacteria susceptibility to physical stimuli. Such approaches are important to further define suitable anti- and pro-microbial strategies, intended for pathogenic and functional bacteria, respectively (Carvalho et al, 2019). …”