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

Abstract

Despite being very simple organisms, bacteria possess an outstanding ability to adapt to different environments. Their long evolutionary history, being exposed to vastly different physicochemical surroundings, allowed them to detect and respond to a wide range of signals including biochemical, mechanical, electrical, and magnetic ones. Taking into consideration their adapting mechanisms, it is expected that novel materials able to provide bacteria with specific stimuli in a biomimetic context may tailor their behavior and make them suitable for specific applications in terms of anti-microbial and pro-microbial approaches. This review maintains that electroactive smart materials will be a future approach to be explored in microbiology to obtain novel strategies for fighting the emergence of live threatening antibiotic resistance.

Keywords: antimicrobial resistance; bacteria; biomimetics; electroactive materials; physical stimuli.

Figure 1

Schematic representation of the biochemical, mechanical, electrical, and magnetic cues to which mammalian and bacterial cells are sensitive.

Figure 2

Schematic representation of (A) the timeline for the development of bacterial resistance and (B) its impact on the natural flora present in human intestine. Previous to penicillin discovery in 1940 bacteria-causing infections killed millions of people but the microbiome of our gut were “untouched” and widely “crowded” by harmless microbes (flora). After 1940, the introduction of antibiotics allowed to cure previously deadly diseases and saved a large amount of lives, extending life span and allowing further medical procedures. Nevertheless, the constant application of antibiotics soon resulted in antibiotic resistant strains. Harmless microbes from the flora in our guts are also killed giving space for the resistant strains to proliferate.

Figure 3

Stimuli that bacteria sense and the mechanism of action of each bactericidal effect.

Figure 4

(A) Simplified QS system of Gram-negative bacteria, general chemical formula of the signaling molecules and (B) strategies to QQ including the enzymatic degradation of AHL signals by AHL-lactonase and AHL-acylase.

Figure 5

Schematic representation of the (A) mechanoelectric properties of a material upon the application of mechanical stimuli and (B,C) magnetoelectric properties of scaffolds upon the application of magnetic stimuli.

Figure 6

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).