Conformal Electrodeposition of Antimicrobial Hydrogels Formed by Self‐Assembled Peptide Amphiphiles

Abstract

The colonization of biomedical surfaces by bacterial biofilms is concerning because these microorganisms display higher antimicrobial resistance in biofilms than in liquid cultures. Developing antimicrobial coatings that can be easily applied to medically‐relevant complex‐shaped objects, such as implants and surgical instruments, is an important and challenging research direction. This work reports the preparation of antibacterial surfaces via the electrodeposition of a conformal hydrogel of self‐assembling cationic peptide‐amphiphiles (PAs). Hydrogels of three PAs are electrodeposited: C16K2, C16K3, and C18K2, where Cn is an alkyl chain of n methylene groups and Km is an oligopeptide of m lysines. The processing variables (electrodeposition time, potential, pH, salt concentration, agitation) enable fine control of film thickness, demonstrating the flexibility of the method and allowing to unravel the mechanisms underlying electrodeposition. The electrochemically prepared hydrogels inhibit the growth of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa in agar plates, and prevent the formation of biofilms of Acinetobacter baumannii and P. aeruginosa and the formation of A. baumannii colonies in solid media. C16K2 and C16K3 hydrogels outperform the antimicrobial activity of those of C18K2 while maintaining good compatibility with human cells.

Electrogelation: Controlled Fast Formation of Micrometer-Thick Films from Low-Molecular Weight Hydrogelators

“…We observed a steady increase in gel thickness up to 200 nm at higher potentials. Electrogelation of BTA, which is a LWMHG, seems to be comparable in terms of film growth to another LWMHG and the electrodeposition of polyelectrolytes as described by van Tassel and co-workers . In both cases, a nearly linear increase in thickness with time has been observed at least for the first stages of film formation.…”

“…This new experimental approach allowed us to study fibrillar hydrogel films from LMWHGs with thicknesses in the hydrated state between 100 nm and 5 μm. By contrast, comparable studies of LMWGH hydrogel films concentrated on much thicker films …”

“…By contrast, comparable studies of LMWGH hydrogel films concentrated on much thicker films. 32 Electrochemically based deposition of NaBTA at potentials of 1.30−1.40 V vs Ag/AgCl and concentrations of approximately 1 g/L provide the best control over the film thickness. Thus, with relatively small potentials and low NaBTA concentrations, it is possible to deposit hydrogel films on a conductive surface of practically arbitrary form within a few seconds.…”

“…29 During this change of conditions, LMWHGs form physical networks in the entire volume of the liquid, resulting in a macroscopic sol−gel transition. 10,11,30,31 The sol−gel transition/hydrogelation, however, can also take place on electrodes 7,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]32 even though the electrogelation of LMWHGs on an electrode has been reported only sparsely in the literature. 9,11,32−34 Interestingly, the electrogelation of LMWHG based on dipeptides by a hydroquinone oxidationmediated pH shift at an electrode interface 9,11,33 takes place at potentials (<1.5 V) considerably lower than that of the electrochemically induced formation of silk-gels (∼25 V), 22−24 which make LHMWGs appealing candidates for biomedical applications.…”

“…Low-molecular weight hydrogelators (LMWHGs) are small molecules that form typically fibrillar structures via secondary interactions in aqueous media upon application of external stimuli, such as pH changes, the presence of specific ions, or temperature changes . During this change of conditions, LMWHGs form physical networks in the entire volume of the liquid, resulting in a macroscopic sol–gel transition. ,,, The sol–gel transition/hydrogelation, however, can also take place on electrodes ,− , even though the electrogelation of LMWHGs on an electrode has been reported only sparsely in the literature. ,,− Interestingly, the electrogelation of LMWHG based on dipeptides by a hydroquinone oxidation-mediated pH shift at an electrode interface ,, takes place at potentials (<1.5 V) considerably lower than that of the electrochemically induced formation of silk-gels (∼25 V), − which make LHMWGs appealing candidates for biomedical applications.…”