Effect of the Buffer on the Buildup and Stability of Tannic Acid/Collagen Multilayer Films Applied as Antibacterial Coatings

Abstract

The deposition of polyelectrolyte multilayers, obtained by the Layer-by-layer (LbL) method, is a well-established technology to design biocompatible and antibacterial coatings aimed at preventing implant-associated infections. Several types of LbL films have been reported to exhibit anti-adhesive and/or antibacterial (contact-killing or release-killing) properties governed not only by the incorporated compounds but also by their buildup conditions or their postbuildup treatments. Tannic acid (TA), a natural polyphenol, is known to inhibit the growth of several bacterial strains. In this work, we developed TA/collagen (TA/COL) LbL films built in acetate or citrate buffers at pH 4. Surprisingly, the used buffer impacts not only the physicochemical but also the antibacterial properties of the films. When incubated in physiological conditions, both types of TA/COL films released almost the same amount of TA depending on the last layer and showed an antibacterial effect against Staphylococcus aureus only for citratebuilt films. Because of their granular topography, TA/COL citrate films exhibited an efficient release-killing effect with no cytotoxicity towards human gingival fibroblasts. Emphasis is put on a comprehensive evaluation of the physico-chemical parameters driving the buildup and the antibacterial property of citrate films. Specifically, complexation strengths between TA and COL are different in the presence of the two buffers affecting the LbL deposition. This work constitutes an important step toward the use of polyphenols as antibacterial agent when incorporated in LbL films.

Polyelectrolyte Multilayer Films Based on Natural Polymers: From Fundamentals to Bio-Applications

“…Recently, collagen (COL)/tannic acid (TA) multilayer films have been developed using two different buffers, acetate or citrate at pH 4. TA/COL binding is stronger in citrate buffer than in acetate buffer leading to a higher immobilization of TA, a natural polyphenol that inhibits the growth of several bacterial strains, and a granular topography of the resulting films, which also provided a higher surface area for an enhanced local release-killing effect against Staphylococcus aureus ( Figure 6 b) [ 103 ].…”

“…The green channel corresponds to SYTO 24 labeling all bacteria and the red channel only healthy bacteria through metabolism of CTC (5-cyano-2,3-ditolyl tetrazolium chloride) into an insoluble, red fluorescent formazan. (Reprinted with permission from [ 101 ]; Copyright 2016 American Chemical Society); ( b ) Cumulative release profiles of TA from TA/COL films in contact with PBS pH 7.4 at room temperature (left), CFU of S. aureus from the supernatant of TA/COL films after 24 and 48 h of contact (N.D. means not detected, no CFUs were observed; dashed line means CFUs were obtained from the bacterial supernatant in contact with an uncoated glass) (center), and schematic representation of TA release-killing toward bacteria (right) (Adapted and reprinted with permission from [ 103 ]. Copyright 2020 American Chemical Society).…”

Collagen-Based Materials Modified by Phenolic Acids—A Review

“…Collagen forms a complex with tannic acid when solutions are mixed, because strong hydrogen bonds are formed. Such solutions may be prepared in acetate or citric buffers (pH = 4), which affects the physicochemical and antimicrobial properties of the final structures [102]. The study of tannic acid released from collagen-tannic acid complexes suggests that it has a killing effect for microbes which are not cytotoxic to human cells.…”

Chitosan-miRNA functionalized microporous titanium oxide surfaces via a layer-by-layer approach with a sustained release profile for enhanced osteogenic activity

“…In this study, multilayers of CS and HA fabricated by the LbL self-assembly technique were used to load miRNA on the Ti implant surface to realize a larger miRNA loading amount and a long-lasting release. This technique is based on the alternate adsorption of polyanions and polycations via electrostatic interactions on a charged substrate and has been widely used for the controlled release of biological molecules [46][47][48]. To firmly attach the LbL films to the MAO Ti surface, the silane reaction is utilized, as the rigid covalent bond provides a firm chemically crosslinked connection between the MAO surface and chitosan.…”