Polycationic condensed tannin/polysaccharide-based polyelectrolyte multilayers prevent microbial adhesion and proliferation

https://doi.org/10.1016/j.eurpolymj.2020.109677Get rights and content

Highlights

  • Polyelectrolyte multilayers based on a cationic condensed tannin are produced.

  • The cationic tannin derivative is blended with pectin and iota-carrageenan.

  • The polyelectrolyte multilayers prevent bacterial adhesion and biofilm formation.

Abstract

Bacterial adhesion and biofilm formation are significant issues associated with microbial infections in biomedical applications. It has been a challenge to prepare durable coatings with antiadhesive and antimicrobial activities. We show that a condensed tannin derivative (amino-functionalized) can be assembled with polysaccharides (pectin and iota-carrageenan) to create polyelectrolyte multilayers (PEMs). PEMs were prepared from the layer-by-layer approach by assembling polycationic-polyanionic pairs in an acetic acid-acetate buffer (pH 5.0). The tannin-based material (polycationic polymer) was characterized by X-ray photoelectron spectroscopy (XPS), while PEMs were characterized through XPS, in-situ Fourier transform surface plasmon resonance, atomic force microscopy, and water contact angle measurements. Compared to the native glass substrate, all PEMs present nanoscale surface roughness, and hydrophilic surfaces. A stability test performed in PBS for 7 days confirms that 15-layer PEMs are durable in aqueous environments. Initial adhesion and antimicrobial tests against Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) show that the PEMs exhibit antiadhesive and bactericidal activities after 6 h. The antibacterial test in-vitro indicates that PEMs can kill and prevent the attachment and proliferation of bacteria significantly, especially during initial exposure. These PEMs can be applied as coatings to avoid infections imparted by microbial adhesion in biomedical applications.

Introduction

The simple and versatile layer-by-layer (LbL) approach has been used to create hierarchical polyelectrolyte multilayer coatings (PEMs) for biomedical purposes. PEMs can be developed upon solid substrates to prevent bacterial attachment and biofilm formation, and thereby avoid microbial infections in biomedical devices [1]. Several studies report the use of chitosan-based PEMs as suitable coatings for preventing bacterial deposition and provide bactericidal traits. Chitosan and its N-quaternized derivatives are cationic polysaccharides with well-known antimicrobial properties [2].

Antimicrobial and antiadhesive coatings have been produced by assembling chitosan or chitosan-based derivatives with heparin [3], [4], hyaluronic acid [5], pectin [6], carrageenan [7], tannic acid [8] and other anionic polymers. Chitosan-based PEMs have demonstrated antimicrobial and antiadhesive properties against Escherichia coli (E. coli) [3], [4], Staphylococcus aureus (S. aureus) [8], and Pseudomonas aeruginosa (P. aeruginosa) [9]. However, these coatings have not been efficient in imparting high antibacterial efficacy, especially in initial stages of application.

Results have suggested that the surface roughness affects the interactions with bacteria. Heterogeneous surfaces, i.e., higher surface roughness enable more biofilm formation. Nano-scale surface roughness usually enhances the attachment of bacteria to substrates during the initial steps of colonization, providing more surface area for cell anchorage [10], [11]. The bacteria P. aeruginosa preferentially attached to heterogeneous ion-exchange membranes (surface roughness of approximately 25 nm) compared to homogeneous ion-exchange membranes (surface roughness lower than 15 nm) [11]. On the other hand, chitosan-pectin and chitosan-carrageenan PEMs (15 layers) with low surface roughness (between 2.6 and 3.5 nm) prevented the adhesion of P. aeruginosa after 6 h of exposure. However, S. aureus attached to these PEMs at the same time of exposure [7]. Chitosan-heparin PEMs with low surface roughness (between 2.4 and 7.5 nm) did not suppress the adhesion of E. coli after 4 h of incubation as well [4]. These findings have also implied that the initial colonization steps of bacteria mainly depend on the surface polarity and composition [7], [11].

Microbial infections caused by S. aureus and P. aeruginosa include pneumonia [12], perianal/genital, urinary [13], and skin and soft tissues (acute otitis) infections [13], [14]. A surface coating for tissue engineering scaffolds and biomedical devices must prevent the adhesion and biofilm formation of these bacteria. Poly(2-(dimethylamino) ethyl methacrylate)-poly(styrene sulfonate) and hyaluronic acid-polycationic amino-cellulose nanosphere-based coatings (5 layers) constructed on silicone surfaces suppressed the formation of S. aureus and P. aeruginosa biofilms over urinary catheters, respectively [15], [16]. PEMs (75–15 bilayers) based on poly(allylamine hydrochloride)-poly(acrylic acid) embedded with silver nanoparticles (10–30% wt/wt) also inhibited the adhesion (99.9%) of S. aureus and P. aeruginosa on endotracheal tubes [17]. PEMs are also used as drug delivery carriers for preventing bacterial attachment on biomedical devices [18], [19]. Vancomycin-poly(lactic acid)-vancomycin loaded into noisome (a drug delivery device composed of hydrated bilayer vesicles based on non-ionic surfactants and cholesterol) coatings can be applied in orthopedic implants. The assembled material acted as an efficient vancomycin delivery agent (for two weeks), preventing the formation of S. aureus biofilm on bone tissue [18].

In this study, we show that a cationic tannin derivative (TN) can replace chitosan to develop active antimicrobial coatings from the LbL method. The TN is synthesized from condensed tannins at the presence of ammonium chloride and formic acid [20]. Polyphenols [21] (such as tannic acid), as well as polymers with ammonium salt moieties in their structures, have well-known bactericidal traits [2], [22]. Therefore, the TN can play a dual role because it comprises both cationic and polyphenolic moieties. For the first time, we assemble TN with iota-carrageenan (CA) or pectin (PC) to prepare PEMs with excellent antimicrobial and antiadhesive properties against both S. aureus (Gram-positive) and P. aeruginosa (Gram-negative).

We show that hydrophilic, bactericidal, and antiadhesive PEMs with nanoscale roughness can be prepared by assembling TN with anionic polysaccharides. PEMs were prepared from polyelectrolyte solutions prepared in a dilute aqueous acetic acid-acetate buffer (pH 5.0). This weak acid pH condition was chosen for the PEM assembly because it yields cytocompatible PEMs (TN and chitosan-based coatings) and it provides ionized polymers (TN, CA, and PC) in solution [5]. PEMs were characterized by X-ray photoelectron spectroscopy (XPS), in situ Fourier transform surface plasmon resonance (FT-SPR), atomic force microscopy (AFM), water contact angle measurements, and stability tests (performed in phosphate buffered saline, PBS, for 7 days). We demonstrate that these durable TN-based PEM assemblies have potent antiadhesive and antimicrobial properties against both P. aeruginosa and S. aureus.

Section snippets

Materials

The amino-functionalized tannin derivative (TN, molar weight of approximately 600 kDa), commercially called Tanfloc-SG was graciously donated by Tanac SA (Montenegro-RS, Brazil) [23], [24]. GENU® pectin principally composed of linear homogalacturonan moieties (65%), connected through α(1 → 4) glycoside bonds to d-galacturonic acid units, O-methylation degree of 56% and molar weight of 190 × 103 g mol−1, as well as GENUVISCO® iota-carrageenan (277 × 103 g mol−1) formed by alternating α-(1  3)-d

Polyelectrolyte multilayer characterization

The layer-by-layer assembly of the (TN-PC)5 PEM was monitored by Fourier-transform surface plasmon resonance (FT-SPR) in situ (Fig. 1). The first 6 min (blue arrow) represents an acidified water rinse on the gold-coated glass chip modified with MUA. The green arrow indicates the beginning of the next 6-minute interval when the polycation solution (TN) is introduced into the flow cell. The large drop in the FT-SPR peak position during this adsorption step is due to the adsorption of polycation

Conclusion

Durable polyelectrolyte multilayers (PEMs) developed by assembling commercial polyelectrolytes (cationic tannin derivative (TN), iota-carrageenan (CA) and pectin (PC)) demonstrated potent antimicrobial and antiadhesive activity toward both Gram-negative and Gram-positive bacteria. The PEMs can prevent the attachment and growth of microbial cells and can be used to coat biomedical devices to promote healing and protection against the proliferation of bacteria. Preventing bacterial infections is

CRediT authorship contribution statement

Suelen P. Facchi: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Writing - original draft, Visualization. Ariel C. Oliveira: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Visualization. Ewerton O.T. Bezerra: Conceptualization, Methodology, Validation, Formal analysis, Investigation. Jessi Vlcek: Conceptualization, Methodology, Validation, Formal analysis, Investigation. Mohammadhasan Hedayati: Conceptualization, Methodology, Writing -

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors thank CAPES agency for the master fellowship destined to the S.P. Facchi and A.F. Martins thanks “National Council for Scientific and Technological Development – CNPq” for financial support (protocol 0008678964988973).

“This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES)-Finance Code 001”

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

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