Review
The growing importance of materials that prevent microbial adhesion: antimicrobial effect of medical devices containing silver

https://doi.org/10.1016/j.ijantimicag.2009.01.017Get rights and content

Abstract

Research has clarified the properties required for polymers that resist bacterial colonisation for use in medical devices. The increase in antibiotic-resistant microorganisms has prompted interest in the use of silver as an antimicrobial agent. Silver-based polymers can protect the inner and outer surfaces of devices against the attachment of microorganisms. Thus, this review focuses on the mechanisms of various silver forms as antimicrobial agents against different microorganisms and biofilms as well as the dissociation of silver ions and the resulting reduction in antimicrobial efficacy for medical devices. This work suggests that the characteristics of released silver ions depend on the nature of the silver antimicrobial used and the polymer matrix. In addition, the elementary silver, silver zeolite and silver nanoparticles, used in polymers or as coatings could be used as antimicrobial biomaterials for a variety of promising applications.

Introduction

Antimicrobial polymers that contain silver represent a great challenge for academics and industry [1]. These materials capture attention because of their novelty in being a long-lasting biocidal material with high temperature stability and low volatility [1]. The large increase in the number and occurrence of antibiotic-resistant bacterial strains has prompted a renewed interest in the use of silver as an antibacterial agent [2].

Silver is a metal known for its broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria, fungi, protozoa and certain viruses [3], including antibiotic-resistant strains [2], [4]. It can be used to reduce infections in the treatment of burned areas [5], [6], [7], to prevent bacterial colonisation on medical devices [7], [8], [9], [10], [11], [12] as well as in textile fabrics [7], [13] and for water treatment [14]. Silver, as an antiseptic agent, has been effective in a variety of materials, including glass, titanium and polymers [15].

The antimicrobial activities of commercially available silver-impregnated dressings and catheters have been reported [8], [16], [17]. It has been suggested that impregnation of silver into a coating can be more effective than direct surface coating alone, since surface silver can be readily deactivated by protein anions [2], [18]. This impregnation of silver ions (SI) would also be beneficial in protecting the inner and outer catheter surfaces against bacterial attachment [2], [19].

However, the use of medical devices containing silver must be undertaken with caution, since a concentration-dependent toxicity has been demonstrated. Braydich-Stolle et al. [20] assessed the suitability of a mouse spermatogonial stem cell line as an in vitro model to assess the nanotoxicity of silver. Concentrations of silver nanoparticles (SN) between 5 μg/mL and 10 μg/mL induced necrosis or apoptosis of mouse spermatogonial stem cells [20]. Moreover, heavy metal accumulation in the environment has been mentioned in the US Agency for Toxic Substances and Disease Registry (ATSDR) Comprehensive Environmental Response, Compensation, and Liability Act 2007 Priority List [http://www.atsdr.cdc.gov/cercla/] as well as by the European Commission on heavy metals waste [21]. Nevertheless, silver has not been cited amongst the most prevalent heavy metals in the priority list of hazardous substances to public health [21].

Despite this, as the use of silver and the number of available silver-based products has increased, it is becoming important to clarify the efficacy of silver against different microorganisms and biofilms. It is also essential to answer questions related to the mechanisms of the various silver forms as antimicrobial agents as well as the dissociation of SI and the resulting antimicrobial efficacy. Thus, this literature review was carried out using references from the last 35 years regarding silver as an antimicrobial agent, specifically silver zeolite (SZ) and SN, SI release and biofilm formation.

Section snippets

Antimicrobial properties

Medical devices such as endotracheal tubes, vascular and urinary catheters, and hip prosthetics are responsible for over one-half of nosocomial infections in the USA [22], [23]. To create surfaces resistant to bacterial adhesion and colonisation, several methods of incorporating silver on medical devices have been described [3], [22], [23]. Silver has been used in ionised and elementary forms, as SZ or as nanoparticles.

Biofilm formation

Biofilms are defined as communities of bacteria that colonise surfaces in an aqueous environment [28]. Biofilm formation occurs as a result of a sequence of events: microbial surface attachment, cell proliferation, matrix production and detachment [45].

The conditioning film, formed by a layer of organic molecules adhered to the surface, is considered a precursor for the initial attachment of planktonic cells [28]. Once the microorganisms reach critical proximity to the surface, the

Conclusion

Silver antimicrobial agents have been pursued as an alternative strategy for reducing bacterial adhesion and to prevent biofilm formation. Antibacterial experiments demonstrated that silver is effective against a broad range of bacterial cells and mature biofilms, however the concentration is an important factor. The current review suggests that elementary silver, SZ and SN in polymers can constitute effective antimicrobial biomaterials for a variety of promising applications. Owing to the much

Acknowledgments

The authors are thankful to the Laboratório Interdisciplinar de Eletroquímica e Cerâmica, Universidade Federal de São Carlos (LIEC-UFSCar) for preparing the SN and performing the transmission electron micrograph and scanning electron micrograph investigations, as well as Jeremy Matis and Rosimeiri Dainez for the English review.

Funding: No funding sources.

Competing interests: None declared.

Ethical approval: Not required.

References (64)

  • K. Kawahara et al.

    Antibacterial effect of silver–zeolite on oral bacteria under anaerobic conditions

    Dent Mater

    (2000)
  • T. Matsuura et al.

    Prolonged antimicrobial effect of tissue conditioners containing silver-zeolite

    J Dent

    (1997)
  • L. Balan et al.

    A new and convenient route to polyacrylate/silver nanocomposites by light-induced cross-linking polymerization

    Prog Org Coat

    (2008)
  • I. Sondi et al.

    Silver nanoparticles as antimicrobial agent: a case study on E. coli as a model for Gram-negative bacteria

    J Colloid Interface Sci

    (2004)
  • Y. Li et al.

    Antimicrobial effect of surgical masks coated with nanoparticles

    J Hosp Infect

    (2006)
  • S.J. Ahn et al.

    Experimental antimicrobial orthodontic adhesives using nanofillers and silver nanoparticles

    Dent Mater

    (2009)
  • C. Damm et al.

    The antimicrobial efficacy of polyamide 6/silver-nano- and microcomposites

    Mater Chem Phys

    (2008)
  • J.M. Schierholz et al.

    Efficacy of silver-coated medical devices

    J Hosp Infect

    (1998)
  • R. Van Houdt et al.

    Role of bacterial cell surface structures in Escherichia coli biofilm formation

    Res Microbiol

    (2005)
  • K.K. Jefferson

    What drives bacteria to produce a biofilm?

    FEMS Microbiol Lett

    (2004)
  • T.F. Mah et al.

    Mechanisms of biofilm resistance to antimicrobial agents

    Trends Microbiol

    (2001)
  • A. Melaiye et al.

    Silver and its application as an antimicrobial agent

    Expert Opin Ther Pat

    (2005)
  • D.V. Parikh et al.

    Antimicrobial silver/sodium carboxymethyl cotton dressings for burn wounds

    Text Res J

    (2005)
  • A. Panácek et al.

    Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity

    J Phys Chem B

    (2006)
  • U. Samuel et al.

    Prevention of catheter-related infections: the potential of a new nano-silver impregnated catheter

    Int J Antimicrob Agents

    (2004)
  • S. Ohashi et al.

    Antibacterial activity of silver inorganic agent YDA filler

    J Oral Rehabil

    (2004)
  • W.L. Chou et al.

    The preparation and characterization of silver-loading cellulose acetate hollow fiber membrane for water treatment

    Polym Adv Technol

    (2005)
  • Gibbins B, Warner L. The role of antimicrobial silver nanotechnology. Portland, OR: AcryMed Inc.; 2005....
  • M. Ip et al.

    Antimicrobial activities of silver dressings: an in vitro comparison

    J Med Microbiol

    (2006)
  • F. Furno et al.

    Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?

    J Antimicrob Chemother

    (2004)
  • L. Braydich-Stolle et al.

    In vitro cytotoxicity of nanoparticles in mammalian germline stem cells

    Toxicol Sci

    (2005)
  • J.J. Harrison et al.

    Multimetal resistance and tolerance in microbial biofilms

    Nat Rev Microbiol

    (2007)
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