Chitosan–cobalt(II) and nickel(II) chelates as antibacterial agents

https://doi.org/10.1016/j.ijbiomac.2010.12.004Get rights and content

Abstract

Antibacterial behavior of chitosan–bivalent metal chelates (Co and Ni) was investigated in vitro against standard bacteria, Staphylococcus aureus ATCC 4533, S. faecalis ATCC 8043 and Escherichia coli ATCC 25923. The chitosan–metal chelates were prepared by varying the molar ratio of metal ions to a fixed amount of chitosan. The metal ion contents, structural properties and morphology of the chelates were respectively determined using ICP-OES, FT-IR and SEM. All the chitosan–metal chelates showed wide spectrum of effective antibacterial activities better than free chitosan and the individual metal ions. The results indicated that inhibitory effects of the chelates were dependent not only on the property of the coordinated metal ion, but also on the molar ratio of the metal ion. Consequently, the ideal inhibitory effects could be obtained with metal ion of high charge intensity and when the molar ratio of chitosan to metal was above 1:1. These chelates are promising materials for novel antibacterial agents.

Introduction

Chitosan is a powerful chelating agent which easily forms complexes with transition metals and heavy metals [1], [2], [3]. Most researches on chitosan–metal complexes focused on their applications in the sequestration or removal of metal ions, dyeing, catalysis, water treatment and other industrial processes [4], [5], [6], [7], [8], [9], [10]. However, a few researchers paid attention to their biological activities [1]. Antimicrobial activity of chitosan was observed against a wide variety of microorganisms including fungi [11], [12], [13], [14], algae [15] and some bacteria strains [1], [2], [16], [17], [18], [19]. The advantage of chitosan over other type of disinfectants is demonstrated in its higher antibacterial activity [2] plus the fact that it possesses a lower toxicity towards mammalian cells. Many attempts such as structural modification, adjustment of molecular factors and forming various derivatives [13], [20], [21], [22] have been taken up to improve the antimicrobial activity of chitosan. Interestingly, the few available research effort has shown that chitosan–metal complexes are much better antimicrobial agents than free chitosan and metal salts [23].

Metal ions such as Ag+, Cu2+, Zn2+, Co2+ and Ni2+ etc., form an important group of antimicrobial agents which have different active target from most bacteriostatic polymers [24], [25], [26], [27]. In order to explain the phenomenon of chitosan–metal complexes’ antimicrobial activity, the complex reaction between chitosan and metal ions may be described according to the Lewis acid–base theory [28]. Metal ions are referred to as “super acid” as they are stronger acceptor of electrons than H+. More so, chitosan possesses a lot of poly-cationic amines in low pH medium which interact readily with negatively charged substances such as proteins, phospholipids and fatty acid on the cell surface of bacteria, and in turn inhibit the growth of microorganisms [29]. Chitosan–metal ion chelation will increase the positive charge density of chitosan. This is expected to lead to enhanced adsorption of polycation onto the negatively charged cell surface causing enhanced growth inhibition.

This work therefore, focused on the chelation of chitosan with two closely related bivalent metal ions (Co2+ and Ni2+) and subsequent growth inhibitory studies against standard bacteria, Staphylococcus aureus ATCC 4533, S. faecalis ATCC 8043 and Escherichia coli ATCC 25923. The results of this finding which depict the effects of the metal coordination to chitosan antibacterial activity is herein reported.

Section snippets

Materials

The chitosan sample preparation (involving sample procurement, deproteinization, demineralization and N-deacetylation of the chitin) was carried out using literature methods of Adewuyi et al. [3]. The viscosity average molecular weight was determined by measuring the relative viscosity with an Ostwald viscometer. The solvent system used was 0.10 M CH3COOH/0.20 M NaCl. Molecular weight was calculated from the intrinsic viscosity based on the Mark–Houwink equation. All chemicals were of analytical

Characterization

The metal ion analysis results showed that the chelate ratios of complexes increased with metal ions, although not all the ions (Co(II) and Ni(II)) involved in chelation (Table 1). The FT-IR Spectra of chitosan, chitosan–Co and chitosan–Ni chelates are shown in Fig. 1. The amide 1 band (υCdouble bondO) around 1637 cm−1 stretching frequency, characteristic of chitosan with acetylated units is present in all the spectra. However, in chitosan–metal chelates, a new band around 1625–1635 cm−1 appears. These

References (30)

  • X. Wang et al.

    Carbohydr. Polym.

    (2004)
  • W.S.W. Ngah et al.

    Bioresour. Technol.

    (2005)
  • M. Eweis et al.

    Int. J. Biol. Macromol.

    (2006)
  • H.K. No et al.

    Int. J. Food Microbiol.

    (2002)
  • G.J. Tsai et al.

    J. Food Prot.

    (1999)
  • R. Huang et al.

    React. Funct. Polym.

    (2004)
  • W.-L. Du et al.

    Carbohydr. Polym.

    (2009)
  • R.A.A. Muzzarelli

    Carbohyr. Polym.

    (1996)
  • X. Wang et al.

    Polym. Bull.

    (2005)
  • S. Adewuyi et al.

    J. Chem. Soc. Nig.

    (2008)
  • J.I. Simionato et al.

    Polym. Int.

    (2006)
  • R. Schmuhl et al.

    Water SA

    (2001)
  • E. Taboada et al.

    Chilean Chem. J.

    (2003)
  • X. Wang et al.

    Polym. Int.

    (2006)
  • A.M. Saad et al.

    J. Appl. Sci. Res.

    (2006)
  • Cited by (31)

    • Investigation of DNA/BSA binding and cytotoxic properties of new Co(II), Ni(II) and Cu(II) hydrazone complexes

      2021, Inorganica Chimica Acta
      Citation Excerpt :

      With its ability to bind various types of small molecules, BSA plays an inevitable role in the determination of physiological function. The role of metal complexes in the therapeutic effect induced by copper, nickel and cobalt compounds is wide-ranging [7-18]. Moreover, this type of study could facilitate the understanding of mechanism of drugs on protein level to cure diseases.

    • Cu(II)-carboxymethyl chitosan-silane schiff base complex grafted on nano silica: Structural evolution, antibacterial performance and dye degradation ability

      2018, International Journal of Biological Macromolecules
      Citation Excerpt :

      CS can be cross-linked easily through its reactive amino groups which enhances its mechanical strength and metal ion affinity. The metal complexes of CS are reported as better antimicrobial agents than free CS and free metal ions [8–10]. Schiff’sbases of CS have been proven to be superior in many aspects as compared to chitosan [11,12].

    • Chitosan-bound pyridinedicarboxylate Ni(II) and Fe(III) complex biopolymer films as waste water decyanidation agents

      2016, Carbohydrate Polymers
      Citation Excerpt :

      Chitosan is a non toxic, bio-degradable polymeric material which can be shaped into any desired form such as flakes, beads, powder and film (Portes, Gardrat, Castellan, & Coma, 2009; Sundaram, Viswanathan, & Menakshi, 2009). Its chelating power has been well established to form complexes with transition metals and heavy metals (Adewuyi, Kareem, Atayese, Amolegbe, & Akinremi, 2011; Wang, Du, Fan, Liu, & Hu, 2005; Wang, Du, & Liu, 2004). Hence, it is mostly subjected to sorption of transition metal ions and research effort is scanty on its use for the removal of toxic anions, especially cyanide.

    • Nickel nanoparticle-chitosan-reduced graphene oxide-modified screen-printed electrodes for enzyme-free glucose sensing in portable microfluidic devices

      2013, Biosensors and Bioelectronics
      Citation Excerpt :

      A possible deposition process of CS-RGO–NiNPs nanocomposites is assumed as follows. In the deposition solution, positively charged CS and Ni2+ cations interact by chelating (Adewuyi et al., 2011), while negatively charged GO sheets can form composites with both CS and Ni2+ via electrostatic interactions in the solution. Hydrophobic moieties in CS such as acetyl groups and glucosidic rings might interact with the hydrophobic part of GO basal planes via partially hydrophobic interactions.

    • Cobalt derivatives as promising therapeutic agents

      2013, Current Opinion in Chemical Biology
      Citation Excerpt :

      The properties of the complexes can be adjusted depending on the oxidation state and ancillary ligands, affording a versatile scaffold to target biomolecules of therapeutic relevance [4••]. Bioactive small molecules that elicit therapeutic action in vivo, such as non-steroidal anti-inflammatory drugs (NSAIDs) [17–19], antibacterial agents [20,21], antiprotozoal agents [22,23], antifungal agents [24,25], and antihelmintic agents [26], have been attached to cobalt complexes to improve or alter their therapeutic efficacy. Although mechanisms for many of these agents are not understood, complexation to cobalt scaffolds is thought to influence the physicochemical properties of the bioactive ligand [2,6,27,28•].

    View all citing articles on Scopus
    View full text