Flexible camphor diamond-like carbon coating on polyurethane to prevent Candida albicans biofilm growth

https://doi.org/10.1016/j.jmbbm.2017.02.013Get rights and content

Highlights

  • Camphor:DLC film to avoid Candida albicans biofilm growth.

  • Flexible DLC containing camphor on polyurethane substrate.

  • DLC film with terpenoid radical from camphor identified by Raman maps.

Abstract

Camphor was incorporated in diamond-like carbon (DLC) films to prevent the Candida albicans yeasts fouling on polyurethane substrates, which is a material commonly used for catheter manufacturing. The camphor:DLC and DLC film for this investigation was produced by plasma enhanced chemical vapor deposition (PECVD), using an apparatus based on the flash evaporation of organic liquid (hexane) containing diluted camphor for camphor:DLC and hexane/methane, mixture for DLC films. The film was deposited at a low temperature of less than 25 °C. We obtained very adherent camphor:DLC and DLC films that accompanied the substrate flexibility without delamination. The adherence of camphor:DLC and DLC films on polyurethane segments were evaluated by scratching test and bending polyurethane segments at 180°. The polyurethane samples, with and without camphor:DLC and DLC films were characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and optical profilometry. Candida albicans biofilm formation on polyurethane, with and without camphor:DLC and DLC, was assessed. The camphor:DLC and DLC films reduced the biofilm growth by 99.0% and 91.0% of Candida albicans, respectively, compared to bare polyurethane. These results open the doors to studies of functionalized DLC coatings with biofilm inhibition properties used in the production of catheters or other biomedical applications.

Introduction

Diamond-Like Carbon (DLC) is a very attractive material for biological applications because it has physical and chemical properties similar to diamond such as hardness and relatively high modulus of elasticity. DLC is easily deposited on large and 3D areas (Hauert, 2003). Although, there are a significant number of manuscripts about DLC (Choudhury et al., 2016) and DLC with metallic nanoparticles (Widoniak et al., 2005; Marciano et al., 2009), little is known about the use of DLC in polymeric materials (Wang et al., 2004). Some studies mention silver used as a possible inhibitor of microbial growth and catheters coated with a mixture of silver and DLC (Dearnaley and Arps, 2005). On the other hand, only a few studies have used Camphor as a carbon precursor for DLC production, and these prioritized manufacturing process of only carbon bonds, and terpenes radicals were not preserved (Fadzilah et al., 2013, Liu and Kwek, 2008, Zani et al., 2013). No literature was found about camphor:DLC as a material to combat candidiasis proliferation. Candidiasis contamination is related to parenteral nutrition, and it is transmitted through the hands of healthcare workers and especially the use of catheters [6]. Candidiasis contamination has been a big problem for hospitalized patients, especially those in critical condition, and is the fourth leading cause of bloodstream infection. Bloodstream infection increases hospital costs, patient's hospitalization time and mortality rate (Morrison et al., 2006, van Asbeck et al., 2007). Biofilm is responsible for conducting catheter infection, due to a set of micro-organisms that live in association with biofilm (Bazaka et al., 2012, Griffiths and Hall, 2010). Most microorganisms involved in colonization of catheters are not virulent in planktonic form but can cause persistent infection when they are in a group (Co-investigator, 2013).

Camphor is cetonic terpenoid (C10H6O) obtained from the camphor tree that is native to China, and it is part of a class of bioactive compounds synthesized by plants (Frizzo et al., 2000, Gershenzon and Dudareva, 2007, Moreno et al., 2010). Terpenes are several open-chained or cyclic compounds, usually oxygenates such as aldehydes, alcohols, and ketones. Gershenzon and Dudareva (Gershenzon and Dudareva, 2007) reported previously that plants with terpenes are resistant to diseases, due to their action on fungi and bacteria. Terpenes have detergent properties that are toxic to fungi due to their ability to complex with sterols in fungi membranes, which leads to loss of membrane integrity (Gershenzon and Dudareva, 2007).

The aim of this work was to develop a DLC film that comprises camphor with properties to prevent biofilm of Candida albicans for use on catheters and biomedical instruments. For this, we developed a simple apparatus that was coupled in a commercial plasma enhanced chemical vapor deposition (PECVD) reactor for camphor delivery during DLC production. This process allows the deposition of DLC films containing radicals for functionalized surfaces or nanoparticles, covering materials three-dimensionally at low temperature.

Section snippets

Material and methods

For this study, we used three samples: bare polyurethane (PU) and polyurethane covered with camphor:DLC (Camphor:DLC/PU) and DLC (DLC/PU) films. The PU sheets used in this work is smooth, flat, transparent, and has 2 mm thickness they are commercial and widely used to produce peripherally inserted central catheters (PICC) - Uni Lumen Biomedical®. Biological tests were performed in three triplicates for each sample. Each triplicate was carried out on different days. Mechanical adhesion tests

Results and discussion

The PU, camphor:DLC/PU and DLC/PU samples were analyzed by Raman spectroscopy to verify their chemical composition. AFM and optical profilometry were used to evaluate roughness. SEM and AFM were used to analyze Candida albicans morphology, and counting of colony-forming units (CFU/mL) was used to analyze Candida albicans proliferation.

Conclusions

We produced DLC film and DLC containing terpenes from camphor deposited on polyurethane surface. Both films presented high adhesion even when the substrate was folded many times. The Raman spectra found the signature of DLC and showed that camphor peaks contributed to broadening DLC peaks on camphor:DLC film. The Raman map showed terpenoid bond from camphor distribution on DLC surface, which indicates that Raman in confocal images is a powerful tool to analyze mixed materials such as

Acknowledgements

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Project number 313280/2014-2, and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Project number 05 Capes/ITA. The authors are also grateful to Evado José Corat from INPE for Raman support, Carlos Costa and Evandro Martin Lanzoni from the Brazilian Nanotechnology National Laboratory (LNNano) for AFM analysis support.

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