title: Domination of volumetric toughening by silver nanoparticles over interfacial strengthening of carbon nanotubes in bactericidal hydroxyapatite biocomposite.
abstract: In order to address the problem of bacterial infections in bone-substitution surgery, it is essential that bone replacement biomaterials are equipped with bactericidal components. This research aims to optimize the content of silver (Ag), a well-known antibacterial metal, in a multiwalled carbon nanotube (CNT) reinforced hydroxyapatite (HA) composite, to yield a bioceramic which can be used as an antibacterial and tough surface of bone replacement prosthesis. The bactericidal properties evaluated using Escherichia coli and Staphylococcus epidermidis indicate that CNT reinforcement supports growth of Gram negative E. coli bacteria (~8.5% more adhesion than pure HA); but showed a strong decrease of Gram positive S. epidermidis bacteria (~diminished to 66%) compared to that of pure HA. Small amounts of silver (2-5wt.%) already show a severe bactericidal effect when compared to that of HA-CNT (by 30% and ~60% respectively). MTT assay confirmed enhanced biocompatibility of L929 cells on HA-4wt.% CNT (~121%), HA-4wt.% CNT-1wt.% Ag (~124%) sample and HA-4wt.% CNT-2wt.% Ag (~100%) when compared to that of pure HA. The samples with higher silver content showed decreased biocompatibility (77% for HA-4wt.% CNT-5wt.% Ag sample and 73% for HA-4wt.% CNT-10wt.% Ag). Though reinforcement of 4wt.% CNT has shown an increase of fracture toughness by ~62%, silver reinforcement has shown enhancement of up to 244% (i.e. 3.43 times). Accordingly, isolation of toughening contribution indicates that volumetric toughening by silver dominates over interfacial strengthening contributed by CNTs towards enhanced fracture toughness of potential HA-Ag-CNT biocomposites.
authors.affiliation: MVM - Department for Mechanical Process Engineering & Mechanics, Karlsruhe Institute of Technology, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Herkendell
authors.forename: Vishnu Raj
authors.initials: VR
authors.lastname: Shukla
authors.forename: Anup Kumar
authors.initials: AK
authors.lastname: Patel
authors.forename: Kantesh
authors.initials: K
authors.lastname: Balani
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001672:Biocompatible Materials / Q000494:pharmacology*; D002452:Cell Count; D015169:Colony Count, Microbial; D017886:Durapatite / Q000494:pharmacology*; D055119:Elastic Modulus / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects; D006244:Hardness; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D051379:Mice; D008826:Microbial Sensitivity Tests; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D044367:Phase Transition / Q000187:drug effects; D012834:Silver / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013059:Spectrum Analysis, Raman; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000648:ultrastructure; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D001672:Biocompatible Materials; D037742:Nanotubes, Carbon; D012834:Silver; D017886:Durapatite
keywords: Antibacterial; Carbon nanotubes (CNTs); Cytocompatibility; Fracture toughness; Hydroxyapatite (HA); Silver (Ag)