title: Do crosslinking and vitamin E stabilization influence microbial adhesions on UHMWPE-based biomaterials?
abstract: BACKGROUND
  Microorganism adhesion on polyethylene for total joint arthroplasty is a concern. Many studies have focused on vitamin E-stabilized ultrahigh-molecular-weight polyethylene (UHMWPE), whereas first-generation, highly crosslinked UHMWPE, which is the most commonly used in clinical practice, has been scarcely evaluated.
  
  
  OBJECTIVE
  We aimed (1) to compare the adherence of Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Candida albicans with virgin (untreated) UHMWPE (PE) and crosslinked UHMWPE (XLPE); (2) to correlate the results with the biomaterial surface properties; and (3) to determine whether the decreased adhesion on vitamin E-stabilized UHMWPE (VE-PE) previously recorded for bacteria can also be confirmed for C albicans.
  
  
  METHODS
  Microbial adhesion of biofilm-producing American Type Culture Collection (ATCC) and clinical strains on XLPE and VE-PE were compared with PE at 3, 7, 24, and 48 hours of incubation and quantified, as colony forming units (CFU)/mL, using a sonication protocol. Sample surfaces were characterized by scanning electron microscopy, roughness and contact angle measurements, attenuated total reflection-Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy (XPS) to reveal qualitative differences in surface composition and topography that could influence the microbial adhesion. The results were analyzed by descriptive statistics and tested by unpaired t-tests.
  
  
  RESULTS
  All microorganisms, both ATCC and clinical strains, showed lower adhesion (p < 0.05) on XLPE with adhesion percentages ranging from 18% to 25%, compared with PE with adhesion percentages ranging from 51% to 55%, after 48 hours. Only the ATCC S epidermidis showed a reduced adhesion profile even at 3 hours (adhesion ratio of 14% on XLPE versus 50% on PE) and 24 hours (19% on XLPE versus 55% on PE) of incubation. ATCC and clinical C albicans were less adherent to XLPE than to PE (p < 0.05) showing even at the earlier incubation time points adhesion values always of 10(3) CFU/mL and 10(4) CFU/mL, respectively. Roughness and contact angle were 0.8 ± 0.2 μm and 92° ± 3°, respectively, with no differences among samples. Qualitative differences in the surface chemical composition were revealed by XPS only. A confirmation of the decreased adhesion on VE-PE respect to PE was also registered here for C albicans strains (p < 0.05).
  
  
  CONCLUSIONS
  Vitamin E stabilization and crosslinking of UHMWPE are capable of reducing microbial adhesion. Further studies are needed to fully elucidate the mechanisms of modulation of microbial adhesion to medical-grade UHMWPE.
  
  
  CONCLUSIONS
  Our results suggest that VE-PE and XLPE may have an added benefit of being more resistant to bacterial adhesion, even fungal strains.
authors.affiliation: Department of Public Health and Pediatrics, University of Torino, Turin, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Banche
authors.forename: Pierangiola
authors.initials: P
authors.lastname: Bracco
authors.forename: Valeria
authors.initials: V
authors.lastname: Allizond
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bistolfi
authors.forename: Michele
authors.initials: M
authors.lastname: Boffano
authors.forename: Andrea
authors.initials: A
authors.lastname: Cimino
authors.forename: Elena Maria
authors.initials: EM
authors.lastname: Brach del Prever
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Cuffini
mesh_terms: D001672:Biocompatible Materials; D018441:Biofilms / Q000187:drug effects*; D002176:Candida albicans; D004926:Escherichia coli; D006801:Humans; D008422:Materials Testing; D011095:Polyethylenes / Q000737:chemistry*; D011474:Prosthesis Design; D016459:Prosthesis-Related Infections / Q000188:drug therapy / Q000382:microbiology / Q000517:prevention & control*; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000517:prevention & control*; D013211:Staphylococcus aureus; D013212:Staphylococcus epidermidis; D013499:Surface Properties; D014810:Vitamin E / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D001672:Biocompatible Materials; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D014810:Vitamin E