Surface Free Energy Dominates the Biological Interactions of Postprocessed Additively Manufactured Ti-6Al-4V

Victor Manuel Villapun Puzas, Luke N Carter, Christian Schröder, Paula E Colavita, David A Hoey, Mark A Webber, Owen Addison, Duncan E T Shepherd, Moataz M Attallah, Liam M Grover, Sophie C Cox

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Abstract

Additive manufacturing (AM) has emerged as a disruptive technique within healthcare because of its ability to provide personalized devices; however, printed metal parts still present surface and microstructural defects, which may compromise mechanical and biological interactions. This has made physical and/or chemical postprocessing techniques essential for metal AM devices, although limited fundamental knowledge is available on how alterations in physicochemical properties influence AM biological outcomes. For this purpose, herein, powder bed fusion Ti-6Al-4V samples were postprocessed with three industrially relevant techniques: polishing, passivation, and vibratory finishing. These surfaces were thoroughly characterized in terms of roughness, chemistry, wettability, surface free energy, and surface ζ-potential. A significant increase in Staphylococcus epidermidis colonization was observed on both polished and passivated samples, which was linked to high surface free energy donor γ- values in the acid-base, γAB component. Early osteoblast attachment and proliferation (24 h) were not influenced by these properties, although increased mineralization was observed for both these samples. In contrast, osteoblast differentiation on stainless steel was driven by a combination of roughness and chemistry. Collectively, this study highlights that surface free energy is a key driver between AM surfaces and cell interactions. In particular, while low acid-base components resulted in a desired reduction in S. epidermidis colonization, this was followed by reduced mineralization. Thus, while surface free energy can be used as a guide to AM device development, optimization of bacterial and mammalian cell interactions should be attained through a combination of different postprocessing techniques.

Original languageEnglish
Pages (from-to)4311-4326
Number of pages16
JournalACS Biomaterial Science and Engineering
Volume8
Issue number10
Early online date20 Sept 2022
DOIs
Publication statusE-pub ahead of print - 20 Sept 2022

Keywords

  • additive manufacturing
  • biological interactions
  • medical devices
  • physicochemical characterization
  • powder bed fusion

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