title: Calcium phosphate nucleation on surface-modified PTFE membranes.
abstract: Highly porous PTFE membranes are currently being used in facial reconstructive surgery. The present study aims at improving this biomaterial through creating a more bioactive surface by introducing ionic groups onto the surface. The unmodified PTFE membrane does not induce inorganic growth after immersion in simulated body fluid (SBF) for up to 4 weeks. Copolymeric grafting with acrylic acid (AAc) by means of gamma irradiation and subsequent in vitro testing in SBF reveals that this copolymer initially acts as an ion-exchange material and subsequently induces growth of a calcium phosphate phase (Ca/P=2.7) when large amounts (15%) of pAAc are introduced onto the membrane surface. This copolymer is not expected to function well from a biomaterials perspective since SEM showed the pores on the surface to be partly blocked. In contrast, the surface of monoacryloxyethyl phosphate (MAEP)-modified samples is altered at a molecular level only. Yet the modified materials are able to induce calcium phosphate nucleation when the external surface coverage is 44% or above. The initial inorganic growth on these membranes in SBF has a (Ca+Mg)/P ratio of 1.1 (presumably Brushite or Monetite). The secondary growth, possibly calcium-deficient apatite or tricalcium phosphate, has a (Ca+Mg)/P ratio of 1.5. This result is a promising indicator of a bioactive biomaterial.
authors.affiliation: Centre for Instrumental and Developmental Chemistry, Queensland University of Technology, GPO Box 2434, Brisbane QLD 4001, Australia.
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Grøndahl
authors.forename: Francisco
authors.initials: F
authors.lastname: Cardona
authors.forename: Khang
authors.initials: K
authors.lastname: Chiem
authors.forename: Edeline
authors.initials: E
authors.lastname: Wentrup-Byrne
authors.forename: Thor
authors.initials: T
authors.lastname: Bostrom