title: Polyelectrolyte multilayer-calcium phosphate composite coatings for metal implants.
abstract: The preparation of organic-inorganic composite coatings with the purpose to increase the bioactivity of bioinert metal implants was investigated. As substrates, glass plates and rough titanium surfaces (Ti-SLA) were employed. The method comprises the deposition of polyelectrolyte multilayers (PEMLs) followed by immersion of the coated substrate into a calcifying solution of low supersaturation (MCS). Single or mixed PEMLs were constructed from poly-L-lysine (PLL) alternating with poly-L-glutamate, (PGA), poly-L-aspartate (PAA), and/or chondroitin sulfate (CS). ATR-FTIR spectra reveal that (PLL/PGA)10 multilayers and mixed multilayers with a (PLL/PGA)5 base contain intermolecular β-sheet structures, which are absent in pure (PLL/PAA)10 and (PLL/CS)10 assemblies. All PEML coatings had a grainy topography with aggregate sizes and size distributions increasing in the order: (PLL/PGA)n < (PLL/PAA)n < (PLL/CS)n. In mixed multilayers with a (PLL/PGA)n base and a (PLL/PAA)n or (PLL/CS)n top, the aggregate sizes were greatly reduced. The PEMLs promoted calcium phosphate nucleation and early crystal growth, the intensity of the effect depending on the composition of the terminal layer(s) of the polymer. In contrast, crystal morphology and structure depended on the supersaturation, pH, and ionic strength of the MCS, rather than on the composition of the organic matrix. Crystals grown on both uncoated and coated substrates were mostly platelets of calcium deficient carbonate apatite, with the Ca/P ratio depending on the precipitation conditions.
authors.affiliation: Casali Center for Applied Chemistry, The Institute of Chemistry, The Hebrew University of Jerusalem , Edmond J. Safra Campus, Givat Ram, Jerusalem 9190401, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Elyada
authors.forename: Nissim
authors.initials: N
authors.lastname: Garti
authors.forename: Helga
authors.initials: H
authors.lastname: Füredi-Milhofer
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry*; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003460:Crystallization / Q000379:methods; D018698:Glutamic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000737:chemistry; D008670:Metals / Q000737:chemistry*; D009994:Osmolar Concentration; D011108:Polymers / Q000737:chemistry*; D019736:Prostheses and Implants; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D008670:Metals; D011108:Polymers; D001224:Aspartic Acid; D018698:Glutamic Acid; C020243:calcium phosphate; D014025:Titanium; D008239:Lysine