title: Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability.
abstract: Al-free glasses of general composition 0.340SiO2:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na2O:0.060P2O5 (a, b=0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements was evaluated using poly(acrylic acid) and water. We evaluated the influence of the poly(acrylic acid) molecular weight and glass particle size in the cement mechanical performance. Higher compressive strength (25±5 MPa) and higher compressive elastic modulus (492±17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and glass particle sizes between 63 and 125 μm. Cements prepared with glass formulation a=0.125 and b=0.000 were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer saline containing α-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial degradation. Zn release studies (concentrations between 413 μM and 887 μM) evidenced the necessity to tune the cement formulations to reduce the Zn concentration in the surrounding environment.
authors.affiliation: 3B's Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, 4806-909 Taipas, Guimarães, Portugal.
authors.forename: Filipa O
authors.initials: FO
authors.lastname: Gomes
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Pires
authors.forename: Rui L
authors.initials: RL
authors.lastname: Reis
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000535:Aluminum / Q000737:chemistry*; D001672:Biocompatible Materials / Q000494:pharmacology*; D001673:Biodegradation, Environmental; D001843:Bone Cements / Q000494:pharmacology*; D002118:Calcium / Q000032:analysis; D019245:Compressive Strength / Q000187:drug effects; D055119:Elastic Modulus / Q000187:drug effects; D005899:Glass Ionomer Cements / Q000494:pharmacology*; D021621:Imaging, Three-Dimensional; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D010316:Particle Size; D010758:Phosphorus / Q000032:analysis; D016062:Porosity; D011208:Powders; D013054:Spectrophotometry, Atomic; D017550:Spectroscopy, Fourier Transform Infrared; D013213:Starch / Q000494:pharmacology; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D015032:Zinc / Q000032:analysis
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; D001843:Bone Cements; D005899:Glass Ionomer Cements; D011208:Powders; D014867:Water; D010758:Phosphorus; C006903:carbopol 940; D013213:Starch; D000535:Aluminum; D015032:Zinc; D002118:Calcium
keywords: Bioactive; Biodegradable; Bone cements; Glass-ionomer cements; Mechanical properties