Analysis of Bioglass~circleR surface layers: comparing in vitro models of hca formation

摘要

In recent experiments we have revealed the incorporation of amino acids, DNA and RNA within Bioglass~circleR surface reaction layers (SRLs) after exposure to minimal essential medium ( alpha -MEM). The purpose of the experiment described herein was to compare the in vitro growth of the SRLs formed on 45S5 Bioglass~circleR after immersion in either Simulated Body Fluid (SBF), or in SBF which contained serum proteins. Low resolution compositional XPS showed significant elemental concentrations of nitrogen present in the surface when incubated in the presence of proteins (>10percent). Incubation in only SBF for identical (and longer) periods resulted in insignificant amounts of detectable nitrogen. Immersion in serum-containing SBF resulted in the creation of a calcium phosphate (CP) SRL as demonstrated by EDX, but negligible Ca and P signals were seen by XPS. These findings indicated that the newly forming CP-SRL was covered with a layer of adsorbed serum proteins. High resolution XPS confirmed that the deconvoluted N1s envelope corresponded to that of the peptide backbone characteristic of proteins. Deconvolution of the Cls envelope showed similar results. These results demonstrate that immersion in SBF is too simple a model of in vivo growth of Bioglass~circleR SRLs. Since SRLs which form in the presence of proteins are compositionally different from those which form in SBF, tissue bonding hypotheses based on interfacial reactions with only CP-SRLs should be modified because adsorbed proteins covering the CP will be presented to the biological milieu.