FURTHER-STUDIES OF CALCIUM-PHOSPHATE GROWTH ON PHOSPHORYLATED COTTON FIBERS

Further studies using scanning electron microscopy/energy dispersive X -ray analysis (SEM/EDX), micro-fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and solid state magic angle spinning nuclear magnetic resonance (MAS NMR) techniques of calc ium phosphate growth on Ca(OH)a-treated urea/H3PO3- and urea/H3P4-modi fied cotton fibres are reported. In the case of the Ca(OH)(2)-treated urea/H3PO3-modified fibres which have been reported in an earlier pape r, further experiments subjecting the urea/H3PO3-modified cotton to al ternative soaking treatment procedures to Ca(OH)(2) as well as differe nt calcium phosphate growth media such as the alkaline phosphatase-cat alysed hydrolysis of disodium p-nitrophenyl phosphate to free phosphat e have reaffirmed the importance of the Ca(OH)(2) treatment step for t he stimulus and growth of calcium phosphate growth on the fibres. Stud ies on cotton phosphorylated by a slightly different method using urea /H3PO4 instead of urea/H3PO3 show that a phosphorylated cotton with si milar properties to the urea/H3PO3-modified fibres can be produced. So aking of these fibres in saturated Ca(OH)(2) solution leads to cotton coated with thin layers of calcium phosphate formed by partial hydroly sis of the PO4 functionalities in the phosphorylated cotton which are believed to act as nucleation layers for further calcium phosphate dep osition when the fibres are subsequently soaked in 1.5 x SBF solution. SEM/EDX studies of the calcium phosphate coatings formed on the Ca(OH )(2)-treated urea-H3PO4 fibres as a function of soaking time in 1.5 x SBF show that coatings deposit and become noticeably thick after appro ximately 9 days. XPS studies indicated the presence of carbonate speci es in the calcium phosphate coating deposited. In common with the calc ium phosphate coated Ca(OH)(2)-treated urea/H3PO3-modified fibres stud ied earlier, the average EDX-measured Ca:P ratios of the coatings form ed on the Ca(OH)(2)-treated urea/H3PO4 fibres are similar to 1.60 and give very similar micro-FTIR spectra with evidence of carbonate which suggests that amorphous calcium deficient apatite has deposited.