High field (1)H and (51)V NMR spectroscopies were employed to determine the oxidation state and complexation status of vanadium ions in intact osteoarthritic knee-joint synovial fluid (OA SF) when pre-added as V(III)((aq.)), V(IV)((aq.)) and V(V)((aq.)).
Aliquots of each vanadium solution were added to the SF samples and their (1)H NMR spectra recorded. (51)V NMR spectra were also recorded for the samples to which V(III)((aq.)) had been added. Theoretical computer simulations of the competitive complexation of vanadium ions by a range of low-molecular-mass biomolecules were also performed.
The spectroscopic results demonstrated that addition of vanadium ions to intact OA SF gave rise to their complexation by a range of low-molecular-mass biomolecules. The results indicated the physiologically-significant complexing abilities of histidine, threonine, glycine, tyrosine and citrate for each of the added metal ions. The computer simulations revealed that the relative capacity of OA SF complexants to compete for available V(III), V(IV) and V(V) ions reflected the thermodynamic stability constants for such complexes and their available concentrations in this biofluid.
Since comparatively low concentrations of added metal ion are required to selectively influence spectral properties, the "speciation" of prostheses-derived metal ions in biofluids and tissues can be ascertained through the facile employment of high resolution NMR spectroscopy.