Diagnostic utility of fluorogenic peptide-conjugated Au nanoparticle probe corroborated by rabbit model of mild cartilage injury and panel of osteoarthritic patients.

Using a rabbit model of early-stage osteoarthritis (OA) and a sampling patients with OA, we evaluated the diagnostic utility of a fluorogenic peptide-conjugated gold nanoparticle (AuNP) probe in detecting mild cartilage injury, based on the a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) enzyme. Synthesis of this fluorescent turn-on probe (or AU-probe) required conjugation of AuNPs with a fluorescein isothiocyanate (FITC)-modified ADAMTS-4-specific peptide (DVQEFRGVTAVIR). Synovial fluid samples were then collected from 48 adult rabbits and 100 patients for comparative testing (ADAMTS-4 ELISA and AU-probe). Rabbit and patient MRI images were also evaluated and scored. Receiver operating characteristic (ROC) curve analysis was applied to various diagnostic methods (MRI, ELISA, AU-probe, and arthroscopy), performing comparisons via logistic regression. In rabbits, the AU-probe proved nonsuperior to MRI T2 mapping and ELISA (fluorescence cutpoint > 864.965 au). In patient groups, logistic regression analysis indicated that combined AU-probe/MRI testing outperformed MRI alone, thus offsetting low MRI sensitivity and low AU-probe specificity for improved detection of mild cartilage injury (sensitivity, 82.5%; specificity, 80.0%). We have consequently confirmed the efficacy of this AU-probe, using ADAMTS-4 activity in synovial fluid to diagnose mild cartilage injury. Combining the AU-probe with conventional MRI assessment proved optimal in this setting.