Magnetic Capture of a Molecular Biomarker from Synovial Fluid in a Rat Model of Knee Osteoarthritis

Abstract

Biomarker development for osteoarthritis (OA) often begins in rodent models, but can be limited by an inability to aspirate synovial fluid from a rodent stifle (similar to the human knee). To address this limitation, we have developed a magnetic nanoparticle-based technology to collect biomarkers from a rodent stifle, termed magnetic capture. Using a common OA biomarker - the c-terminus telopeptide of type II collagen (CTXII) - magnetic capture was optimized in vitro using bovine synovial fluid and then tested in a rat model of knee OA. Anti-CTXII antibodies were conjugated to the surface of superparamagnetic iron oxide-containing polymeric particles. Using these anti-CTXII particles, magnetic capture was able to estimate the level of CTXII in 25 µL aliquots of bovine synovial fluid; and under controlled conditions, this estimate was unaffected by synovial fluid viscosity. Following in vitro testing, anti-CTXII particles were tested in a rat monoiodoacetate model of knee OA. CTXII could be magnetically captured from a rodent stifle without the need to aspirate fluid and showed 10 fold changes in CTXII levels from OA-affected joints relative to contralateral control joints. Combined, these data demonstrate the ability and sensitivity of magnetic capture for post-mortem analysis of OA biomarkers in the rat.

Comparing intra-articular CTXII levels assessed via magnetic capture or lavage in a rat knee osteoarthritis model

“…Magnetic capture was performed as described previously [9]. Briefly, anti-CTXII antibody was obtained from the ImmunoDiagnostic Systems Cartilaps kit (Copenhagen, Denmark).…”

“…#107319-02). The ability of particles to bind and recover CTXII was assessed prior to use, as described in [9]. The change in particles between timepoints was due to commercial availability.…”

“…Then, using a magnetic probe, a portion of the particles was collected from the joint, washed, and treated to release CTXII (see [9]). Samples were then analyzed for CTXII using ELISA (kit AC-08F1, ImmunoDiagnostic Systems, Copenhagen, Denmark) and for the amount of collected particles via absorbance (450 nm) or fluorescence (530/590 nm).…”

“…Previously, magnetic capture was demonstrated through in vitro tests and a proof-of-concept study in the rat monoiodoacetate (MIA) model [9]. While this work demonstrates improved sensitivity over published lavage data [10], direct comparison of magnetic capture and lavage has not yet been conducted.…”

“…To address these challenges, our group developed a magnetic nanoparticle-based technology to collect biomarkers from synovial fluid, termed magnetic capture [8,9]. Previously, magnetic capture was demonstrated through in vitro tests and a proof-of-concept study in the rat monoiodoacetate (MIA) model [9].…”