Behavior of Monosodium Urate Crystals in a Highly Viscous Model of Synovial Fluid

To develop gout diagnosis using magnetic fields and near-infrared light, the orientation behavior of monosodium urate crystals in a highly viscous suspension was characterized. The transmitted light intensity was used to monitor orientation time and behavior within an electromagnet. In glycerol with a viscosity of 1250 mPa · s , the crystals were oriented in 4500 s at 100 mT. This was shortened to 360 s when the magnetic field was 500 mT. Similar behavior was observed in a hyaluronic acid solution, which is one component of synovial fluid and which had a viscosity of $960 mPa · s . The crystal orientation times followed theoretical values when the viscosity was $10 mPa · s or less but were shorter than expected at higher viscosities. In general, the viscosity decreases to about $300 mPa · s when inflammation occurs in a joint. In this case, the orientation time is expected to be about 1 min. Device applications are possible given the orientation times.