Magnetic isolation of particles suspended in synovial fluid for diagnostics of natural joint chondropathies.

Millions of people are stricken with the degenerative joint disease known as osteoarthritis. Osteoarthritis is associated with biochemical and mechanical processes, and is characterized by loss of articular cartilage and hypertrophy of bone. As cartilage and bone particles are released into the synovial fluid, a variety of biomarkers have been suggested for the analysis of this fluid. Here we have developed a method for isolating bone and cartilage wear particles suspended in the synovial fluid of the hip, knee and ankle joints of humans, based on specific magnetization of collagens I and II. Bio-ferrography is used to capture the particles on glass slides, allowing microscopic, chemical and statistical analyses. The relations between the level of the disease and the number, dimensions, shape and chemical composition of the particles were established. The method, which was found to be sensitive and reliable, can easily be extended to other applications, such as diagnosis of cancer and infectious diseases, determination of the efficacy of drugs or optimization of implants.