Jul 18, 2007
SFM analyses cartilage on the nanoscale
Swiss researchers have developed a prototype "arthroscopic scanning force microscope" that could be used to detect osteoarthritis in its early stages. The device, which is just 5 mm thick, could be inserted directly into a patient's joint like a needle to measure the elastic properties of cartilage on the nanoscale. The non-destructive technique could also monitor how new cartilage forms and might even be used to locally deliver medicines in the future.
It was the Nobel laureate Richard Feynman who first put forward the idea of using "nanotools" to detect diseases and repair the human body. One such tool is the scanning force microscope (SFM), which uses a fine nanometre-sized tip on the end of a cantilever to scan over a sample surface and accurately map its troughs and peaks. The SFM can image biological matter at scales ranging from nanometres to millimetres. It can also probe the stiffness of a sample by pressing the tip onto the sample surface and measuring the deformation produced.
Now, Martin Stolz and colleagues of the Swiss Nanoscience Institute (SNI) have shown that the SFM can be used to diagnose osteoarthritis, a painful and disabling disease that affects millions of people worldwide. The disease progressively degrades articular cartilage, so changing its elastic properties, and generally begins by attacking different joints long before middle age. However, it cannot be diagnosed until symptoms start to appear, by which time it is usually too late because the cartilage has been irreversibly damaged. To make things worse, current devices for measuring the biomechanical properties of cartilage typically work at millimetre lengths or above, so are useless at the sub-cellular scales at which pathological lesions start.
The new device fits into a standard arthroscopic canula and can be inserted into a joint to measure the elastic properties of cartilage (figures 1 and 2). The device could also be used to deliver drugs to a particular point in the joint and monitor how the disease progresses.
Previously, the team measured the mechanical stiffness of samples of healthy and diseased cartilage ex vivo and found that the osteoarthritic cartilage was significantly stiffer than normal cartilage (figure 2). Moreover, the collagen fibrils, which are normally oriented in 3D, were seen to bundle together in one direction – that in which the joint moves. The technique developed by the NCCR team can detect these changes long before clinical symptoms of osteoarthritis, such as pain, start.
"We are now looking for industrial partners to turn the arthroscopic SFM from a prototype into a full product and be on the market," Stolz told nanotechweb.org. “We are also looking for partners in the pharmaceutical industry for using our SFM method as a tool to develop drugs and treatments against osteoarthritis."
Stolz says he also wants to use the technique to develop tissue-engineered cartilage with improved qualities, that is, one that has the properties of native cartilage. "This will enable more effective repair of diseased cartilage, stimulate transplanted cartilage and help design and produce tissue-engineered cartilage with long-term mechanical stability and biocompatibility," he adds.
The arthroscopic SFM could be used to examine other parts of the body too – for example, for detecting "vulnerable" plaques in the heart coronary arteries responsible for heart attacks by using a catheter-based approach.
The researchers reported their work in Nanomedicine.
About the author
Belle Dumé is contributing editor at nanotechweb.org