This page summarises some of our recent bio-medical applications of FFC. Further details can be found in the downloadable abstracts and manuscripts on our Publications page.
Thrombosis monitored by FFC relaxometry
Blood clot formation (thrombosis) involves the controlled polymerisation and cross-linking of fibrinogen to form a network of fibrin fibres which form the rigid skeleton of the clot. Fibrinogen protein is dissolved in blood plasma; due to its mobility in solution, it does not give rise to quadrupolar peaks in its R1 dispersion plot. However, the polymerisation of fibrinogen and its cross-linking to form a fibrin network leads to immobilisation of the protein, and the associated observation of quadrupole peaks.
In this study model thrombi were produced in the laboratory, using a range of starting concentrations of fibrinogen in solution. Clot formation was initiated by the addition of thrombin enzyme, after which FFC relaxometry was carried out on the 1-mL (approximately) samples, using our bench-top FFC-NMR relaxometer. The figure below shows an R1 dispersion plot of fibrinogen solution at 10 mg/mL concentration (open circles), together with a dispersion plot obtained after clot formation (closed circles).
|R1 dispersion plots of fibrinogen in solution (open circles) and fibrin clot (closed circles). Quadrupole peaks are absent prior to clotting, but evident afterwards due to immobilisation of the protein.|
The experiment was repeated using a range of starting concentrations of fibrinogen, in order to see if the 'height' of the quadrupole peaks (ΔR1 in the figure above) was proportional to the immobile protein concentration. The figure below shows the result of these experiments:
|Effect of fibrinogen concentration on the 'height' of the quadrupole peaks ΔR1. The expected linear relationship is observed.|
This study showed that FFC-NMR relaxometry can monitor clot formation in a model of thrombosis. Work is progressing to investigate more complex thrombosis models. We plan to extend this work, in the hope that FFC-MRI can provide extra information on blood clots in patients.
Detection of osteoarthritis in knee and hip joints by FFC NMR
Osteoarthritis is a debilitating disease of the joints. There is a great need for a diagnostic method that can detect osteoarthritic changes in joint tissues early in the progress of the disease, when drug treatment may be possible. However, at present no such technique is sufficiently reliable.
It is known that the concentration of proteins called glycans decreases in osteoarthritis. We are investigating whether FFC NMR relaxometry can detect differences in the measured quadrupole peaks, between normal and diseased joints, since the quadrupole peaks are strongly dependent on a tissue's immobile protein content. If so, FFC-MRI may be a viable method of detecting disease.
Ethical approval for the study was granted by the North of Scotland Research Ethics Committee. Samples of cartilage were obtained from patients with osteoarthritis during hip or knee surgery. Samples of normal cartilage were obtained from patients undergoing hip replacement for osteoporotic fractured neck of femur with no preceding osteoarthritis of the hip.
Relaxometry measurements of cartilage were carried out using our bench-top FFC NMR relaxometer. The figure below shows a comparison of R1 dispersion curves obtained from cartilage samples from normal and osteoarthritic patients - there is clearly a difference between the two.
|FFC-NMR relaxometry on normal cartilage (squares) and cartilage from patient with osteoarthritis (circles). The difference between the two is clear.|
The data were further analysed by subtracting the "background" from the curves, in order to isolate the quadrupole peaks, as shown below.
|Isolated (background-subtracted) quadrupole peaks obtained using FFC-NMR relaxometry on normal cartilage (left) and cartilage from an osteoarthritic joint (right). The amplitude of the quadrupolar peaks is clearly reduced in the osteoarthritic cartilage.|
These preliminary results indicate that there appears to be significant potential for the detection of osteoarthritic changes in joints using FFC methods. Further research is being carried out in our labs, funded by a grant from Arthritis Research UK.