Coating processes – Medical or dental purpose product; parts; subcombinations;... – Analysis – diagnosis – measuring – or testing product
Patent
1993-11-10
1996-03-05
Dudash, Diana
Coating processes
Medical or dental purpose product; parts; subcombinations;...
Analysis, diagnosis, measuring, or testing product
427 23, 427301, 427535, 427240, 427421, 4274301, B05D 304, B05D 102, B05D 118, A61K 4100
Patent
active
054965810
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the treatment of the surfaces of materials to prevent or inhibit adsorption of protein or reduce thrombogenicity.
In blood contacting devices problems can arise from thrombogenic reaction at untreated metal, glass or plastic surfaces. Such a reaction can lead to platelet adhesion and clotting, which can have severe, sometimes disastrous, consequences. It is desirable therefore to develop a treatment for surfaces which reduces and preferably avoids such a reaction.
Problems can also arise from non-specific protein adsorption at the surface of devices used in many applications, such as medical devices. For instance, in many modern diagnostic devices, such as many biosensors, a specific interaction between an analyte and a detector species is relied upon. In such situations non-specific protein adsorption can cause a dramatic loss in sensitivity or even render the device inoperable. Similarly, where bioseparation membranes are used, non-specific protein adsorption can cause clogging and thus fouling of the membranes.
Protein adsorption is also recognised as a problem in sight correction devices such as contact lenses. Protein build up on such devices leads to a loss in comfort to the wearer and a deterioration in vision.
Many modern surgical and other medical procedures involve the use of blood-contacting devices, such as surgical implants, prostheses, catheters, drains and extra-corporeal circuitry. Such devices are used and then discarded for hygiene reasons: such devices must therefore be constructed from the most economical materials available, usually polymeric plastics or glass. However as already mentioned glass and most synthetic and natural polymers tend to induce platelet adhesion and activation. Initiation of the clotting cascade follows, leading to blockage of tubing and clogging of other apparatus such as filtration and dialysis membranes and interference with test procedures which, in certain cases, may have disastrous consequences for patients. Moreover in cases where a device is intended to be implanted into a patient and to remain for a prolonged period, such platelet aggregation and clotting must be avoided over a prolonged period.
With existing technology, in order to prevent the formation of blood clots during extra-corporeal circulation for haemodialysis, long term gas exchange at states of severe respiratory failure and cardiac support, e.g. after cardiac surgery, systemic heparinisation is employed. Owing to the risk of excessive bleeding after such systemic anticoagulant treatment many patients are disqualified from possible therapeutic measures. Likewise, commercial catheter sensors, e.g. for continuous determination of arterial oxygen, carbon dioxide concentration and of pH in the critically ill patient require systemic heparinisation to prevent microclotting on the sensor membranes and failure of the device.
It has been suggested that heparinisation of apparatus, particularly involving end point attachment of heparin fragments, will result in anti-thrombogenic coating of surfaces and thereby overcome the need for systemic heparinisation. Thus a method was developed in which heparin was coupled by end point attachment [Hoffman, J. et al., Carboyhdr. Res., 117:328(1983), Larm, O. et. al., Biomat. Med. Dev. Art. Org., 111161(1983)]. The resulting surfaces adsorbed antithrombin and large amounts of thrombin which were rapidly inhibited in the presence of antithrombin [Pasche, B, et al., Thromb. Res., 44 739(1986)]. It is interesting to note that end-point attached heparin and the endothelium behave both quantitatively and qualitatively alike with respect to the inhibition of thrombin in the presence of plasma [Arnander C., et al., J. Biomed. Mat. Res., 20:235(1986)] and that a polyethylene surface furnished with end-point attached heparin showed considerable capacity to inhibit Factor Xa [Kodama, K. et al., Thromb. Haemostas. (1987)].
Rigid polyethylene tubing sections with end-point attached heparin have been kept in the thoracic aorta of pigs for up to
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Wiles Martin C.
Yianni Yiannakis P.
Biocompatibles Limited
Dudash Diana
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