Surgery – Diagnostic testing – Liquid collection
Reexamination Certificate
2000-02-24
2001-09-18
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Liquid collection
C600S577000, C604S317000, C604S403000, C436S018000
Reexamination Certificate
active
06290655
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to blood collection and, more particularly, relates to a plastic blood sample collection assembly and method for its manufacture.
2. Background
Blood samples are routinely taken in glass evacuated tubes. One end of a double-ended needle is inserted into a patient's vein. The other end of the needle then punctures a septum covering the open end of the tube so that the vacuum in the tube draws the blood sample through the needle into the tube. Using this technique, a plurality of samples can be taken using a single needle puncture of the skin.
In addition, recent advancements in analytical instrumentation have made it possible to carry out a variety of hematological or chemical diagnostic procedures on very small quantities of blood, such as may be obtained by puncture of a patient's finger, earlobe or an infant's heel. Accordingly, a variety of blood sample microcollection devices have been disclosed in the art.
Plastic tubes have been proposed for blood collection. Plastic offers a number of advantages over glass such as lower breakage, less weight in shipment, and easier disposal by incineration. However, blood does not flow smoothly over hydrophobic surfaces, and blood components, such as platelets, fibrin or clotted blood generally adhere tenaciously to plastic surfaces and hang up on the walls of plastic collection tubes. This is a particular problem in small diameter gravity actuated microcollection tubes during sample collection or in vacuum tubes during subsequent centrifugation. Thus, in any collection apparatus, it is highly advantageous if the collection tube has a surface which resists adherence to blood components at any stage of the collection process or analysis procedure.
Adherence of blood components is not a problem with glass collection tubes, and accordingly, one approach to overcoming this problem in plastic has been to modify the plastic surface to be more glass-like, i.e., to present a hydrophilic surface to the blood. To this end, collection tubes have been treated with a gas plasma to alter the surface chemistry by introduction of heteroatoms. In another, the interior wall surface of the plastic tube has been modified by coating with materials such as surface active agents, water soluble polymers or water insoluble polymers carrying hydrophilic-hydrophobic copolymers.
While the above disclosures have improved blood flow and reduced adherence to plastic blood collection tubes, the problem has not been totally solved because the copolymers on the prior art surfaces are partially or completely removed by the blood so that the surfaces revert back to hydrophobic. There is a need for a collection tube in which adherence is avoided until analysis is complete, and no foreign materials are introduced into the plasma, serum or clot which may interfere with subsequent blood analysis.
SUMMARY OF THE INVENTION
An assembly for blood sample collection comprises a hydrophobic plastic tube which does not undergo any structural deformation when heated above its glass transition temperature and is thus capable of sealingly engaging a closure for an open end of the tube. The assembly includes a block or graft copolymer having a hydrophilic domain and a hydrophobic domain compatible with and interpenetrated into the tube polymer. In this disclosure, the term domain includes the total hydrophobic or hydrophilic segments present in the copolymer. The term compatible, as known in the art, refers to polymers which contain identical or similar functional moieties which blend together into a single polymeric phase when heated. The term interpenetrated is used to describe compatible polymeric domains which are intimately mixed throughout at least a portion of an article's cross-section so that they form a substantially single polymeric phase. It is believed, although not proven, that the long polymer molecules become entangled to form this phase whereas non-compatible domains do not entangle. Preferred assemblies are polyester evacuated collection tubes with puncturable closure or polypropylene microtubes having a cap and an integral lip.
The interpenetration of the hydrophobic domain in the tube polymer prevents exudation of the copolymer into a blood sample, and the block or graft nature of the copolymer allows at least a portion of the hydrophilic domain to extend to the interior wall surface of the tube and provide hydrophilicity thereto.
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Lin Fu-chung
Serpentino Peter
Shankar Hariharan
Weir Theodore S.
Becton Dickinson and Company
Brown Richard E.
Marmor II Charles
Winakur Eric F.
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