Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-11-20
2004-03-02
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S297000, C526S298000, C526S310000, C526S312000, C526S319000, C525S255000, C525S295000, C525S302000
Reexamination Certificate
active
06699940
ABSTRACT:
BACKGROUND TO THE INVENTION
The exceptionally fast rate of anionic polymerization of cyanoacrylates in the presence of a base, including water, made this class of monomers unique among all acrylic and vinyl monomers. Of the alkyl cyanoacrylate family of monomers, the methyl- and ethyl-esters are used extensively in industrial and consumer-type adhesives. Meanwhile, the isobutyl, n-butyl, and n-octyl cyanoacrylate esters are used clinically as blocking agents, sealants, and/or tissue adhesives in different parts of the world due to their much lower toxicity as compared with their more reactive methyl and ethyl counterparts. In the past few decades, there has been a great deal of interest in using tissue adhesives in many surgical procedures in favor of sutures and staples for a variety of reasons, including (1) ease of application and reduced clinician time; (2) location of repairable site as in contoured locations; (3) biomechanical properties as in weak organs, such as liver and pancreas; and (4) minimized hypertrophy and scar formation as in plastic surgery. However, there have been also a number of concerns associated with the alkyl cyanoacrylates. These include (1) their low viscosity and associated difficulties in precise delivery at the application site in non-medical and medical applications; (2) poor shear strength of the adhesive joint, particularly in aqueous environments in both medical and non-medical applications; (3) high modulus or stiffness of cured polymers at soft tissue application sites and associated mechanical incompatibility, which can lead to adhesive joint failure and/or irritation of the surrounding tissue; (4) excessive heat generation upon application of monomers to living tissue due to exceptionally fast rate of curing resulting in necrosis; and (5) site infection, among other pathological complications, associated with prolonged residence of the non-absorbable tissue adhesives. In response to these concerns, and particularly the ones associated with the non-absorbable cyanoacrylate that are used clinically, Shalaby and Linden (U.S. Pat. No. 5,350,798) disclosed a novel, absorbable tissue adhesive compositions that addressed, to a practical extent, the drawbacks of the absorbable as well as non-absorbable cyanoacrylates. In effect, the absorbable tissue adhesive compositions disclosed in U.S. Pat. No. 5,350,798, were based (1) primarily on a methoxy alkylcyanoacrylate and preferably methoxypropyl cyanoacrylate as the precursor of an absorbable tissue adhesive polymer; and (2) a polymeric, highly absorbable, liquid comprising an oxalate ester of triethylene glycol as a modifier to modulate the viscosity of the overall composition, lower the heat of polymerization, and increase the compliance and absorption rate of the cured adhesive joint. In a recent disclosure by this inventor (U.S. Pat. No. 6,299,631), a number of other useful modifiers were described and the functional performance of the new adhesive compositions was reported.
Although the admixture of polymeric modifier has been shown to be effective in addressing most of the medical and non-medical drawbacks of cyanoacrylate-based adhesives represented by methoxy propyl cyanoacrylate, there remain a number of technical drawbacks that exist in these systems. Such drawbacks disadvantage cyanoacrylates as precursors of absorbable and non-absorbable adhesives in both medical and non-medical applications and are due to having a mixture of two or more polymers or precursors thereof. This is related to the fact that the polymeric modifier(s) is usually present as a solute in the cyanoacrylate before application, but phase separation of the modifier may take place as the polycyanoacrylate is formed due to mutual immiscibility of two or more polymers, a common phenomenon associated with polymer miscibility. Naturally, there are a few exceptions to this phenomenon, and carefully chosen polymeric modifiers with specially tailored chains and monomeric cyanoacrylate may remain as a one-phase system after the latter is polymerized. This may very well be the case in some examples cited in U.S. Pat. Nos. 5,350,798 and 6,299,631. Nevertheless, the likelihood of encountering immiscibility in the formed adhesive joint can compromise not only the adhesive, but also the cohesive properties of such joint. This created a distinct need for the novel design of tissue adhesive/sealant compositions, subject of this invention, comprising covalently linked components in the cured adhesive joint or sealant. In effect, this invention deals with precursors of tissue adhesives/sealants (PT-A/S) as prepared as single-phase liquids that cure into their final functional forms as a homogeneous material, and not a physical mixture of two or more separable components. Moreover, the precursors of these compositions are designed to contain in one molecule two or more cyanoacrylate functionalities capable of fast anionic polymerization in aqueous environments (or in presence of a weak base), that are covalently linked to heterochain polymeric components responsible for most or all of the modulating features described in U.S. Pat. Nos. 5,350,798 and 6,299,631 without contending with the drawbacks of the aforementioned physical mixtures. Such design is applicable to both absorbable and non-absorbable cyanoacrylate-based adhesives/sealants for non-medical or medical applications.
SUMMARY OF THE INVENTION
This invention deals with a cyanoacrylate-based tissue adhesive or sealant composition comprising a cyanoacrylate-capped heterochain polymer having two or more cyanoacrylate ester groups per chain. The heterochain polymer used for capping can be one or more absorbable polymer of the following types: polyester, polyester-carbonate, polyether-carbonate, and polyether-ester. The capped polymer can also be derived from a polyalkylene glycol such as polyethylene glycol, or a block copolymer of polyethylene glycol and polypropylene glycol. Capping of the heterochain polymer can be achieved using an alkyl cyanoacrylate, or an alkoxyalkyl cyanoacrylate such as ethyl cyanoacrylate or methoxypropyl cyanoacrylate, respectively, in the presence of phosphorus-based acids or precursors thereof, such as pyrophosphoric acid and polyphosphoric acid in amounts exceeding 10 ppm. The formulations, subject of this invention, are intended for use as tissue adhesives or sealants for topical application. Radiochemically sterilized formulations, subject of this invention, can also be used as sterile adhesives, sealants, or blocking agents in repairing mechanically or pathologically compromised internal organs or tissues, or in blocking body conduits, such as blood vessels.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
This invention deals with cyanoacrylate-capped heterochain polymers with two or more cyanoacrylate functionalities per molecule and their use as absorbable or non-absorbable tissue adhesives, sealants, blocking agents, and/or hemostatic adhesives in medical or non-medical applications. Another aspect of this invention deals with a cyanoacrylate-based composition comprising a cyanoacrylate-capped heterochain polymer and a stabilizer against premature anionic polymerization such as pyrophosphoric acid and polyphosphoric acid and preferably an organic dye. One aspect of this invention deals with covalent binding of a cyanoacrylate functionality to a heterochain polymer molecule. A more specific feature of this aspect is using the process of transesterification between a hydroxyl group and a simple cyanoacrylate ester, such as methyl cyanoacrylate (MC), ethyl cyanoacrylate (EC), and methoxypropyl cyanoacrylate (MPC) to yield a cyanoacrylate-capped heterochain polymer in the presence of catalytic amounts of pyrophosphoric acid or polyphosphoric acid at a concentration that exceeds 10 ppm. Another aspect of this invention deals with the preparation of cyanoacrylate-capped (CC) polyalkylene oxide or copolymers thereof to produce a range of anionically fast polymerizing CC polyethers with a broad range of hydrophilic/hydrophobic content. In one more aspec
Gregory Leigh P.
Pezzuto Helen L.
Poly - Med, Inc.
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