Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-05
2002-05-21
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S106000, C523S111000, C524S017000, C524S018000, C524S021000, C524S027000, C524S028000, C524S035000, C524S047000, C524S054000, C524S056000, C524S058000, C527S101000, C527S200000, C522S087000, C522S088000
Reexamination Certificate
active
06391939
ABSTRACT:
The present invention relates to a biocompatible, non-toxic collagenous material which is potentially adherent and rapidly biodegradable. It relates more specifically to a collagenous material which is able to inhibit the formation of post-operative adhesions.
The invention also relates to a process for obtaining such a material.
Post-operative adhesions develop following surgical intervention in a patient, certain of whose organs have been subjected to trauma engendered by the surgical act itself.
The wounds created by dissecting organs or tissues, or by any other intervention, are characterized by two phenomena:
these wounds are not watertight and spontaneously exude a plasma fluid containing fibrin, sometimes even blood, if perfect haemostasis has not been achieved; certain organs ooze other liquids such as liver bile or cerebrospinal fluid in the case of the nervous system.
the damaged surfaces no longer possess an organized and stable tissue barrier and are occasionally even strewn with foreign bodies: suture threads, staples, blood clots, infectious agents, or tissues burnt by diathermy knives or laser beams.
These two characteristics bring about a reaction in the organism which starts with inflammation and continues with an intense and generally poorly organized migration and proliferation of cells. These usually give rise to neo-formed, fibrous, vascularized tissues which connect the damaged organs to adjacent organs.
Many reviews have been published on the subject (see, in particular, DI ZEREGA (1994)).
A variety of solutions have already been proposed, particularly at the pharmacological level, with varying degrees of success.
The most effective solution known to date is to place on the wound a physical barrier which isolates the organs from each other and which allows them to cicatrize independently without developing inter relationships.
Artificial, non-degradable tissues, to which cells do not attach, constitute the physical barriers which lead to the best results. Teflon® and silicone are examples of the most efficient polymers.
The major drawback is that these physical barriers have to be removed, several weeks later, by means of a second surgical operation which can, furthermore, itself give rise to other secondary adhesions at the site of the laparotomy.
It is therefore vital to develop biodegradable barriers which avoid the necessity of a second intervention.
With this aim in mind, a large number of natural biodegradable polymers made from gelatin, collagen, polysaccharides, mucopolysaccharides, etc. have already been proposed; however, these polymers have not led to satisfactory results.
According to RODEHEAVER's team (HARRIS et al., 1995), the minimum objective is that the barrier should remain in place for at least 36 hours. This is explained by the fact that a minimum time is required to enable the complex mechanisms of cicatrization to take their course.
However, the resorption time should not be too long. If the material remains in contact with the wound for several weeks it can give rise to persistent inflammatory reactions which favour a disorganized and more substantial fibrous reaction and which can cause anatomical problems locally: thickness, rigidity, shrinkage, ischaemia, granuloma or a persistent focus of infection, particularly in contact with the intestines and the digestive organs.
Furthermore, it appears that the material which is to serve as a physical barrier should adhere correctly to the damaged tissues, in particular when protecting organs which are mobile or which are subjected to variable distension, such as the intestine, or simply to prevent the barrier migrating in response to the movements of the patient and to the mechanical constraints which these movements entail.
The difficulty of obtaining all these properties combined in one and the same biomaterial explains why the solutions and products proposed to date are still found to be very inadequate.
The biodegradable products which are currently marketed for preventing adhesions are only partially active and yield results which are still inadequate.
The cellulose derivatives which are marketed by Johnson & Johnson Medical (Arlington, Tex., United States), such as the products SURGICELL® or INTERCEED®, cannot be used in the presence of blood and give disappointing results in some animal models (HARRIS et al., 1995).
The product SEPRAFILM®, which is marketed by Genzyme, (Cambridge, Mass., United States), is a film composed of hyaluronic acid and carboxymethyl cellulose and which only appears to be effective in 50% of cases (BECKER et al., 1996). While it degrades very rapidly in a few days, it is difficult to manipulate. It is fragile and brittle and impossible to use through a trocar in association with laparoscopy. Finally, it progressively loses its initial adherence and can migrate some distance, thereby leaving the wound unprotected.
The products which have been recently described by research workers in the literature or in published patent applications still appear to leave a large number of problems unresolved.
Products which have been recently proposed include a variety of collagenous materials.
KHOURY et al. (1994) propose, on behalf of COLETICA (Lyon, France), a collagen membrane which consists of two layers, with one layer being based on native collagen and forming the support and being covered with a second layer of gelatin. The idea for this membrane is inspired by a visceral surgery patch which was developed by TAYOT et al. (1988). This material has a degradation time which is very much longer than one month and does not, therefore, possess the essential property, which is that of disappearing very rapidly. It also suffers from the drawback of not being sufficiently adherent and, as a consequence, of having to be applied with suture stitches, which can give rise to undesirable complications.
In 1994, ORLY I. (6) proposed, on behalf of COLETICA, a transparent collagen membrane which consists of a single layer or of two layers, depending on the examples, and is usually combined with an undegradable prosthesis for treating hernias or eventrations. This membrane consists of undenatured native collagen. It has to be stapled or sutured. In order to make the stapling easier, it is necessary for the membrane to be transparent in order to avoid injuring sensitive zones (nerves and blood vessels), as in the case of inguinal hernias. The risks associated with stapling hernial prostheses, in particular, are well known. For this reason, surgeons will be more interested in gluing these prostheses, thereby avoiding any sutures or staples. ORLY I. specifies, surprisingly, that this membrane should not be adhesive since it is not possible to use the membrane developed by KHOURY et al., in the same Company, i.e. COLETICA (cited above), in this indication due to its adhesive properties, which hinder insertion in association with abdominal surgery. The time taken for resorption in the case of this membrane is considerably longer than one month since resorption is not complete at 5 weeks and 3 months are required for the material to have been almost totally eliminated. Despite these very long periods, the Applicant asserts, paradoxically, that the material has the advantage of a “relatively” rapid resorption time.
In 1995, YEUNG et al. (7) proposed, on behalf of Collagen Corporation (Palo Alto, Calif., United States), linking an anti-adhesion agent derived from polyethylene glycol to a collagenous substrate by means of covalent bonds. This product is very complicated to produce and requires the use of polyethylene glycol derivatives which are difficult to manufacture, expensive and not devoid of toxic risks associated with their chemical reactivity. Finally, the resorption time which is indicated for this material consisting of dense collagen is usually from 30 to 50 days.
In 1994, TARDY et al. (8) proposed, in a patent on behalf of IMEDEX, now called SADUC, a liquid biological glue which is derived from collagen and which has anti-adhesion properties. The particular advantages of t
Gravagna Philippe
Tardy Michel
Tayot Jean-Louis
Berman Susan W.
Imedex Biomateriaux
Larson & Taylor PLC
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