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Biotransplants Retaining Resorbable Polymer Films

#A-1745


Elaboration of the Resorbable Polymer Films for Crashed Osteogenic Transplants’ Secure Fixing in Bone Defect for Quality Increasing of the Regenerate

Tech Area / Field

  • CHE-POL/Polymer Chemistry/Chemistry
  • MAT-COM/Composites/Materials
  • MED-OTH/Other/Medicine

Status
3 Approved without Funding

Registration date
20.04.2009

Leading Institute
Scientific Center of Traumatology and Orthopeadics, Armenia, Yerevan

Supporting institutes

  • Yerevan Institute "Plastpolymer", Armenia, Yerevan

Collaborators

  • Texas Scottish Rite Hospital for Children, USA, TX, Dallas\nFeinstein Institute for Medical Research, USA, NY, Manhasset\nUniversity of Lund / Center for Chemistry and Chemical Engineering, Sweden, Lund\nNara Medical University, Japan, Kashihara-shi

Project summary

Project Goal: To improve the quality of bone regenerate using new resorbable polymer films for secure fixing of crashed osteogenic transplants.

.Advance weapons of war continuously undergo qualitative changes that result in multi-profile gunshot wounds that require new treatment approaches. Greatest difficulties are encountered upon treatment of gunshot wounds with extensive soft-tissue injuries and bone defects.

Etiology of bone defect might be either primary, caused by immediate influence of kinetic energy of firing, or secondary – as a result of surgical treatment of a gunshot fracture or its complication. The advancement of bone-and-joints surgery resulted in elaboration of treatment procedures with application of different osteoplastic materials for regeneration of bone defects. Treatment approach for bone defects depends on anatomical localization, type and dimensions. Currently, various transplants are used for regeneration that are either biological in origin, artificial or used in combination

In the current treatments, transplants are unevenly localized in the site of the defect thus do not secure the anatomic integrity of a bone segment and frequently do not result in adequate regeneration of bone. The latter affects the quality of life and level of disability.

In case of osteoplastic replacement a part of transplantation material is subject to displacement or unintended migration and being ectopically in soft tissues causing osteogenesis. All these circumstances become more significant in case of gunshot injuries, as gunshot fractures are mainly accompanied by massive injuries and damage of both bone and soft tissues.

Development of polymer films with specified target properties in combination with operative methods will allow the technical implementation of reconstructive interventions. As well as fixing the transplantation materials in the site of injury would secure their enhanced replacing ability. The main goal of the project is to find non-toxic in vitro and in vivo resorbable polymers with the optimum resorption time interval. Such materials might be vinyl acetate based polymers, including modified polyvinyl alcohol (PVA) – a synthetic polymer that is widely applied in medicine and food industry. PVA is used as a packaging material in composite materials for replacement of bones, coatings and coverings of medicines and dietic food additives. PVA gels were successfully used as replacement of cartilage tissue, in maxillofacial surgery. In contrast the contemporary bioresorbable polymers that are used as fixing devices (ping, screws, nails, plates) are composed of co-polymers of hydroxyl- carbonic acids (glycolic and lactic acid) as well as co-polymers of methylmetacrylate and N-vinylpyrrolidone are used. At the turn of 1990s, procedure for fixing a bone defect with the help of a special barrier (membrane) was developed. The applied membrane generated favorable results where the proliferation of the bone cell was the only parameter affected. Resorbable polymer membranes were first studied for treatment of bone defects in view of dental implantation and then in maxillofacial surgery. Despite the promising results obtained in most experiments with the use of resorbable membranes, it observed that the percent of “filling-in” the bone defect underneath the membranes was lower than under e-PTFR non-resorbable membranes. The majority of approbated materials reabsorb during 6-8 weeks, whereas under the most favorable conditions no less than 3 months are required for bone regeneration. Thus, the most important challenge in elaboration of bio-resorbable membranes applicable for treatment of bone defect is selection of a material with adequate resorption period.

The aim of this study is to elaborate the method of osteoplastic replacement of extended bone defects with the use of artificial film that will serve as a folder for fixing of osteogenic plastic material in the implantation site and will not require post surgical removal and should have the following features: inertia and biocompatibility, with prolonged resorption ability; sterility and, if necessary, the ability to be treated by antiseptic and antibacterial substances; sufficient elasticity to wrap the transplants and facilitate regeneration of a defect; porosity and unevenness for better adaptation and creation of conditions for penetration of proliferating tissue elements and vessels simultaneously facilitate excretion of excess liquids from the zone of implantation.

Reabsorbable polymer membranes studied till present were obtained on the base of polylactides. Our experience gained in the frames of ISTC A-1358 project allows considering it expedient to use Vinyl Acetate based polymer films as material with optimal resorption period in the animal organism. Distinctive features of Vinyl Acetate based polymers are the high transparency of films, good adhesion, to different substrates, elasticity and sufficient strength. To shortcomings of Vinyl Acetate based polymers one can relate low glass transition temperature and it is supposed to raise it adding 15-20% of another monomer, which form rigid chain polymer. In the proposed project the achievement of the aims seems possible by co-polymerization of Vinyl Acetate with other monomers; obtaining PVA and new co-polymers of vinyl alcohol; subsequent addition of medicinal substances to their composition; and film formation.

To substantiate the application of developed films the experimental research in animals is planned. Radiological, biochemical, serological, immunological, and histological studies will be performed in laboratory animals and data will be compared with controls (intact animals).

To achieve the above purpose the following steps will be implemented: synthesis of polymers, obtaining polymer films, medical and biological studies, data processing and monitoring for issuing recommendations on application in case of osteoplastic surgery (interventions).

The methods used will include but are not limited to: evaluation of biocompatibility, determination of mechanisms and terms (time-intervals) for formation of bone regenerates, highly technological methods of synthesis and modern physical-and-chemical methods of analysis.

The Scientific Center of Traumatology and Orthopeadics of Health Ministry of Republic of Armenia was selected as the main research base for the project implementation. For over 40 years the main focus of this medical, methodological and educational center is the study on reparative regeneration of bone tissue and development of methods for stimulation of these processes upon regeneration of bone defects of various etiologies. This medical center is equippied by scientific and technical facilities for medical and biological studies; including vivarium.

Project methodology embraces known and newly developed methods elaborated by project participants: for evaluation of biocompatibility, determination of mechanisms and terms for formation of bone regenerates, highly technological methods of synthesis and modern physical-and-chemical methods of analysis.

In compliance with the aims set forth by ISTC the following tasks will be realized upon implementation of this project: reorientation of weapons scientists, resolution of public health challenges, integration of Armenian scientists into international collaboration; support of research in the field of public health and natural sciences.

The purpose of this summary is to engage the scientist in collaborative efforts in seeing this project through. The role of foreign collaborators might include rendering methodic recommendations, joint discussions of results and information exchange/sharing in the course of project implementation; providing comments to Technical Reports; joint publications.


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