Bioresorbable Composition for Repairing Skeletal Tissue

Description:

Reference #:  00504

The University of South Carolina is offering licensing opportunities for the development of novel macromers used for tissue regeneration.

Invention Description:

This invention involves the development of novel PLA, PGA and PLGA macromers. These macromers can be formed into a paste and are able to conform to the shape of irregular defects or made into viscous liquid compositions for injection into defects in minimally invasive procedures. The invention also features the addition of unsaturated reactive groups to the short polymer chains for in situ crosslink-ability.

Advantages and Benefits:

The novel PLA, PGA and PLGA macromers from this invention can be used in situations where the defect has irregular shape (most clinically relevant skeletal defects have irregular shape).

Potential Applications:

There are about 6.3 million fractures in the United States annually and closed fractures constitute a vast majority of these fractures. There are roughly 1 million patients who have skeletal defects each year in the United States that require bone graft procedures to achieve union. These include applications arising from resection of primary and metastatic tumors, bone loss after skeletal trauma, primary and revision total arthroplasty with bone deficiency, spinal arthrodesis, and trabecular voids following osteoporotic insufficiency fractures. Bone grafts are also required to fill voids in metaphysical bone fractures, which include the distal radius, tibial plateau, proximal femur, and calcaneous fractures. Other orthopedic applications are as bone fixative, suture reinforcement, and as scaffolds for guided regeneration of the alveolar bone in dentistry and reconstruction and reconstruction of mandibular, femoral neck osteonecrosis, and fusion of spinal processes.

 

Background:

Current clinical methods of treating skeletal defects involve bone transplantation or the use of other materials to restore continuity. Autologous bone graft has been the gold standard of bone replacement because it provides essential elements such as osteogenic cells, osteoinductive factors, and an osteoconductiove matrix for healing. However, the limited supply of auto-graft bone, and donor site morbidity both restrict their use. Allograft bone, although available in abundant supply, has drawbacks that include reduced rates of graft incorporation compared to autograft bone, and the possibility of pathogen transfer from donor to host. Metals provide immediate mechanical support at the defect site but exhibit less than ideal overall integration with host tissue and can eventually fail due to fatigue loading if the bone does not heal prior to fatigue failure of the metal. Ceramics, such as -tricalcium phosphate (B-TCP) and hydroxyapatite (HA) are both osteocanductive, and have found clinical use as surface coating on metal prostheses to enhance bonding to bone. In particulate form, they offer increased mechanical strength to polymeric composite materials primarily in compression, but are less effective in enhancing resistance to torsional and bending forces.

The problem solved:

Poly(lactic acid) {PLA}, poly(glycolic acid) {PGA}and their copolymers (PLGA) are used in a variety of orthopedic applications as bone fixative, suture reinforcement, and as scaffolds for cell transplantation and guided regeneration. PLGA copolymers are biocompatible and bio-resorbable copolymers and are FDA approved for certain clinical applications. The use of PLGA copolymers as scaffolds in tissue regeneration applications is limited to preformed rigid scaffolds because casting from toxic organic solvents such as methylene chloride or from melts at high temperatures is required for fabrication. Rigid preformed scaffolds have to be implanted surgically requiring tissue dissection and patient recovery and rehabilitation after surgery. Moreover, rigid preformed scaffolds cannot be used in situations where the defect has irregular shape (most clinically relevant skeletal defects have irregular shape). The other approach is to use in-situ crosslink-able pastes that conform to the irregular shape of the defect or to use injectable in-situ crosslink-able compositions with minimum tissue dissections and short patient recovery time. However, for pastes and injectables, the crosslinking step takes place in-situ physically by crystallization of the composition or chemically by reaction between unsaturated functional groups. PLA, PGA and PLGA polymers cannot be cross-linked in-situ due to the lack of unsaturated groups in their chemical structure.

 

Patent Information:
Title App Type Country Serial No. Patent No. File Date Issued Date Expire Date Patent Status
Bioresorbable Composition for Repairing Skeletal Tissue PCT United States PCT/US2006/026948 7/12/2006      
Bioresorbable Composition for Repairing Skeletal Tissue Nationalized PCT United States 11/995,612 9,101,654 1/14/2008 8/11/2015   Issued
For Information, Contact:
Technology Commercialization
University of South Carolina
technology@sc.edu
Inventors:
Esmaiel Jabbari
Keywords:
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