Influence of sterilization on injectable bone biomaterials

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Polymer Chemistry

Background:

• Injectable bone cements are crucial in orthopedic surgery.
• Common materials include acrylic bone cements, calcium phosphate cements, and novel composites.
• Biopolymers like cellulose derivatives and chitosan are explored as modifiers.

Purpose of the Study:

• To evaluate the effects of sterilization on the physico-chemical properties of novel polyester copolymer (copolylactic acid)-based bone biomaterials.
• To assess the suitability of different sterilization techniques for injectable bone biomaterials.
• To investigate the in vivo performance of modified calcium phosphate cements.

Main Methods:

• Physico-chemical analysis of biomaterials after gamma, heat, and steam sterilization.
• Capillary electrophoresis and gel exclusion chromatography were used to assess degradation and crosslinking.
• In vivo implantation of calcium phosphate cement modified by copolylactic acid in a rabbit metaphyseal defect model.

Main Results:

• Gamma sterilization degraded chitosan solutions and caused hydrolysis in aqueous copolylactic acid solutions.
• Heat sterilization also degraded chitosan solutions, complicating ultrafiltration.
• Apatite-copolylactic acid solids demonstrated stability after steam sterilization.
• Ultrafiltration was used to prepare hydrolysis-free aqueous copolylactic acid solutions.
• In vivo studies showed progressive bone tissue substitution and biomaterial resorption with mild inflammation.

Conclusions:

• Sterilization methods critically affect the properties of injectable bone biomaterials.
• Steam sterilization is suitable for apatite-copolylactic acid solids.
• Copolylactic acid-modified calcium phosphate cements exhibit favorable bone regeneration potential.
• Specialized sterilization methods are necessary for fragile biopolymers and reactive monomers in injectable forms.