Development of a novel method for the strengthening and toughening of irradiation-sterilized bone allografts

Abstract

Reconstruction of large skeletal defects is a significant and challenging issue. Bone allografts are often used for such reconstructions. However, sterilizing bone allografts by using γ-irradiation, damages collagen and causes the bone to become weak, brittle and less fatigue resistant. In a previous study, we successfully protected the mechanical properties of human cortical bone by conducting a pre-treatment with ribose, a natural and biocompatible agent. This study focuses on examining possible mechanisms by which ribose might protect the bone. We examined the mechanical properties, crosslinking, connectivity and free radical scavenging potentials of the ribose treatment. Human cortical bone beams were treated with varying concentration of ribose (0.06-1.2 M) and γ-irradiation before testing them in 3-point bending. The connectivity and amounts of crosslinking were determined with Hydrothermal-Isometric-Tension testing and High-Performance-Liquid-Chromatography, respectively. The free radical content was measured using Electron Paramagnetic Resonance. Ribose pre-treatment improved the mechanical properties of irradiation sterilized human bone in a pre-treatment concentration-dependent manner. The 1.2 M pre-treatment provided >100% of ultimate strength of normal controls and protected 76% of the work-to-fracture (toughness) lost in the irradiated controls. Similarly, the ribose pre-treatment improved the thermo-mechanical properties of irradiation-sterilized human bone collagen in a concentration-dependent manner. Greater free radical content and pentosidine content were modified in the ribose treated bone. This study shows that the mechanical properties of irradiation-sterilized cortical bone allografts can be protected by incubating the bone in a ribose solution prior to irradiation.

Effects of ex vivo ionizing radiation on collagen structure and whole-bone mechanical properties of mouse vertebrae

“…Here, we observed that despite a substantial (95%) increase in crosslink concentration, we could not detect any effect on vertebral strength. Indeed, studies have demonstrated that an increase in non-enzymatic crosslinks induced via ribose incubation can be used to counter the loss of strength due to the fragmentation of the collagen network, not degrade it further [38,47,48]. Taken together, our results strengthen the argument that the contribution of non-enzymatic crosslinks to diminished bone strength with disease and aging plays a smaller role in comparison to other factors, such as collagen network connectivity [49].…”

“…To mitigate the loss of mechanical integrity, further studies are needed to investigate how to safeguard the bone with a radioprotectant. Several radioprotectants have been considered for their ability to preserve tissue properties following irradiation [4,48,59]. Based on our results, we would recommend studies focused on radioprotectants which can prevent or offset the fragmentation of collagen, as these types of radioprotectants may preserve bone mechanics to a greater degree than those which protect against non-enzymatic collagen crosslinks.…”

Pre‐clinical evaluation of bone allograft toughened with a novel sterilization method: An in vivo rabbit study

“…In this way, the collagen connectivity, which would otherwise be degraded following irradiation, can be reinforced and strengthened by the newly created crosslinks. Biomechanical testing of cortical bone pretreated ex vivo with our novel sterilization technique showed protection of the mechanical properties otherwise lost to conventional irradiation . Both human and bovine bone samples treated with ribose prior to irradiation showed protection of ultimate strength, strain‐to‐failure, and work‐to‐fracture.…”

“…Biomechanical testing of cortical bone pretreated ex vivo with our novel sterilization technique showed protection of the mechanical properties otherwise lost to conventional irradiation. [29][30][31] Both human and bovine bone samples treated with ribose prior to irradiation showed protection of ultimate strength, strain-to-failure, and work-to-fracture.…”

Vreden Russian Research Institute of Traumatology and Orthopedics

“…В одном из последних исследований, опубликованных T. Attia c соав-торами, показаны хорошие радиопротекторные свойства рибозы. Ее применение при стерили-зации позволяет лучше сохранять остеокондук-тивные свойства костных материалов [62].…”