Influence of the Degree of Deacetylation of Chitosan and BMP-2 Concentration on Biocompatibility and Osteogenic Properties of BMP-2/PLA Granule-Loaded Chitosan/β-Glycerophosphate Hydrogels.

Andrey Vyacheslavovich Vasilyev,Valeriya Sergeevna Kuznetsova,Sergey Nicolaevich Chvalun,Dmitry Vadimovich Goldstein,Timofei Evgenevich Grigoriev,Igor Ivanovich Babichenko,Anatoliy Alekseevich Kulakov,Yuriy Dmitrievich Zagoskin,Irina Alekseevna Nedorubova,Tatyana Borisovna Bukharova

doi:10.3390/molecules26020261

Abstract

Compositions based on chitosan/β-glycerophosphate hydrogels with highly porous polylactide granules can be used to obtain moldable bone graft materials that have osteoinductive and osteoconductive properties. To eliminate the influence of such characteristics as chain length, degree of purification, and molecular weight on a designed material, the one-stock chitosan sample was reacetylated to degrees of deacetylation (DD%) of 19.5, 39, 49, 55, and 56. A study of the chitosan/β-glycerophosphate hydrogel with chitosan of a reduced DD% showed that a low degree of deacetylation increased the MSCs (multipotent stromal cells) viability rate in vitro and reduced the leukocyte infiltration in subcutaneous implantation to Wistar rats in vivo. The addition of 12 wt% polylactide granules resulted in optimal composite mechanical and moldable properties, and increased the modulus of elasticity of the hydrogel-based material by approximately 100 times. Excessive filling of the material with PLA (polylactide) granules (more than 20%) led to material destruction at a ~10% strain. Osteoinductive and osteoconductive properties of the chitosan hydrogel-based material with reacetylated chitosan (39 DD%) and highly porous polylactide granules impregnated with BMP-2 (bone morphogenetic protein-2) have been demonstrated in models of orthotopic and ectopic bone formation. When implanted into a critical-size calvarial defect in rats, the optimal concentration of BMP-2 was 10 μg/mL: bone tissue areas filled the entire material’s thickness. Implantation of the material with 50 μg/mL BMP-2 was accompanied with excessive growth of bone tissue and material displacement beyond the defect. Significant osteoinductive and osteoconductive properties of the material with 10 μg/mL of BMP-2 were also shown in subcutaneous implantation.

Highlights

The number of bone grafting procedures in Europe and America grows by an average of 13–14.4%, and approximately 2.2 million operations are performed every year [1,2,3]
We have previously shown that highly porous polylactide granules can be used as a BMP-2 carrier
A comprehensive comprehensivein in vitro in study vivo of study of chitosan/β-glycerophosphate vitro and and in vivo chitosan/β-glycerophosphate hydrohydrogels that a high degree of deacetylation chitosan led to acute gels showedshowed that a high degree of deacetylation of chitosan led of to acute inflammation and inflammation and cell death

Summary

Introduction

The number of bone grafting procedures in Europe and America grows by an average of 13–14.4%, and approximately 2.2 million operations are performed every year [1,2,3]. The consistency of bone substitutes is divided into bone granules, cement, paste, sponge, and putty. Putty is the most useful material because it can be molded into any shape Unlike cements, it cannot cure in the wound and hold its shape [7]. Unlike bone granules, registered putty has a continuous surface that prevents the vessel’s ingrowth and resorption of material, which limit bone formation inside the putty [8]. In this regard, the design of thermosetting biocompatible and bioresorbable putty, with pores for vascular ingrowth and cell migration, is a crucial task

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