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Theranostics 2017; 7(5):1072-1087. doi:10.7150/thno.18193 This issue Cite

Research Paper

Zero-order controlled release of BMP2-derived peptide P24 from the chitosan scaffold by chemical grafting modification technique for promotion of osteogenesis in vitro and enhancement of bone repair in vivo

Yan Chen^1*, Xujie Liu^{2, 3*}, Rui Liu^4*, Yong Gong⁴, Mingbo Wang⁵, Qianli Huang⁶, Qingling Feng^6✉, Bo Yu^4✉

1. Department of Ultrasonic Diagnosis, Zhujiang Hospital of Southern Medical University, Guangzhou 510282, China;
2. Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China;
3. State key laboratory of new ceramics and fine processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China;
4. Department of Orthopedics, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, China;
5. Key Laboratory of Biomedical Materials and Implants, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057, P. R. China;
6. Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
* These authors contributed equally to this work.

✉ Corresponding authors: Bo Yu: gzyubocom; Qingling Feng: biomatertsinghua.edu.cn.

Abstract

Combination of tissue-engineered bone scaffolds with cell-adhesive, osteoconductive, or osteoinductive biomolecules is a critical strategy to improve their properties that significantly influence cellular behaviors, such as adhesion, proliferation, and differentiation, which is beneficial for critical-sized bone defects repairing. However, the traditional surface modification techniques, such as physical adsorption, coating, and plasma treatment, et al, have great limitations for immobilization of bioactive molecules due to undesirable controlled delivery performance or overly complex multistep procedures. In this study, we functionalized the chitosan/hydroxyapatite (CS/HA) biomimetic composite scaffold for controlled delivery of BMP2-derived peptide (P24) by the chemical grafting modification technique: firstly, P24 was conjugated with a thiolated chitosan, chitosan-4-thiobutylamidine (CS-TBA); secondly, the resultant CS-P24 was then combined with HA to prepare CS-P24/HA scaffolds. The effect of CS-P24/HA scaffolds on bone regeneration was evaluated, along with the underlying biological mechanisms responsible in vitro and in vivo. In vitro, the controlled and sustained release of bioactive P24 could last up to 90 days, furthermore, the release profiles of CS-5%P24/HA and CS-10%P24/HA were linear and could be fitted according to zero-order kinetic model (R²=0.9929; R²=0.9757); P24 on the scaffold significantly promoted cell adhesion, proliferation, osteodifferentiation, and mineralization with synergistic effects. Bone marrow stromal cells (BMSCs) revealed spindle-shaped surface morphology, indicating the CS-P24/HA scaffolds supported cell adhesion and possessed a high proliferation rate that varied according to the P24 concentration levels. Furthermore, mRNA levels for OCN, Runx2, and collagen I were significantly up-regulated on CS-P24/HA scaffolds compared with cells grown on CS/HA scaffolds in vitro (p < 0.05). Similarly, the BMSCs exhibited a higher ALP expression and calcium deposition level on CS-P24/HA scaffolds compared with CS/HA scaffolds (p < 0.05). In vivo, osteoinductive studies revealed a significantly higher ectopic osteogenesis level of CS-10%P24/HA scaffolds in rat dorsal muscle pockets compared with that of CS/HA scaffolds. Finally, CS-P24/HA scaffolds showed superior performance in the reconstruction of rat calvarial bone defects. This novel CS-P24/HA scaffold is deemed a strong potential candidate for the repair of bone defects in human bone tissue engineering.

Keywords: Controlled release, BMP2-derived peptide, thiolated chitosan, hydroxyapatite, scaffolds, bone defect repair.

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