Sericin/Nano-Hydroxyapatite Hydrogels Based on Graphene Oxide for Effective Bone Regeneration via Immunomodulation and Osteoinduction

Abstract

Background Immune responses and osteogenesis differentiation induced by implants are crucial for bone tissue regeneration. Consideration of only one of those properties is not sufficient. To investigate the synergistic actions, we designed alginate/graphene oxide/sericin/nanohydroxyapatite (Alg/GO/Ser/nHAP) nanocomposite hydrogels with both osteoimmunomodulatory and osteoinductive activities. This study aimed to explore the effect of hydrogel with osteoimmunomodulatory properties on promoting osteogenesis of bone marrow stem cells (BMSCs). Methods Alg/GO/Ser/nHAP nanocomposite hydrogel was fabricated and was characterized by SEM, FTIR, XRD, stress-strain, rheology, swelling and degradation. After the impact of sericin on M2 macrophage polarization was identified, the BMSCs viability and adhesion were evaluated by CCK8 assay, live/dead staining, cytoskeleton staining. The cell osteogenic differentiation was observed by ALP/ARS staining, immunofluorescence staining, RT-PCR, and Western blotting, respectively. Rat cranial defect model was used to assess osteoimmunomodulatory effects of scaffolds in vivo by micro‑computed tomographic, histological, and immunohistochemical analyses after 8 weeks of healing. Results In vitro experiments revealed that the hydrogel presented desirable mechanical strength, stability, porosity, and biocompatibility. Significantly, sericin and nHAP appeared to exert synergistic effects on bone regeneration. Sericin was observed to inhibit the immune response by inducing macrophage M2-type polarization to create a positive osteoimmune microenvironment, contributing to improving osseointegration at the bone-implant interface to promote osteogenesis. However, the osteogenic differentiation in rat BMSCs was further enhanced by combining nHAP and sericin in the nanocomposite hydrogel. Eventually, the hydrogel was implanted into the rat cranial defect model, assisting in the reduction of local inflammation and efficient bone regeneration. Conclusion The nanocomposite hydrogel stimulated bone formation by the synergistic effects of immunomodulation of macrophage polarization by sericin and direct osteogenic induction by nHAP, demonstrating that such a scaffold that modulates the osteoimmune microenvironment to promote osteogenesis is a promising approach for the development of bone tissue engineering implants in the future.

Exploring the Application of Graphene Oxide-Based Nanomaterials in the Repair of Osteoporotic Fractures

“…It has been demonstrated that GO-based nanocomposites can promote the polarization of M1 to M2 macrophages for regulating the immune microenvironment [ 72 ]. For instance, Fu et al developed a GO-based composite hydrogel (Alg/GO/Ser/nHAP) that fostered conducive bone growth and bone immune microenvironment, which enhanced the osseointegration process at the bone–implant interface by shifting the macrophage phenotype from M1 to M2 [ 41 ]. Similarly, Xue et al found that quaternized chitosan scaffolds with GO modification were more effective than pure quaternized chitosan scaffolds in promoting the polarization of M2-type macrophages and osteogenesis [ 73 ].…”

Relevant Properties and Potential Applications of Sericin in Bone Regeneration

“…Implanted in rat calvarial defects, the scaffold facilitated new bone regeneration within 12 weeks by inducing autologous bone marrow-derived mesenchymal stem cell differentiation [ 57 ]. Further research by Fu et al [ 58 ] explored the combination of sericin with nanohydroxyapatite and graphene oxide in an alginate-based nanocomposite hydrogel. This scaffold not only promotes osteogenesis but also creates a favorable osteoimmune microenvironment by inducing M2 macrophage polarization [ 58 ].…”

“…Further research by Fu et al [ 58 ] explored the combination of sericin with nanohydroxyapatite and graphene oxide in an alginate-based nanocomposite hydrogel. This scaffold not only promotes osteogenesis but also creates a favorable osteoimmune microenvironment by inducing M2 macrophage polarization [ 58 ]. The synergistic effect of immunomodulation and osteoinduction exhibited by this scaffold leads to effective bone regeneration [ 58 ].…”

“…This scaffold not only promotes osteogenesis but also creates a favorable osteoimmune microenvironment by inducing M2 macrophage polarization [ 58 ]. The synergistic effect of immunomodulation and osteoinduction exhibited by this scaffold leads to effective bone regeneration [ 58 ].…”

Osteo-immunomodulatory effects of macrophage-derived extracellular vesicles treated with biphasic calcium phosphate ceramics on bone regeneration

“…macrophages) before the arrival of mesenchymal stem cells (MSCs). In recent years, the development of osteoimmunology has revealed that the degree of inflammation significantly affects the performance of orthopedic implants [3]. Excessive and chronic inflammation may cause the formation of fibrous capsules, resulting in implant failure, while, mild inflammation may induce new bone formation and enhance implant integration [4].…”