Fabrication of a Free Radical Scavenging Nanocomposite Scaffold for Bone Tissue Regeneration

Hydroxyapatite-chitosan composites derived from sea cucumbers and shrimp shells ameliorate femoral bone defects in an albino rat model

Background and Aim

A bone defect is defined as a critically sized autologous bone and a bone gap. Bone grafting is one of the most commonly used surgical methods to enhance bone regeneration in orthopedic procedures. A composite of collagen, hydroxyapatite (HA), and chitosan (Ch) is suitable as a bone matrix and stimulates ossification. This study aimed to evaluate the use of natural HA-Ch composites derived from sea cucumbers and shrimp shells and quantify the levels of cytokines, polymorphonuclear neutrophils (PMNs), serum liver enzymes, calcium, phosphate, and procollagen type 1 N-terminal propeptide (PINP) in albino rats with femoral bone defects.

Materials and Methods

A total of 48 albino rats with femoral bone defects were divided into 4 groups (n = 12 each): (C-) placebo, (C+) polyethylene glycol, (T1) HA, and (T2) HA-Ch groups. Each group was divided into two subgroups (n = 6 each), with euthanization on 7- and 42-day post-treatment, respectively. Procollagen Type 1 N-terminal propeptide and the cytokines interleukin (IL)-4, IL-6, IL-10, and tumor necrosis factor-alpha were quantified using enzyme-linked immunosorbent assay. Flow cytometry was performed to evaluate PMNs. A clinical chemistry analyzer was used to measure the serum levels of liver enzymes, calcium, and phosphate.

Results

There was a significant decrease in the level of IL-6 on 7 days and in the level of IL-10 on 42 days in the HA-Ch group. The level of PMNs also decreased significantly on 7 and 42 days in the HA-Ch group. Regarding serum liver enzymes, alkaline phosphatase (ALP) levels in the HA-Ch group increased significantly on 42 days. Calcium and phosphate levels increased significantly on 7 and 42 days in the HA and HA-Ch groups, and PINP levels increased significantly on 7 and 42 days in the HA-Ch group.

Conclusion

The HA-Ch composite derived from sea cucumbers and shrimp shells ameliorated femoral bone defects in albino rats. The HA-Ch composite modulated the levels of IL-6, IL-10, PMNs, ALP, calcium, phosphate, and PINP on 7- and 42-day post-treatment.

Recent Developments in Polymer Nanocomposites for Bone Regeneration

Most people who suffer acute injuries in accidents have fractured bones. Many of the basic processes that take place during embryonic skeletal development are replicated throughout the regeneration process that occurs during this time. Bruises and bone fractures, for example, serve as excellent examples. It almost always results in a successful recovery and restoration of the structural integrity and strength of the broken bone. After a fracture, the body begins to regenerate bone. Bone formation is a complex physiological process that requires meticulous planning and execution. A normal healing procedure for a fracture might reveal how the bone is constantly rebuilding as an adult. Bone regeneration is becoming more dependent on polymer nanocomposites, which are composites made up of a polymer matrix and a nanomaterial. This study will review polymer nanocomposites that are employed in bone regeneration to stimulate bone regeneration. As a result, we will introduce the role of bone regeneration nanocomposite scaffolds, and the nanocomposite ceramics and biomaterials that play a role in bone regeneration. Aside from that, recent advances in polymer nanocomposites might be used in a variety of industrial processes to help people with bone defects overcome their challenges will be discussed.

Carbonaceous Nanomaterials-Mediated Defense Against Oxidative Stress

The concept of nanoscale materials and their applications in industrial technologies, consumer goods, as well as in novel medical therapies has rapidly escalated in the last several years. Consequently, there is a critical need to understand the mechanisms that drive nanomaterials biocompatibility or toxicity to human cells and tissues. The ability of nanomaterials to initiate cellular pathways resulting in oxidative stress has emerged as a leading hypothesis in nanotoxicology. Nevertheless, there are a few examples revealing another face of nanomaterials - they can alleviate oxidative stress via decreasing the level of reactive oxygen species. The fundamental structural and physicochemical properties of carbonaceous nanomaterials that govern these anti-oxidative effects are discussed in this article. The signaling pathways influenced by these unique nanomaterials, as well as examples of their applications in the biomedical field, e.g. cell culture, cell-based therapies or drug delivery, are presented. We anticipate this emerging knowledge of intrinsic anti-oxidative properties of carbon nanomaterials to facilitate the use of tailored nanoparticles in vivo.

MechanoBioTester: A Decoupled Multistimulus Cell Culture Device for Studying Complex Microenvironments In Vitro

Increasingly being recognized is the role of the complex microenvironment to regulate cell phenotype; however, the cell culture systems used to study these effects in vitro are lagging. The complex microenvironment is host to a combination of biological interactions, chemical factors, and mechanical stimuli. Many devices have been designed to probe the effects of one mechanical stimulus, but few are capable of systematically interrogating all combinations of mechanical stimuli with independent control. To address this gap, we have developed the MechanoBioTester platform, a decoupled, multi-stimulus cell culture model for studying the cellular response to complex microenvironments in vitro. The system uses an engineered elastomeric chamber with a specially defined region for incorporating different target materials to act as the cell culture substrate. We have tested the system with several target materials including: polydimethylsiloxane elastomer, polyacrylamide gel, poly(1,8-octanediol citrate) elastomer, and type I collagen gel for both 2D and 3D co-culture. Additionally, when the chamber is connected to a flow circuit and our stretching device, stimuli in the form of fluid flow, cyclic stretch, and hydrostatic pressure are able to be imparted with independent control. We validated the device using experimental and computational methods to define a range of capabilities relevant to physiological microenvironments. The MechanoBioTester platform promises to function as a model system for mechanobiology, biomaterial design, and drug discovery applications that focus on probing the impact of a complex microenvironment in an in vitro setting. The protocol described within provides the details characterizing the MechanoBioTester system, the steps for fabricating the MechanoBioTester chamber, and the procedure for operating the MechanoBioTester system to stimulate cells.

In vitro and in vivo biocompatibility assessment of free radical scavenging nanocomposite scaffolds for bone tissue regeneration

Bone is the second most transplanted tissue in the world, resulting in increased demand for bone grafts leading to the fabrication of synthetic scaffold grafting alternatives. Fracture sites are under increased oxidative stress after injuries, affecting osteoblast function and hindering fracture healing and remodeling. To counter oxidative stress, free radical scavenging agents, such as cerium oxide nanoparticles, have gained traction in tissue engineering. Toward the goal of developing a functional synthetic system for bone tissue engineering, we characterized the biocompatibility of a porous, bioactive, free radical scavenging nanocomposite scaffold composed of poly(1,8 octanediol-co-citrate), beta-tricalcium phosphate, and cerium oxide nanoparticles. We studied cellular and tissue compatibility utilizing in vitro and in vivo models to assess nanocomposite interactions with both human osteoblast cells and rat subcutaneous tissue. We found the scaffolds were biocompatible in both models and supported cell attachment, proliferation, mineralization, and infiltration. Using hydrogen peroxide, we simulated oxidative stress to study the protective properties of the nanocomposite scaffolds via a reduction in cytotoxicity and recovered mineralization of osteoblast cells in vitro. We also found after implantation in vivo the scaffolds exhibited biocompatible properties essential for successful scaffolds for bone tissue engineering. Cells were able to infiltrate through the scaffolds, the surrounding tissues elicited a minimal immune response, and there were signs of scaffold degradation after 30 days of implantation. After the array of biological characterization, we had confirmed the development of a nanocomposite scaffold system capable of supporting bone-remodeling processes while providing a protective free radical scavenging effect.