Biocompatibility of wollastonite-poly(N-butyl-2-cyanoacrylate) composites

Current State of Bone Adhesives-Necessities and Hurdles

The vision of gluing two bone fragments with biodegradable and biocompatible adhesives remains highly fascinating and attractive to orthopedic surgeons. Possibly shorter operation times, better stabilization, lower infection rates, and unnecessary removal make this approach very appealing. After 30 years of research in this field, the first adhesive systems are now appearing in scientific reports that may fulfill the comprehensive requirements of bioadhesives for bone. For a successful introduction into clinical application, special requirements of the musculoskeletal system, challenges in the production of a bone adhesive, as well as regulatory hurdles still need to be overcome. In this article, we will give an overview of existing synthetic polymers, biomimetic, and bio-based adhesive approaches, review the regulatory hurdles they face, and discuss perspectives of how bone adhesives could be efficiently introduced into clinical application, including legal regulations.

Biocompatibility of n-butyl-2-cyanoacrylate (Histoacryl) in cervical structures of rats: prospective in vivo study

Purpose

We investigated the biocompatibility of n-butyl-2-cyanoacrylate (NBCA) in the cervical deep tissues of rats to assess its biocompatibility.

Methods

A total of 30 Sprague-Dawley rats were injected with NBCA. After 30, 90, 180, and 360 days, cubes of tissue (1 cm × 1 cm × 1 cm) surrounding the NBCA and normal tissue from the other side of the neck were excised from each rat. The adhesion of NBCA to adjacent structures was examined histologically. Cells were counted per high-power field (HPF), and fibrosis was graded with the measurement of fibrotic thickening.

Results

All animals displayed normal behavior without any symptoms of distress throughout the study. There was no recognizable inflammatory reaction, foreign body reaction, or fibrosis in the 30 control samples. The analyses of experimental samples showed significantly decreased inflammatory cell counts over time (lymphoplasma cell count decreased from 100 (range, 70–100) to 30 (range, 30–50) per HPF, P = 0.010; neutrophil count decreased from 2 (range, 2–30) to 0 (range, 0–2) per HPF, P = 0.017). However, there was no significant difference in the number of multinuclear giant cells throughout the study period (a decrease from 22 [range, 16–34] to 16 [range, 12–22] per HPF, P = 0.287). The level of fibrosis was Common Toxicity Criteria ver. 4.0 Grade 1 without further thickening (P = 0.600). However, maturation of fibrosis progressed gradually.

Conclusion

NBCA was biologically tolerable in the cervical deep tissues of rats. However, precautions are needed with respect to preventing a sustained foreign body reaction and fibrosis.

Reconstruction of radial bone defect in rat by calcium silicate biomaterials

AIMS

Despite many attempts, an appropriate therapeutic method has not yet been found to enhance bone formation, mechanical strength and structural and functional performances of large bone defects. In the present study, the bone regenerative potential of calcium silicate (CS) biomaterials combined with chitosan (CH) as calcium silicate/chitosan (CSC) scaffold was investigated in a critical radial bone defect in a rat model.

MAIN METHODS

The bioimplants were bilaterally implanted in the defects of 20 adult Sprague-Dawley rats. The rats were euthanized and the bone specimens were harvested at the 56th postoperative day. The healed radial bones were evaluated by three-dimensional CT, radiology, histomorphometric analysis, biomechanics, and scanning electron microscopy.

KEY FINDINGS

The XRD analysis of the CS biomaterial showed its similarity to wollastonite (β-SiCO₃). The degradation rate of the CSC scaffold was much higher and it induced milder inflammatory reaction when compared to the CH alone. More bone formation and higher biomechanical performance were observed in the CSC treated group in comparison with the CH treated ones in histological, CT scan and biomechanical examinations. Scanning electron microscopic observation demonstrated the formation of more hydroxyapatite crystals in the defects treated with CSC.

SIGNIFICANCE

This study showed that the CSC biomaterials could be used as proper biodegradable materials in the field of bone reconstruction and tissue engineering.

"Steel-Concrete" Inspired Biofunctional Layered Hybrid Cage for Spine Fusion and Segmental Bone Reconstruction

In this paper we report a "steel-concrete" inspired layered hybrid spine cage combining a titanium mesh and a bioceramic scaffold, which were welded together through a bioglass bonding layer using a novel multistep manufacturing methodology including three-dimensional slip deposition, gel casting, freeze-drying, and cosintering. The interfacial welding strength achieved 27 ± 0.7 MPa, indicating an excellent structural integrity of the hybrid cage construct. The biocramic scaffold layer consisting of wollastonite and hydroxyapatite had an interconnected, highly porous structure with a pore size of 100-500 μm and a porosity of >85%, well fufilling the structural requirements of bone regeneration. Simulated body fluid immersion assay showed that the hybrid cage exhibited excellent biodegradability to facilitate rapid bone-like apatite formation. In vitro studies demonstrated that the bioceramic scaffold on the hybrid cage supported attachment, spreading, growth, and migration of bone/vessel-forming cells and triggered osteogenic differentiation of human mesenchymal stem cells. In vivo studies further suggested that the bioceramic scaffold on the hybrid cage could actively promote fast generation of new bone tissues within 12 weeks of implantation in a rabbit femoral condyle model. This study has provided a new design and fabrication methodology of hybrid cages by integrating strong mechanical properties with excellent biological activities including osteoinductivity and bone regeneration ability, for spine fusion and segmental bone reconstruction.

Degradation and silicon excretion of the calcium silicate bioactive ceramics during bone regeneration using rabbit femur defect model

The investigation of the bone regeneration ability, degradation and excretion of the grafts is critical for development and application of the newly developed biomaterials. Herein, the in vivo bone-regeneration, biodegradation and silicon (Si) excretion of the new type calcium silicate (CaSiO3, CS) bioactive ceramics were investigated using rabbit femur defect model, and the results were compared with the traditional β-tricalcium phosphate [β-Ca3(PO4)2, β-TCP] bioceramics. After implantation of the scaffolds in rabbit femur defects for 4, 8 and 12 weeks, the bone regenerative capacity and degradation were evaluated by histomorphometric analysis. While urine and some organs such as kidney, liver, lung and spleen were resected for chemical analysis to determine the excretion of the ionic products from CS implants. The histomorphometric analysis showed that the bioresorption rate of CS was similar to that of β-TCP in femur defect model, while the CS grafts could significantly stimulate bone formation capacity as compared with β-TCP bioceramics (P < 0.05). The chemical analysis results showed that Si concentration in urinary of the CS group was apparently higher than that in control group of β-TCP. However, no significant increase of the Si excretion was found in the organs including kidney, which suggests that the resorbed Si element is harmlessly excreted in soluble form via the urine. The present studies show that the CS ceramics can be used as safe, bioactive and biodegradable materials for hard tissue repair and tissue engineering applications.