Ak Bassi

The Chemical and Physical Properties of Poly(ε-Caprolactone) Scaffolds Functionalised with Poly(vinyl phosphonic acid-co-acrylic acid)

There is a clinical need for a synthetic alternative to bone graft substitute (BGS) derived from demineralised bone matrix. We report the electrospinning of Poly(ε-caprolactone) (PCL) to form a 3-dimensional scaffold for use as a synthetic BGS. Additionally, we have used Poly(vinyl phosphonic acid-co-acrylic acid) (PVPA) to improve bone formation. Fibres were formed using a 10% w/v PCL/acetone solution. Infrared spectroscopy confirmed that the electrospinning process had no effect on the functional groups present in the resulting structure. The electrospun scaffolds were coated with PVPA (PCL/PVPA), and characterised. The stability of the PVPA coating after immersion in culture medium was assessed over 21 days. There was rapid release of the coating until day 2, after which the coating became stable. The wettability of the PCL scaffolds improved significantly, from 123.3 ± 10.8° to 43.3 ± 1.2° after functionalisation with PVPA. The compressive strength of the PCL/PVPA scaffolds (72 MPa) was significantly higher to that of the PCL scaffold (14 MPa), and an intermediate between trabecular and cortical bone (7 MPa and 170 MPa, resp.). The study has demonstrated that the PCL/PVPA scaffold has the desired chemical and biomechanical characteristics required for a material designed to be used as a BGS.

A novel phosphonate for the repair of critical size bone defects

Bone has the ability to spontaneously regenerate itself. However, the treatment of critical size bone defects can be problematic. In this study, the healing potential of critical size neonatal mouse parietal defects was evaluated using a scaffold composed of poly (ε‐caprolactone) (PCL) and polyvinyl phosphonic co‐acrylic acid (PVPA) (referred to as PCL/PVPA). Full thickness 1.5 mm circular defects were created in parietal bones obtained from one litter of 4‐day‐old CD1 mice. The bones were divided into two groups and embedded with PCL or PCL/PVPA scaffolds. The healing response was evaluated using microcomputed tomography, dissecting microscopy, phase contrast microscopy, scanning electron microscopy, and energy dispersive spectroscopy. There was a significant increase (P < 0.05) in bone fill percentage in the presence of the PCL/PVPA scaffold (63.57%) compared with PCL scaffolds (29.64%). The formation of tissue and deposition of extracellular matrix was confirmed by scanning electron microscopy. There was evidence of collagen fibre deposition as well as hydroxyapatite and overall woven bone formation. PCL/PVPA scaffolds were better integrated into the defect site. The potential formation of hydroxyapatite was evaluated using energy dispersive spectroscopy. Results showed a significant increase in calcium and phosphorus levels in the presence of PCL/PVPA scaffold. Histological analysis using Massons trichrome staining confirmed the presence of collagen above and below the PCL/PVPA scaffold within the defect site. In conclusion, this study showed that the PCL/PVPA scaffold is a novel system that has the potential for use as a bone graft substitute and in assisting in the healing of critical size defects. Copyright

Bone tissue regeneration

Abstract: The area of bone tissue engineering is a broad field expanding at a rapid rate. Electrospinning is becoming the first choice of many researchers who are considering producing scaffolds that could be used as synthetic bone graft substitutes. This versatile, fibre-forming technique is ideal as the resulting submicrometre fibres mimic the structure of the natural extracellular matrix found in bone. Poly( e -caprolactone) is commonly used in bone tissue engineering; the bioactivity of this polymer can be further improved through the incorporation of bioactive agents such as hydroxyapatite. Osteoporotic patients are often treated in the same way as healthy individuals when surgical intervention is required. For these patients, this can lead to fracture or failure at the site of reduced bone mass. The design of a material which reduces the activity of osteoclasts in osteoporotic patients would be favourable in increasing bone mass.