326 Resorbable Composite Materials for Fracture Fixation

Introduction

Titanium-based fracture fixation devices often necessitate removal in the maxillofacial region. Resorbable composite implants negate the need for a revision operation; however, concurrent devices either possess a prolonged degradation profile or bioactivity, resulting in undesirable bone deposition. To that end, a novel, fast-resorbing, non-bioactive composite material is proposed, which still possesses an osteoinductive potential, thereby aiding fracture healing.

Method

Three bioglasses were available (NCL1-3) as filler material. NCL2 was selected and different concentrations (5%; 20%) were added to reinforce medical grade poly(lactic-co- glycolide) (PLGA). The final compression moulded samples underwent material characterisation and an 8-week degradation assay.

Results

No significant difference was found between the cytotoxicity of the glasses and both the positive (apatite wollastonite) and negative (absence of glass) controls in relation to mesenchymal stem cells or osteoblasts. pH and weight change analyses showed an increased rate of degradation with an increase in glass concentration. Although reinforcement with NCL2 did not increase the mechanical properties of the polymer, no significant difference was present between the mechanical properties of the composites, and, as made, both 5% and 20% composites had flexural strengths of 13MPa±5, which did not decrease significantly during degradation.

Conclusions

NCL1-3 are non-toxic in the context of fracture healing. The PLGA/NCL2 composite is not suitable for fracture fixation as produced currently, due to increased polymer degradation and lower mechanical properties. However, 20% compositions are recommended for future research, as they would hypothetically provide a superior osteoinductive response without significantly lowering the mechanical properties of the composite.

Lactose-crosslinked fish gelatin-based porous scaffolds embedded with tetrahydrocurcumin for cartilage regeneration

Tetrahydrocurcumin (THC) is one of the major colourless metabolites of curcumin and shows even greater pharmacological and physiological benefits. The aim of this work was the manufacturing of porous scaffolds as a carrier of THC under physiological conditions. Fish-derived gelatin scaffolds were prepared by freeze-drying by two solutions concentrations (2.5% and 4% w/v), cross-linked via addition of lactose and heat-treated at 105 °C. This cross-linking reaction resulted in more water resistant scaffolds with a water uptake capacity higher than 800%. Along with the cross-linking reaction, the gelatin concentration affected the scaffold morphology, as observed by scanning electron microscopy images, by obtaining a reduced porosity but larger pores sizes when the initial gelatin concentration was increased. These morphological changes led to a scaffold's strength enhancement from 0.92 ± 0.22 MPa to 2.04 ± 0.18 MPa when gelatin concentration was increased. THC release slowed down when gelatin concentration increased from 2.5 to 4% w/v, showing a controlled profile within 96 h. Preliminary in vitro test with chondrocytes on scaffolds with 4% w/v gelatin offered higher metabolic activities and cell survival up to 14 days of incubation. Finally the addition of THC did not influence significantly the cytocompatibility and potential antibacterial properties were demonstrated successfully against Staphylococcus aureus.

Synthesis of bioinspired collagen/alginate/fibrin based hydrogels for soft tissue engineering

Hydrogels based on natural polymers offer a range of properties to mimic the native extracellular matrix, and provide microenvironments to preserve cellular function and encourage tissue formation. A tri-component hydrogel using collagen, alginate and fibrin (CAF) was developed and investigated at three collagen concentrations for application as a functional extracellular matrix analogue. Physical-chemical characterization of CAF hydrogels demonstrated a thermo-responsive crosslinking capacity at physiological conditions with stiffness similar to native soft tissues. CAF hydrogels were also assessed for cytocompatibility using L929 murine fibroblasts, pancreatic MIN6 β-cells and human mesenchymal stem cells (hMSCs); and demonstrated good cell viability, proliferation and metabolic activity after 7 days of in vitro culture. CAF hydrogels, especially with 2.5% w/v collagen, increased alkaline phosphatase production in hMSCs indicating potential for the promotion of osteogenic activity. Moreover, CAF hydrogels also increased metabolic activity of MIN6 β-cells and promoted the reconstitution of spherical pseudoislets with sizes ranging between 50 and 150 μm at day 7, demonstrating potential in diabetic therapeutic applications.

Design and fabrication of 3D-printed anatomically shaped lumbar cage for intervertebral disc (IVD) degeneration treatment

Spinal fusion is the gold standard surgical procedure for degenerative spinal conditions when conservative therapies have been unsuccessful in rehabilitation of patients. Novel strategies are required to improve biocompatibility and osseointegration of traditionally used materials for lumbar cages. Furthermore, new design and technologies are needed to bridge the gap due to the shortage of optimal implant sizes to fill the intervertebral disc defect. Within this context, additive manufacturing technology presents an excellent opportunity to fabricate ergonomic shape medical implants. The goal of this study is to design and manufacture a 3D-printed lumbar cage for lumbar interbody fusion. Optimisations of the proposed implant design and its printing parameters were achieved via in silico analysis. The final construct was characterised via scanning electron microscopy, contact angle, x-ray micro computed tomography (μCT), atomic force microscopy, and compressive test. Preliminary in vitro cell culture tests such as morphological assessment and metabolic activities were performed to access biocompatibility of 3D-printed constructs. Results of in silico analysis provided a useful platform to test preliminary cage design and to find an optimal value of filling density for 3D printing process. Surface characterisation confirmed a uniform coating of nHAp with nanoscale topography. Mechanical evaluation showed mechanical properties of final cage design similar to that of trabecular bone. Preliminary cell culture results showed promising results in terms of cell growth and activity confirming biocompatibility of constructs. Thus for the first time, design optimisation based on computational and experimental analysis combined with the 3D-printing technique for intervertebral fusion cage has been reported in a single study. 3D-printing is a promising technique for medical applications and this study paves the way for future development of customised implants in spinal surgical applications.