3D printing and electrospinning of composite hydrogels for cartilage and bone tissue engineering

Injuries of bone and cartilage constitute important health issues costing the National Health Service billions of pounds annually, in the UK only. Moreover, these damages can become cause of disability and loss of function for the patients with associated social costs and diminished quality of life. The biomechanical properties of these two tissues are massively different from each other and they are not uniform within the same tissue due to the specific anatomic location and function. In this perspective, tissue engineering (TE) has emerged as a promising approach to address the complexities associated with bone and cartilage regeneration. Tissue engineering aims at developing temporary three-dimensional multicomponent constructs to promote the natural healing process. Biomaterials, such as hydrogels, are currently extensively studied for their ability to reproduce both the ideal 3D extracellular environment for tissue growth and to have adequate mechanical properties for load bearing. This review will focus on the use of two manufacturing techniques, namely electrospinning and 3D printing, that present promise in the fabrication of complex composite gels for cartilage and bone tissue engineering applications

Harnessing the antibacterial properties of fluoridated chitosan polymers against oral biofilms

Dental caries are a worldwide endemic chronic disease affecting people of all ages. Due to the limitations of daily used oral hygiene products, there is an unmet need for new, effective, safe, and economic oral products. We have recently demonstrated that N-(2(2,6-diaminohexanamide)-chitosan (CS3H Lys) has enhanced antibacterial properties against Streptococcus mutans, the main cariogenic bacterium, and here we investigated the effect of fluoridation of this polymer (CS3H Lys F) on its antibacterial properties and the ability to protect teeth from acid demineralization. We further formulated this polymer into mouthwash preparations and studied their cytocompatibility and physicochemical stability over 6 months. CS3H Lys F was 1.6-fold more effective than the highest tested oral NaF dose in preventing acid demineralization. CS3H Lys F has a 3-to 5-fold lower minimum inhibitory concentration value against S. mutants than the values reported for chitosan polymers and showed negligible cell toxicity. The mouthwashes were stable at both 25 and 40◦C. Further work is under way towards other CS3H Lys F oral hygiene products such as a toothpaste

Enhancing the antibacterial effect of chitosan to combat orthopaedic implant-associated infections

The development of antibacterial resistance imposes the development of novel materials to relieve the burden of infection. Chitosan, a material of natural and sustainable origin, possesses ideal characteristics to translate into a novel biomaterial with antibacterial properties, as it already has these properties and it allows easy and scalable chemical modification to enhance its activity. The aim of the present work was that of producing low molecular weight chitosans that have higher solubility and can remain protonated at physiological pH, thus enhancing the antimicrobial action. This was achieved by reacting acid hydrolysed low molecular weight chitosan with 2-bromoethyleneamine hydrobromide or Fmoc-Lys(Fmoc)-OH to elicit N-(2-ethylamino)-chitosan and N-2(2,6-diaminohexanamide)-chitosan polymers. The latter derivative, CS3H Lys, that was synthesised for the first time, showed superior efficacy against Staphylococcus aureus, supporting further studies for its inclusion in implant coating materials to tackle the burden of orthopaedic implant-associated infections