No abstract

Over the past few decades, bone related disorders have constantly increased. Among all pathological conditions, osteoporosis is one of the most common and often leads to bone fractures. This is a massive burden and it affects an estimated 3 million people only in the UK. Furthermore, as the population ages, numbers are due to increase. In this context, novel biomaterials for bone fracture regeneration are constantly under development. Typically, these materials aim at favoring optimal bone integration in the scaffold, up to complete bone regeneration; this approach to regenerative medicine is also known as tissue engineering (TE). Hydrogels are among the most promising biomaterials in TE applications: they are very flexible materials that allow a number of different properties to be targeted for different applications, through appropriate chemical modifications. The present review will focus on the strategies that have been developed for formulating hydrogels with ideal properties for bone regeneration applications. In particular, aspects related to the improvement of hydrogels’ mechanical competence, controlled delivery of drugs and growth factors are treated in detail. It is hoped that this review can provide an exhaustive compendium of the main aspects in hydrogel related research and, therefore, stimulate future biomaterial development and applications.

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.

Clinical treatments of significant bone defects involve invasive procedures such as the application of auto- and allografts. These procedures present many limitations including the potential for infection and rejection. There is therefore a need to develop novel therapeutic strategies able to exploit the natural regenerative potential of bone and that can be delivered in a less invasive manner. Among the materials studied for the development of novel scaffolds, stimuli-responsive gels containing hydroxyapatite and carbon nanotubes as nanofillers have generated great interest. In the present work, chitosan gels containing chitosan grafted CNTs and chitosan-hydroxyapatite complex have been formed by cross-linking with glycerol phosphate. The addition of the nanofillers afforded hydrogels with a faster sol/gel transition at 37 °C and enhanced mechanical properties. The thermosensitive composite gels also showed a good bioactivity profile associated with potential for the prolonged delivery of protein drugs. The inclusion of chemically cross-linked CNTs and HA in thermosensitive gels afforded injectable composite materials with enhanced properties, including reduction of gelation time, improved mechanical properties, good bioactivity, and prolonged drug release.

Abstract:Silver is well known for its antibacterial properties and low toxicity, and it is currently widely used both in the form of ions and of nanoparticles in many diverse products. One-dimensional silver nanowires (AgNWs) have the potential to further enhance the properties of nanosilver-containing products, since they appear to have higher antimicrobial efficacy and lower cytotoxicity. While they are widely used in optics and electronics, more studies are required in order to better understand their behavior in the biological environment and to be able to advance their application in uses such as wound healing, surface coating and drug delivery.