The fields of tissue engineering and regenerative medicine aim at promoting the regeneration of tissues or replacing failing or malfunctioning organs, by means of combining a scaffold/support material, adequate cells and bioactive molecules. Different materials have been proposed to be used as both three-dimensional porous scaffolds and hydrogel matrices for distinct tissue engineering strategies. Among them, polymers of natural origin are one of the most attractive options, mainly due to their similarities with the extracellular matrix (ECM), chemical versatility as well as typically good biological performance. In this review, the most studied and promising and recently proposed naturally derived polymers that have been suggested for tissue engineering applications are described. Different classes of such type of polymers and their blends with synthetic polymers are analysed, with special focus on polysaccharides and proteins, the systems that are more inspired by the ECM. The adaptation of conventional methods or non-conventional processing techniques for processing scaffolds from natural origin based polymers is reviewed. The use of particles, membranes and injectable systems from such kind of materials is also overviewed, especially what concerns the present status of the research that should lead towards their final application. Finally, the biological performance of tissue engineering constructs based on natural-based polymers is discussed, using several examples for different clinically relevant applications.

The bio- and eco-friendly nature of biocompatible ionic liquids contributes to their widespread use in a wide range of fields.

Ionic liquids (ILs) have huge potential to provide advances in many areas such as energy, pharmaceutical formulations, biomedical sciences, and technology. In the biomedical field, ILs have been intensively investigated for use as potential solvents for some polysaccharides to overcome their lack of solubility and processability. This review focuses on the application of ILs as solvents and reaction media to develop chitin- and chitosan-based materials. Dissolution of chitin and chitosan in ILs such as 1-butyl-imidazolium acetate (BMIMAc) and 1-ethyl-3-methylimidazolium chloride (BMIMCl) has been used to create materials including sponges, films, microspheres, and aerogels. Moreover, ILs have a key role in chemical reactions, hydrolysis, acetylation, deacetylation and graft copolymerization of chitin/chitosan, promoting homogeneous media and thus enhancing the efficiency of the reactions. The resulting materials can be applied in wound healing, tissue regeneration, gene delivery, and drug delivery systems. In particular, they have been designed to support tissue regeneration and to act as hemostatic and antibacterial agents and/or delivery vehicles for drugs. Although IL platforms offer new ways for the sustainable processing of chitin and chitosan to a variety of matrices, studies involving their in vivo biocompatibility are scarce, and this has prevented these advances being turned into clinical solutions.

Marine organisms are constituted by materials with a vast range of properties and characteristics that may justify their potential application within the biomedical field. Moreover, assuring the sustainable exploitation of natural marine resources, the valorisation of residues from marine origin, like those obtained from food processing, constitutes a highly interesting platform for development of novel biomaterials, with both economic and environmental benefits. In this perspective, an increasing number of different types of compounds are being isolated from aquatic organisms and transformed into profitable products for health applications, including controlled drug delivery and tissue engineering devices. This report reviews the work that is being developed on the isolation and characterisation of some polysaccharides, proteins, glycosaminoglycans and ceramics from marine raw materials. Emphasis is given to agar, alginates, carrageenans, chitin and chitosan, among other polysaccharides, collagen, glycosaminoglycans such as chondroitin sulphate, heparin and hyaluronic acid, calcium phosphorous compounds and biosilica. Finally, this report ends by reviewing the application of the previously mentioned materials on specific biomedical applications, in particular their participation on the development of controlled drug delivery systems and tissue engineering scaffolds.