Natural-Based Nanocomposites for Bone Tissue Engineering and Regenerative Medicine: A Review (original) (raw)

REVIEW phosphates (CaPs) (e.g., β-tricalcium phosphate, hydroxyapatite) have favourable osteoconductivity, resorbability, and biocompatibility. [ 10 ] The present review provides a comprehensive overview of the most recent achievements relating to the design, processing, and properties of resorbable nanocomposites for tissue engineering and regenerative medicine. 2. Natural Polymers and Calcium Phosphate Material Properties Different materials, such as natural/synthetic polymers, carbon nanotubes, hydroxyapatite (HAp), and silicates have been exploited for nanocomposite designing and processing, attending to diverse needs in TERM. Special interest has been given to the combination of biopolymers (i.e., proteins, polysaccharides, and glycosaminoglycans) and inorganic/ceramic fi llers as CaPs, which will provide biomaterial composites with optimized properties. Natural materials are usually the components of the ECM, playing an important role in maintaining their structure. Besides, they have great design advantages and can easily promote cellular adhesion. On the other hand, CaPs are biocompatible, osteoconductive and biodegradable, but they have a limited range of mechanical strength that does not allow load-bearing applications. A brief description of the most promising material properties is herein presented. 2.1. Biopolymers 2.1.1. Proteins 2.1.1.1. Collagen and Gelatin. Collagen and its denatured form, gelatin, are the most preferred ECM proteins used in tissue engineering due to the presence of several functional groups that can enhance osteoblast adhesion and migration. [ 9 ] Collagen and gelatin structures are presented in Figure 2. Collagen is a fi brous protein, the major component of ECM and presents different morphologies in different tissues. It is, for example, found in bone (Type I), cartilage (Type II) and in blood vessel walls (Type III). This protein is non-cytotoxic, biocompatible, and biodegradable, but has low elasticity and mechanical strength, poor dimensional stability due to swelling in vivo, ability of being cross-linked to tailor the mechanical, degradation, and water-uptake properties, and the possibility of an antigenic response. [ 9 ] Collagen can be processed in fi lms, [ 7 ] fi bers, [ 8,10,12 ] and foams, [ 13-15 ] to engineer various tissues such as bone, cartilage, heart, ligament, and nerve. Collagen is also suitable to produce scaffolds for the culture of mesenchymal stem cells (MSCs) in tissue engineering. [ 16,17 ] Considering the recognized biological properties of collagen, nanocomposites developed from this natural polymer and CaPs show increased mechanical strength as compared to pure collagen. This behavior has been attributed to an increased rigidity of the nanocomposites with the addition of CaPs nanoparticles and to the strong interaction between calcium-binding residues on the polymer macromolecules and the surface of the nanoparticles. [ 18 ] Collagen/CaPs nanocomposites have been prepared using different processes, such as the direct addition of nano CaPs to the collagen solution, deposition of CaPs Sandra Pina received her MSc and a European PhD in Science and Engineering of Materials from the University of Aveiro. Her doctoral research focused on ionic-substituted calcium phosphate cements for bone regeneration. Currently, she is a postdoctoral fellow at the Portuguese Government Associate Laboratory ICVS/3B's, University of Minho. Her research interests are related to the development of novel biomimetic composites from natural origin and calcium phosphates for tissue engineering and regenerative medicine approaches. She is referee of different journals and member of the Editorial Board of Dataset Papers in Science.