Chitosan-based biomaterials for tissue engineering

This review describes the most common methods for recovery of chitin from marine organisms. In depth, both enzymatic and chemical treatments for the step of deproteinization are compared, as well as different conditions for demineralization. The conditions of chitosan preparation are also discussed, since they significantly impact the synthesis of chitosan with varying degree of acetylation (DA) and molecular weight (MW). In addition, the main characterization techniques applied for chitin and chitosan are recalled, pointing out the role of their solubility in relation with the chemical structure (mainly the acetyl group distribution along the backbone). Biological activities are also presented, such as: antibacterial, antifungal, antitumor and antioxidant. Interestingly, the relationship between chemical structure and biological activity is demonstrated for chitosan molecules with different DA and MW and homogeneous distribution of acetyl groups for the first time. In the end, several selected pharmaceutical and biomedical applications are presented, in which chitin and chitosan are recognized as new biomaterials taking advantage of their biocompatibility and biodegradability.

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Chitin and Chitosan Preparation from Marine Sources. Structure, Properties and Applications

With advances in tissue engineering, the possibility of regenerating injured tissue or failing organs has become a realistic prospect for the first time in medical history. Tissue engineering - the combination of bioactive materials with cells to generate engineered constructs that functionally replace lost and/or damaged tissue - is a major strategy to achieve this goal. One facet of tissue engineering is biofabrication, where three-dimensional tissue-like structures composed of biomaterials and cells in a single manufacturing procedure are generated. Cell-laden hydrogels are commonly used in biofabrication and are termed "bioinks". Hydrogels are particularly attractive for biofabrication as they recapitulate several features of the natural extracellular matrix and allow cell encapsulation in a highly hydrated mechanically supportive three-dimensional environment. Additionally, they allow for efficient and homogeneous cell seeding, can provide biologically-relevant chemical and physical signals, and can be formed in various shapes and biomechanical characteristics. However, despite the progress made in modifying hydrogels for enhanced bioactivation, cell survival and tissue formation, little attention has so far been paid to optimize hydrogels for the physico-chemical demands of the biofabrication process. The resulting lack of hydrogel bioinks have been identified as one major hurdle for a more rapid progress of the field. In this review we summarize and focus on the deposition process, the parameters and demands of hydrogels in biofabrication, with special attention to robotic dispensing as an approach that generates constructs of clinically relevant dimensions. We aim to highlight this current lack of effectual hydrogels within biofabrication and initiate new ideas and developments in the design and tailoring of hydrogels. The successful development of a "printable" hydrogel that supports cell adhesion, migration, and differentiation will significantly advance this exciting and promising approach for tissue engineering.

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25th Anniversary Article: Engineering Hydrogels for Biofabrication

Polymeric Materials for Bone and Cartilage Repair

Natural and synthetic polymers for wounds and burns dressing

Chitosan—A versatile semi-synthetic polymer in biomedical applications

Purpose – This paper aims to report a detailed study regarding the influence of process parameters on the morphological/mechanical properties of poly(e‐caprolactone) (PCL) scaffolds manufactured by using a novel extrusion‐based system that is called BioExtruderDesign/methodology/approach – In this study the authors focused investigations on four parameters, namely the liquefier temperature (LT), screw rotation velocity (SRV), deposition velocity (DV) and slice thickness (ST) Scaffolds were fabricated by employing three different values of each parameter Through a series of trials, scaffolds were manufactured varying iteratively one parameter while maintaining constant the other ones The morphology of the structures was investigated using a scanning electron microscope (SEM), whilst the mechanical performance was assessed though compression testsFindings – Experimental results highlight a direct influence of the process parameters on the PCL scaffolds properties In particular, DV and SRV have the hig

Effect of process parameters on the morphological and mechanical properties of 3D Bioextruded poly(ε‐caprolactone) scaffolds

One of the most promising approaches in tissue engineering (TE) comprises the development of 3D porous scaffolds which are able to promote tissue regeneration. Biocompatible and biodegradable poly(ϵ-caprolactone) (PCL) structures are increasingly used as temporary extra-cellular matrices for bone tissue engineering. To ensure an appropriate bone restoration over the long term, the selected material must have a degradation rate that match the in-growth of new bone. The in vivo process, by which the scaffold degrades and is resorbed transferring the load and function back to the host tissue, is complex. Consequently, an appropriate preliminary in vitro study is required. A novel extrusion-based technology called BioExtruder was used to produce PCL porous scaffolds made with layers of directionally aligned microfilaments. The in vitro degradation behaviour in both simulated body fluid (SBF) and phosphate buffer solution (PBS) were investigated over 6 months. The characterization of the degradation behaviour ...

Evaluation of in vitro degradation of PCL scaffolds fabricated via BioExtrusion. Part 1: Influence of the degradation environment

The objective of this study was to evaluate the bioerodible polymer poly(maleic anhydride-alt-2-methoxyethyl vinyl ether) n-butyl hemiester, for multicomponent drug-loaded nanofibers produced by electrospinning. Diclofenac sodium (DS) and human serum albumin (HSA) were used as conventional drug and biopharmaceutical models. The influence of drug loading was correlated to beads presence, morphology and fibers diameter. When DS and HSA were loaded separately, a uniform distribution within fibers and beads was observed. However, when both components were loaded simultaneously, a heterogeneous distribution of DS was observed with a prominent amount in the cylindrical beads. The in vitro drug release evaluation from these nanomaterials displayed an independent delivery of the two components. These studies support the feasibility of multicomponent, bioerodible polymeric nanofibers preparation loaded with combination of traditional drugs and proteins.

E. Chiellini

Papers

Chitosan—A versatile semi-synthetic polymer in biomedical applications

Effect of process parameters on the morphological and mechanical properties of 3D Bioextruded poly(ε‐caprolactone) scaffolds

Evaluation of in vitro degradation of PCL scaffolds fabricated via BioExtrusion. Part 1: Influence of the degradation environment

New Multicomponent Bioerodible Electrospun Nanofibers for Dual-controlled Drug Release

Flavonoids from Ficus pumila