Advances in 3D bioprinting for regenerative medicine applications.

Biofabrication techniques allow for the construction of biocompatible and biofunctional structures composed from biomaterials, cells and biomolecules. Bioprinting is an emerging 3D printing method which utilizes biomaterial-based mixtures with cells and other biological constituents into printable suspensions known as bioinks. Coupled with automated design protocols and based on different modes for droplet deposition, 3D bioprinters are able to fabricate hydrogel-based objects with specific architecture and geometrical properties, providing the necessary environment that promotes cell growth and directs cell differentiation towards application-related lineages.

Bioactive and biomimetic 3D scaffolds for bone tissue engineering using graphitic carbon nitride as a sustainable visible light photoinitiator.

Graphitic carbon nitride (g-CN) is explored as a novel sustainable visible light photoinitiator for the preparation of biomimetic 3D hydrogel scaffolds comprising gelatin methacrylamide (GelMA) and dopamine methacrylamide for use in tissue engineering. The initiator efficiency was assessed by comparing the swelling behavior and the stability of photopolymerized hydrogels prepared with GelMA of different degrees of functionalization and different comonomer compositions. Bioactive composite hydrogels with a 50 wt% nanohydroxyapatite (nHAp) content, to closely mimic the actual bone composition, were successfully obtained by the introduction of nHAp in the prepolymer solutions followed by photopolymerization.

Thermoresponsive Alginate-Graft-pNIPAM/Methyl Cellulose 3D-Printed Scaffolds Promote Osteogenesis In Vitro.

In this work, a sodium alginate-based copolymer grafted by thermoresponsive poly(-isopropylacrylamide) (PNIPAM) chains was used as gelator (Alg-g-PNIPAM) in combination with methylcellulose (MC). It was found that the mechanical properties of the resulting gel could be enhanced by the addition of MC and calcium ions (Ca). The proposed network is formed via a dual crosslinking mechanism including ionic interactions among Ca and carboxyl groups and secondary hydrophobic associations of PNIPAM chains.

Effect of Uniaxial Compression Frequency on Osteogenic Cell Responses in Dynamic 3D Cultures.

The application of mechanical stimulation on bone tissue engineering constructs aims to mimic the native dynamic nature of bone. Although many attempts have been made to evaluate the effect of applied mechanical stimuli on osteogenic differentiation, the conditions that govern this process have not yet been fully explored. In this study, pre-osteoblastic cells were seeded on PLLA/PCL/PHBV (90/5/5 wt.

Kappa-Carrageenan/Chitosan/Gelatin Scaffolds Provide a Biomimetic Microenvironment for Dentin-Pulp Regeneration.

This study aims to investigate the impact of kappa-carrageenan on dental pulp stem cells (DPSCs) behavior in terms of biocompatibility and odontogenic differentiation potential when it is utilized as a component for the production of 3D sponge-like scaffolds. For this purpose, we prepared three types of scaffolds by freeze-drying (i) kappa-carrageenan/chitosan/gelatin enriched with KCl (KCG-KCl) as a physical crosslinker for the sulfate groups of kappa-carrageenan, (ii) kappa-carrageenan/chitosan/gelatin (KCG) and (iii) chitosan/gelatin (CG) scaffolds as a control. The mechanical analysis illustrated a significantly higher elastic modulus of the cell-laden scaffolds compared to the cell-free ones after 14 and 28 days with values ranging from 25 to 40 kPa, showing an increase of 27-36%, with the KCG-KCl scaffolds indicating the highest and CG the lowest values.

Nanocomposite Bioprinting for Tissue Engineering Applications.

Bioprinting aims to provide new avenues for regenerating damaged human tissues through the controlled printing of live cells and biocompatible materials that can function therapeutically. Polymeric hydrogels are commonly investigated ink materials for 3D and 4D bioprinting applications, as they can contain intrinsic properties relative to those of the native tissue extracellular matrix and can be printed to produce scaffolds of hierarchical organization. The incorporation of nanoscale material additives, such as nanoparticles, to the bulk of inks, has allowed for significant tunability of the mechanical, biological, structural, and physicochemical material properties during and after printing.

Kappa-carrageenan/chitosan/gelatin scaffolds enriched with potassium chloride for bone tissue engineering.

Kappa-carrageenan is a biocompatible natural polysaccharide able to form hydrogels for tissue regeneration. In bone tissue engineering, achieving a bioactive microenvironment with appropriate mechanical properties in polysaccharide-based scaffolds remains a challenge. This study aims to fabricate 3D scaffolds comprising kappa-carrageenan, chitosan and gelatin, crosslinked with KCl, and evaluate their mechanical and biological properties for bone tissue engineering.

Responsive Polyesters with Alkene and Carboxylic Acid Side-Groups for Tissue Engineering Applications.

Main chain polyesters have been extensively used in the biomedical field. Despite their many advantages, including biocompatibility, biodegradability, and others, these materials are rather inert and lack specific functionalities which will endow them with additional biological and responsive properties. In this work, novel pH-responsive main chain polyesters have been prepared by a conventional condensation polymerization of a vinyl functionalized diol with a diacid chloride, followed by a photo-induced thiol-ene click reaction to attach functional carboxylic acid side-groups along the polymer chains.