In recent years, three-dimensional (3D) bioprinting has attracted wide research interest in biomedical engineering and clinical applications. This technology allows for unparalleled architecture control, adaptability and repeatability that can overcome the limits of conventional biofabrication techniques. Along with the emergence of a variety of 3D bioprinting methods, bioinks have also come a long way. From their first developments to support bioprinting requirements, they are now engineered to specific injury sites requirements to mimic native tissue characteristics and to support biofunctionality. Current strategies involve the use of bioinks loaded with cells and biomolecules of interest, without altering their functions, to deliver in situ the elements required to enhance healing/regeneration. The current research and trends in bioink development for 3D bioprinting purposes is overviewed herein.

Intervertebral disc (IVD) degeneration is a challenging clinical problem that urgently demands viable nucleus pulposus (NP) implant materials. The best suited biomaterial for NP regeneration has yet to be identified, but it is believed that biodegradable hydrogel‐based materials are promising candidates. In this work, we have developed ionic‐ and photo‐crosslinked methacrylated gellan gum (GG–MA) hydrogels to be used in acellular and cellular tissue‐engineering strategies for the regeneration of IVDs. The physicochemical properties of the developed hydrogels were investigated by Fourier‐transform infrared spectroscopy, ¹H nuclear magnetic resonance and differential scanning calorimetry. The swelling ability and degradation rate of hydrogels were also analysed in phosphate‐buffered saline solution at physiological pH for a period of 30 days. Additionally, the morphology and mechanical properties of the hydrogels were assessed under a scanning electron microscope and dynamic compression, respectively. An in vitro study was carried out to screen possible cytotoxicity of the gellan gum‐based hydrogels by culturing rat lung fibroblasts (L929 cells) with hydrogel leachables up to 7 days. The results demonstrated that gellan gum was successfully methacrylated. We observed that the produced GG–MA hydrogels possess improved mechanical properties and lower water uptake ability and degradation rate as compared to gellan gum. This work also revealed that GG–MA hydrogels are non‐cytotoxic in vitro, thus being promising biomaterials to be used in IVD tissue‐engineering strategies. Copyright © 2010 John Wiley & Sons, Ltd.

Gellan gum, a microbial exopolysaccharide fermentation product of Pseudomonas elodea, is a natural biomaterial that has shown promise for tissue engineering and regenerative medicine applications. Although this exopolysaccharide possesses many advantages, such as interesting physicochemical properties and non-cytotoxicity, the mechanical properties and processability of gellan gum are not totally satisfactory in different tissue engineering contexts, i.e. gellan gum hydrogels are mechanically weak and the high gelling temperature is also unfavourable. An additional critical limitation is the lack of specific attachment sites for anchorage-dependent cells. However, the multiple hydroxyl groups and the free carboxyl per repeating unit of gellan gum can be used for chemical modification and functionalization in order to optimize its physicochemical and biological properties. A number of physical modification approaches have also been employed. This review outlines the recent progress in gellan gum hydrogels and their derivatives, and identifies the new challenges in tissue engineering, provided by blending and/or chemical modification.