Shape-memory collagen scaffold combined with hyaluronic acid for repairing intervertebral disc.

BACKGROUND: Intervertebral disc degeneration (IVDD) is a common cause of chronic low back pain (LBP) and a socioeconomic burden worldwide. Conservative therapies and surgical treatments provide only symptomatic pain relief without promoting intervertebral disc (IVD) regeneration. Therefore, the clinical demand for disc regenerative therapies for disc repair is high. METHODS: In this study, we used a rat tail nucleotomy model to develop mechanically stable collagen-cryogel and fibrillated collagen with shape-memory for use in minimally invasive surgery for effective treatment of IVDD. The collagen was loaded with hyaluronic acid (HA) into a rat tail nucleotomy model. RESULTS: The shape-memory collagen structures exhibited outstanding chondrogenic activities, having completely similar physical properties to those of a typical shape-memory alginate construct in terms of water absorption, compressive properties, and shape-memorability behavior. The treatment of rat tail nucleotomy model with shape-memory collagen-cryogel/HA alleviated mechanical allodynia, maintained a higher concentration of water content, and preserved the disc structure by restoring the matrix proteins. CONCLUSION: According to these results, the collagen-based structure could effectively repair and maintain the IVD matrix better than the controls, including HA only and shape-memory alginate with HA.

4D Bioprinting: Technological Advances in Biofabrication.

The development of the three-dimensional (3D) printer has resulted in significant advances in a number of fields, including rapid prototyping and biomedical devices. For 3D structures, the inclusion of dynamic responses to stimuli is added to develop the concept of four-dimensional (4D) printing. Typically, 4D printing is useful for biofabrication by reproducing a stimulus-responsive dynamic environment corresponding to physiological activities. Such a dynamic environment can be precisely designed with an understanding of shape-morphing effects (SMEs), which enables mimicking the functionality or intricate geometry of tissues. Here, 4D bioprinting is investigated for clinical use, for example, in drug delivery systems, tissue engineering, and surgery in vivo. This review presents the concept of 4D bioprinting and smart materials defined by SMEs and stimulus-responsive mechanisms. Then, biomedical smart materials and applications are discussed along with future perspectives.

Recent cell printing systems for tissue engineering.

Three-dimensional (3D) printing in tissue engineering has been studied for the bio mimicry of the structures of human tissues and organs. Now, it is being applied to 3D cell printing, which can position cells and biomaterials, such as growth factors, at desired positions in the 3D space. However, there are some challenges of 3D cell printing, such as cell damage during the printing process and the inability to produce a porous 3D shape owing to the embedding of cells in the hydrogel-based printing ink, which should be biocompatible, biodegradable, and non-toxic, etc. Therefore, researchers have been studying ways to balance or enhance the post-print cell viability and the print-ability of 3D cell printing technologies by accommodating several mechanical, electrical, and chemical based systems. In this mini-review, several common 3D cell printing methods and their modified applications are introduced for overcoming deficiencies of the cell printing process.