4D bioprinting and stimuli-responsive tissue constructs: Brief report

New technological advancements in smart biomaterials, such as shape memory polymer, hydrogel composite, nanomaterial-reinforced matrix, and bioactive hybrid scaffold, have enabled us to create constructs that have tunable mechanical and biological properties. The addition of stem cells, growth factors, and extracellular matrix components to bioprinted constructs has improved cell viability and differentiation and helped mature the tissue. Design strategies like computational modelling, AI guided scaffold optimization, and multi-material printing are becoming more widely used for the accurate creation and functional optimization of 4D bioprinted constructs. The range of applications for 4D bioprinted constructs is expanding beyond bone and cartilage regeneration, vascularised tissue generation, cardiac patches, neural repair, and soft tissue regeneration to include engineering organoid tissues. Even though there have been significant advances in the development of 4D bioprinted constructs there remain a number of technical and translational challenges to their clinical use. These challenges include material biocompatibility, manufacturing scalability, long-term stability, regulatory issues, and the ability to reproduce the dynamic behaviour of materials in vivo. There is an increasing recognition of the need for standardized fabrication protocols, real-time monitoring technology, and clinically validated bioinks for successful translation and clinical application of dynamic biofabrication technologies. This work aims to discuss the mechanisms of stimuli-responsive biomaterials used to create dynamic tissue reconstruction and the associated translational barriers in developing clinically applicable tissue constructs. Conflicting data regarding the function of these materials and emerging avenues of research has been discussed.

Impact Statement: 4D bioprinting provides a revolutionary approach to creating dynamic, adaptive and responsive bio-printed tissues, compared to traditional methods, which produce static bio-printed tissues. Smart biomaterials, programmable bio-fabrication techniques and cellular behaviours that transform over time can be combined to create adaptive bio-printed tissues that closely mimic the development of physiological tissues and enable better co-integration with the host. By summarising current developments in responsive hydrogels, shape-memory polymers, multi-material printing and computer-aided design, this mini-review aims to provide researchers with a foundation for creating the next generation of dynamic scaffolds and bioactive implants. Challenges related to translating laboratory innovations into clinical applications, including scaling-up operations, long-term viability and regulatory requirements, are also addressed to provide relevant insights for researchers. In conclusion, 4D bioprinting has the potential to enable the creation of personalised regenerative therapies, enhanced disease models and advanced drug-delivery systems, thereby helping propel the field of tissue engineering towards the development of adaptive, patient-specific biomedical solutions.