Application of 3D, 4D, 5D, and 6D bioprinting in cancer research: what does the future look like?

Smart hydrogel: A new platform for cancer therapy

Cancer is a significant contributor to mortality worldwide, posing a significant threat to human life and health. The unique bioactivity, ability to precisely control drug release, and minimally invasive properties of hydrogels are indispensable attributes that facilitate optimal performance in cancer therapy. However, conventional hydrogels lack the ability to dynamically respond to changes in the surrounding environment, withstand drastic changes in the microenvironment, and trigger drug release on demand. Therefore, this review focuses on smart-responsive hydrogels that are capable of adapting and responding to external stimuli. We comprehensively summarize the raw materials, preparation, and cross-linking mechanisms of smart hydrogels derived from natural and synthetic materials, elucidate the response principles of various smart-responsive hydrogels according to different stimulation sources. Further, we systematically illustrate the important role played by hydrogels in modern cancer therapies within the context of therapeutic principles. Meanwhile, the smart hydrogel that uses machine learning to design precise drug delivery has shown great prospects in cancer therapy. Finally, we present the outlook on future developments and make suggestions for future related work. It is anticipated that this review will promote the practical application of smart hydrogels in cancer therapy and contribute to the advancement of medical treatment.

Engineering in vitro vascular microsystems

Blood vessels are hierarchical microchannels that transport nutrients and oxygen to different tissues and organs, while also eliminating metabolic waste from the body. Disorders of the vascular system impact both physiological and pathological processes. Conventional animal vascular models are complex, high-cost, time-consuming, and low-validity, which have limited the exploration of effective in vitro vascular microsystems. The morphologies of micro-scaled tubular structures and physiological properties of vascular tissues, including mechanical strength, thrombogenicity, and immunogenicity, can be mimicked in vitro by engineering strategies. This review highlights the state-of-the-art and advanced engineering strategies for in vitro vascular microsystems, covering the domains related to rational designs, manufacturing approaches, supporting materials, and organ-specific cell types. A broad range of biomedical applications of in vitro vascular microsystems are also summarized, including the recent advances in engineered vascularized tissues and organs for physiological and pathological study, drug screening, and personalized medicine. Moreover, the commercialization of in vitro vascular microsystems, the feasibility and limitations of current strategies and commercially available products, as well as perspectives on future directions for exploration, are elaborated. The in vitro modeling of vascular microsystems will facilitate rapid, robust, and efficient analysis in tissue engineering and broader regenerative medicine towards the development of personalized treatment approaches.

From Stents to Smart Implants Employing Biomimetic Materials: The Impact of 4D Printing on Modern Healthcare

The sector of 4D printing represents a new frontier in additive manufacturing that allows for a material's capability to adapt and respond to various stimuli, such as thermal transitions, humidity, and pH levels. The adaptability of such a material has great potential in healthcare applications, especially in designing personalized and responsive medical devices. This article looks into the revolutionary potential of healthcare applications of 4D printing, referencing applications in self-repairable implants, smart stents, personalized drug delivery systems, and response-based prosthetic devices. The advances in 3D printing have created a platform for such innovations to take place, while the material properties unique to 4D printing allow new methods of tackling existing health issues. However, the large-scale application of 4D printing in medicine is currently hampered by material limitations, regulation challenges, and financial challenges. In spite of these challenges, ongoing advances in technologies, combined with artificial intelligence and machine learning, provide the potential to surpass such challenges, hence improving the precision, efficacy, and personalization of medical devices. This work outlines existing applications, looks at potential areas of application in the future, and analyzes potential applications of 4D printing contributing to healthcare, recognizing challenges that need to be overcome in order to unlock its full potential.

3D and 4D printing of MXene-based composites: from fundamentals to emerging applications

The advent of three-dimensional (3D) and four-dimensional (4D) printing technologies has significantly improved the fabrication of advanced materials, with MXene-based composites emerging as a particularly promising class due to their exceptional electrical, mechanical, and chemical properties. This review explores the fundamentals of MXenes and their composites, examining their unique characteristics and the underlying principles of their synthesis and processing. We highlight the transformative potential of 3D and 4D printing techniques in tailoring MXene-based materials for a wide array of applications. In the field of tissue regeneration, MXene composites offer enhanced biocompatibility and mechanical strength, making them ideal for scaffolds and implants. For drug delivery, the high surface area and tunable surface chemistry of MXenes enable precise control over drug release profiles. In energy storage, MXene-based electrodes exhibit superior conductivity and capacity, paving the way for next-generation batteries and supercapacitors. Additionally, the sensitivity and selectivity of MXene composites make them excellent candidates for various (bio)sensing applications, from environmental monitoring to biomedical diagnostics. By integrating the dynamic capabilities of 4D printing, which introduces time-dependent shape transformations, MXene-based composites can further adapt to complex and evolving functional requirements. This review provides a comprehensive overview of the current state of research, identifies key challenges, and discusses future directions for the development and application of 3D and 4D printed MXene-based composites. Through this exploration, we aim to underscore the significant impact of these advanced materials and technologies on diverse scientific and industrial fields.