Additive manufacturing, widely known as 3D printing, has revolutionized the production of biomaterials. While conventional 3D-printed structures are perceived as static, 4D printing introduces the ability to fabricate materials capable of self-transforming their configuration or function over time in response to external stimuli such as temperature, light, or electric field. This transformative technology has garnered significant attention in the field of biomedical engineering due to its potential to address limitations associated with traditional therapies. Here, we delve into an in-depth review of 4D-printing systems, exploring their diverse biomedical applications and meticulously evaluating their advantages and disadvantages. We emphasize the novelty of this review paper by highlighting the latest advancements and emerging trends in 4D-printing technology, particularly in the context of biomedical applications.

Green nanotechnology is now well established, showcasing how natural precursors can replace hazardous synthesis routes. This review analyzes the diverse biotechnological applications of biogenic nanomaterials. In the biomedical field, they have demonstrated significant efficacy as antimicrobial agents, targeted drug delivery vehicles, wound healers, and theragnostic platforms. They also enhance food packaging security, optimize nano-fertilizers, and control insect pests. Additionally, their unique surface properties and catalytic activity make them key candidates for pollutant remediation and advanced chemical sensors. Ultimately, while green nanoparticles offer clear advantages over traditional chemical methods, key bottlenecks, like batch-to-batch reproducibility, industrial scalability, and long-term ecotoxicological and multigenerational impacts, still need to be addressed.