Delft researchers use porous iron to 3D print biodegradable bone implants

China3D printingNet January 13th, Delft University of Technology’s team of engineers has used extrusion-based3D printingTo make temporary bone implants made of porous iron. Like magnesium or zinc, porous iron is biodegradable, which means that it has great potential as a temporary bone substitute that degrades as new bones regrow. By reabsorbing into the body, temporary implants can reduce the risk of long-term inflammation, which is usually associated with permanent bone implants made of metal (such as titanium). The lead author of the study, Amir A. Zadpoor, pointed out: “Compared with other biodegradable metals or polymers used in bone implants, iron has high mechanical strength, so that it can be designed and manufactured for the treatment of critical bones. Porous structure.

SEM image of porous iron scaffold. Picture from TU Delft.

Improbable technology choice

At first glance, it seems that the use of iron for3D printingBioabsorbable bone implants are very interesting. This metal is used by the human body to transport oxygen. It accelerates certain enzyme reactions, plays a major role in immune responses, and is a key component of bone regeneration. This problem occurs when looking at the most common form of iron, which is bulk (dense) iron. Unlike porous iron, bulk iron has a very low biodegradation rate due to its relatively small surface area.Unfortunately, technologies such as powder bed fusion were previously used3D printingAttempts to porous bone scaffolds have been limited, mainly involving accessibility, cost or porosity control.Although based on extrusion3D printingSome of these obstacles can be overcome, but it is usually synonymous with low-quality parts that are not suitable for end-use medical products. Therefore, the Delft team chose to try their own dedicated squeeze-based setup. Zadpoor ​​added: “We want to verify the use of extrusion-based3D printingTo make porous iron feasibility, and explore the potential to solve the basic problems of bulk iron, bulk iron has a very low biodegradation rate, while maintaining other important properties (such as structural integrity) and mechanical properties during bone healing. ” 3D printing, Sintering and testing porous iron bone implants” alt=” 3D printing, Sintering and testing porous iron bone implants” width=”620″ height=”248″ /> 3D printing, Sintering and testing porous iron bone implants. Picture from TU Delft. The team’s method involves mixing polymer solvents with iron particles to make composite inks. Once the support structures are printed, they are heated to burn off the polymer, leaving behind iron. The remaining iron structure is then further heat treated to sinter it into a porous solid. Zadpoor ​​and his colleagues immersed their printed porous stent in a specially formulated simulated body fluid and determined that the implant has a high biodegradability rate, with iron losing 7% of its mass every 28 days. The research team also found that corrosion occurs around and even inside the implant, but their mechanical properties are still consistent with human bones. Zadpoor ​​said: “We have confirmed that the squeeze-based3D printingThe technology can provide porous iron scaffolds with enhanced biodegradability and bone-like mechanical properties, which may be used as bone substitutes. “The next phase of the research involves testing extrusion-based3D printingPotential in other more advanced implant-related functions. This involves injecting nano-bioceramics to promote bone growth, and even injecting antibacterial agents to reduce the risk of infection after surgery. 3D printingBone implant” alt=”Before and after body fluid immersion3D printingBone implant” width=”620″ height=”405″ /> Before and after body fluid immersion3D printingBone implants. Picture from TU Delft. Although titanium is largely considered the metal of choice for bone implantation, additive manufacturing researchers are constantly demonstrating the suitability of other materials for this application.In the second half of last year, scientists at Skolkovo Institute of Technology developed a novel3D printingA method of personalizing bone implants made of ceramics. Much like Delft implants, Skolkovo implants have large pores, allowing them to better integrate with organic tissues.Elsewhere, researchers have previously developed nanoclay-based3D bioprintingThe scaffold is used to assist bone regeneration. Injecting human bone marrow stromal cells and human umbilical vein endothelial cells into the bone replacement scaffold further promotes bone growth.

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