Laser-Printed Bone Grafts Could Transform Bone Healing

A team of engineers from ETH Zurich unveiled a more efficient and practical way to create bone grafts. Their approach uses new materials and laser printing to enable faster recovery with less risk. Here’s what you need to know.

Why Bone Fractures Are Increasing

You likely have, at the very least, known someone who has broken a bone in their lifetime. While these experiences can range from childhood accidents to major trauma, they all require some sort of medical attention to ensure the bone heals properly.

Sadly, the number of people who experience broken bones has steadily increased globally. This increase reflects the aging baby boomer demographic. Reports from the International Osteoporosis Foundation (IOF) show over 37 million fragile fractures were registered last year alone among the elderly, and this trend is predicted to continue alongside the aging population.

How Bones Naturally Heal

The human body is incredible, and it can heal fractures and mild breaks on its own. As part of this capability, it will first deploy a variety of soft tissue cells to the damaged area. These temporary cells act like scaffolding, allowing the new bone growth to take form and eventually harden.

Part of this success is due to the unique mix of microscopic passageways and spaces found throughout your bone. Impressively, reports show that a tiny bone fragment smaller than a quarter can have more than 54 kilometers of microscopic tunnels running through it.

When Bone Fractures Require Surgical Intervention

There are scenarios in which the break is so severe that the human body is unable to heal the wound without additional assistance from healthcare professionals. Specifically, severe compound fractures require a setting that is held in place via metal pins and implants.

Also, the removal of any tumors can leave a portion of the bone missing. Doctors must fill this missing bone segment to properly set the bone. In some cases, a graft is made using bone from the patient.

Autografts

Autografts are the most popular way in which healthcare professionals deal with this situation. Autografts can come in many forms, with the most popular using bone from the patient, ceramic, or metal options.

Problems with Autografts

Autografts can improve the healing process, but they aren’t without their own issues. For one, the process requires an additional surgery to secure the bone tissue to be used to create the graft. This step adds costs and risks to the scenario, alongside time delays and the requirement for additional professionals.

ETH Zurich’s Laser-Printed Bone Graft Breakthrough

The scientific paper “A Water-Soluble PVA Macrothiol Enables Two-Photon Microfabrication of Cell-Interactive Hydrogel Structures at 400 mm s−1”¹ published in Advanced Materials highlights a completely new approach that has the potential to revolutionize healthcare moving forward.

2PP Microfabrication

To accomplish their task of creating better and more stable grafts, the team looked towards a method known as Two-photon polymerization (2PP). Originally developed as a direct laser writing technique used in tissue engineering and drug development, it relies on femtosecond laser pulses.

These tiny high-intensity lasers are used to harden special photosensitive materials. The advantage of this approach is that it allows engineers to develop high-resolution 3D architectures at (sub)-micron-scale resolution. It’s this last capability that caught the attention of Professor of Biomaterials Engineering at ETH Zurich, Xiao-Hua Qin, and his team.

New Hydrogel Was Needed

Mimicking the extracellular matrix (ECM) of a human being is no easy task, as it requires an unmatched level of intricacy that traditional 2PP strategies lacked. They noted that the use of a dual-photon laser allows the photochemical reaction to be focused exactly on a single area, providing much more control versus single-laser approaches in the past.

However, the gel wasn’t stiff enough to take shape or reactive enough to stay in place. To address these issues, the team turned its focus towards creating a new hydrogel.

Notably, the current form of 2PP fabrication uses hydrogel containing (meth)acrylated proteins.  Commercial water-soluble thiol crosslinkers, like dithiothreitol, are commonly used. These proteins lack the strong cross-linking mechanisms required to support bone growth.

Source – ETH Zurich

This material can’t support the level of intricacy required for human bone, and when they attempted to use this material, they registered a high number of structural defects. Traditionally, adding more polymer concentrations would be the option, but the team decided against this move.

PVA Thiol Crosslinker (PVASH)

The engineers decided it was best to develop a completely new hydrogel to accomplish their goals. The water-soluble, polyvinyl alcohol macromolecular thiol crosslinker (PVASH) hydrogel uses specialized molecules to remain stable and non-intrusive.

Specifically, the team mixed PVASH with norbornene-functionalized PVA (nPVA) as the first part of the procedure. The next step involved adding photoinitiators to ensure the laser process worked correctly.

The main change in this approach is that it introduces multiple reactive groups. This strategy makes the gel harden faster and more thoroughly when the laser radiation hits it. It also enabled the developers to utilize one molecule for linking the polymer chain and the other to ensure the light reaction.

Laser-Printed

The use of laser-printing is a major advantage that enables engineers to achieve natural bone structures that often have details as small as 500 nanometers in width. Specifically, the team integrated a 20 mW laser for the task.

This microscopic capability ensures that the bone structures have natural cavities and pathways. Also, these designs can be preprogrammed and delivered at an impressive 400 millimeters per second. This rate represents a new world record, while also showcasing the importance of this advancement in terms of speeding up patient recovery.

Micro-Scaffolds

The material appears to be able to replicate the complexities of human bone to the point that cells will begin the traditional healing process without delay. Keenly, the miles of microscopic tunneling and passageways provide the perfect amount of adhesion to attract and support healthy cell growth.

Laboratory Testing of Laser-Printed Bone Scaffolds

The scientists conducted several lab tests to see if their theory could hold up under real-world conditions. Notably, the engineers were delighted to see that the test tube studies showed rapid cell growth.

Specifically, the hydrogel was printed into the custom formation, and within days, the body began creating collagen, which is one of the most important steps in bone growth. The engineers also took this time to register how the polymer disintegrated into the body, noting that it’s completely harmless.

They then spent some time evaluating their hydrogel and the thiol-ene crosslinking molecules. They noted their performance exceeded expectations, creating a strong and natural repair to the damaged tissue in a shorter time than other methods.

Laser-Printed Bone Grafts Test Results

The test results highlight how important this work is to the healthcare sector. The scientists were able to register a massive improvement in every aspect of the process. From molding the graft, to cells moving in, and finally the scaffolding biodegrading, the researcher’s work proved to be accurate, creating healed bone cells that are exactly like those created naturally.

Advantages of Laser-Printed Bone Grafts

There are many benefits that this new hydrogel brings to the table. For one, it offers more flexibility in terms of structure and placement. Traditional hydrogels don’t have any moldability. The addition of additional linking molecules creates far more stability, enabling direct molding based on the individual’s personal needs.

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Fidelity

Another major advantage that can’t be overlooked is the added fidelity that this approach provides. The new PVASH-based hydrogels provide engineers with more options in terms of design and the overall complexity of the structure on a microscopic level.

Better Patient Response

While the scientists have only conducted lab trials, they did note that the healing process using the new strategy showed much less swelling. The reduced swelling is because the hydrogel is biocompatible, which is easier for your body’s cells to accept versus metal or ceramic options.

Real-World Applications & Timeline:

The real-world application for this discovery can stretch across multiple industries. For one, it’s obvious use is in the healthcare industry where it could help to reduce the costs and recovery time of broken bones for patients.

Prosthetics

This technology could eventually be used to create more realistic prosthetics that look and feel like real body parts rather than replacements. The technology could lay the foundation and enable cell growth to do the rest in an ideal scenario.

Robotics

The robotics market could also leverage this technology to create stronger biomechanical designs. These units could leverage a combination of living cells and structure alongside mechanical devices to create more efficient and capable machines in the future.

Timeline

It could be at least ten years before this technology is mature enough for human use. The research is still in its early stage and despite a lot of success so far, there are still many scientific and regulatory hurdles that will need to be overcome before this technology becomes mainstream.

Laser-Printed Bone Grafts Researchers

Researchers from ETH Zurich led the Laser-printed Bone Grafts study. The paper lists Xiao-Hua Qin and Ralph Müller as the lead authors. They received support from  Wanwan Qiu, Margherita Bernero, Muja Emilie Ye, Xianjun Yang, and Philipp Fisch.

Future

The future of laser-printed bone grafts is yet to be determined. The technology makes sense and has shown a lot of promise. However, there’s still so much more testing to complete, including human trials.

The next step will be to move on to animal testing. Already, the scientists have announced a strategic partnership with AO Research Institute Davos to facilitate this next stage of development. Depending on the results of this test, the research will move on towards human patients.

Investing in HealthTech Innovation

There are several companies that continue to drive innovation in the HealthTech sector. These firms have demonstrated a willingness to look outside the box for solutions to this critical problem. Here’s one company that remains a pioneer in the market worth knowing.

Xtant Medical Holdings

Xtant Medical Holdings originated as Bacterin International at Montana State University’s lab in the early 90s. The goal of the project was to research better medical practices with a focus on regenerative medicine implants.

Xtant Medical Holdings rebranded in 2000, and in 2006, it released a line of surgical implants. These products gained a lot of attention, and in 2013, the company hosted a successful IPO. At the same time, the company began acquiring other regenerative bone research companies like X-spine in 2016.

In 2020, Xtant pivoted its attention towards spine reconstruction.  As part of this strategy, it continued to make acquisitions and form strategic partnerships. Since that time, the company has expanded back into other regenerative bone sciences.

Today, Xtant is recognized as one of the leading orthobiological companies in the world. The firm has several products designed to improve patient outcomes and continues to invest in creating more efficient options. Those seeking a reputable med-tech firm should do more research into Xtant’s offerings.

Latest Xtant Medical Holdings (XTNT) News and Performance

Laser-Printed Bone Grafts Conclusion

It’s easy to understand why there is a strong push to find a better solution for patients suffering from difficult bone injuries like spinal trauma. The population is aging, and these kinds of injuries are going to become more common in the future. As such, this work could lay the foundation for faster and more reliable healing strategies.

Learn about other cool developments in the Health-Tech sector here.

References

^{1. Qiu, W., Bernero, M., Ye, M. E., Yang, X., Fisch, P., Müller, R., & Qin, X. H. A Water-Soluble PVA Macrothiol Enables Two-Photon Microfabrication of Cell-Interactive Hydrogel Structures at 400 mm s−1. Advanced Materials, e10834. https://doi.org/10.1002/adma.202510834}