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Nano-Shells Teach Bone how to Repair Itself

Scientists at the University of Michigan (Ann Arbor, MI) have developed a polymer sphere that delivers a molecule to bone wounds that tells cells already at the injury site to repair the damage.

Using the polymer sphere to introduce the microRNA molecule into cells elevates the job of existing cells to that of injury repair by instructing the cells’ healing and bone-building mechanisms to switch on, said Peter Ma, professor of dentistry and lead researcher on the project.The polymer sphere delivers the microRNA into cells already at the wound site, which turns the cells into bone repairing machines.

It’s similar to a new supervisor ordering an office cleaning crew to start constructing an addition to the building, he said.

Using existing cells to repair wounds reduces the need to introduce foreign cells—a very difficult therapy because cells have their own personalities, which can result in the host rejecting the foreign cells, or tumors. The microRNA is time-released, which allows for therapy that lasts for up to a month or longer, said Ma, who also has appointments in the university’s College of Engineering.

The findings are published in the Jan. 14 issue of Nature Communications. The technology can help grow bone in people with conditions like oral implants, those undergoing bone surgery or joint repair, or people with tooth decay.

“The new technology we have been working on opens doors for new therapies using DNA and RNA in regenerative medicine and boosts the possibility of dealing with other challenging human diseases,” Ma said.

It’s typically very difficult for microRNA to breach the fortress of the cell wall, Ma said. The polymer sphere developed by Ma’s lab easily enters the cell and delivers the microRNA.

Bone repair is especially challenging in patients with healing problems, but Ma’s lab was able to heal bone wounds in osteoporotic mice, he said. Millions of patients worldwide suffer from bone loss and associated functional problems, but growing and regenerating high-quality bone for specific applications is still very difficult with current technology.

The next step is to study the technology in large animals and evaluate it for use in humans.

The paper, “Cell-Free 3D Scaffold with Two-Stage Delivery of miRNA-26a to Regenerate Critical Sized Bone Defects,” was written by Ma and colleagues Xiaojin Zhang, Yan Li, Y. Eugene Chen and Jihua Chen.

 

Laserless ‘Inkjet’ Printing of 3D Metals and Alloys

A team of Northwestern University (Evanston, IL) engineers has created a new way to print 3D metallic objects using rust and metal powders.

While current methods rely on vast metal powder beds and expensive lasers or electron beams, Northwestern’s new technique uses liquid inks and common furnaces, resulting in a cheaper, faster, and more uniform process. The Northwestern team also demonstrated that the new method works for an extensive variety of metals, metal mixtures, alloys, and metal oxides and compounds.

“This is exciting because most advanced manufacturing methods being used for metallic printing are limited as far as which metals and alloys can be printed and what types of architecture can be created,” said Ramille Shah, assistant professor of materials science and engineering, who led the study. “Our method greatly expands the architectures and metals we’re able to print, which really opens the door for a lot of different applications.”A copper lattice structure created with Northwestern Engineering’s new 3D printing process.

Conventional methods for 3D printing metallic structures are both time and cost intensive. The process takes a very intense energy source, such as a focused laser or electron beam, that moves across a bed of metal powder, defining an object’s architecture in a single layer by fusing powder particles together. New powder is placed on top of the previous layer, and these steps are repeated to create a 3D object. Any unfused powder is subsequently removed, which prevents certain architectures, such as those that are hollow and enclosed, from being created. This method is also significantly limited by the types of compatible metals and alloys that can be used.

Northwestern Engineering’s new method completely bypasses the powder bed and energy beam approach as well as uncouples the two-step process of printing the structure and fusing its layers. By creating a liquid ink made of metal or mixed metal powders, solvents, and an elastomer binder, Shah was able to rapidly print densely packed powder structures using a simple syringe-extrusion process, in which ink dispenses through a nozzle, at room temperature.

Despite starting with a liquid ink, the extruded material instantaneously solidifies and fuses with previously extruded material, enabling very large objects to be quickly created and immediately handled. Then, with collaborator David Dunand, the team fused the powders by heating the structures in a simple furnace in a process called sintering, where powders merge together without melting.

Instead of one laser slowly working its way across a large powder bed, Shah and Dunand’s method can use many extrusion nozzles at one time. Their method potentially can quickly 3D print full sheets that are meters wide and can be folded into large structures. The only limitation is the size of the furnace.

The research is described in a paper published in the journal Advanced Functional Materials. Postdoctoral fellow Adam Jakus, graduate student Shannon L. Taylor and undergraduate Nicholas R. Geisendorfer also co-authored the paper.

 

Self-Adaptive Material Heals Itself

An adaptive material invented at Rice University (Houston) combines self-healing and reversible self-stiffening properties.

The Rice material called SAC (for self-adaptive composite) consists of what amounts to sticky, micron-scale rubber balls that form a solid matrix. The researchers made SAC by mixing two polymers and a solvent that evaporates when heated, leaving a porous mass of gooey spheres. When cracked, the matrix quickly heals, over and over. And like a sponge, it returns to its original form after compression.

The labs of Rice materials scientists Pulickel Ajayan and Jun Lou led the study that appears in the American Chemical Society journal ACS Applied Materials and Interfaces. They suggested SAC may be a useful biocompatible material for tissue engineering or a lightweight, defect-tolerant structural component.

Other “self-healing” materials encapsulate liquid in solid shells that leak their healing contents when cracked. “Those are very cool, but we wanted to introduce more flexibility,” said Pei Dong, a postdoctoral researcher who co-led the study with Rice graduate student Alin Cristian Chipara. “We wanted a biomimetic material that could change itself, or its inner structure, to adapt to external stimulation and thought introducing more liquid would be a way. But we wanted the liquid to be stable instead of flowing everywhere.”

In SAC, tiny spheres of polyvinylidene fluoride (PVDF) encapsulate much of the liquid. The viscous polydimethylsiloxane (PDMS) further coats the entire surface. The spheres are extremely resilient, Lou said, as their thin shells deform easily. Their liquid contents enhance their viscoelasticity, a measure of their ability to absorb the strain and return to their original state, while the coatings keep the spheres together. The spheres also have the freedom to slide past each other when compressed, but remain attached.

“The sample doesn’t give you the impression that it contains any liquid,” Lou said. “It’s more like a sugar cube that you can compress quite a lot. The nice thing is that it recovers.”

The polymer components begin as powder and viscous liquid, said Dong. With the addition of a solvent and controlled heating, the PDMS stabilizes into solid spheres that provide the reconfigurable internal structure. In tests, Rice scientists found a maximum of 683% increase in the material’s storage modulus—a size-independent parameter used to characterize self-stiffening behavior. This is much larger than that reported for solid composites and other materials, they said.

 

Cloud-Based Micro Additive Manufacturing Shows Promise

Cloud-based computing holds enormous potential for collaboration, cost-saving, streamlining, and versatility of manufacturing. Additive manufacturing, being a computer-based system that can save point-by-point data of parts to be manufactured, can be easily integrated into the cloud. So Anne Brant and Murali M. Sundaram of the Department of Mechanical and Materials Engineering at the University of Cincinnati (Cincinnati, OH) have executed an experiment to test the cloud-based application of an in-house micro metal additive manufacturing process. Their findings are published in “A Novel System for Cloud-based Micro Additive Manufacturing of Metal Structures,” which appears in a special “all-additive” edition of SME’s Journal of Manufacturing Processes.

The system was linked to commercial cloud and e-mail access for constant real-time communication from any user with a phone, tablet, or personal computer. The process could be started, stopped, altered, and queried remotely via the cloud.

Plots of output performance, time, and current information were communicated back to the user on demand, as well as stored on the cloud long-term. The cloud could then link input parameters to the history of system performance on such input parameters in a cloud-stored database. An experiment was set up to optimize horizontal deposition parameters based on deposition resolution, and save these values into the cloud for future use,

The experiment was successfully executed and demonstrates the advantage of long-term storage, knowledge sharing, and convenience that the cloud offers for the manufacturing realm. The potential for Smart Manufacturing applied to micro additive manufacturing was shown by saving experimental data of a current-feedback experiment and using it to generate a constant-time experiment. Read the entire paper at tinyurl.com/JMP-cloud-additive.

 

 

This article was first published in the March 2016 edition of Manufacturing Engineering magazine. Click here for PDF.


Published Date : 3/1/2016

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