Laser-Processes May Help Create Better Artificial Joints, Arterial Stents

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WASHINGTON – Scientists hope that laser-based processes may help create arterial stents and longer-lasting medical implants 10 times faster, and less expensively.

Yung Shin, a professor of Mechanical Engineering and director of Purdue’s Center for Laser-Based Manufacturing, stresses the need for new technologies to meet the huge global market for artificial hips and knees, insisting that the worldwide population of people younger than 40 who receive hip implants is expected to be 40 million annually by 2010, and double to 80 million by 2030.

Besides speeding production to meet the anticipated demand, Shin says that another goal is to create implants that last longer than the ones that are made presently.

“We have 200,000 total hip replacements in the United States. They last about 10 years on average. That means if you receive an implant at 40, you may need to have it replaced three or four times in your lifetime,” he said.

In one of their techniques, the researchers deposit layers of a powdered mixture of metal and ceramic materials, melting the powder with a laser and then immediately solidifying each layer to form parts.

Shin says that, given that the technique enables parts to be formed one layer at a time, it is ideal for coating titanium implants with ceramic materials that mimic the characteristics of natural bone.

“Titanium and other metals do not match either the stiffness or the nature of bones, so you have to coat it with something that does. However, if you deposit ceramic on metal, you don’t want there to be an abrupt change of materials because that causes differences in thermal expansion and chemical composition, which results in cracks. One way to correct this is to change the composition gradually so you don’t have a sharp boundary,” Shin said.

The gradual layering approach is called a “functionally gradient coating”.

The researchers have revealed that they used their laser deposition processes to create a porous titanium-based surface and a calcium phosphate outer surface, both designed to better match the stiffness of bone than conventional implants.

The laser deposition process enables researchers to make parts with complex shapes that are customized for the patient.

“Medical imaging scans could just be sent to the laboratory, where the laser deposition would create the part from the images. Instead of taking 30 days like it does now because you have to make a mold first, we could do it in three days. You reduce both the cost and production time,” Shin said.

According to the researchers, the laser deposition technique lends itself to the requirement that each implant be designed specifically for each patient.

“These are not like automotive parts. You can’t make a million that are all the same,” Shin said.

He says that the process creates a strong bond between the material being deposited and the underlying titanium, steel or chromium.

The researcher further reveals that tests have shown that the bond is at least seven times as strong as industry standards require.

Using computational modelling, the researchers simulate, study and optimise the processes.

The researchers, however, admit that more studies are required before the techniques are ready for commercialisation.

They have revealed that their future work will involve studying “shape-memory” materials that are similar to bone and also have a self-healing capability for longer-lasting implants.

They are also working on a technique that uses an “ultra short pulse laser” to create arterial stents, which are metal scaffolds inserted into arteries to keep them open after surgeries to treat clogs.

Since the laser pulses last only a matter of picoseconds, or quadrillionths of a second, they do not cause heat damage to the foil-thin stainless steel and titanium material used to make the stents.

The laser removes material in precise patterns in a process called “cold ablation”, which turns solids into a plasma. The patterns enable the stents to expand properly after being inserted into a blood vessel.

Bacteria Can Help Build Durable Bone Implants

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BIRMINGHAM – Can bacteria help build bones implants? Well, at least scientists at the University of Birmingham say “Yes”.

Lead researcher Lynne Macaskie suggests that Serratia bacteria that manufacture hydroxyapatite (HA) could be used to make stronger, more durable bone implants.

In a study, the researchers showed that the bacterial cells stuck tightly to surfaces like as titanium alloy, polypropylene, porous glass and polyurethane foam by forming a biofilm layer containing biopolymers that acted as a strong adhesive.

The HA coating then builds up over the surface. For practical use, the HA layer must stick tightly, then the material is dried and heated to destroy the bacteria.

With the help of micro-manipulation technique, the researchers measured the force needed to overcome the bioglue adhesion, and showed that dried biofilm stuck 20-times more tightly than fresh biofilm.

When coated with HA the adhesion was several times more again. Slightly roughening the surface made the bioglue much more effective.

Presently, implant materials are made by spraying-on hydroxyapatite. This does not have good mechanical strength and the spraying only reaches visible areas.

The new biocoating method reaches all the hidden surfaces as the bacteria can “swim” into hidden nooks and crannies.

Macaskie insists that bacterial HA has better properties than HA made chemically as the nanocrystals of HA produced by the bacteria are much smaller than HA crystals produced chemically, giving them a high mechanical strength.

“The bacteria are destroyed by heating, leaving just the HA stuck to the surface with their own glue – rather akin to a burnt milk-saucepan,” said Macaskie.

“We need to do more work actually to turn the materials into materials we can use in biomedicine and the environment,” she added.

The study was presented at Society for General Microbiology’s meeting at Heriot-Watt University, Edinburgh.

Joint and Bone Health are Connected

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Joint and Bone Health are Connected

“The boomer and senior population is growing, so joint and bone health are top of mind for that demographic,” says Mintel’s Krista Faron, senior new-product analyst. “When it comes to supplements, calcium, vitamin D and magnesium dominate for bone health. Glucosamine, chondroitin and omega-3s are dominating the joint category. These traditional ingredients will continue to dominate but unexpected forms will emerge.”

For example, Bonemilk, a milk product with extra calcium plus glucosamine, was just recently launched. However, Minute Maid Active with glucosamine — despite the marketing heft of a leading mainstream brand — was pulled from the shelves after two years on the market. Formulators are also taking traditional joint-health ingredients and re-orienting them to the performance field, as with Vuel grape sports drink, a joint-rejuvenating beverage containing glucosamine, MSM and electrolytes.

“Once you move away from pills, joint health is an untapped area for joint-health drinks and foods,” Faron says. More consumers are now turning to foods — up 29 per cent— and beverages — up 11 per cent — fortified with joint-health ingredients, according to Nielsen data.

A compelling option is type II collagen, an ingredient that provides a naturally occurring matrix of chondroitin sulphate, hyaluronic acid and hydrolysed collagen type II, as well as glucosamine and other proteoglycans. Its dollar sales in 2007 were up 98.75 per cent, accoding to Nutrition Business Journal.

MSM, third in ingredient sales for the category, is worth $5 million. “A strong evidence base supports the utility of MSM for the promotion of joint health,” says Tony Keller, president of TandemRain Innovations, supplier of ActivMSM. “With ActivMSM being FDA GRAS, we see a significant opportunity for the entry of MSM into conventional foods and beverages, extending its joint-health pedigree and ushering in new applications for cardiovascular health. The suggestion of MSM being a sulphur metabolism modifier also opens up platforms for skin/hair/nails applications.” Beyond these major players, there is no shortage of ingredients looking to get in on the joint-health action.