Published on May 19th, 2014 | By: firstname.lastname@example.org
Ceramics & MedicinePublished on May 19th, 2014 | By: email@example.com
[Image above] Credit: Pranjal Mahna; Flickr CC BY-NC-ND 2.0
A wide range of ceramic and glass materials are being used in biomedical applications; ranging from bone implants to biomedical pumps. Dentistry has also advanced with ceramic teeth that can be matched to a patient’s natural ones and other applications for improving a patient’s smile. In the future, ceramics will find applications in gene therapy and tissue engineering.
Glass beads offer hope for liver cancer patients
Currently used treatments for inoperable liver cancer can reduce symptoms of this disease but require hospitalization and usually cause side effects that reduce the quality of life for patients. For example, chemotherapy often produces nausea, vomiting and hair loss. For this reason, there is a need for new treatments that offer the convenience of outpatient therapy and fewer and milder side effects. More importantly, the life expectancy for persons with liver cancer is short, usually less than a year.
Glass microspheres, originally developed at the Missouri University of Science & Technology, are now FDA approved and are being used to treat patients with primary liver cancer at 29 hospital sites in the U.S. Called TheraSpheresTM, these microspheres are made radioactive by neutron activation in a nuclear reactor. The microspheres, which are about one third the diameter of a human hair, are then inserted into the artery that supplies blood to the tumor using a catheter. The radiation destroys malignant tumor with only minimum damage to the normal tissue.
The treatment usually takes less than an hour and patients can go home the same day. Side effects are generally minimal, with some fatigue lasting for several weeks until the radiation disappears. Most patients receive a single injection, but there are an increasing number of patients which have been given multiple injections. There is a growing body of evidence showing that life expectancy is increased with documented cases of patients surviving up to eight years. Other potential uses for these radioactive beads include treating other forms of cancer (kidney, brain, prostate) and treating rheumatoid arthritis.
Ceramic braces make Tom Cruise smile
Traditionally, braces have consisted of metal brackets and wires. However, some people have feared the idea of a “metal mouth” so much that they refuse to wear braces altogether, missing out on the possibility of a beautiful smile. For this reason, orthodontic research began to focus on less visible options. This is how ceramic braces-the braces responsible for Tom Cruise’s straightened smile-came to be.
Transparent polycrystalline alumina (TPA) was originally identified by NASA and a ceramic company called Ceradyne for helping track heat-seeking missiles. Ceradyne went on to partner with Unitek Corporation/3M to develop Transcend brackets, made from TPA. These orthodontic braces are as effective as metal braces, but are nearly invisible when viewed at normal distances, thus providing a more attractive cosmetic option for the wearer. Because this material is non-porous and 99.9 percent pure, it is extremely resistant to staining or discoloration.
Hip replacements become stronger
Over the last twenty years there has been a considerable increase in the use of ceramic materials for implant devices. With an excellent combination of strength and toughness together with bio-inert properties and low wear rates, a special type of oxide called zirconia is now displacing alumina in applications such as femoral heads for total hip replacements.
The zirconia heads display double the strength of comparable alumina heads and consequently the diameter of the femoral head can be reduced to < 26 mm, leading to a reduction in patient trauma during the hip replacement operation. Other applications which could benefit from a zirconia implant include knee joints, shoulders, phalangeal joints and spinal implants. This material is also being used for endoscopic components and pace maker covers.
Ceramic coatings for drug release
MIV Therapeutics, Inc., a leading developer of new generation biocompatible coatings and advanced drug delivery systems for cardiovascular stents and other implantable medical devices, is developing coatings based on hydroxyapatite (HAp), a ceramic material that has a similar composition to natural bone. These proprietary coatings show potential for outperforming technologies and products currently in use that release drugs after stent implantation. The microporous films are designed to remain highly biocompatible even after all drug material is eluted from the coating. In this respect, HAp performance far exceeds polymer-based coatings, wherein drugs are necessary to sustain acceptable coating performance.
The ultra-thin films are designated as a surface modification of metallic implants, whereas the micro-thin films are evaluated also as a potential vehicle for drug delivery purposes for implantable medical devices. In the extremely demanding application on stents the coating not only has to withstand deformation during manufacturing (i.e. stent crimping) and at the implantation stage and remain un-damaged in such operation. If this was not enough, the coating has to maintain its integrity and resist fatigue stresses in concert with the heart beat over the years after deployment in human heart.
Composite layers for gene therapy
An efficient and safe gene transferring system is a key technology in gene therapy and tissue engineering. Particles of DNA/calcium phosphate complex have long been used for facilitating gene transfer because of their low toxicity. The gene transferring efficiency of this reagent is, however, insufficient compared with other reagents such as DNA/lipid complexes. Recent research has shown that gene transfer on the surface of a DNA/apatite composite layer is as efficient as an optimized commercial lipid-based reagent.
A laminin/DNA/apatite composite layer was successfully formed on the surface of an ethylene/vinyl alcohol copolymer by Japanese researchers. The immobilized DNA was transferred to the cells adhering onto the laminin/DNA/apatite composite layer more efficiently than those adhering onto a laminin-free/DNA/apatite composite layer. It is considered that laminin immobilized in the surface layer enhances cell adhesion and spreading, and DNA locally released from the layer is effectively transferred into the adhering cells, taking advantage of the large contact area. The present gene transferring system, which shows high efficiency and safety, would be useful in gene therapy and tissue engineering.
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