Articular cartilage defects heal very poorly and lead to degenerative arthritis. Existing medications cannot promote healing process; cartilage defects eventually require surgical replacements with autografts. As there is not enough source of articular cartilage that can be donated for autografting, materials that promote cartilage regeneration are important in both research and clinical applications. Tissue engineering involves cell growth on biomaterial scaffolds in vitro. These cells are then injected into cartilage defects for biological in vivo regeneration of the cartilage tissue. This review aims first to provide a brief introduction to the types of materials in medicine (biomaterials), to their roles in treatment of diseases, and to design factors and general requirements of biomaterials. Then, it attempts to sum up the recent advances in engineering articular cartilage; one of the most challenging area of study in biomaterials based tissue engineering, as an example to the research on regenerative solutions to musculoskeletal problems with an emphasis on the biomaterials that have been developed as scaffolds for cartilage tissue engineering. The definitive goal on cartilage regeneration is to develop a system using biomimetic approach to produce cartilage tissue that mimics native tissue properties, provides rapid restoration of tissue function, and is clinically translatable. This is obviously an ambitious goal; however, significant progress have been made in recent years; and further advances in materials design and technology will pave the way for creating significantly custom- made cellular environment for cartilage regeneration. (Turk J Rheumatol 2009; 24: 206-17)
Materials scientists and engineers have been able to develop new materials and modify physical, chemical, mechanical, electronic, magnetic and optical properties of new or existing materials to meet the ever increasing demands for more advanced and/or tailor-made materials for specific applications. These developments in materials science and materials technology have been central to many technological advances in all areas of our modern civilization including communication, transportation, energy, construction, aerospace, defense, and health care sectors. Researches on interrelation between structure, processing, properties and service conditions of materials intended to be utilized in biological applications have also been increasing in number and funds to further increase the quality of lives of human beings by providing novel materials or modifying the properties of existing ones with more functionality and biocompatibility. Biomaterials have already being used in a range of established medical applications, including implants to replace diseased joints, surgical-repair materials such as sutures and repair meshes, and tissue such as breast implants. For these established products, continuing R&D will improve key requirements, such as more durable joint implants. Further developments in biomaterials' design and biocompatibility will enable production of novel implant structures. Biomaterials having properties that enhance drug delivery and provide technologies for alternative delivery routes and release mechanisms make a significant contribution in the fast-growing field of drug-delivery systems (DDS). Finely tuned drug delivery is becoming a reality with the support of biomaterials, particularly for the growing range of protein therapeutics emerging from research in genomics and proteomics.
material science van vlack 6th edition solution
This review aims to provide a brief introduction to the types of materials in medicine (biomaterials), and to design factors and general requirements of biomaterials, and attempts to sum up the recent advances in engineering articular cartilage, one of the most challenging area of study in biomaterials based tissue engineering as an example to the research on regenerative solutions to musculoskeletal problems.
2.4. Nanotechnology Effects on Biomaterials Development Nanotechnology is a rapidly evolving field that involves material structures on a size scale around 100 nm or less. New areas of biomaterials applications may develop using nanoscale materials or devices. For example, drug delivery methods have made use of a microsphere encapsulation technique. Nanotechnology may help in the design of drugs with more precise dosage, oriented to specific targets or with timed interactions. Nanotechnology may also help to reduce the size of diagnostic sensors and probes. Transplantation of organs can restore some functions that cannot be carried out by artificial materials, or that are better done by a natural organ. For example, in the case of kidney failure many patients can expect to derive benefit from transplantation because an artificial kidney has many disadvantages, including high cost, immobility of the device, maintenance of the dialyzer, and illness due to imperfect filtration. The functions of the liver cannot be assumed by any artificial device or material. Liver transplants have extended the lives of people with liver failure. Organ transplants are widely performed, but their success has been hindered due to social, ethical, and immunological problems. Since artificial materials are limited in the functions they can perform, and transplants are limited by the availability of organs and problems of immune compatibility, there is current interest in the regeneration or regrowth of diseased or damaged tissue. Tissue engineering refers to the growth of a new tissue using living cells guided by the structure of a substrate made of synthetic material. This substrate is called a scaffold. The scaffold materials are important since they must be compatible with the cells and guide their growth. Most scaffold materials are biodegradable or resorbable as the cells grow. Most scaffolds are made from natural or synthetic polymers, but for hard tissues like bone and teeth ceramic materials such as calcium phosphate compounds can be utilized. The tissue is grown in vitro and implanted in vivo. There have been some clinical successes in repair of injuries to large areas of skin, or small defects in cartilage. Following section is a discussion on tissue engineering for finding solutions to musculoskeletal health problems, an area of current research activity.
TE provides an opportunity to overcome the limitations associated with conventional treatment methods of cartilage tissue loss. As stated, TE triad includes a scaffolding system, tissue specific or progenitor cells and growth factors (cell signaling molecules). The scaffolding system is central to TE strategy as they provide cells with a surface for adherence and 3D growth. Scaffolds can also be used as a reservoir for growth factors that can be delivered locally for a specific duration at a suitable rate. Cartilage tissue is made up of a small population of cartilage cells (chondrocytes) and largely extra-cellular matrix (ECM) that is in turn mainly made up of type II collagen and glucoaminoglycans (GAGs). These ECM components are fibrous in nature and have diameters in nanometer scales. From biomimetic approach, studies are concentrated to develop nanofibrous 3D scaffolds that mimic the type II collagen and GAG fibrils[22]. The nanofibrous scaffolds can be fabricated using the electrospinning technique that involves the application of a high voltage field (up to 10 kV/cm) to a polymer at the tip of a needle by virtue of its viscosity. The polymer solution is then provided with a voltage potential that in turn provides charge to the polymer solution. As the potential gradually increased the charge density on the polymer solution increases and eventually leads to columbic repulsion. When the repulsive forces exceed the viscous forces of the polymer, a jet ensues from the tip of the needle that initially has a straight path and then undergoes instabilities to traverse a spiral path with increasing diameter. This trajectory of the jet allows for continuous thinning of the polymer jet as well as evaporation of the solvent from the jet, eventually leading to the formation of charged dry nanofibers that are collected on a grounded metallic collector. The fibers obtained using the electrospinning technique can be altered both in terms of morphology and diameter via modification in the fabrication parameters. The morphology can vary from elliptical bead containing fibers to smooth fibers and the diameters can range from 10's to 1000's nanometers. In one approach it is proposed to use the nanofibrous scaffolds as growth factor delivery system, wherein the growth factors will be linked to the scaffolding system covalently using a linker molecule. This system when implanted into an arthritic knee will be exposed to proteases (enzymes that selectively cleave specific bonds) that will cleave the covalent bond that connects the growth factor to the nanofibrous scaffold, thereby leading to the release of the growth factor. It is expected that the released growth factor will then provide the necessary signaling to enable enhanced cell proliferation and function. Some nanofibers systems can also be applied to other applications such as filter media, sensors, electrically conducting nanofibers, optical applications, material reinforcement, protective clothing and cosmetics[23].
Darcy J.M. ClarkCONTENTSINTRODUCTIONTHE WEB-SUPPORTED MATERIALS SCIENCE COURSEEDUCATIONAL WEB DEVELOPMENT TOOLS—A PRIMERHTMLWeb ServingAnimation and Video FormatsJava and JavascriptVRMLRemote InstrumentationA SHARED DEVELOPMENT MODEL FOR EDUCATIONAL RESOURCESINTELLECTUAL PROPERTYCONCLUSIONSACKNOWLEDGEMENTSReferencesAs the World Wide Web matures, multimedia and programming technologies are evolving to enable the development of instructional software containing significant depth and interactivity. This article discusses the development and integration of web-based tools to support introductory materials science courses and demonstrates how these tools (including QuickTime, Java, Javascript, and virtual reality modeling language) can be used in an educational setting. Such approaches have been successfully integrated into an introductory materials science course for several consecutive terms, and four different lecturers have been able to utilize the same core resource with only minor adjustments. The changes to the course have been very well received by students. In light of this success, we are exploring ways in which web-based content can be more widely distributed such that resources are optimized and development is not duplicated. Issues motivating and arising from this sharing of educational resources will be discussed, and an archive of multimedia objects for materials science will also be demonstrated.INTRODUCTION "No course in science or engineering may remain static. Not only does technology advance and scientific understanding increase, the academic framework undergoes changes. Thus, periodic revisions are desirable to optimize the value of a textbook for students who will be tomorrow's engineers."—L.H. Van Vlack1
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