Alzheimer's disease (AD), a brain disorder named for German physician Alois Alzheimer who first described it in 1906, is a disease that destroys brain cells, causing problems with memory, thinking and behavior. Alzheimer's gets worse over time, and it is fatal. It is also the most common form of dementia. The latest estimate is that 26.6 million people were suffering from Alzheimer's disease worldwide in 2006, and this number will rise to 100 million by 2050 - 1 in 85 of the total population. The latest 2008 data for the US alone estimates that 5 million Americans have the disease, with an estimated increase to 11 to 16 million by 2050. Not only does Alzheimer's have no cure, even its cause is unknown (research has led to several theories that are still being investigated). The onset of AD is usually very slow and gradual and, since there is no test for it, there is no clear-cut line between normal age-related changes and warning signs. An absolute diagnosis of AD can only be determined during the examination of brain tissue, which is usually done during an autopsy. A recent report provides an overview of the promises that nanotechnology brings in research on diagnosis and therapy of AD.
In proteomics research, the study of the structure and function of proteins, chemical as well as physical methods are used to detect proteins. Physical methods are mostly applied after chromatography. They are either based on spectroscopy like light absorption at certain wavelengths or mass determination of peptides and their fragments with mass spectrometry. Chemical methods are used after two-dimensional electrophoresis and employ staining with organic dyes, metal chelates, fluorescent dyes, complexing with silver, or pre-labeling with fluorophores. What these various methods have in common is that they are not very fast, can be expensive, sometimes don't offer the sensitivity required, and are not always easy to handle. Since protein detection can be a powerful tool for diagnosing, prognosing, and monitoring cancers and other medical conditions, researchers are working towards developing detection platforms that can multiple specific molecules from the complex mixture present in serum, and is rapid, sensitive, and simple to administer. Researchers now have demonstrated a simple and rapid way of detecting proteins of interest using nanoparticles. This single step reaction starts with nanoparticle-antibody conjugates that form large aggregates if the intended protein molecules are present in the solution. The large aggregates can be characterized individually by laser scattering and fluorescence.
Polymethylmethacrylate (PMMA), a clear plastic, is a pretty versatile material. Plexiglas windows are made from PMMA. Acrylic paints contain PMMA. It also remains one of the most enduring materials in orthopedic surgery where it has a central role in the success of total joint replacement. Being part of a group of medical materials called 'bone cement', its use includes the fixation of biomaterials such as artificial joints to bone, the filling of bone defects and, also, as a drug-delivery system. Beginning in the 1970s, many successful results have been reported for total hip replacement using PMMA cement; however, failures of fixation have also occurred. The fixation strength of PMMA cement to bone is mainly dependent on mechanical interlocking, but it is known that a fibrous tissue layer intervenes between cement and bone - PMMA cement never bonds directly to the bone. One of the problems associated with the conventional types of bone cement used is their unsatisfactory mechanical and exothermic reaction properties. Other problems with PMMA cement include the biological response, leakage of the monomer of methylmethacrylate and a high curing temperature, which can damage cell activity. Ideally, a bone cement material must functionally match the mechanical behavior of the tissue to be replaced, it must be able to form a stable interface with the surrounding natural tissue and be effective in guided tissue regenerative procedures, it should be easy to handle, biologically compatible, non-supporting of microbial growth, and non-allergenic. A novel nanocomposite of carbon-nanotube-reinforced PMMA/HA is a demonstration of how nanomaterials will play an increasing role in the synthesis of next-generation biomedical applications.
A new study reveals that nanoparticles do not just act as simple, passive carriers but are actively involved in mediating biological activity. These findings have significant implications in understanding the interactions of nanostructures with biological systems. But, once properly understood, they could be important in assisting in the design of intelligent nanodevices, with great potential for the development of novel molecular-based diagnostics and therapeutics. On the other hand, they could also be useful in understanding nanotoxicity. In spite of what has been achieved so far by scientists and clinical researchers, a complete understanding of how cells interact with nanostructures of well-defined sizes, at the molecular level, remains poorly understood.
Since their discovery in 1961, liposomes - nanoscale vesicles composed of phospholipids - have been developed as nano-vectors that are used for a variety of biomedical applications including diagnostic imaging, gene therapy, biosensing and targeted drug delivery. In fact, the FDA-approved drugs Ambisome, Doxil and DaunoXome all contain liposomal formulations. Such liposomes are typically comprised of glycerol-based phospholipids that contain a hydrophilic (water-soluble) head-group and one or two hydrophobic (water-insoluble) hydrocarbon chains of varying length. In aqueous solution, these phospholipids self-assemble into a lipid bilayer, with the hydrophilic lipid groups oriented toward the aqueous solution and the hydrophobic groups protected in the bilayer's interior. The bilayers form spherical vesicles that are used to carry drugs and diagnostic imaging agents to sites of interest within the body. The hollow interior of the vesicles is hydrophilic and can easily encapsulate a variety of hydrophilic drugs or imaging agent molecules, which are then released from the liposomes in a controlled fashion. But what about hydrophobic molecules - those that aren't water-soluble and therefore aren't easily encapsulated within the interior of traditional phospholipid liposomes? Many beneficial, yet water-insoluble drugs do exist, but the current methods used to administer to these drugs to patients, such as dissolving them in alcohols, castor oil or other hydrophobic liquids for injection, can cause patients much discomfort or other side effects. For these reasons, the development of a nano-vector with a hydrophobic interior - one that could successfully encapsulate and release hydrophobic molecules - is of great interest to the nanomedicine community.
The process of bringing a major new drug to market, from discovery to marketing, takes about 10-12 years and costs an average of $500-$800 million in industrialized countries. And still, most drugs fail before they even make it to market. About 80 percent of drugs never make it through their clinical trials. Of the medications that actually enter consumer use, an average of just 60 percent provide therapeutic benefits to patients. For a pharmaceutical company the results of the process designing new drugs leads to a library of novel compounds that are created with a specific goal, a given set of criteria. Often these criteria include the selectivity for a particular known receptor. A new drug treatment can be discovered by testing those drugs on other receptors by trial and error. Since this is a very expensive approach, pharma companies have developed sophisticated computer models that help reduce the risk and uncertainty inherent in the drug-development process. Here, one starts with a computer model of the structure of a receptor and a drug. The goal is to predict by simulation how a drug will dock (interact with a receptor), or how the receptor will fold. Drug design based on mathematical models will also become a massive task within the emerging field of nanomedicine. Although nanotechnology offers great visions of improved, personalized treatment of disease, at the same time it renders the problem of selecting the candidates for biological testing astronomically more complex. The new notion of 'design maps' for nanovectors - similar to the concept of the periodic table for chemical elements - could provide guidance for the development of optimized injectable nanocarriers through mathematical modeling.
Carbon nanotubes (CNTs) have shown promise as an important new class of multifunctional building blocks and innovative tools in a large variety of nanotechnology applications, ranging from nanocomposite materials through nanoelectronics to biomedical applications. The exploration of CNTs in biomedical applications is well underway and exploratory uses have included CNT-coated implants, drug delivery and CNTs as components of biosensors. Notwithstanding the still not satisfactorily addressed issue of toxicity, CNTs' properties such as high strength, high electrical and thermal conductivities, and high specific surface area render them particularly useful in the fabrication of nanocomposite-derived biomedical devices. In one particular area - biomaterials applied to bone - CNTs are anticipated to improve the overall mechanical properties for applications such as high-strength arthroplasty prostheses expected to remain in the body for a long time, or fixation plates and screws that will not fail or impede healing of bone. In addition, CNTs are expected to be of use as local drug delivery systems or scaffolds to promote and guide bone tissue regeneration. A new study by Japanese scientists clearly demonstrates that multi-walled CNTs (MWCNTs) have good bone-tissue compatibility, permitting bone repair and becoming closely integrated with bone tissue. Furthermore, under certain circumstances, their results indicate that MWCNTs accelerate bone formation.
Much has been written about the fascinating properties of spider silk, a biopolymer that is stronger than steel and more elastic than rubber. The silken threads possess a unique combination of mechanical properties: strength, extensibility and toughness. Of course this begs the obvious question: How is it possible that spider silk, produced by little creatures that evolved about 400 million years ago, can be as strong as steel - a modern alloy that plays a critical role in our infrastructure and which still attracts considerable R&D investments in its production technology? What is perplexing is that the atomic interactions (H-bonds) in spider silk are actually 100 to 1,000 times weaker than those in steel, or than those in the superfiber Kevlar, where covalent bonds are used. Hydrogen bonds are the basic chemical bonds that hold together proteins, similar to trusses and beams in buildings, and play a key role in controlling the behavior of these structures. In order to reach silk's mechanical properties, most synthetic materials must be much denser, thus much heavier and consume much more energy during their synthesis and transport. New analysis performed at MIT's Laboratory for Atomistic and Molecular Mechanics shows that the intriguing strength of spider silk may be made possible by precisely controlling the number and the geometry of H-bonds at a characteristic length scale. The physical concept is that by making many small elements work together cooperatively, the weaknesses of the individual components can be overcome. All this must happen at the nanoscale in order to be effective.