Just a few days ago we ran a Spotlight on nanobionics that addressed some of the issues of bridging the interface between electronics and biology. Today we'll take a look at some leading edge research in the field of neural engineering - an emerging discipline that uses engineering techniques to investigate the function and manipulate the behavior of the central or peripheral nervous systems. Neural engineering is highly interdisciplinary and relies on expertise from computational neuroscience, experimental neuroscience, clinical neurology, electrical engineering and signal processing of living neural tissue, and encompasses elements from robotics, computer engineering, neural tissue engineering, materials science, and nanotechnology. In order for neural prostheses to augment or restore damaged or lost functions of the nervous system they need to be able to perform two main functions: stimulate the nervous system and record its activity. To do that, neural engineers have to gain a full understanding of the fundamental mechanisms and subtleties of cell-to-cell signaling via synaptic transmission, and then develop the technologies to replicate these mechanisms with artificial devices and interface them to the neural system at the cellular level. The first steps toward precise, informative and biocompatible neural interfaces have been made already.
In case you are not old enough to remember the TV series The Six Million Dollar Man during the 1970s, the show was about an astronaut, Steve Austin, who got severely injured during a crash and became a guinea pig for bionics experiments by the CIA. In an operation that cost six million dollars, his right arm, both legs and the left eye are replaced by bionic (cybernetic) implants that vastly enhanced his strength, speed and vision. Never mind Hollywood, though, but bionics - a word formed from biology and electronics - has become a serious research field. In particular the development of artificial muscles is progressing rapidly. Nature's solution to producing fast contracting muscles is to use nanotechnology. The challenge for scientists is to mimic the intricacy of natural muscle in their artificial-muscle systems. As material scientists and engineers delve into the nanodomain, the boundaries between electronics and biology become fuzzy and this is exactly what they want: a seamless transition between the hard world of electronics and the soft world of biology.
Curing cancer is on of the many promises of nanotechnology. Although scientists have been making amazing progress in this area, there are still significant challenges that need to be overcome before highly selective, targeted anti-cancer therapy becomes available for everyday clinical use. A nanotechnology-based system to eradicate cancer needs four elements: 1) Molecular imaging at the cellular level so that even the slightest overexpressions can be monitored; 2) effective molecular targeting after identifying specific surface or nucleic acid markers; 3) a technique to kill the cells, that are identified as cancerous based on molecular imaging, simultaneously by photodynamic therapy or drug delivery and 4) a post molecular imaging technique to monitor the therapeutic efficacy. One of the problems today is that these four techniques are used separately or ineffectively, resulting in an overall poor therapeutic outcome. In what could amount to a quantum leap in cancer nanotechnology, researchers have now integrated these techniques simultaneously in vitro and shown that this results in higher therapeutic efficacies for destroying cancer cells. Their demonstration of multi-component molecular targeting of surface receptors and subsequent photo-thermal destruction of cancer cells using single-walled carbon nanotubes (SWCNTs) could lead to a new class of molecular delivery and cancer therapeutic systems.
For the over 100 million people worldwide who suffer from diabetes, testing blood glucose is the only way to be sure that it is within normal range and allows them to adjust the insulin dose if it is not. The current method for monitoring blood glucose requires poking your finger to obtain a blood sample. The equipment needed to perform the blood test includes a needle device for drawing blood, a blood glucose meter, single-use test strips, and a log book. Now imagine this scenario: your doctor implants a tiny device the size of a rice grain under your skin. This device automatically and accurately measures your blood glucose levels at whatever intervals, even constantly if required. It transmits the data to an external transceiver. If any abnormality is detected, the device warns you and automatically transmits the data to your doctor's computer. This scenario is one of the many promises of nanomedicine where in-situ, real-time and implantable biosensing, biomedical monitoring and biodetection will become an everyday fact of normal healthcare. Nanosensors are already under intense development in laboratories around the world. One of the important components for implantable nanosensors is an independent power source, either a nanobattery or a nanogenerator that harvests energy from its environment, so that the sensor can operate autonomously. Not only has such a nanogenerator now been developed, but a new prototype has been demonstrated to effectively generate electricity inside biofluid, e.g. blood. This is an important step towards self-powered nanosystems.
If you have seen the movie The Matrix then you are familiar with 'jacking in' - a brain-machine neural interface that connects a human brain to a computer network. For the time being, this is still a sci-fi scenario, but don't think that researchers are not heavily working on it. What is already reality today is something called neuroprosthetics, an area of neuroscience that uses artificial microdevices to replace the function of impaired nervous systems or sensory organs. Different biomedical devices implanted in the central nervous system, so-called neural interfaces, already have been developed to control motor disorders or to translate willful brain processes into specific actions by the control of external devices. These implants could help increase the independence of people with disabilities by allowing them to control various devices with their thoughts (not surprisingly, the other candidate for early adoption of this technology is the military). The potential of nanotechnology application in neuroscience is widely accepted. Especially single-walled carbon nanotubes (SWCNT) have received great attention because of their unique physical and chemical features, which allow the development of devices with outstanding electrical properties. In a crucial step towards a new generation of future neuroprosthetic devices, a group of European scientists developed a SWCNT/neuron hybrid system and demonstrated that carbon nanotubes can directly stimulate brain circuit activity.
Biomarkers are of increasing importance in modern medicine for the purpose of early detection and diagnosis of a disease, for instance cancer. Biomarkers are mostly protein molecules that can be measured in blood, other body fluids, and tissues to assess the presence or state of a disease. For example, the presence of an antibody may indicate an infection or an antigen, such as PSA, might indicate the presence of prostate-specific cancer cells. Although protein-based approaches to early detection and diagnosis of cancer have a clear advantage over other, more invasive, methods, protein detection is a challenging problem owing to the structural diversity and complexity of the target analytes. State-of-the-art detection methods have limited application due to their high production cost and instability. Another limitation of current proteomic diagnostics is the limitation of arrays to one or a few markers only; in other words, you can only test for the specific markers that you are looking for and not generally measure levels of proteins in your blood in order to detect anomalies. A novel nanotechnology based protein detector array could change that.
In chemotherapy doctors are using a carpet bombing approach to destroy cancer cells: the patient is pumped full of cytotoxic drugs, that go everywhere in the body, with the hope that enough of the drugs reach the cancer cells and target their nuclear DNA to damage it or destroy the cell. Not only do chemotherapeutic techniques have a range of often serious side effects, mainly affecting all the fast-dividing cells of the body, it also has been shown that often less than 1% of the administered drug molecules enter tumor cells and bind to the nuclear DNA. Another complication is drug resistance of cancer cells. This actually is one of the main causes of failure in the treatment of cancer. Dividing cancer cells acquire genetic changes at a high rate, which means that the cells in a tumor that are resistant to a particular drug will survive and multiply. The result is the re-growth of a tumor that is not sensitive to the original drug. Cancer researchers are looking to nanoparticles as a drug carrier capable of localizing and directly releasing drugs into the cell nucleus, thereby circumventing the multidrug-resistance and intracellular drug-resistance mechanisms to effectively deliver drugs to the vicinity of DNA, leading to a high therapeutic efficacy. Scientists now have developed nanoparticles capable of localizing into the nucleus, giving hope to a much more effective cancer chemotherapy that allows to pinpoint individual cells.
The ideal drug carrier may be something out of science fiction. In principle, it is injected into the body and transports itself to the correct target, such as a tumor, and delivers the required dose at this target. This idealized concept was first proposed by Paul Ehrlich at the beginning of the 20th century and was nicknamed the "magic bullet" concept. With the advent of nanotechnology and nanomedicine this dream is rapidly becoming a reality. Nanotechnology has already been applied to drug delivery and cosmetics through the use of liposomal technology, and now nanoparticles and nanotubes present an exciting and more promising alternative.