Tsai Nano Bio by b8z9wwC6


									                                                                        MatE 297 4/5/2006
           Nanotechnologies: Applications in medicine
                           Eric Tsai
 Nanotechnology can be defined as the science and engineering involved in the design,
synthesis, characterization, and application of materials and devices whose smallest
functional organization in at least one dimension is on the nanometer scale or one
billionth of a meter [1] In medical practices, nano materials and devices are designed for
interaction with the human body at sub molecular scales; In recent years, significant
effort has been devoted to develop nanotechnology for drug delivery since it offers a
suitable means of delivering small molecular weight drugs, as well as macromolecules
such as proteins, peptides or genes by either localized or targeted delivery to the tissue of
interest [3]; In fact, the tremendous potential nanotechnology offers in engineering,
science and medicine has led to a total global investment of over five billion dollars up to
date [2]. This paper will investigate nanotechnology used in the medical industry. More
specifically, nanotechnology used for controlled drug delivery and tissue regeneration,
growth and repair are the topics investigated. These emerging technologies will continue
to help improve the health of the population as nanomaterials can offer unique properties
that are different from those of the bulk material. The innovations made possible by
nanomaterials and nanotechnology has lead to creation of new medical devices never
thought possible.
 Similar in size to biological molecules such as enzymes and receptors, nanoscale devices
are 100-10,000 times smaller than human cells [2]. Therefore, nanoscale devices can
interact with both the surface and the inside of cells, leading to new ways for disease
detection and drug delivery. Figure 1 below shows the size range for nano- medicines. [2]
For example, it might be possible to produce artificial nano devices that can sense and
repair damage parts of our body, like white blood cells, a natural biological nanostructure;
Since nanocomponents can be produced to share some of the same properties as natural
nanoscale structures [2].
 The possibilities for medical applications with nanotechnology are endless. Some
examples include cancer treatments by attacking the tumor directly, diabetes treatments
by regulating and maintaining the body's own hormonal balance, restoration,
maintenance and improvement of human organs and biocompatible implants [2];
Significant research has gone into controlled drug delivery as it offers a way to deliver
molecular weight drugs, as well as macromolecules as mentioned previously.
Fundamentals of controlled drug delivery: In most situations, constant drug delivery is
not an effective option pharmacologically. In fact, almost all functions of the human body
show daily pattern fluctuations, making the coordination between medical treatments and
this natural biological pattern very important in drug delivery. With nanotechnology,
drugs can be delivered at specific rates to targeted organs; this can be achieved with
nanocarriers in the form of nanospheres, naoncapsules, microemulsions, macromolecular
complexes and ceramic nanoparticles. Figure 2 below shows the difference between
traditional drug delivery and controlled drug delivery.
 [2] Figure 2a shows how traditional medicines will be distributed evenly through out the
body, but the drug level increases and decreases following each dose. This is dangerous
for patients fighting bone cancer with chemotherapy as both healthy cells and mutated
cells are being eliminated, making the patient susceptible to infections. Figure 2b shows
how controlled drug delivery can target specific organs in the body and the blood drug
level can be maintain at an optimum level for an extended amount of time. The ability to
deliver the right drug at the right time can minimize side effects, medical emergencies
and costs as compliance is improved [2]. Fundamentals of tissue regeneration, growth
and repair:
Tissue engineering involves in vitro new tissue creation, followed by surgical placement
in the body or the stimulation of normal repair in situ using bioartificial implants of living
cells introduced in or near the area of damage [2]; With current techniques, a mediocre
degree of success is achieved, due to risks of disease transmission and immune rejection.
Current synthetic materials have limited usefulness because their dimensions exceed 1um,
therefore they can not regenerate tissues that make these techniques useful. On the other
hand, nanomaterials offer a promising new alternative, since these materials have
dimensions close to the components found in natural tissues. Synthetic polymeric
nanomaterials can be made to be reactive and interact with proteins that control cell
adhesion and tissue regeneration.
 Therefore, synthetic polymers can be produced as a three-dimensional structure to act
like an effective scaffold in tissue regeneration. These synthetic polymers eliminate the
risk of disease transmission and can be synthesized to degrade over time so there are no
long term effects on the body. Current research in aimed at developing complex organs,
such as nanopolymeric heart valves and nanocomposites for bone scaffolds [2]. Current
research and development in drug delivery:
 Currently, drugs are incorporated within a biodegradable and biocompatible polymer
nanostructure. This approach allows for the drug to travel in stealth mode through the
blood stream without rejection. Figure 3 below shows a schematic of this controlled drug
delivery technique.
 [2] Figure 3 Scheme of the stimuli drug release system. In this system, the drug is
encapsulated with an environmentally sensitive hydro gel within a micro or nano porous
polymer matrices. This is an intelligent drug delivery system because these polymer gels
swell reversibly as a response to small changes in pH, temperature, intensity of light,
magnetic fields and electric fields. This causes the release of the drugs at predetermined
rates. So, by integrating the delivery system with pH, temperature, intensity of light,
magnetic fields and electric fields, precise control over the release of the drug can be
achieved. This system allows for the release of drugs at the right place in the right
amounts [2]. Figure 4 shows this drug release by stimulation. The most popular example
of the encapsulation technique is the use of biodegradable nanoparticles formulated from
poly (D,L-lactitide-co-glycolide) or PLGA. PLGA is used in the medical industry for a
targeted and localized delivery of drugs. The drug is entrapped in the PLGA matrix and
released at a controlled rate. This rate is controlled by diffusion of the drug through the
polymer matrix and degradation of the matrix. By altering the block copolymer
composition and molecular weight, the rate of degradation can be controlled. Release of
drugs can span from a few days to months, making it a superior alternative to traditional
ways of delivering medicine [4]. The production of PLGA encapsulation can be scaled up
for mass production as several common extrusion techniques have been found to be
compatible with the formulation of PLGA nanoparticles. Current research and
development tissue regeneration, growth and repair:
 To emulate the nanometer scale structure of living tissues, a freezing-drying approach is
used to generate different porous structures from unique water in oil emulsion solution.
Basically, two unmixable components such as oil and water are mixed together by the
addition of a surfactant. Surfactants are molecules in which one end likes the water and
the other end likes the oil. By adding a small amount of surfactant and water to a large
quantity of oil, reverse micelles are created. The polymer structure created with the
process is very similar to the body's extra cellular matrix, which is highly porous,
usually 30-80% air by volume. By changing the type of polymer and temperature,
porosity can be controlled to match the pore size of specific tissues. This flexibility
makes this freezing-drying approach an attractive option for tissue regeneration. The high
porosity created with this process permits the cells to grow into the structure and allows
for the transport of nutrients and metabolic waste, which are critical elements in tissue
growing [2].
 Nanotechnology offers tremendous potential for applications in the medical industries.
There are endless possibilities since nanodevices and systems are similar in size to large
biological molecules such as enzymes and receptors. Current technologies utilize a
microemulsion technique to produce porous polymer coatings and membranes. These
films can be used for the encapsulation of medical substances and tissue scaffolds for
new tissue growth. These new materials offer excellent properties in terms of
biocompatibility and tailorability. Since the materials can be controlled to deliver precise
amounts of drugs by stimulation to identified areas, medical efficiency will be greatly
improved by nanotechnology. Currently, PLGA is the most common polymer matrix
used for drug delivery. Formulation of PLGA nanoparticles has been verified to be
compatible with common extrusion processing techniques. This will allow a smooth
transition to scale up the production of PLGA nanoparticles. Nanotechnology has proven
to provide a far superior way for delivering medicine and growing tissues and I predict
will become a big part of the medical industry in the near future. References: 1. G. A.
Silva, "Introduction to nanotechnology and its applications to medicine,"
Surgical Neurology, Volume 61, Issue 3, March 2004, pp. 216-220
 2. G. K. Stylios, P. V. Giannoudis, and T. Wan, "Applications of nanotechnologies
in medical practice," Injury, Volume 36, Issue 4, Supplement 1, November 2005,
Pages S6-S13
 3. S.M. Moghimi, A.C. Hunter, J.C. Murray, "Long-circulating and target specific
nanoparticles: theory to practice," Pharmacol Review. Volume 53, 2001, pp. 283-
 4. J. Panyam, V. Labhasetwar, "Biodegradable nanoparticles for drug and gene
delivery to cells and tissue," Advanced Drug Delivery Reviews, Volume 55, Issue
3, 24 February 2003, pp. 329-347

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