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The advancements made in nanotechnology over the last decade have significantly influenced developments in biological and medical applications. It is widely believed that the adoption of nanotechnology in medical diagnostics will radically change the field of medicine, making it preventive and precautionary.
Nanoparticles already play an essential role in modern approaches to areas such as cancer treatment, MRI, targeted drug delivery, tissue and organ repair, detection of infectious diseases etc.
A Series of Different Challenges
The application of nanoparticles in targeted medicines and drug delivery systems presents a series of different challenges depending on the desired outcome.
The size of nanoparticles can present critical differences with to those found on the macroscale. For example, there can be changes in chemical reactivity and magnetic properties which can have an overall impact on the material characteristics and how it performs in the final application.
In addition to this there is an important question of biocompatibility and toxicity.
The use of nanoparticles in medicine can present a higher level of toxic and unpredictable characteristics compared to that of the macro-dispersion form of the same material.
Currently there are no common standards for determining the toxicity of nanomaterials, methods of toxicity detection, identification and quantification of nanoparticles in the environment and its objects (such as food and air). Although this is the case, nanoparticles are already seeing wide commercial use in medical applications.
Novel manufacturing methods have allowed material scientists to engineer nanoparticles with certain properties, such as selectivity, size, shape and biocompatibility.
For example, nanoparticles are being applied as a contrast agent in MRI applications. The contrast enhancement can increase the acoustic reflectivity for ultrasonography, in particular, iron oxide nanoparticles are used to detect lymph node metastasis in prostate cancer patients.
However, one of the most advanced application areas currently being researched is in drug delivery and cancer treatment.
PH-responsive nanoparticles can protect drug molecules while traveling in blood flow and release it at optimal pH due to their structure and surface characteristics. This is essential for cancer treatment as tumor tissue has a lower pH than normal healthy tissue.
Nanoparticle Agents - Cancer Treatment
Nanoparticles can also be used as agents in magnetic field hyperthermia cancer treatment due to their magnetic parameters.
For example, iron nanoparticles could have paramagnetic or ferromagnetic properties depending on their size.
Such properties allow them to remain in a state of constant rotation from one orientation to another in changing magnetic fields. This causes the self-destruction of cancer cells.
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Silver nanoparticles have a higher antimicrobial effect than bulk silver. This is because at a nano level the material has a much larger active surface area, which interacts with the sulfur and phosphorous compounds found in bacterial membrane proteins, such as DNA. This allows them to target the right cells. In addition to colloid silver, titanium dioxide and platinum nanoparticles also have the ability to neutralize toxins and other harmful organic materials.
With the exception of anti-microbial formulations and dressings, containing nanomaterials, all of the above-listed applications require intravenous injections.
Nanoparticles vs Bulk Materials
It is commonly known throughout the industry that nanoparticles can cause the same effects as bulk materials (allergy, inflammation, cancer), but they could also cause another effect, atypical of micro-particles or bulk chemicals.
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Some of these characteristics include bioaccumulation in liver and kidneys, generation of free radicals (mitochondrial and DNA damage), immune reactions (autoimmune diseases, suppression of immune system), cytotoxicity, cardiovascular effects etc.
However, some disadvantages can be very useful, such as nanomaterials ability to overcome the blood–brain barrier. This is already being used to treat neurodegenerative diseases. Another example is enhancing cytotoxic atomic oxygen for use in photodynamic cancer therapy.
Successfully Using These Materials
The successful use of these nanomaterials depends on covering them with different biocompable substances such as PEG or sodium oleate, liposome-based drug delivery systems, creation of biodegradable and/or biocompatible polymeric nanoparticles, polymeric layer coating with antibodies etc. Coating nanoparticles with natural or biocompatible components reduces their toxicity.
One area that has seen a lot of success with nanomaterials is tissue engineering.
Orthopedic implants is one example that is wide-spread in modern surgery. However, orthopedic implants do have some limitations. Even if the implants are made from inert material, they can cause untoward reactions. For example, rejection of artificial bones due to differences between the smooth surface of implant and ribbed bone surface. The layer of growing fibrous tissue reduces the bone-implant contact area and causes loosening of the implant which can result in inflammation.
Creating nano-sized features reduces the probability of rejection and stimulates production of the bone matrix. Irrespective of the material, a nanostructured surface is more effective than the more commonly used materials. For example, titanium coated materials with a nanoporous layer of apatite, supports cell adhesion and cell growth better than “naked” metal.
There are a lot of issues surrounding the use of nanomaterials in medicine. While several applications of nanomaterials, such as contrast agents and drug delivery systems are well-established, every year new technologies and concepts emerge.
There is lack of experimental data about the emergent properties of these new synthesized nanoscale products and their influence on common processes of the human body.
Due to the knowledge gaps and complexity of the subject, it is difficult to provide complete information about nano instruments for diagnosis, prevention and therapy.