User:Jjiang0326/nanomaterials

Safety

Nanomaterials behave differently than other similarly-sized particles. It is therefore necessary to develop specialized approaches to testing and monitoring their effects on human health and on the environment. The OECD Chemicals Committee has established the Working Party on Manufactured Nanomaterials to address this issue and to study the practices of OECD member countries in regards to nanomaterial safety. While nanomaterials and nanotechnologies are expected to yield numerous health and health care advances, such as more targeted methods of delivering drugs, new cancer therapies, and methods of early detection of diseases, they also may have unwanted effects. Increased rate of absorption is the main concern associated with manufactured nanoparticles.

The easiest way for nanomaterials to enter a human body is by inhalation, and by nasopharyngeal syster, some particles may end up in the brain. Silver nanoparticles limit cell viability of alveolar macrophages as well as lung epithelial cells. Moreover, the oxidative stress of silver nanoparticles in alveolar macrophages mediates based on size. Consumer products such as feminine cosmetics and contraceptive devices have silver nanoparticles that are able to reach the reproductive system. Reduction in membrane seepage, apoptosis, and in mitochondrial capability may occur if there are DNA damages in mammalian cells, embryonic stem cells, and embryonic fibroblasts. Even by using coated and uncoated, polysaccharide surface functionalized and non functionalized, silver nanoparticles, respectively. Both types of silver nanoparticles induce DNA damages to the subject, however, coated silver nanoparticles create more damages than that of uncoated silver nanoparticles. Different coatings of silver nanoparticles are also toxic to biomolecule and animals, such coatings include starch, bovine serum albumin, and polyvinyl pyrolidine.

When materials are made into nanoparticles, their surface area to volume ratio increases. The greater specific surface area (surface area per unit weight) may lead to increased rate of absorption through the skin, lungs, or digestive tract and may cause unwanted effects to the lungs as well as other organs. However, the particles must be absorbed in sufficient quantities in order to pose health risks.

The nanomaterials associated with health risks, especially through the skin, will need a form of barrier capable of preventing nanoparticles from penetrating. However, the complexity of the skin interface is able to prevent nano-substances to diffuse underneath the epidermis. For example, nanocrystals called QD621 would not be in the perfusate if the crystals were applied to porcine skin. Human skin is complex in the cellular level. A coated carboxylic acid nano-substance, QD565, can be applied to the human skin for hours and leave no traces in the blood stream. Instead, QD565 would be trapped in the hair follicle invaginations or on top of the stratum comeum. If some nanoparticles were to permeate into the blood stream, careful engineering of those particles will leave humans with no harm. Such engineering like coating nano-substances with biocompatible materials would reduce toxicity.

As the use of nanomaterials increases worldwide, concerns for worker and user safety are mounting. To address such concerns, the Swedish Karolinska Institute conducted a study in which various nanoparticles were introduced to human lung epithelial cells. The results, released in 2008, showed that iron oxide nanoparticles caused little DNA damage and were non-toxic. Zinc oxide nanoparticles were slightly worse. Titanium dioxide caused only DNA damage. Carbon nanotubes caused DNA damage at low levels. Copper oxide was found to be the worst offender, and was the only nanomaterial identified by the researchers as a clear health risk.

Damages in DNA

Nanomaterials have complex features such as physico-chemical properties, contaminants from metals, and electrically charged surfaces. Once nanomaterials get in to a human body, interferences in the body will take place. Some nanomaterials pass through cells and be able to interact with the nucleus, where DNA is stored, and corrupt cell division with DNA mutations and/or deletion. Once nanomaterials get into the body by the means of inhalation, dermal or oral, there are different mechanisms that give rise to the damages in the DNA. The nanoparticles can transport themselves through cellular pores, through force penetration or might even be enclosed by the nucleus by chance during the phases of cell division. Even without directly contacting the cell nucleus, with enough nanomaterials accumulating within a cell, there will still be an opportunity for the sub-100 nm size to come in contact with the DNA during mitosis phase when the nucleus membrane dissolves. With nanomaterials meddling inside the nucleus, it can damage any DNA related molecules and proteins which then can lead to bodily dysfunctions. Intranuclear protein aggregates are created by intruding nanoparticles of titanium dioxide and silica that prohibits cellular functions such as replication, transcription, and cell proliferation. Additionally, quantum dots, too, can impale the nucleus using nuclear pore complexes and target histone proteins . These complications give nanomaterials more than one way to interfere with the human genome.

Skin Penetration

Nanomaterials can get inside of a body in several ways. Ways include diffusing directly across the plasma membrane, via membrane channels or other methods involving the use of energy to get across (endocytosis). Nanomaterials can also get across a membrane by locking on some membrane receptors like a lock and key which facilitates receptor-mediated endocytosis. Furthermore, if either clathrin- or caveolae- mediated endocytosis happens to be nearby, a nanomaterial can then rest in the pits created and the process of endocytosis will carry it across the membrane. Most nanoparticles that are up to 200 nm can get across membranes using clathrin- or caveolae- mediated endocytosis, with 50 nm particles being transported across the fastest when compared to other sizes.

Benefits

The nano-world is not always a threat to human beings; scientists today are incorporating medical nanotechnology to improve health care. Because nanotechnology can be used in parallel with scientific fields such as biology, chemistry, physics, medicine, and genetics, there has been a great deal of increased development in nanomedicine. In therapeutic applications, metallic nanoparticles, iron oxide, is coated with dextran, surfactants, and phospholipids are used as a passive agent. Patients with brain tumors are treated with aminosilane-coated iron oxide nanoparticles. Another metallic nanoparticle is gold; it has a potential in high infrared phototherapy. Not only metallic nanomaterials, but ceramic nanoparticles like silica, titania, and alumina also play a crucial role in treating cancer patients. Diagnostics or imaging, and therapeutic or drug delivery are the two main categories that have emerged in nanomedicine. Due to its advantage in larger surfaces area per volume than its counterpart, macron scale, nanomaterials are able to pick up larger signals and quicker reception signals in continuous glucose monitoring sensors for diabetic patients. Other properties of nanomaterials were recognized and used in diabetes treatment include quantum dot fluorescence and gold nanoparticle quenching. Through these which results in the improved accuracy and usability of diabetes sensors. With as many as 24 million people in the U.S. diagnosed with diabetes, it is imperative that effective treatments and monitoring can reach all patients.