Advantages+and+Safety

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**__Advantages of Oral/Intranasal Delivery of Insulin vs. Subcutaneous Injections:__**

In subcutaneous administration of insulin, a rapid decrease is observed in blood glucose levels from 38% to 53% after administration (Joshi et al. 2006). In oral administration of insulin bound to gold nanoparticles, as well as aspartic acid capped gold nanoparticles, a reduction in blood glucose levels of 19% and 31% respectively is observed. These results show that insulin is bioactive and the aspartic acid capped gold nanoparticle surface enhances insulin uptake (Joshi et al. 2006). However, intranasal administration of insulin did not result in decrease in blood glucose levels.

Although, when gold nanoparticles and aspartic acid gold nanoparticles were used to deliver insulin, a reduction of glucose level was observed of 50% and 55% respectively (Joshi et al. 2006). Within intranasal delivery, the release rate of insulin produced maximum blood glucose reduction 180 minutes after administration when gold nanoparticles were used. The use of aspartic acid gold nanoparticles showed that there is a more rapid release of insulin when aspartic acid capped gold nanoparticles are used. In this case, theich the maximum blood glucose reduction occurred after 120 minutes. This result also shows that the there is a greater membrane permeability of gold nanoparticle insulin formulations across mucosal cells in comparison to gastrointestinal mucous (Joshi et al. 2006). By comparing subcutaneous administration in which a 53% reduction in blood glucose levels was observed, to aspartic capped nanogold intranasal administration, the results indicate that transmucosal delivery of insulin using gold nanoparticles is an new alternative for insulin drug delivery in comparison to painful subcutaneous delivery (Joshi et al. 2006).

__**Safety Considerations:** __

The use of gold nanoparticles for medical and biological purposes shows a promising future in nanotechnology (Cho, et. al, 2009) . However, these drug treatments also require large numbers of drug-nanoparticles to enter the bloodstream, potentially causing hazardous effects if interacted within the body in unexpected ways. Scienetists fear that the gold nanoparticles could be identified as foreign substances by the immune system, causing the cells to react against the surface of the gold nanoparticle and the contents inside of it. The above mentioned reaction can result in an inflammatory response by the body.

Aggregation has also been found to be problematic. Proteins in the blood have been shown to stick to nanoparticles that are either floating freely in the bloodstream or have entered the bloodstream for drug delivery purposes. Coatings such as chitosan promotes nanoparticles to form large aggregates due to the chitosan's 'sticky' coating (Parrish 2010). Research has shown that the larger the nanoparticle diameter, the more ‘sticky’ the nanoparticle becomes, enhancing aggregation ability.

Aggregation in the bloodstream often leads to a toxic response in the body. In addition, it is believed that once the nearby cells begin their inflammatory defense mechanism, other signalling molecules would be secreted, leading to other cells attempting to destroy the foreign substance. However, with all the benefits provided by nanotechnology, one has to look at the safety and toxicity of the nanoparticles that are being inserted into the bloodstream.

In a study performed (Cho, et.al, 2009), 13 nm PEG-coated gold nanoparticles were injected in mice at 0, 0.17, 0.85, and 4.26 mg/kg of body weight. This concentration indicates that there were approximately 1.76x1011, 8.8x1011, and 4.4x1012 gold nanoparticles injected in the low, medium, and high dose. The results obtained showed that liver inflammation occurred in the mice tested, and it did so in two phases of toxicity.

One phase was seen immediately after the administration of nanoparticles, while the other phase was seen after seven days when the nanoparticles had had a chance to move from blood circulation and localize in the neighbouring tissues. At seven days post-treatment, the liver inflammation was significantly higher in animals administered with the medium and high dose. In addition, at seven days post-treatment, the apoptosis, the programmed cell death, of liver cells was most evident in the mice given 4.26 mg/kg PEG-coated gold nanoparticles.

The present study presents the concerns of using gold nanoparticles in the human system, and the side effects that can result from the immune system. Therefore, further research needs to be conducted to confirm the safety of the metal nanoparticles.

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