Introduction

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Nanomaterials have recently produced a great interest in biology and medicine due to their varying applications. Currently the use of nanomaterials, such as nanoparticles, nanotubes, and nanorods have been researched as emerging techniques in the field of nanomedicine. Such nanomaterials have been explored as carriers for small molecule drugs, proteins, and genetic materials due to their unique physical and chemical properties (Han et al. 2007).

One of the most attractive properties of nanomaterials is the potential ability to target specific tissues and cell types. The use of nanomaterials has provided the opportunity to improve bio distribution, stability, solubility, and pharmacokinetics of drugs (Han et al. 2007). Gold nanoparticles are composed of a hybrid of organic and inorganic materials, comprised of an inorganic metallic gold core which is surrounded by an organic/ biomolecular monolayer (Han et al. 2007). Gold nanoparticles provide many desireable properties for a leading edge drug delivery system. Such properties include the chemically inert and nontoxic core gold materials.

Gold nanoparticles are the drug carriers to carry small drug molecules or large biomolecules such as protein, DNA, or RNA (Ghosh et al. 2008). They are easy to synthesize with core sizes from 1nm to 150nm. The gold core of these gold nanoparticles are inert, non-toxic and stable (Ghosh et al. 2008).Gold nanoparticles can also be synthetically designed to have a tunable core shape and size, which provides a wide range of properties available for different purposes. The gold nanoparticles also provide nanoscale dimensions, which increase aspects such as bioavailability and ability to move through nano-sized spaces within the body in order to transport drugs.

Efficient conjugation and protection of drugs and target ligands is also achieved due to the large surface area of gold nanoparticles (Han et al. 2007). Non-covalent interactions or chemical conjugation interactions allow for the small molecule drugs to be encapsulated within the gold nanoparticles. The well-defined surface chemistry of the gold nanoparticles allows for a wide range of ligand functionality. Overall, gold nanoparticles are able to provide an effective drug delivery system to ensure cellular uptake, controlled drug release, as well as specific cell targeting.

Metal nanoparticles, especially gold, are excellent candidates for bioconjugation with biological molecules (Bhumkar et.al., 2007). Studies have shown that biologically active molecules with an amine functional group are quite reactive towards gold, and can bind strongly to the metal. This finding indicates that the gold nanosized metal can bind with the amine functional group present in amino acids.

Gold nanoparticles have recently been used in the development of oral delivery of insulin to diabetes patients. Insulin is a hormone made up of a series of amino acids, and acts as the major treatment for type 1 diabetes. Insulin aids in diabetes treatment by causing cells in the liver, muscles, and fat tissues to take up glucose from the blood when blood sugar levels are low (Damge et al. 2008). The uptake of glucose is then stored as glycogen in the liver and muscles. To this date, diabetes has been controlled via subcutaneous insulin injections totaling up to 80,000 injections over a patients lifetime (Damge et al. 2008).

Oral administration of insulin has long been studied and desired by diabetes patients as a painless and less invasive drug delivery system. It was observed that oral delivery of insulin is both degraded by enzymes in the gastrointestinal tract, as well as resulting in reduced absorption by the intestinal epithelium due to the large size and hydrophilic properties of insulin. Therefore, gold capped nanoparticles have recently been used to encapsulate the insulin molecules to facilitate transport through the gastrointestinal tract without degradation, as well as facilitating transport through the tight junctions of the intestinal epithelium using chitosan-reduced nanoparticle coatings in order to reach the blood.

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