Review Article: Pharmacology
Emerging nanopharmaceuticals

https://doi.org/10.1016/j.nano.2008.06.002Get rights and content

Abstract

A budding interest in nanopharmaceuticals has generated a number of advancements throughout recent years with a focus on engineering novel applications. Nanotechnology also offers the ability to detect diseases at much earlier stages, such as finding hidden or overt metastatic colonies often seen in patients diagnosed with breast, lung, colon, prostate, and ovarian cancer. Diagnostic applications could build upon conventional procedures using nanoparticles, such as colloidal gold, iron oxide crystals, and quantum dots. Additionally, diseases may be managed by multifunctional agents encompassing both imaging and therapeutic capabilities, thus allowing simultaneous monitoring and treatment. A detailed evaluation of each formulation is essential to expand our current nanopharmaceutical repertoire. However, the safety and long-term effects of nanoformulations must not be overlooked. This review will provide a brief discussion of the major nanopharmaceutical formulations as well as the impact of nanotechnology into the future.

Section snippets

Nanopharmaceutical templates

Nanotechnology provides endless opportunities across a wide array of industries. Some of these include titanium dioxide (TiO2) nanoparticles found in sunscreen and cosmetics, silver (Ag) nanoparticles in clothing and disinfectants, and cerium oxide (CeO2) nanoparticles as a fuel catalyst. The National Nanotechnology Initiative (NNI) defines nanotechnology as the “understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications,”4

Liposomes: progressing to nanopharmaceuticals

Liposomes are spherical vesicles composed of amphiphilic phospholipids and cholesterol, which self-associate into bilayers to encapsulate an aqueous interior.7, 8 The amphiphilic phospholipid molecules form a closed bilayer sphere in an attempt to shield their hydrophobic groups from the aqueous environment, while still maintaining contact with the aqueous phase via the hydrophilic head group. Drugs with widely varying lipophilicities can be encapsulated in liposomes, in the phospholipid

Polymeric micelles: enhancing solubility

Micelles are nanosized, spherical colloidal particles with a hydrophobic interior (core) and a hydrophilic exterior (shell). Their main utility is in the preparation of pharmaceutical formulations, notably agents that are regularly soluble in water.9 Drugs or contrast agents may be entrapped within the hydrophobic core or linked covalently to the surface of micelles. Their individual particle size is less than 50 nm in diameter, which provides obvious benefits over liposomes. Polymeric micelles

Dendrimers: utilizing multivalent moieties

Dendrimers are a unique class of polymeric macromolecules synthesized via divergent or convergent synthesis by a series of controlled polymerization reactions. Characteristically, the structure of these polymers is repeated branching around the central core that results in a nearly-perfect three-dimensional geometrical pattern. At higher generations (greater than five) dendrimers resemble spheres with countless cavities within their branches to hold therapeutic and diagnostic agents. In theory,

Quantum dots: enhancing in vivo imaging

QDs are colloidal semiconductor nanocrystals ranging from 2 to 10 nm in diameter. QDs can be synthesized from various types of semiconductor materials via colloidal synthesis or electrochemistry. The most commonly used QDs are cadmium selenide (CdSe), cadmium telluride (CdTe), indium phosphide (InP), and indium arsenide (InAs). In bioimaging these particles serve as contrast agents, providing much greater resolution than existing fluorescent dyes. These particles can absorb white light and

Solid nanoparticles: constructing versatile drug carriers

Most commonly used solid nanoparticles (SNPs) are spherical objects made of biodegradable materials, such as proteins (i.e., albumin or collagen), fats, or polymers.42 First SNPs were constructed to deliver drugs. Ranging in size from 10 to 1000 nm, current SNPs can multitask, providing simultaneous imaging and drug delivery. Analogous to other nanoparticles, SNPs can be modified with surface molecules for guided drug delivery. A major advantage of this formulation is that SNPs can be prepared

Surface modifications: targeting drug delivery

Currently, the major struggle surrounding administration of anticancer agents is differentiating between cancerous and normal cells, thereby avoiding systemic toxicity and adverse events associated with conventional therapies. Targeted nanomedicines may aid in evading the adverse effects (such as immunosuppression, cardiomyopathy, and neurotoxicity) of traditional therapies, while also providing improved therapeutic efficacy. Throughout recent years, targeting nanomedicines have rapidly evolved.

Toxicity

Although there is a tremendous increase in applications of nanoparticles in industrial materials, medical imaging, disease diagnoses, drug delivery, cancer treatment, gene therapy, and other areas, the possible toxic health effects of these nanoparticles associated with human exposure have not been studied properly. There is a good chance that these tiny particles may acquire unique surface properties in their nanosized form and may be toxic, causing adverse health effects. Although the use of

Prospective applications

Researchers at Rice University have constructed the world's smallest car—the “nanocar.” Composed of four C60 molecules (the wheels), connected by organic molecules (the chassis), the nanocar measures just 3-by-4 nm.84 This provides support that materials can be moved around in a controlled manner at the nanoscale level using fullerene-based technology. Nanocars can be applied to targets and further enhance drug delivery systems. Nanomedicine may be the key to unlocking the innovation of oral

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