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Unformatted text preview: ased vesicles) commonly used in topical
lotions and titanium nanoparticles used in
sunscreen produced by Procter & Gamble
(Cincinnati, OH, USA) and L’Oréal
(Westfield, NJ, USA).
Liposomes have been under development
as delivery vehicles since the early 1990s.
They have low toxicity, are versatile in size,
composition and bilayer fluidity, and are
capable of displaying drugs on their surface
or encapsulating them within. However, they
also have suffered from low delivery efficiencies (particularly in gene therapy applications) and high drug leakage (although the
latter problem may be remedied by the
introduction of colloidally stabilized liposomes). As liposomes have been covered in
detail elsewhere, I will not discuss them further here. Figure 3 Neurons (neurons) penetrating into a
three-dimensional network of the self-assembling
nanofibers. Source: NanoMateria The surface chemistry of nanoparticles
can be modified to display high concentrations of a therapeutic drug and/or molecules for tissue-specific recognition.
structured as concentric shells—are one
type of nanoparticle that can be functionalized with chemical groups to allow attachment of drugs or molecules of interest (Fig. 2). Companies such as Dendritic
Nanotechnologies (Mt. Pleasant, MI, USA)
and Alnis Biosciences (Emeryville, CA,
USA) are already marketing dendrimers for
use in research. In July, a first dendrimer
(Melbourne, Australia) for use against HIV,
received regulatory clearance for phase 1
clinical trials from the US Food and Drug
Administration (FDA; Rockville, MD, USA).
The drug is a topical gel containing an
anionic polyamidoamine dendrimer that is
postulated to interfere with the entry and
fusion process of the HIV particle.
Other types of nanoparticle are also
being developed for use in drug delivery.
For example, C Sixty (Houston, TX, USA) is
investigating fullerenes (clusters of 60 carbon atoms) as a means of delivering therapeutics, and Nanospectra Biosciences
(Houston, Texas, USA) is developing
nanoshells comprising a silica core and an
ultrathin gold coat that will allow localized
payload delivery or tissue ablation triggered
by a secondary mechanism, such as light
activation. Clearly, such platforms are Box 1 Making things grow
Taking a page from nature, researchers are using biological
molecules and structures as scaffolds for building and growing
materials at the nanoscale. Exploiting the molecular recognition
properties of DNA, for example, Chad Mirkin (Northwestern
University, Evanston, IL, USA) and others have organized inorganic
nanoparticles (such as colloidal gold) into ordered macrostructures3.
Another approach that has seen some success is the use of viruses
as templates for nanostructures. For Angela Belcher, a biochemist
turned electrical engineer turned molecular biologist at the
Massachusetts Institute of Technology (MIT; Cambridge, MA, USA),
the inspiration came from abalone shell...
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This document was uploaded on 09/24/2013.
- Fall '13