Biomedical Engineering Reference
In-Depth Information
Considering these factors, it is desirable to modify the drug with features that
would pharmacologically guarantee increased stability, solubility, and specific
targeting to the site of action.
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To this end, nanotechnology promises to revo-
lutionize the area of pharmacology. Owing to their unique size and properties,
NMs hold promise in improving the curative abilities of various conventional
drugs which is the driving force behind the concept of nanotherapeutic drug
delivery: to enhance therapeutic effects of drugs in spite of poor intrinsic phar-
macological properties. NMs as drug carriers are being developed and investi-
gated for individualized therapeutic and imaging contrast agents based on the
simultaneous, anticipated advantages of targeted drug delivery at the site of the
disease such as tumor growths and atherosclerotic plaque.
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This promise is
based on the ability of NMs to cross the various obstacles between the adminis-
tration of the drug and the site of drug delivery.
5.3 FACTORS TO CONSIDER FOR NPS THAT WILL BE USED
FOR DRUG DELIVERY
Nanotechnology is an empowering technology that holds promise in cancer
therapeutics by increasing the ratio of tumor control probability to normal tissue
complication probability.
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NM drug carriers can increase the bioavailability
of the drug at the target site, reduce the frequency of administration, and reach
sites that are otherwise inaccessible. In order for the NM drug carriers to be use-
ful for drug delivery, it must possess very important characteristics. Foremost
among these characteristics is for the nanocarrier to be biocompatible and easy
to load with the drugs.
5.3.1 Surface Charge
The surface charge of NPs plays a very important role in loading the drug for
drug delivery. Furthermore, the surface charge is also important in the modifica-
tion of the NMs for targeted drug delivery.
Surface charge is usually expressed and measured in terms of the NMs' zeta
potential which reflects the electrical potential of particles that is influenced by
its composition and the medium in which it is dispersed.
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NMs exhibiting a
zeta potential above ± 30 mV have been shown to be stable in suspension indi-
cating that the surface charge prevents aggregation of the particles.
1
The surface charge of an NM is important in deciding the manner by which
a drug or drugs are loaded. Drugs may be loaded through covalent conjugation,
hydrophobic interaction (HI), charge-charge interaction, or encapsulation. The
choice of the methodology depends not only upon the surface charge but also
on the nature of the drug and of the targeting molecule. Loading of the drug on
the NM usually alters the surface charge. Change in the zeta potential can be
used to determine whether a charged molecule has been attached or adsorbed on
the NP surface. The zeta potential is measured with a zeta tracker (Chapter 2).
