Micelle is an aggregate of amphipathic molecules in water, with the nonpolar
portions in the interior and the polar portions at the exterior surface, exposed to
water. Amphiphilic molecules form micelle above a particular concentration
which is called as critical micellar concentration (CMC). Micelles are known to
have an anisotropic water distribution within their structure, means water
concentration decreases from the surface towards the core of the micelle, with
a completely hydrophobic (water-excluded) core. Hence hydrophobic drugs can
be encapsulated/solubalized, into inner core. Consequently, the spatial position
of a solubilized drug in a micelle will depend on its polarity, nonpolar molecules
will be solubilized in the micellar core, and substances with intermediate polarity
will be distributed along the surfactant molecules in certain intermediate
positions.
What are polymeric micelles?
Copolymers with amphiphilic character, having a large solubility difference
between hydrophilic and hydrophobic segments, are known to assemble in an
aqueous milieu into polymeric micelles with a mesoscopic size range (few to ten
nanometers). These micelles have a fairly narrow size distribution and are
characterized by their unique core-shell architecture (hence they are also called
as “core-shell nanoparticles), where hydrophobic segments are segregated from
the aqueous exterior to form an inner core surrounded by a hydrophilic
segments.
Compared to surfactant micelles, polymeric micelles are generally more stable,
with a remarkably lowered CMC, and have a slower rate of dissociation,
allowing retention of loaded drugs for a longer period of time and, eventually,
achieving higher accumulation of a drug at the target site. Furthermore,
polymeric micelles have mesoscopic size range with a considerably narrow
distribution. Size is certainly a crucial factor in determining their body
disposition, especially when an enhanced permeation retention effect (EPR
effect) is involved. It is also possible to functionalize the shell of the
nanoparticles for targeted drug delivery. This technology is under clinical study
for various applications some enlisted bellow in the table.
Companies
Intradigm Corporation
LaboPharm
NanoCarrier
NanoViricides
Novavax
Moelor Plc
Samyang
and drug solution (in water miscible solvent)
| Product |
Application |
Company |
| Genexol PM |
Non-small cell lung cancer |
Samyang |
| Estrasorb |
Estrogen therapy |
Novavax |
| Medicelle |
Cancer treatment |
NanoCarrier |
| Flucide |
Anti-influenza |
NanoViricides |
| Basulin |
Long acting Insulin |
Flamel Technologies |
| DO/NDR/02 |
Paclitaxel delivery |
Dabur Research Foundation |
| DDS-2001 |
Not disclosed |
LaboPharm |
Novel composite core-shell nanoparticles as busulfan carriers NEW
Journal of Controlled Release, 111,2006, 271-280
Block copolymer micelles for drug delivery: design, characterization and
biological significance
Advanced Drug Delivery Reviews, 2001, 47, 113-131.
Cisplatin-incorporating polymeric micelles (NC-6004) can reduce
nephrotoxicity and neurotoxicity of cisplatin in rats
British Journal of Cancer, 2005, 93, 678-687.
pH-induced micelle formation of
poly(histidine-co-phenylalanine)-block-poly(ethylene glycol) in aqueous media
Macromolecular Biosciences, 2005, 5, 1118-1124.
Patent Watch
Biodegradable polymeric micelle-type drug composition and method for the
preparation thereof
Kim , et al. USPT 6,322,805, November 27, 2001.
Formulations of paclitaxel, its derivatives or its analogs entrapped into
nanoparticles of polymeric micelles, process for preparing same and the use
thereof
Maitra , et al. USPT, 6,322,817 November 27, 2001.
Particles comprising amphiphilic copolymers, having a crosslinked shell
domain and an interior core domain, useful for pharmaceutical and other
applications
Wooley , et al. USPT, 6,383,500 May 7, 2002.
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