Biomedical Engineering Reference
In-Depth Information
size, additives added during formulation, molecular weight of drug, and
the ratio of lactide to glycolide moieties have a strong influence on the re-
lease and effective response of formulated nanomedicines. For those of an
acidic nature, PLGA monomers are blended with alginate, chitosan, pectin,
poly(propylenefumarate) polyvinylacohol, and poly(orthoester). Paclitaxel
promotes the polymerization of tubulin causing cell death by disrupting
the cell division process. This drug show neoplastic activity against primary
ovarian carcinoma as well as breast and colon cancers. It is one of the po-
tent anticancer agent but less useful for clinical administration due to its
poor solubility. PLGA intermingled with vitamin E, and tocopheryl poly-
ethylene glycol succinate (TPGS) has been used to encapsulate this drug.
This formulation has shown good activity, and a much faster administra-
tion in comparison to traditional formulation. Using some additive with the
PLGA-NPs, 100% drug encapsulation efficiency was achieved with full an-
titumor activity [97]. Cisplatin is a valid anticancer drug, but the full thera-
peutic exploitation of cisplatin is limited due to its toxicity in healthy tissues.
The cisplatin have been encapsulated on PLGA-mPEG NPs prepared by
double emulsion methods. PLGA-methoxy(polyethylene glycol) (mPEG)
NPs revealed prolonged drug residence in blood upon intravenous admin-
istration [98]. Tamoxifen prevents proliferation of pre-cancerous cells. This
compound competitively binds to estrogen receptors on tumors, producing
a nuclear complex that decreases DNA synthesis and inhibits estrogen ef-
fects. Tamoxifen loaded polyethylene oxide (PEO) modified PCL was pre-
pared by a solvent displacement method. About 90% drug encapsulation
efficiency has been achieved when tamoxifen was loaded in the ratio of 10%
by weight of polymer. PEO-PCL nanoparticles exhibited a significantly
increased level of accumulation of the drug within the tumor with time,
as well as extended presence in the systemic circulation [99]. Polyethylene
glycol-PCL amphiphilic block copolymeric nanospheres containing taxol
are reported to show promising anticancer activity. It was reported that this
mPEG/PCL diblock copolymeric nanospheres system could be potentially
useful as a novel delivery system for the anticancer drug taxol, having an
outer shell of mPEG and a hydrophobic inner core of PCL [99].
Polymers can also be used to coat other types of nanoparticles.
Polyethylene glycol (PEG) is a hydrophilic polymer that has been used to
coat the surface of NPs, which allows them to avoid clearance by the RES
and cross the BBB [100]. The mechanism of this phenomenon is thought
to arise from receptor-mediated phagocytosis and passive leakage through
permeable capillaries in tumors [100]. In the 9L gliosarcoma model, PEG
coating of a NP MRI contrast agent increased the amount of MRI signal in-
tensity from the agent [101]. Other hydrophilic polymers, including hydro-
gel (polyacrylamide), dextran, and polysorbate, have been used to coat the
surface of nanoparticles to prolong plasma circulation and improve delivery
across the BBB [100].
