Biomedical Engineering Reference
In-Depth Information
are largely dependent on the time and temperature. Awad et al. studied the impact
of different cooling and heating rates on polymorphic transformations and gela-
tion of tripalmitin SLN dispersion and found that increasing cooling or heating
rates retards the phase transformation process resulting in greater stability of SLN
(Awad et al. 2008). The gelation of SLN dispersion can also be stimulated by
exposure of light, shear forces and the surface of the packaging material (Freitas
and Müller 1999). Gelation of SLN can have severe effects on the recipient. If this
happens in case of intravenous administration, the life of that living organism can
be at risk of death.
6.9 Other Lipid Based Nanoparticles
6.9.1 Liposomes
Liposomes are the clinically established vectors for the delivery of drugs and
imaging agents simultaneously comprising an excellent theranostic agent.
Liposome vesicles are comprised of single or multiple concentric lipid bilayers
enclosing an aqueous environment. These are the vehicles of interest in cancer
therapy because of their high biocompatibility, reduced toxicity, biodegradability
and ease of surface modification. In addition to this, liposomes are capable to hold
both hydrophobic as well as hydrophilic molecules. These protect the payload
from the external environment and prolong the circulation time in the blood (Wafa
et al. 2011).
There are multiple examples of liposomes acting as a carrier for different
types of therapeutics and imaging agents. Muthu et al. (2012) developed a new
type of theranostic (multi-functional) liposomes coated by
d
-alpha-tocoph-
eryl polyethylene glycol 1,000 succinate mono-ester (TPGS) which were car-
rying both quantum dots and docetaxel for cancer diagnosis and treatment
respectively. The folate receptor targeting multi-functional TPGS liposomes
were much efficient when compared to the non-targeting liposomes in MCF-7
cell lines. The IC
50
value for the targeted liposomes in MCF-7 cell lines was
0.23 0.05
ʼ
g/mL which was lower than the value observed for non-targeted
liposomes i.e. 1.56 0.19
ʼ
g/mL. Besides the various anticancerous drugs
incorporated in the liposomes, in one study siRNA delivery was done with the
gold nanorods (AuNR)-liposomes nano-carriers. These nano-vectors were used
for the multispectral optoacoustic tomography (MSOT) which enables us to
visualize the localization of siRNA complexed AuNR liposome hybrids at the
tumour site longitudinally. Here, siRNA is an excellent anticancerous agent and
Au nanorods provide high optical absorption per particle thus enabling sensi-
tive imaging of AuNR enhanced vectors (Taruttis et al. 2014). Liposome pro-
vides much flexibility as a drug delivery vehicle but its high cost, drug leakage,
low loading capacity and fast release are the main drawbacks. Storage problems
may occur if we employ this nanocarrier.
