Biomedical Engineering Reference
In-Depth Information
surfactant influence the formation of microemulsion as well as the physiochemical
properties of SLN. For example, Boonme et al. investigated the effect of lipid com-
position by selecting lipids with different molecular structure, different carbon num-
ber in fatty acids and different polarity (tristearin, trimyristate, triolein) and Fadda
et al. described the effect of different ratios of surfactant: alcohol on the quality of
SLN (Boonme et al. 2013; Fadda et al. 2013). Recently, Jesus et al. proposed a new
method microemulsion extrusion method for the preparation of drug loaded SLN. It
is advantageous to use when using rare or expensive ingredients or drugs. This tech-
nique includes extrusion of microemulsion through 100 nm polycarbonate mem-
brane several times to obtain stable and versatile SLN (Jesus et al. 2013).
6.2.5 Double Emulsion-Evaporation Technique
Firstly, the drug is dissolved in an organic solvent/water to form phase I. The oily
phase is prepared by dissolving the lipids (solid lipid, soy lecithin) in chloroform
which is then dispersed in the already prepared phase I under constant stirring
followed by sonication to obtain nano-emulsion. A double emulsion is obtained
by dispersing the resultant nano-emulsion in a surfactant solution (outer aqueous
phase) followed by sonication or high shear homogenisation. After that the organic
solvents are evaporated resulting in the formation of SLN (Mulla et al. 2011;
Yang et al. 2011). Nabi-Meibodi et al. has detailed the effective encapsulation of
Raloxifene HCl, (poorly water soluble drug) in SLN using modified double emul-
sion-evaporation technique for the treatment of osteoporosis and breast cancer. To
overcome the loading problem of Raloxifene inside the core of SLN they modified
the technique by using the mixture of water and organic solvents (Nabi-Meibodi
et al. 2013).
6.2.6 Solvent Injection Technique
It is a very simple, easily available and versatile approach for SLN synthesis
which is based on the lipid precipitation from lipid solution. In this technique, the
solution of solid lipid in water-miscible solvent or water-immiscible solvent mix-
ture is rapidly injected into an aqueous medium with or without surfactant. This
method provides several advantages over the other existing methods, such as the
use of less toxic (pharmaceutically acceptable) organic solvents, avoids the use
of extreme conditions like high pressure as in case of high pressure homogenisa-
tion, ease of handling with faster production process and no need of technically
sophisticated equipments (Schubert and Goymann 2003). In one study, solvent
injection method was compared with the ultrasonication technique and found the
former be better than the latter. However particle size produced by the solvent
injection method was higher than that of ultrasonication but higher entrapment
efficiency and sustained release rate was obtained with the former technique
(Rawat et al. 2010).
