Solid lipid nanoparticles of lauric Acid: A prospective drug carrier for oral drug delivery

Lauric acid, a naturally occurring medium-chain saturated fatty acid, is known to exhibit high intestinal absorption and a higher propensity for lymphatic absorption. To tap these advantages for nanoparticle-mediated sustained drug delivery, solid lipid nanoparticles of lauric acid (LA-SLN) were prepared by the hot homogenization method. A fluorescent lipophilic dye, Rhodamine B (RhB), was incorporated into the LA-SLN (R-LA-SLN) as a model drug. The particle size and the zeta potential of the LA-SLN were 21.42 ± 1.83 nm and −3.17 ± 0.21 mV, respectively, in phosphate buffer. The encapsulation efficiency and drug loading capacity achieved by R-LA-SLN were about 80.31 ± 0.18 % and 1.02 ± 0.02 %, respectively. In vitro studies revealed a biphasic drug release pattern and were found to follow a Fickian diffusion model. It was found that 52 % RhB was released from R-LA-SLN in the initial 4 h and 71 % in 10 h. The cytotoxic response of LA-SLN was tested on colorectal cancer cells and it elicited only mild cytotoxicity. The cellular uptake studies conducted with colon cancer cells revealed that R-LA-SLN uptake by the cells was twice that of free RhB. The confocal microscopy and Raman mapping showed localization of R-LA-SLN in the cytoplasm on cellular uptake. R-LA-SLN was found to mediate tight junction opening and increased the paracellular permeability by 6 times over free RhB. Mucoadhesion of LA-SLN to the rat intestinal colon mucosa was 1.7 times higher than that of chitosan control, indicating the probability of a longer-duration drug release in the colon.