Effect of polymer charge on the formation and stability of anti-inflammatory drug loaded nanostructured lipid carriers: physicochemical approach

Nanostructured lipid carriers (NLCs), with potential drug delivery capabilities, were formulated using soy lecithin (SLC), tristearin (TS) and palmitic acid (PA) in the absence and presence of two anti-inflammatory drugs, diclofenac sodium (DNa) and indomethacin (IMC). Tween 60 was used as a stabilizer separately and in combination with sodium carboxymethyl cellulose (NaCMC, anionic), polyethylene glycol (PEG, nonionic) and an N,N-dimethyl-N-dodecyl derivative of hydroxyethyl cellulose (LM200, cationic). Both DNa and IMC substantially decreased the size and increased the polydispersity index (PDI) of the NLCs. The hydrodynamic parameters, viz., size, zeta potential, and polydispersity index, as well as the thermal behaviour of the NLCs, depended on the type and charge of the added polymers. Weak interactions between the drug and lipid matrices in the bulk mixtures were confirmed through FT-IR studies. The NLC formulations exhibited lower entrapment efficiency and loading content in the case of DNa compared to IMC due to the higher ionic nature of the former drug. The polymers influenced the entrapment efficiency and loading ability of the NLCs in case of both DNa and IMC. 85% of the entrapped DNa was released from the NLC, compared to 54% release in the case of IMC; the drug release rates were higher for the PEG and NaCMC coated systems. LM200 delayed the drug release process with respect to NaCMC and PEG. Both DNa- and IMC-loaded NLCs inhibited the growth of Gram-positive bacteria, Bacillus amyloliquefaciens. It was concluded that the physicochemical properties of NLCs could effectively be modified using polymers; thus, the biomimetic characteristics of lipids and architectural advantage of polymers can be combined to yield a superior drug delivery system.