Polymeric nanoparticle composed of fatty acids and poly(ethylene glycol) as a drug carrier

Diamine-terminated poly(ethylene glycol) (ATPEG) was hydrophobically modified with long-chain fatty acids (FAs) through a coupling reaction using N,N'-dicyclohexyl carbodiimide (DCC). FA-PEG-FA conjugates have different physico-chemical properties according to the chain length of the fatty acid (FA). Synthesized FA-PEG-FA conjugate was confirmed by Fourier transform-infrared (FT-IR). Since FA-PEG-FA conjugates have the amphiphilic characteristics in aqueous solution, polymeric nanoparticles of FA-PEG-FA conjugates were prepared using a simple dialysis method in water. The results of 1H nuclear magnetic resonance (NMR) spectroscopy and fluorescent spectroscopy suggest that the FA-PEG-FA conjugate has a typical core-shell type nanoparticle structure made by a self-assembling process. From the analysis of fluorescence excitation spectra, especially, the critical micelles concentration (CMC) of this conjugate was changed unpredictably, i.e. the critical association concentration (CAC) value was decreased below a FA carbon number of 16 but, above increased a FA carbon number of 16. Transmission electron micrograph readings showed the spherical morphologies of the polymeric nanoparticles. The particle size was continuously decreased until below a FA carbon number of 20, but it was increased above a FA carbon number of 20. Clonazepam (CNZ), as a model drug, was easy to entrap into polymeric nanoparticles of the FA-PEG-FA conjugates. The drug release behavior was changed according to the FA chain length and was mainly diffusion controlled from the core portion.