Fabrication of poly(D, L-lactic acid) nanoparticles as delivery system for sustained release of L-theanine

L-theanine is present in tea as a unique, free, non-protein amino acid. Due to various beneficial effects on brain activity, it is widely used as a nutraceutical. After consumption, it is rapidly absorbed and metabolised followed by excretion through urine. Therefore, the authors developed an L-theanine delivery system by encapsulating into polymeric nanoparticles to release it slowly and make it available for a longer period of time. Poly(D, L-lactic acid) nanoparticle (PLANP) was fabricated by the double emulsion method and L-theanine was encapsulated into it (PLANP-T). Spherical nanoparticles with a hydrodynamic diameter of 247 and 278 nm and surface charge of -14.5 and -25.7 mV for PLANP and PLANP-T, respectively, were fabricated. The Fourier transform infrared spectroscopic data indicated encapsulation of L-theanine into PLANP. The PLANP showed high L-theanine encapsulation capacity (71.65%) with a sustained release character. The maximum release (66.3%) of L-theanine was recorded in pH 7.3 at 48 h. The release kinetics followed the Higuchi model and the release mechanism was determined as super case-II transport (erosion). This slow release will make it available to the target tissue for a longer period of time (sustain release effect) and will also avoid immediate metabolism and clearance from the circulation.