The Thyme essential oils was dissolved in ethanol (1:1, v/v) and
mixtures of nanogels (500 mg/l) and essential oils (5000 mg/l),
were prepared by sonication (70 kHz) for 5 min. The encapsulation
efficiency was measured by a Shimadzu spectrophotometer (Japan,
http://www.shimadzu.com), based on the optical density spectra of
the essential oils (400e650 nm). The spectroscopic readings were
performed after precipitating the nanogel by centrifugation
(10,000 g, 15 min).