Nanohydrogels were synthesized by microemulsion polymerization. These nanohydrogels were pre-designed to be pH and temperature stimuli-response materials, using N-isopropylacrilamide as a base monomer and 1-vinyl imidazole as ionizable comonomer. The pH sensitivity was confirmed by measuring the increase or decrease in volume in the nanoparticles by changing the pH of the medium. Nanoparticles were properly characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). Glass-transition temperature increased with vinyl imidazole content, and nanoparticles with average diameter of 68 nm were obtained. Particle size decreases with the increase in pH. After characterization, nanohydrogels were functionalized with folic acid to take advantage that the folate receptor is overexpressed in different types of cancer cells. The nanoparticles were loaded with the drugs: metformin, terfenadine, and 5-fluorouracil. The amount of drug loaded and released by nanoparticles was measured by UV-vis spectroscopy. Then, cellular viability and internalization studies were performed obtaining promising results.
Chitosan nanogels present a very interesting combination of valuable characteristics for drug delivery; those derived from their nanometric size, such as, large surface area, rapid stimuli-response, and easy functionalization; and those emerged especially from their biocompatibility, biodegradability and mucoadhesive nature. Due to this, chitosan nanogels have reached a prominent position as nanocarriers and have originated accelerated research worldwide. Diverse methods to prepare chitosan nanogels have been reported, showing a dependence on final swelling, drug encapsulation capability and release properties with different synthesis variables, in such a way that they can be exploited to be modulated. The present review describes the properties of chitosan nanogels, along with the different methods of crosslinking and confining chitosan in nanosized particles, and the various fields of drug delivery where they have been applied. This work aims to emphasize the connection between the characteristics of chitosan and the synthetic variables with the final properties of chitosan nanogels in order to enhance controlled drug loading and a sustained release.
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