Synthesis of stimuli-responsive poly(ethylene glycol) diacrylate/methacrylic acid-based nanogels and their application as drug delivery vehicle

A series of poly(ethylene glycol) diacrylate/methacrylic acid (PEGDA/MAA)-based nanogels showing multiresponsiveness toward temperature, salt concentration, and pH value were synthesized by aqueous precipitation polymerization. The effect of monomer loading amount, cross-linking degree, and cross-linker type on synthesis of hydrogels was investigated, and so were the influences of MAA content in the feed of synthesis of hydrogel, pH value, and NaCl concentration on the thermosensitivity of hydrogels. The lower critical solution temperature (LCST) of poly(PEGDA/MAA) hydrogels decreased with an increase of MAA content or NaCl concentration and a decrease of pH value. One of the resultant hydrogels (PEGDA575/MAA, 40/60 mol/mol) displayed a distinct LCST of 35 °C under a gastric liquid-like condition (pH 1.0, 150 mM NaCl). Such hydrogel showed a good potential in controlling the release of 5-fluorouracil (5-FU), an anticancer agents, under the above gastric liquid-like condition and also an intestinal liquid-like one.