A thermally responsive
nanogel was developed through the radical polymerization based on
chitosan (CTS) and
N-isopropylacrylamide (NIPAAm) with acrylamide (AAm) blended to explore the possibility of increasing the volume phase transition temperature (VPTT). The thermally sensitive features of resultant
nanogels were studied by determining variance of transmittance and changeable size. The VPTT of the CTS-poly(NIPAAm-co-AAm5.5)
nanogel, coplymerized with 5.5% wt. AAm /wt. NIPAAm, was 38 °C in contrast to 32 °C of the CTS-poly(NIPAAm)
polymer and the former was studied thereafter. The critical aggregation concentration of CTS-poly(NIPAAm-co-AAm5.5)
nanogels was 1.11 μg/mL, much smaller than CTS-poly(NIPAAm)
nanogels (5.00 μg/mL).
Paclitaxel (PTX) was encapsulated in CTS-poly(NIPAAm-co-AAm5.5)
nanogels with loading efficiency of about 9.06 ± 0.195% (n = 3). Thermally responsive PTX in vitro release fromPTX-loaded
nanogels was verified. Coumarin-6-loaded
nanogels showed thermally responsive cellular uptake because of electrostatic absorptive endocytosis. Furthermore, the half maximal inhibitory concentration of PTX-loaded
nanogels was about 2.025 nmol/L, 10-fold improved relative to PTX solutions against SMMC 7721 cells. In vivo, PTX-loaded
nanogels presented remarkably higher antitumor efficacy against human colon
carcinoma cells HT-29 xenograft nude mice model after
intravenous administration. Accordingly, our results reinforced the potential means of CTS-poly(NIPAAm-co-AAm5.5)
nanogels for the combination of thermal
therapy and
chemotherapy.