Synthesis And Characterization Of PNIPAM/SA Core-Shell Microgels

Microgels composed of environmentally responsive polymers continue to attract attention due to their diminutive particle size and high machinability. The main reason for attracting great attention of poly(N-isopropylacrylamide) (PNIPAAm) is its convenient phase transition temperature(LCST) that is close to human body temperature. And PNIPAM microgels play a vital role in field of biomedicine. Nevertheless, an important limitation of PNIPAAm microgels is their lack of biocompatibility and biodegradability. Alginate, as the most abundant marine biopolymer in nature, can remedy this because of its high biocompatibility and biodegradability. Core particles composed of cross-linked Poly(N-isopropylacrylamide) (PNIPAM) were synthesized via radical polymerization and then through the subsequent addition of CaCl2 and PNIPAM to the alginate solution, PNIPAM/Alginate Core-Shell Microgels were obtained. Properties of microgels were evaluated through analysis of transparency, temperature sensitivity, size distribution and morphology via violet spectrophotomer, dynamic light scattering (DLS) and transmission electron microscopy (TEM) method. And the preliminary studies on drug loading properties and drug release of microgels for 5-fluorouracil.1、The PNIPAAm thermoresponsive microgels were prepared via radical polymerization and the optimum conditions of the synthesis are proved. The optimized formula dosage of monomer (NIPAAm), cross-linker (BIS), surfactant (SDS) and initiator (AP) were 7.6 g/L,0.26 g/L,0.18 g/L and 0.15 g/L respectively. The PNIPAM microgels prepared under optimized conditions were in the smaller size of 249 nm and the lesser PDI of 0.032.2、The effects of the concentrations of monomer (NIPAAm), cross-linker (BIS), initiator (AP) and surfactant (SDS) on the mean diameters of the microgels and their LCST were carried out. The results showed that all of them affected the phase transition behavior of the microgels except the concentration of monomer. And all the PNIPAM microgels in the phase transition temperature range of 30.5℃ to 33.5℃.3、PNIPAM/Alginate core-shell microgels was successfully synthesized, and the optimized formula dosage of shell (SA), cross-linker (CaCl2), and core (PNIPAM microgels) were 2.5 g/L,2.0 g/L and 20 ml respectively. The PNIPAM microgels prepared under optimized were in the smaller size of 252 nm and the lesser PDI of 0.24.4、The effects of the concentrations of shell (SA), core (PNIPAAm), cross-linker (CaCl2), on the mean diameters of the core-shell microgels and their LCST were carried out. The results showed that all of them affected the phase transition behavior of the PNIPAM/SA core-shell microgels.The PNIPAM/SA core-shell microgels synthesized under optimized conditions were existed higer phase transition temperature of 33℃.5、TEM analysis indicated that all of the PNIPAM microgels and PNIPAM/SA core-shell dispersions had excellent stability and monodispersity. The TEM shows that the size of PNIPAM microgels was under 50 nm in dry condition and the PNIPAM/SA with larger size of about 80 nm.6、The loading ratio of the PNIPAM microgels and PNIPAM/SA microgels were 60% and 70% respectively. And the releasing ratio of PNIPAM microgels and PNIPAM/SA microgels were 45% and 65% respectively on 25℃,80% and 90% respectively on 40℃. According to drug loading properties and drug release mechanism, PNIPAM/SA core-shell microgels demonstrated the better performances.