Chitosan coated alginate/poly(N-isopropylacrylamide) beads for dual responsive drug delivery

Temperature-/pH-responsive chitosan coated alginate/poly(N-isopropylacrylamide) beads (CAPB) were prepared as a drug delivery system. The obtained beads were characterized by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized light microscope (PLM) and scanning electron microscopy (SEM). Oscillation experiments were used to analyze the mechanical stability of the samples. Effect of chitosan concentration and sodium polyphosphate (SPPP) content on the characteristics of CAPB was discussed. Swelling and drug release behaviors of the beads were investigated in simulated intestinal fluid (pH 7.4) and gastric fluid (pH 2.1) at 25 °C and 37 °C, respectively. Results illustrated that both the equilibrium swelling degree (SDeq) and drug release of the beads were greatly affected by the chitosan shell and were responsive to pH and temperature. The SDeq value of the beads decreased with the increase in chitosan concentration; and the drug release from CAPB was obviously slower than that of alginate/poly(N-isopropylacrylamide) beads without chitosan coating within 720 min. These developed materials could potentially be used as sustained dual-responsive drug delivery device in vivo.