Dual stimulus responsive drug release under the interaction of pH value and pulsatile electric field for a bacterial cellulose/sodium alginate/multi-walled carbon nanotube hybrid hydrogel

A novel hybrid hydrogel composed of sodium alginate (SA), bacterial cellulose (BC) and multi-walled carbon nanotubes (MWCNTs) was synthesized using CaCl2 as a crosslinking agent. The hydrogel (BC/SA/MWCNTs) was proposed as a pH and electric field dual-stimulus responsive drug delivery system. Various amounts of MWCNTs were doped into the BC/SA in order to obtain the highest electric sensitivity of the composite hydrogel. The releasing profile of the drug from the hybrid hydrogels demonstrated the dual pH-/electric-sensitive property of the composite hydrogel. The amount of drug released, which was found to be dependent on the applied electric current strength, was greater under the electrical stimulus compared with that under passive diffusion. The electric-enhanced releasing behaviour was selective to the pH value of the surrounding culture. In neutral conditions, release curves under an electric voltage showed obvious electric-sensitivity. In acidic or alkaline conditions, release curves with or without an applied electric voltage showed little difference. A pulsatile pattern of drug release was observed by switching on and off the electric stimulus. In neutral conditions, drug release from the hydrogel showed a significant pulsatile characteristic. The overall performance of the BC/SA/MWCNTs hybrid hydrogel demonstrated that MWCNTs as additives played a synergistic role in the control release performance of the drug delivery system.