Thermo conductive carbon nanotube-framed membranes for skin heat signal-responsive transdermal drug delivery
Smart carbon nanotube (CNT)-framed (SCNF) membranes were prepared by self-assembly of highly thermo conductive CNT molecules hybridized with chitosan (Chit) in a core–shell structure and then by chemical integration of a temperature-responsive copolymer, poly(NIPAAm-co-BVIm) (or pNIBIm), as an additional outer shell. CNT, Chit, and pNIBIm components used in the SCNF membranes function as a thermally conductive CNT-framework, a biocompatible glue to stick the CNT building blocks together, and a temperature-responsive copolymer, respectively. The SCNF membranes with different Chit/CNT ratios and an almost constant pNIBIm concentration (Chit-CNT25-pNIBIm, Chit-CNT50-pNIBIm and Chit-CNT75-pNIBIm) had a three-dimensional interwoven porous nanostructure. Scanning electron microscopy clearly showed the temperature-responsive swelling and deswelling characteristics of the triple core–shell structured CNT-frames. Temperature-dependent bovine serum albumin (BSA)-loading and -release profiles were obtained at 4 °C, 25 °C, 36.5 °C, and 40 °C. The SCNF membranes, especially the Chit-CNT50-pNIBIm hybrid membrane, showed a markedly high loading capacity of 9.7 mg per mg of membrane at 4 °C. The membrane also showed a temperature-dependent BSA-release characteristic (0.92 mg per mg of membrane at 36.5 °C and 3.41 mg per mg of membrane at 40 °C). The SCNF membranes showing highly effective drug-loading/-releasing characteristics could be potentially used as a skin heat signal-responsive patch type transdermal drug delivery (PTDD) system in the medicinal field.