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Preparation of Carboxylated Multi-Walled Carbon Nanotubes Loaded with Podophyllotoxin and Their Transdermal Penetration

??OBJECTIVE To study the preparation of carboxylated multi-walled carbon nanotubes loaded with podophyllotoxin (PPT-CNTs-COOH) as well as the characteristics of the in vitro transdermal penetration.METHODS PPT-CNTs-COOH was prepared by freezing milling method; IR, UV, XRD, and TGA were used to characterize the PPT-CNTs-COOH; HPLC method was used for determination of the content of podophyllotoxin loaded in the carboxylated multi-walled carbon nanotubes; franze diffusion cells method was used to determine the drug transdermal penetration rate.RESULTS The IR spectrum of PPT-CNTs-COOH showed the main absorption peaks of PPT and CNTs-COOH and the peaks changed obviously. Compared with free PPT, the UV absorption peaks of PPT-CNTs-COOH changed obviously. The PPT content in the CNTs-COOH gel was 58.0 ??g??mg^-1; the transdermal penetration rate of PPT gel was 7.08 ??g??cm^-2??h^-1 and that of the PPT-CNTs-COOH gel was 3.03 ??g??cm^-2??h^-1; the skin retention of PPT-CNTs-COOH gel was 3.04 ??g??cm^-2, far less than the 1.52 ??g??cm^-2 of PPT gel. Mild irritation developed within 24 h following removal of the PPT-CNTs-COOH gel, and disappears after 72 h.CONCLUSION Podophyllotoxin can successfully be loaded into the carboxylated multi-wall carbon nanotubes by using the frozen ball milling method. The product has remarkable sustained release effect in vitro and high retention in skin, which is beneficial to transdermal delivery.