Abstract
The synthesis, characterization, and the influence of single-walled carbon nanotubes (SWCNTs) modified with an anticancer drug doxorubicin (DOx) on the properties of model biological membrane as well as the comparison of the two modes of modification has been presented. The drug was covalently attached to the nanotubes either preferentially on the sides or at the ends of the nanotubes by the formation of hydrazone bond. The efficiency of the modification was proved by the results of FTIR, Raman, and thermogravimetric analysis. In order to characterize the influence of SWCNT-DOx conjugates on model biological membranes, Langmuir technique has been employed. The mixed monolayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) and SWCNT-DOx with different weight ratio have been prepared. It has been shown that changes in the isotherm characteristics depend on the SWCNTs content. While smaller amounts of SWCNTs do not exert significant differences, the introduction of the prevailing content of the nanotubes increases area per molecule and decreases the maximum value of compression modulus, leading to more fluid monolayer. However, upon increasing the surface pressure, the aggregation of carbon nanotubes within the thiolipid matrix has been observed. Mixed layers of DPPTE/SWCNT-DOx were also transferred onto gold electrodes by means of LB method. Cyclic voltammetry showed that SWCNT-DOx conjugates remain adsorbed at the electrode surface and are stable in time. Additionally, higher values of peak current and DOx surface concentration obtained for side modification prove that side modification allows for more efficient conjugation of the drug to carbon nanotubes.Graphical abstractᅟ
Highlights
IntroductionCancer therapy involves the application of drugs such as doxorubicin (DOx), which is often used in the treatment of leukemia, breast cancer, ovarian cancer, lung carcinoma, and several sarcomas
Cancer therapy involves the application of drugs such as doxorubicin (DOx), which is often used in the treatment of leukemia, breast cancer, ovarian cancer, lung carcinoma, and several sarcomas (Cortes-Funes and 143 Page 2 of 16Coronado 2007)
There is a limited number of reports, in which doxorubicin was attached by forming labile, pH-dependent covalent bond, it has been proved that single-walled carbon nanotubes (SWCNTs)-DOx conjugates with the covalently bound drug showed improved cytotoxicity compared to the conjugates, in which DOx was adsorbed on the surface of nanotubes by π-π stacking (Gu et al 2011)
Summary
Cancer therapy involves the application of drugs such as doxorubicin (DOx), which is often used in the treatment of leukemia, breast cancer, ovarian cancer, lung carcinoma, and several sarcomas We report the synthesis, characterization, and the results of the studies on the influence of carbon nanotubes modified with an anticancer drug doxorubicin (Fig. 1) on the properties of model biological membranes as well as the comparison of the type of the modification of the nanotubes with the drug. The influence of the daunorubicin-carbon nanotube adduct on the properties of thiolipid monolayers seemed to be not that significant Another issue that should be taken into account while using DPPTE as a component of model membranes is the fact that the presence of a thiol group in the head group region of a DPPTE molecule leads to the overall negative charge of the polar head of the lipid. Langmuir monolayer studies are accompanied by electrochemistry measurements to characterize the supported mixed layers of DPPTE and modified SWCNTs and to compare the two types of carbon nanotubes’ modification where anticancer drugs are attached preferentially at the ends or at the sides of the nanotubes.
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