| Malignant tumor is one of the major diseases that endanger human life and health. The current strategies for tumor treatment include chemotherapy, radiation therapy and surgical treatment, but none of these is very effective, and the development of metastasis and multidrug resistance (MDR) make tumor treatment more difficult. Thus, it is one of the most urgent and challenging works to develop safe and efficient drug delivery systems to inhibit metastasis and reverse MDR.For metastatic tumor treatment, reduction-responsive shell crosslinked micelles were prepared and used as vehicles for targeted intracellular delivery of disulfiram (DSF) to fully exert its multi-targeted anti-metastasis effect and finally inhibit tumor metastasis. The characteristics of DSF-loaded reduction-responsive shell crosslinked micelles (DCMs), such as size distribution, zeta potential, dilution stability, de-crosslinking and drug release, were investigated. DCMs were spherical micelles with particle size of～85nm and zeta potential of about-20mV. DCMs showed high stability against dilution with water and organic solvent, and were able to de-crosslinking reversibly under a reducing environment. The release of DSF from DCMs was very slow in buffer solution that models the blood environment, however, in the presence of10mM DTT, rapid and sustained release of DSF from DCMs was achieved.The cellular uptake and cytotoxicity of DCMs and their effect on apoptosis, migration and invasion were further evaluated. DCMs could be internalized effectively by4T1tumor cells, leading to high cytotoxicity and high ability to promote cell apoptosis. DCMs could significantly down-regulate the expression of matrix metalloproteinase (MMPs) in4T1cells, impaire tube formation, and subsequently inhibit tumor cell migration and invasion. To evaluate the inhibitory effect of DCMs on tumor metastasis, the biodistribution and anti-metastasis efficacy in vivo were investigated in4T1tumor bearing mice. DCMs displayed quick and high accumulation in tumor site, and could retain for a long time, as a result, DCMs not only significantly inhibited tumor growth, but also remarkably prevented tumor metastasis.In order to co-deliver DSF and doxorubicin (DOX) to tumor tissue to exert their synergistic anti-tumor efficacy and finally reverse MDR, pH-responsive and temporal controlled polymeric micelles (DSMs) were prepared by conjugating DOX to poly(styrene-co-maleic anhydride)(SMA) derivative with adipic dihydrazide (ADH) through a acid-cleavable hydrazone bond, and then encapsulating DSF into the micelles formed by the self-assembly of SMA-ADH-DOX (SAD) conjugate. The characteristics of DSMs, including particle size, zeta potential, drug loading, encapsulation efficiency, colloidal stability and in vitro release rates were investigated. DSMs were about90nm with a narrow distribution and a negative surface charge, which could reduce protein absorption and increase the colloidal stability of micelles. DSMs enabled a temporal release of two drugs:encapsulated DSF was released fast, while conjugated DOX was released in a sustained and pH-dependent manner.To evaluate the effect of DSMs on reversing MDR, DOX accumulation and efflux, cell apoptosis, biodistribution and anti-tumor efficacy in vivo were determined. DSMs significantly increased the accumulation of DOX in MCF-7/ADR cells through enhancing cellular uptake and inhibiting drug efflux, and exhibited strong cytotoxicity. Compared with free DOX, the cytotoxicity of DSMs was increased by～100folds. In addition, DSMs also significantly blocked cell cycle, induced cell apoptosis and inhibited MCF-7/ADR tumor growth with decreased systemic toxicity, compared with free DOX in combination with free DSF. |
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