Thermo- and pH-responsive, Lipid-coated, Mesoporous Silica Nanoparticle-based Dual Drug Delivery System To Improve the Antitumor Effect of Hydrophobic Drugs.

Evodiamine (EVO) and Berberine (BBR), from Euodiae Fructus and Coptidis rhizoma, have been used as an herbal medicine pair in traditional Chinese medicine to exert synergistic antitumor effects against various types of tumor cells. However, their clinical use is limited by their poor solubility and adverse toxic side effects. Mesoporous silica nanoparticles (MSNs) possess excellent properties such as a readily functionalized surface, prominent biocompatibility, and huge specific surface area for loading with hydrophobic and hydrophilic drug. On this basis, a novel temperature- and pH-responsive dual drug delivery platform has been developed, in which lipid-coated MSN@p(NIPAM- co-MA) codelivers EVO and BBR. The results indicate that the nanocarrier improves the efficacy and biocompatibility of the drug pair and maintain desirable drug profiles at the low pH and higher temperature of the tumor microenvironment. The dual drug-loaded MSNs showed excellent synergistic therapy effects in vitro (cytotoxicity, cell migration and invasion, angiogenesis) and in vivo (growth of tumor grafts in mice). Meanwhile, the dual drug-loaded nanoparticles showed lower systemic toxicity than either drug alone, the free drug combination, or Taxol. These results suggest that the temperature- and pH-sensitive lipid-coated MSNs are a promising novel carrier for both hydrophobic and hydrophilic drugs.

Modulation of dynamic modes by interplay between positive and negative feedback loops in gene regulatory networks.

A positive and a negative feedback loop can induce bistability and oscillation, respectively, in biological networks. Nevertheless, they are frequently interlinked to perform more elaborate functions in many gene regulatory networks. Coupled positive and negative feedback loops may exhibit either oscillation or bistability depending on the intensity of the stimulus in some particular networks. It is less understood how the transition between the two dynamic modes is modulated by the positive and negative feedback loops. We developed an abstract model of such systems, largely based on the core p53 pathway, to explore the mechanism for the transformation of dynamic behaviors. Our results show that enhancing the positive feedback may promote or suppress oscillations depending on the strength of both feedback loops. We found that the system oscillates with low amplitudes in response to a moderate stimulus and switches to the on state upon a strong stimulus. When the positive feedback is activated much later than the negative one in response to a strong stimulus, the system exhibits long-term oscillations before switching to the on state. We explain this intriguing phenomenon using quasistatic approximation. Moreover, early switching to the on state may occur when the system starts from a steady state in the absence of stimuli. The interplay between the positive and negative feedback plays a key role in the transitions between oscillation and bistability. Of note, our conclusions should be applicable only to some specific gene regulatory networks, especially the p53 network, in which both oscillation and bistability exist in response to a certain type of stimulus. Our work also underscores the significance of transient dynamics in determining cellular outcome.