RESUMEN
It has been 30 years since the discovery of surface restructuring in thin azopolymer films by two independent research groups. A wide variety of topographical structures have been created by the application of two-/four-beam interference patterns, space light modulators and even helical beams. There are a number of comprehensive reviews which describe in detail the advances in superficial photopatterning of azopolymer films and macroscopic deformations of azonetworks. The theoretical approaches are only briefly touched on in these reviews and often are accompanied by the remark that the phenomenon is far from being understood. In this review, we would like to present the polymer theoretist's point of view on this intriguing problem. We begin by describing a multitude of theoretical approaches and commenting on the pluses and drawbacks of each. Importantly, we show that in most cases the presence of an azopolymer matrix is either ignored or limited to a specific class of azopolymers (liquid-crystalline or elastomeric). We then move to early orientation approaches based on the hypothesis that reorientation of azo-chromophores by modulated polarized light is the sole cause of superficial patterning. At the end of the review a modern orientation approach, as proposed by our own group, is presented. This approach has high predictive power because it can explain a large pool of experimental data for different classes of azopolymers including glassy and liquid-crystalline materials. This is made possible by taking into account both the light-induced orientation process and the change of anisotropic interactions between the chromophores upon their isomerization. Last but not least, this is the only approach that provides an estimate of the light-induced stress large enough to cause plastic deformations of glassy azopolymers. Recent finite element modeling results show remarkable similarity to real patterns and even time-dependent data are well explained. With this, we claim that the puzzle is finally understood and the orientation approach is ready for its implementation for major azopolymer classes.
RESUMEN
We report on solving of two intriguing issues concerning the inscription of surface relief gratings within azopolymer thin films under irradiation with SS, PP and RL interference patterns. For this, we utilize the orientation approach and viscoplastic modeling in combination with experimental results, where the change in surface topography is acquired in situ during irradiation with modulated light. First, the initial orientation state of polymer backbones is proved to be responsible for the contradictory experimental reports on the efficiency of the SS interference pattern. Different orientation states can influence not only the phase of SS grating but also its height, which is experimentally confirmed by using special pretreatments. Second, the faster growth of gratings inscribed by the RL interference pattern is shown to be promoted by a weak photosoftening effect. Overall, the modeled results are in good agreement with the order of relative growth efficiency: RL-PP-SS.
RESUMEN
Effective targeting of metastasis is considered the main problem in cancer therapy. The development of herbal alkaloid Berberine (Ber)-based anticancer drugs is limited due to Ber' low effective concentration, poor membrane permeability, and short plasma half-life. To overcome these limitations, we used Ber noncovalently bound to C60 fullerene (C60). The complexation between C60 and Ber molecules was evidenced with computer simulation. The aim of the present study was to estimate the effect of the free Ber and C60-Ber nanocomplex in a low Ber equivalent concentration on Lewis lung carcinoma cells (LLC) invasion potential, expression of epithelial-to-mesenchymal transition (EMT) markers in vitro, and the ability of cancer cells to form distant lung metastases in vivo in a mice model of LLC. It was shown that in contrast to free Ber its nanocomplex with C60 demonstrated significantly higher efficiency to suppress invasion potential, to downregulate the level of EMT-inducing transcription factors SNAI1, ZEB1, and TWIST1, to unblock expression of epithelial marker E-cadherin, and to repress cancer stem cells-like markers. More importantly, a relatively low dose of C60-Ber nanocomplex was able to suppress lung metastasis in vivo. These findings indicated that Ñomplexation of natural alkaloid Ber with C60 can be used as an additional therapeutic strategy against aggressive lung cancer.
RESUMEN
A herbal alkaloid Berberine (Ber), used for centuries in Ayurvedic, Chinese, Middle-Eastern, and native American folk medicines, is nowadays proved to function as a safe anticancer agent. Yet, its poor water solubility, stability, and bioavailability hinder clinical application. In this study, we have explored a nanosized carbon nanoparticle-C60 fullerene (C60)-for optimized Ber delivery into leukemic cells. Water dispersions of noncovalent C60-Ber nanocomplexes in the 1:2, 1:1, and 2:1 molar ratios were prepared. UV-Vis spectroscopy, dynamic light scattering (DLS), and atomic force microscopy (AFM) evidenced a complexation of the Ber cation with the negatively charged C60 molecule. The computer simulation showed that π-stacking dominates in Ber and C60 binding in an aqueous solution. Complexation with C60 was found to promote Ber intracellular uptake. By increasing C60 concentration, the C60-Ber nanocomplexes exhibited higher antiproliferative potential towards CCRF-CEM cells, in accordance with the following order: free Ber < 1:2 < 1:1 < 2:1 (the most toxic). The activation of caspase 3/7 and accumulation in the sub-G1 phase of CCRF-CEM cells treated with C60-Ber nanocomplexes evidenced apoptosis induction. Thus, this study indicates that the fast and easy noncovalent complexation of alkaloid Ber with C60 improved its in vitro efficiency against cancer cells.
