The effect of radiation wave range on living behavior of ambient temperature reversible addition fragmentation chain transfer (RAFT) radical polymerization mediated by either trithiocarbonates or dithioesters chain transfer agents (CTAs) was investigated using UV−vis radiation sources with various wave ranges. The results indicate that CTAs are strongly sensitive to the UV radiation with wave range around their characteristic absorption wavelength, leading to significant decomposition of CTA moieties in the duration of RAFT polymerization, undermining the living character of polymerization. Cutting off these CTA-sensitive short-wave radiations significantly improves the living behavior of these polymerizations. Addition of highly efficient photoinitiator and optimizing functional groups of CTA remarkably suppress retardation effect in RAFT process, thus significantly shortening the initialization period and accelerating overall RAFT process. These provide a facile way toward rapid and well-controlled ambient temperature RAFT polymerization.

Well-defined polystyrene and its functional derivatives, poly(vinylbenzyl chloride) (PVBC), poly-(N,N-diethyl vinylbenzylamine) (PDEVBA), and poly(vinylbenzyl alcohol) (PVBA) were synthesized via (S)-1-dodecyl-(S′)-(R,R′-dimethyl-R′′-acetic acid) trithiocarbonate-mediated ambient-temperature reversible additionfragmentation chain transfer radical (RAFT) polymerization of the corresponding styrenic-based monomers under mild long-waVe radiation, using a (2,4,6-trimethylbenzoyl) diphenylphosphine oxide photoinitiator. The effect of chloromethyl, hydroxymethyl, and tert-amino functionalities on reactivity and controlled behavior of ambienttemperature RAFT polymerization of styrenic-based monomers under mild conditions was studied in this paper. The results indicated that the photolysis of trithiocarbonate groups and the irreversible termination reactions of their intermediate radicals were significantly suppressed for the duration of the RAFT polymerization under mild long-wave radiation, thus keeping the characteristic living behavior. Kinetic studies confirmed the well-controlled behavior of these RAFT polymerizations. Moreover, the chloromethyl, tert-amino, or hydroxymethyl functionalities significantly improved reactivity of styrenic-based monomers, thus remarkably accelerating the process of ambienttemperature RAFT polymerization. Although RAFT polymerization of DEVBA and VBC monomers proceeded at a comparable rate, the initialization period in RAFT polymerization of DEVBA monomer was clearly longer than that of the VBC monomer. VBA was the most reactive monomer among these styrenic-based monomers. Ambient-temperature RAFT polymerization of VBA under mild long-wave radiation was well controlled up to 31% monomer conversion in 1.5 h. The living behavior of these ambient-temperature RAFT polymerizations facilitated the direct synthesis of well-defined all-styrenic-based block copolymers under mild conditions.

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Metastasis is the major dominant reason for poor prognosis of hepatocellular carcinoma (HCC) after surgical treatment. However, the molecular mechanism of metastasis has not been well characterzied. Here, we report a novel function of Barx homeobox1 (Barx1) in inhibiting HCC invasion and metastasis. Barx1 expression is significantly decreased in human HCC tissues than in adjacent non-tumorous tissues and normal liver tissues. Low Barx1 expression is correlated with higher tumor-nodule-metastasis stage and indicates poor prognosis. Down-regulation of Barx1 promotes HCC migration, invasion and metastasis, whereas up-regulation of Barx1 inhibits HCC migration, invasion and metastasis. Mannosyl (alpha-1,6-)-glycoprotein beta-1,6-N-acetyl-glucosaminyltransferase 5 (MGAT5) and matrix metallopeptidase 9 (MMP9) are direct target genes of Barx1. Knockdown of Barx1 up-regulates MGAT5 and MMP9 expression in HCC cells with low metastatic capability, whereas over-expression of Barx1 suppresses their expression in HCC cells with high metastatic capability. Knockdown of both MGAT5 and MMP9 significantly decreases the invasion and metastasis abilities induced by Barx1 knockdown. Barx1 expression is negatively correlated with MGAT5 and MMP9 expression in human HCC tissues. Patients with low expression of Barx1 and high expression of MGAT5 or MMP9 are associated with poorer prognosis. Thus, loss of Barx1 represents a prognostic biomarker in human HCC patients.