Herein, a series of universal bipolar host materials, 9,9'-([1,2,4]triazolo[1,5- a]pyridine-2,6-diylbis(4,1-phenylene))bis(9 H-carbazole) (TP26Cz1), 3-(2-(4-(9 H-carbazol-9-yl)phenyl)-[1,2,4]triazolo[1,5- a] pyridine-6-yl)-9-phenyl-9 H-carbazole (TP26Cz2), 9,9'-([1,2,4]triazolo[1,5- a]pyridine-2,7-diylbis(4,1-phenylene))bis(9 H-carbazole) (TP27Cz1), and 3-(2-(4-(9 H-carbazol-9-yl)phenyl)-[1,2,4]triazolo[1,5- a]pyridin-7-yl)-9-phenyl-9 H-carbazole (TP27Cz2), using [1,2,4]triazolo[1,5- a]pyridine (TP) as electron-transporting moiety and carbazole as hole-transporting moiety, were designed and synthesized. All four compounds possess remarkable carrier-transporting properties and excellent thermal stability with high glass-transition temperature ( T) in the range of 136-144 °C. The hole- and electron-transporting abilities could be regulated by adjusting the linkage mode between the carbazole and TP units, and balanced charge-transporting properties were realized in TP26Cz2 and TP27Cz2. The phosphorescent and thermally activated delayed-fluorescence (TADF) organic light-emitting diodes (OLEDs) based on these host materials exhibit superior performance with high efficiency and low roll-off. For example, TP26Cz2-hosted phosphorescent OLED (PhOLED) exhibits the maximum external quantum efficiency (η) of 25.6%, and at the high luminance of 5000 cd m, the η still remained at 25.2%. TP27Cz1-hosted TADF device exhibits the maximum η of 15.5% and only dropped to 15.4% at the luminance of 1000 cd m. Moreover, the influence of linking mode of carbazole unit and TP units in these hosts on their photophysical and carrier-transporting properties as well as the electroluminescence (EL) performance of devices was discussed.

The study was aimed to design a novel pH-sensitive carrier to deliver antitumor drugs to increase treatment efficiency. Histidine (His)was used to modify auricularia auricular polysaccharide (AAP) by esterification. Proton nuclear magnetic resonance spectrometry was developed to characterize the His-AAP carrier and the His-AAP Paclitaxel (PTX) micelles were prepared by self-assembled organic solvent evaporation. The formation of His-AAP PTX micelles was confirmed by dynamic light-scattering, transmission electron microscopy and high performance liquid chromatography. It was found that the His-AAP PTX micelles possessed a spherical morphology with an average diameter of 157.2 nm and an 80.3% PTX encapsulation efficiency. In vitro release at pH 7.4, 6.5, 5.0 reached 70%, 71%, and 88%, respectively. The cell viability assay and confocal laser scanning microscope were used to evaluate the cytotoxicity and cell uptake of the His-AAP PTX micelles. Compared with Taxol, the IC50 of the His-AAP PTX micelles were lower after incubating for 24 h, 48 h, or 72 h (0.216 versus 0.199, 0.065 versus 0.060, and 0.023 versus 0.005, respectively). In a test of tumor-bearing mice, the His-AAP PTX micelles significantly inhibited tumor growth. These results showed that His-AAP PTX micelles are a highly promising therapeutic system for anticancer therapy.

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A novel electron-transporting unit, imidazo [1,2-b]pyridazine (IP), was first reported for developing host materials. The IP moiety possesses excellent electron-transporting ability and great thermal stability. Using carbazole as p-type units and IP as n-type units, several bipolar host materials, namely, IP6Cz, IP68Cz, IP36Cz, and IP368Cz, were developed through altering the substitution site of the IP core. Among these four materials, 6-site-substituted IP6Cz and 6,8-sitesubstituted IP68Cz exhibit the best electroluminescence (EL) performance. IP6Cz-and IP68Cz-based red phosphorescent organic light-emitting diodes using Ir(pq) 2 acac as the emitter exhibit extremely high EL efficiency with the maximum external quantum efficiency (η ext,max ) of 26.9 and 25.2% and an insignificant efficiency roll-off. Moreover, IP6Cz-and IP68Cz-based deep-red devices doped by Ir(piq) 2 acac also show satisfactory EL performance with a η ext,max of 20.5 and 19.9%, respectively. The influence of different substitution sites of the IP core on the photophysical and electrochemical properties was systematically investigated. This study demonstrates that IP could be a first-rate electron-transporting unit for bipolar materials for red-emitting devices.

Psammaplin A (PsA) is a bromotyrosine disulfide dimer with histone deacetylase (HDAC) inhibition and acts through reduced monomer PsA-SH. We studied the connection of HDAC inhibition, cell growth inhibition, and apoptosis induction of PsA-SH by modifying the −SH group with deletion (6a) or replacement with hydroxamic acid (10b) or benzamide (12g). PsA-SH inhibits HDAC1/2/3 and 6a loses the HDAC inhibition ability. 10b inhibits HDAC1/2/3/6 while 12g shows selective inhibition of HDAC3. PsA-SH and 10b, but neither 6a nor 12g, induce apoptosis in human leukemia HL-60 cells associated with increased acetylation of Histone H3. PsA-SH and 10b inhibit growth of several solid tumor cell lines in vitro and Lewis lung cancer cell growth in vivo. PsA-SH is a simple scaffold for developing selective HDAC inhibitors and induces apoptosis through inhibiting HDAC1/2.

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