Recently, triplet harvesting via a thermally activated delayed fluorescence (TADF) process has been established as a realistic route for obtaining ultimate internal electroluminescence (EL) quantum efficiency in organic light-emitting diodes (OLEDs). However, the possibility that the rather long transient lifetime of the triplet excited states would reduce operational stability due to an increased chance for unwarranted chemical reactions has been a concern. Herein, we demonstrate dual enhancement of EL efficiency and operational stability in OLEDs by employing a TADF molecule as an assistant dopant and a fluorescent molecule as an end emitter. The proper combination of assistant dopant and emitter molecules realized a “one-way” rapid Förster energy transfer of singlet excitons from TADF molecules to fluorescent emitters, reducing the number of cycles of intersystem crossing (ISC) and reverse ISC in the TADF molecules and resulting in a significant enhancement of operational stability compared to OLEDs with a TADF molecule as the end emitter. In addition, we found that the presence of this rapid energy transfer significantly suppresses singlet-triplet annihilation. Using this finely-tuned rapid triplet-exciton upconversion scheme, OLED performance and lifetime was greatly improved.

Organic semiconductor laser operating in the quasi-CW regime at 80 MHz and under 30 ms long pulse photoexcitation is demonstrated.

Eosinophils are prominent in bullous pemphigoid (BP), and proteases secreted from these and other inflammatory cells may induce disruption of the basement membrane. We used in situ hybridization and immunohistochemistry to localize the sites of 92-kD gelatinase expression in BP lesions. In all samples (20/20), a strong signal for gelatinase mRNA was detected only in eosinophils and was most pronounced where these cells accumulated at the floor of forming blisters. No other cells were positive for enzyme mRNA. Both eosinophils and neutrophils, however, contained immunoreactive 92-kD gelatinase indicating that active expression occurred only in eosinophils. Degranulated eosinophils were also seen near blisters, and as demonstrated by gelatin zymography, immunoblotting, and ELISA, 92-kD gelatinase protein was prominent in BP blister fluid. No other gelatinolytic activity was specifically detected in BP fluid, and only small amounts of 92-kD gelatinase were present in suction blister fluids. As demonstrated in vitro, 92-kD gelatinase cleaved the extracellular, collagenous domain of recombinant 180-kD BP autoantigen (BP180, BPAG2, HD4, type XVII collagen), a transmembrane molecule of the epidermal hemidesmosome. Our results suggest that production and release 92-kD gelatinase by eosinophils contributes significantly to tissue damage in BP.

No abstract

Collagenolytic activity has been reported previously in association with wounds. We used in situ hybridization and immunohistochemistry to localize cellular sites of interstitial collagenase production in acute wounds in human skin at days 1, 2, 4, 6, 9, and 14 after wounding. In vivo, collagenase expression peaked in migrating basal keratinocytes at the wound edge at day 1, then gradually decreased and was undetectable at day 9 when healing was complete. To minimize the effects of crust formation and inflammation, we examined the healing of wounds made with a 3-mm punch in organ-cultured skin. In these in vitro wounds, re-epithelialization occurred by 5-7 d in 10% serum, although remodeling of the connective tissue was minimal. Collagenase expression showed a similar pattern as in the in vivo wounds; it was detected in migrating keratinocytes already 4-6 h after wounding, peaked at 12-24 h, gradually decreased during the next few days, and subsided upon re-epithelialization. In dermal fibroblasts, on the other hand, expression of collagenase started considerably later, after 5-7 d in culture, and persisted after complete re-epithelialization, indicating that collagenase is differentially regulated in different cell types. Our findings also show that collagenase induction in keratinocytes does not require inflammation and occurs as a rapid response to wounding, suggesting that interstitial collagenase is not only necessary for remodeling of the extracellular matrix, but may also have a role in initiating migration of keratinocytes in wound healing.