DPP4 peptide

Diketopyrrolopyrrole (DPP) and isoindigo (ISO) moieties have been widely studied in organic optoelectronic materials, while they have been rarely explored as electron transporting materials in perovskite solar cells (PSCs). In this paper, two organic molecules, tetraphenylethylene-diketopyrrolopyrrole (TPE-DPP4) and tetraphenylethylene-isoindigo (TPE-ISO4), were synthesized and successfully used in inverted PSCs. Cyclic voltammetry measurement revealed the matched energy levels of the TPE- based interlayers with perovskite materials. Steady-state photoluminescence (PL) spectra, time-resolved PL decay results and electrochemical impedance spectroscopy (EIS) indicate the enhanced electron extraction and electron-transporting ability after introducing the TPE-DPP4/TPE-ISO4-based interlayer in PSCs. As a result, devices with TPE-DPP4 and TPE-ISO4 interlayers exhibit high power conversion efficiencies (PCEs) of 18.44% and 18.19%, respectively, and notably, the FF values are as high as 80%. The standard device without an interlayer was also measured, showing an inferior PCE of 16.87%. Therefore, TPE-DPP4 and TPE-ISO4 can work as efficient interfacial materials for improving electron transfer, and finally for enhancing the photovoltaic performance in inverted PSCs. As far as we know, this is the first report on the DPP/ISO-based interfacial layer in perovskite solar cells. The results in this work also demonstrate the great potential of DPP or ISO-based n-type materials for application in PSCs.

Background: Clinical evidence indicates that sitagliptin treatment improves bone quality in diabetic patients, but the mechanisms involved remain elusive. Here, we studied the role of angiogenesis with sitagliptin treatment in diabetes-induced poor osteointegration of titanium implants and the underlying mechanisms. Methods: In vitro, Human Umbilical Vein Endothelial Cells (HUVECs) incubated on titanium (Ti) surface were subjected to 1) normal milieu (NM); 2) diabetic milieu (DM); 3) DM + sitagliptin; 4) NM + macrophage; 5) DM + macrophage; or 6) DM + macrophage + sitagliptin. Microphage and HUVECs were cultured alone or cocultured in a Transwell system. In vivo, DM was induced by high-fat diet and administration of streptozotocin (STZ) in rats. Titanium screws were implanted in the femurs of rats in three groups: Control, DM, Sitagliptintreated DM. Results: In vitro, when cells were incubated alone, DM caused M1 polarization of macrophage, evidenced by the increased iNOS and decreased CD206 expressions, and obvious dysfunctions of HUVECs. The DM-induced injury of endothelial cells were significantly worsened when the two cells were co-cultured. The addition of sitagliptin markedly reversed the changes of macrophage but not of HUVECs in DM when cells were cultured alone. When cells co-cultured, however, both the abnormal macrophage polarization and the endothelial impairment in DM was significantly alleviated by sitagliptin. In vivo, compared with normal animals, DM animals showed imbalanced M1/M2 polarization, angiogenesis inhibition and poor bone formation on the bone-implant interface (BII), which were significantly ameliorated by sitagliptin treatment. Conclusion: Our results demonstrate macrophage polarization imbalance as a crucial mechanism underlying the impaired angiogenesis and bone healing in diabetes, and provide sitagliptin as a promising novel drug for biomaterial-engineering to improve the osteointegration of titanium implants in diabetic patients.