In the last two decades, fluorescent carbon quantum dots (CQDs) have attracted intense interest as a new fluorescent nanomaterial with unique properties. This material offers significant advantages compared with conventional dyes and inorganic QD systems, and is used extensively in many different fields, especially in bioimaging and sensor applications. Despite all the positive values they offer, the production of CQD systems with excitation wavelength-dependent nature and high quantum yield (QY) is still a scientific challenge. In this study, we proposed the fabrication of CQD through a facile and easy-to-tune hydrothermal method using cheap and biocompatible precursors such as urea and lactic acid. The effect of experimental parameters including synthesis time, temperature, and mass ratio of the precursors, were determined to obtain the highest QY (48%). The as-prepared nitrogen-doped (N-doped) CQDs exhibited robust stability in the dark and in a wide range of pH values with excitation wavelength-dependent properties. Additionally, CQDs showed remarkable sensitivity and selectivity in the sensing of Fe3+ in blood plasma with a linear correlation in the range of 0–1000 μM, indicating the high potential of CQDs in practical applications. Lastly, cytotoxicity and antibacterial activity tests demonstrated the low toxicity and high biocompatibility of proposed CQDs. Considering the facile and efficient synthetic method, easy-to-tune optical properties, excitation-dependent nature, high fluorescence activity, and low cytotoxicity, we strongly anticipate that N-doped CQDs could provide unique advantages in various biomedical applications including diagnosis, bioimaging, and biosensors.
This study aims to investigate the protective effect of roflumilast, a phosphodiesterase (PDE)‐4 enzyme inhibitor, and demonstrate its possible role in the development prevention of cerebral ischemia/reperfusion injury (CI/RI) after stroke induced by carotid artery ligation in juvenile rats. The rats were randomly divided into five groups: healthy group without any treatment, healthy group administered with 1 mg/kg roflumilast, CI group not administered with roflumilast, CI group administered with 0.5 mg/kg roflumilast, and CI group administered with 1 mg/kg roflumilast. In the CI groups, reperfusion was achieved 2h after ischemia induction; in the roflumilast groups, this drug was intraperitoneally administered immediately after reperfusion and at the 12th hour. At the end of 24h, the rats were sacrificed and their brain tissues removed for examination. The mRNA expressions obtained with real‐time PCR of IL‐1β, TNF‐α, and NLRP3 significantly increased in the CI/RI‐induced groups compared with the control group, and this increase was significantly lower in the groups administered with roflumilast compared with the CI/RI‐induced groups. Moreover, ELISA revealed that both IL‐1 β and IL‐6 brain levels were significantly higher in the CI/RI‐induced groups than in the controls. This increase was significantly lower in the groups administered with roflumilast compared with the CI/RI‐induced groups. Histopathological studies revealed that the values closest to those of the healthy group were obtained from the roflumilast groups. Nissl staining revealed that the Nissl bodies manifested normal density in the healthy and roflumilast‐administered healthy groups, but were rare in the CI/RI‐induced groups. Roflumilast treatment increased these decreased Nissl bodies with increasing doses. Observations indicated that the Nissl body density was close to the value in the healthy group in the CI/RI‐induced group administered with 1 mg/kg roflumilast. Overall, roflumilast reduced cellular damage caused by CI/RI in juvenile rats, and this effect may be mediated by NLRP3.
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