A Hexanuclear Gadolinium(III)-Based Nanoprobe for Magnetic Resonance Imaging of Tumor Apoptosis.

Magnetic resonance imaging (MRI) is instrumental in the noninvasive evaluation of tumor tissues in patients subjected to chemotherapy, thereby yielding essential diagnostic data crucial for the prognosis of tumors and the formulation of therapeutic strategies. Currently, commercially available MRI contrast agents (CAs) predominantly consist of mononuclear gadolinium(III) complexes. Because there is only one Gd(III) atom per molecule, these CAs often require administration in high doses to achieve the desired contrast quality, which inevitably leads to some adverse events. Herein, we develop a six-nuclei, apoptosis-targeting T1 CA, Gd6-ZnDPA nanoprobe, which consists of a hexanuclear gadolinium nanocluster (Gd6) with an apoptosis-targeting group (ZnDPA). The amplification of Gd(III) by the hexanuclear structure generates its high longitudinal relaxivity (44.67 mM-1 s-1, 1T) and low r1/r2 ratio (0.68, 1T). Based on the Solomon-Bloembergen-Morgan (SBM) theory, this notable improvement is primarily ascribed to a long correlation tumbling time (τR). More importantly, the Gd6-ZnDPA nanoprobe shows excellent tumor apoptosis properties with an enhanced MR signal ratio (∼74%) and a long MRI imaging acquisition time window (∼48 h) in 4T1 tumor-bearing mice. This study introduces an experimental gadolinium-based CA for the potential imaging of tumor apoptosis in the context of MRI.

Development of 3D Printed Biodegradable, Entirely X-ray Visible Stents for Rabbit Carotid Artery Implantation.

Biodegradable stents are considered a promising strategy for the endovascular treatment of cerebrovascular diseases. The visualization of biodegradable stents is of significance during the implantation and long-term follow-up. Endowing biodegradable stents with X-ray radiopacity can overcome the weakness of intrinsic radioparency of polymers. Hence, this work focuses on the development of an entirely X-ray visible biodegradable stent (PCL-KIO3) composed of polycaprolactone (PCL) and potassium iodate via physical blending and 3D printing. The in vitro results show that the introduction of potassium iodate makes the 3D-printed PCL stents visualizable under X-ray. So far, there is inadequate study about polymeric stent visualization in vivo. Therefore, PCL-KIO3 stents are implanted into the rabbit carotid artery to evaluate the biosafety and visibility performance. During stent deployment, the visualization of the PCL-KIO3 stent effectively helps to understand the position and dilation status of stents. At 6-month follow-up, the PCL-KIO3 stent could still be observed under X-ray and maintains excellent vessel patency. To sum up, this study demonstrates that PCL-KIO3 stent may provide a robust strategy for biodegradable stent visualization.

Sediment amino acids as indicators of anthropogenic activities and potential environmental risk in Erhai Lake, Southwest China.

Total hydrolysable amino acids (THAAs) constitute the most important fraction of labile nitrogen. Anthropogenic activities directly influence various biogeochemical cycles and then accelerate lake ecosystem deterioration. This is the first study that has established the relationship between sediment THAAs and anthropogenic activities using dated sediment cores, and evaluated the possibility of THAAs release at the sediment interface based on changes in environmental conditions in Erhai Lake. The results showed that historical distribution and fractions of THAAs could be divided into three stages: a stable period before the 1970s, a clear increasing period from the 1970s to 1990s, and a gradually steady period that started after the 1990s. The chemical fraction, aromatic and sulfur amino acids (AAs) accounted for only ≤3% of THAAs. Basic AAs accounted for 5-17% of THAAs, and remained at a relatively stable level. However, acidic and neutral AAs, which accounted for 19-44% and 35-69% of THAAs, respectively, were the predominant factors causing THAAs to increase due to rapid agricultural intensification and intensification of contemporary sedimentation of phytoplankton or macrophytes since the 1970s. These trends were closely related to both anthropogenic activities and natural processes, which implied that sediment THAAs could act as an effective indicator that reflects anthropogenic activities and aquatic environmental characteristics. The current contributions of sediment THAAs on TN and TOC were <5% and 1.5%, respectively. However, the dramatic increase in THAAs in the sediment cores indicated that there was a huge potential source of labile nitrogen for the overlying water under certain environmental conditions. Correlation analysis suggested that the release of THAAs was negatively correlated with pH, whereas positively correlated with bacterial number and degree of OM mineralization, which particularly depend on the stability of HFOM. Therefore, the risk of sediment THAAs release might increase when the sediment environment continuously changes.

[Distribution of transferable nitrogen in Poyang Lake sediments and its response to the variation of River-Lake relationship].

Amounts and distributions of total transferable nitrogen and different transferable nitrogen forms were studied in the sediments of Poyang Lake with different regimen, in order to reveal the influence of the water level change caused by the River-Lake relationship change on the potential release risks of nitrogen. The results showed that: (1) the contents of the total nitrogen (TN) were between 389 and 3865 mg x kg(-1), and the spatial distribution showed an overall downward trend in the "Five River", the "Hu Xin" and the northern regions; the contents of the transferable total nitrogen (TTN) were between 319.36 and 904.56 mg x kg(-1) and contributed 52% to the TN, and its spatial distribution trend was the same as that of TN. (2) The content of transferable nitrogen followed the order of SOEF-N approximately = SAEF-N > WAEF-N > IEF-N. (3) The dry period advanced and the low water level continued to decline as a result of the change in River-Lake relationship of the Poyang Lake, leading to the prolonged outcropped time of sediments and the increased area, causing the different contents of transferable nitrogen in the sediments at different elevations. The transferable nitrogen content of the sediments in the whole lake during the wet period was lower than that during the dry period. The content of transferable nitrogen followed the order of 12-13 m elevation sediment > 11-12 m elevation deposition material > 10-11 m elevation sediments. The higher the elevation, the longer the sediments were exposed, and the higher the transferable nitrogen content. (4) With the increase of elevation, all forms of N contents increased. The increase of IEF-N and SOEF-N contents as well as their percentages in total transferable nitrogen was relatively small, while the increase of WAEF-N and SAEF-N contents as well as their percentages in total transferable nitrogen was relatively large. If the river-lake relationship changes further, the elevation in the dry period will further decrease, which will lead to the enlarged area and prolonged exposure of sediments, resulting in increase of TN, transferable nitrogen, IEF-N and SOEF-N contents in the sediments. At the coming wet period of next year, the nitrogen release risk from sediments of Poyang Lake might increase.