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This article presents the first work to fundamentally study the effect of steric hindrance in Pdot systems., Semiconducting polymer dots (Pdots) have recently emerged as a new type of ultrabright fluorescent probe that has been proved to be very useful for biomedical imaging. However, Pdots often suffer from serious fluorescence aggregation-caused quenching (ACQ) especially for near-infrared (NIR) fluorescent Pdots. This article compared two strategies to overcome the ACQ effect in near-infrared emissive Pdot systems: aggregation-induced emission (AIE) and anti-aggregation-caused quenching (anti-ACQ). The results show that the anti-ACQ platform outperforms the AIE system. The fluorescence quantum yield of anti-ACQ-based Pdots can be over 50% and the average per-particle brightness of the Pdots is about 5 times higher than that of the commercially available quantum dots. To help understand why the monomer conformations could greatly affect the optical properties of Pdots, molecular dynamics simulations were performed for the first time in such complicated Pdot systems. To demonstrate applications for in vivo fluorescence imaging, both microangiography imaging on living zebrafish embryos and specific tumor targeting on mice were performed. We anticipate that these studies will pave the way for the design of new highly fluorescent Pdot systems.

Carcinosarcoma (CS) is a rare mixed mesodermal malignancy most commonly affecting the female reproductive organs, respiratory tract, head, and neck. Though infrequent, it may affect the gastrointestinal tract, most often the oesophagus and only very rarely the rectum. Histologically, it is composed of two distinct elements of epithelial and mesenchymal origin. Clinically, it is a very aggressive tumour with many patients presenting with metastatic lymph nodes or distant metastases at the time of diagnosis. Prognosis is poor despite intervention with the majority of patients dying within six months. Due to the rarity of this condition, there are no specific treatment guidelines presently available. We describe the case of an 80-year-old patient with carcinosarcoma of the rectum with discussion of the immunohistochemistry and review the available literature pertaining to this rare presentation.