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No abstract

The Covid-19 pandemic has ravaged the globe, and its causative agent, SARS-CoV-2, continues to rage. Prospects of ending this pandemic rest on the development of effective interventions. Single and combination monoclonal antibody (mAb) therapeutics have received emergency use authorization1,2, with more in the pipeline3–6. Furthermore, multiple vaccine constructs have shown promise7, including two with ~95% protective efficacy against Covid-198,9. However, these interventions were directed toward the initial SARS-CoV-2 that emerged in 2019. Considerable viral evolution has occurred since, including variants with a D614G mutation10 that have become dominant. Viruses with this mutation alone do not appear to be antigenically distinct, however11. Recent emergence of new SARS-CoV-2 variants B.1.1.7 in the UK12 and B.1.351 in South Africa13 is of concern because of their purported ease of transmission and extensive mutations in the spike protein. We now report that B.1.1.7 is refractory to neutralization by most mAbs to the N-terminal domain (NTD) of spike and relatively resistant to a number of mAbs to the receptor-binding domain (RBD). It is modestly more resistant to convalescent plasma (~3 fold) and vaccinee sera (~2 fold). Findings on B.1.351 are more worrisome in that this variant is not only refractory to neutralization by most NTD mAbs but also by multiple individual mAbs to the receptor-binding motif on RBD, largely due to an E484K mutation, although some mAb combinations retain activity. Moreover, B.1.351 is markedly more resistant to neutralization by convalescent plasma (~11-33 fold) and vaccinee sera (~6.5-8.6 fold). B.1.351 and emergent variants14,15 with similar spike mutations present new challenges for mAb therapy and threaten the protective efficacy of current vaccines.

Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility.

Highlights d A hPSC-derived cell and organoid platform is used to study SARS-CoV-2 tissue tropism d Human pancreatic alpha and beta cells are permissive to SARS-CoV-2 infection d Human hepatocyte and cholangiocyte organoids are permissive to SARS-CoV-2 infection d hPSC-derived cells/organoids show similar chemokine responses as COVID-19 tissues

During the past decade, fluorescent chemosensors have become an important research field of supramolecular chemistry and have attracted great attention because of their simplicity, high selectivity and sensitivity in fluorescent assays. In the design of new fluorescent chemosensors, exploration of new sensing mechanisms between recognition and signal reporting units is of continuing interest. Based on different photophysical processes, conventional sensing mechanisms including photo-induced electron transfer (PET), intramolecular charge transfer (ICT), metal-ligand charge transfer (MLCT), twisted intramolecular charge transfer (TICT), electronic energy transfer (EET), fluorescence resonance energy transfer (FRET), and excimer/exciplex formation have been investigated and reviewed extensively in the literature. This tutorial review will mainly focus on new fluorescent sensing mechanisms that have emerged in the past five years, such as aggregation-induced emission (AIE) and C=N isomerization, which can be ascribed to fluorescence changes via conformational restriction. In addition, excited-state intramolecular proton transfer (ESIPT) has not been well reviewed yet, although a number of chemosensors based on the ESIPT mechanism have been reported. Thus, ESIPT-based chemosensors have been also summarized in this review.

No abstract

Novel red‐emissive carbon‐dots (C‐dots) with broad absorption in the region from 400 to 750 nm are prepared from polythiophene phenylpropionic acid. Upon near infrared laser irradiation, the red‐emissive C‐dots show strong photoacoustic response and high photothermal conversion efficiency (η ≈ 38.5%). These unique properties enable the C‐dots to act as multifunctional fluorescent, photoacoustic, and thermal theranostics for simultaneous diagnosis and therapy of cancer.