Months after the outbreak of a new flu‐like disease in China, the entire world is now in a state of caution. The subsequent less‐anticipated propagation of the novel coronavirus disease, formally known as COVID‐19, not only made it to headlines by an overwhelmingly high transmission rate and fatality reports, but also raised an alarm for the medical community all around the globe. Since the causative agent, SARS‐CoV‐2, is a recently discovered species, there is no specific medicine for downright treatment of the infection. This has led to an unprecedented societal fear of the newly born disease, adding a psychological aspect to the physical manifestation of the virus. Herein, the COVID‐19 structure, epidemiology, pathogenesis, etiology, diagnosis, and therapy have been reviewed.

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Tumor-selective photodynamic therapy is a successful method for ablation of malignant and cancerous cells. Herein, we introduce the design and preparation of functionalized acrylic copolymer nanoparticles with spiropyran (SP) and imidazole groups through a facile semicontinuous emulsion polymerization. Then, Au ions were immobilized and reduced on their surface to obtain photoresponsive gold-decorated polymer nanoparticles (PGPNPs). The prepared PGPNPs were surface-modified with folic acid as a site-specific tumor cell targeting agent and improve intracellular uptake via endocytosis. Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy analyses, UV-vis spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy images were employed to characterize their spectral and morphological properties. Fluorescence microscopy images and inductively coupled plasma analysis demonstrated the cell line labeling capability and improved targeting efficiency of folate-conjugated PGPNPs (FA-PGPNPs) toward rat brain cancer cells (C6 glioma) with 71.8% cell uptake in comparison with 28.8% for the nonconjugated ones. Nonpolar SP groups are converted to zwitterionic merocyanine isomers under UV irradiation at 365 nm and their conjugation with Au nanoparticles exhibited enhanced photogeneration of reactive oxygen species (ROS). These were confirmed by intracellular ROS analysis and cytotoxicity evaluation on malignant C6 glioma cells. Owing to the strong surface plasmon resonance absorption of gold nanoparticles, FA-PGPNPs provided elevated local photothermal efficiency under near-IR irradiation at 808 nm. The prepared multifunctional FA-PGPNPs with a comprehensive integration of prospective materials introduced promising nanoprobes with targeting ability, enhanced tumor photodynamic therapy, cell tracking, and photothermal therapy.

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