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Objective: The immunosuppressive effects of corticosteroid (CS) injections have come under more scrutiny during the coronavirus disease 2019 (COVID‐19) pandemic. The aim of the study was to explore any relationship between joint/epidural CS injection and SARS‐CoV‐2 (severe acute respiratory syndrome coronavirus 2) polymerase chain reaction (PCR) positivity. Methods: A retrospective chart review was conducted on patients 18 years or over who received at least one joint or epidural CS injection by physiatrists in a tertiary care center between January 1, 2020, and December 31, 2021. This cohort of patients was then compared to a control group who did not receive any CS injection during this time period. Results: A total of 766 patients were identified in the CS injection group and 1546 patients in the control group. Overall, 12.27% of patients turned SARS‐CoV‐2 PCR positive in the CS injection group, which was similar to 11.90% in the control group (p = 0.797). But 3‐month SARS‐CoV‐2 PCR positivity rate showed a statistically significant higher rate among the CS injection group (3.30% in the CS injection group vs. 2.10% in the control group; p = 0.027). In multivariate regression analysis, after adjusting both groups for Charlson Comorbidity Index (CCI), there was statistically significant higher SARS‐CoV‐2 PCR positivity rate in the CS injection group (p = 0.024). However, after adjusting both groups for age and total number of comorbidities, there was no difference between the groups in regard to SARS‐CoV‐2 PCR positivity rate (p = 0.081). In the subgroup analysis of only COVID‐19 vaccinated patients, there was an increased 3‐month SARS‐CoV‐2 PCR positivity rate among patients with severe comorbidities in the CS injection group (p = 0.036). Conclusion: The study was not conclusive on the effect of joint or epidural CS injection on SARS‐CoV‐2 PCR positivity rate, although adjusted analysis suggests higher 3‐month SARS‐CoV‐2 PCR positivity rate after CS injection in patients with severe comorbidities with significant disease burden when compared to controls. [ABSTRACT FROM AUTHOR]

In various reactive oxygen species (ROS)‐based antitumor approaches (e.g., photodynamic therapy), increasing attentions are made to improve ROS level, but the short lifetime that is another decisive hurdle of ROS‐based antitumor outcomes is not even explored yet. To address it, a photocleaved O2‐released nanoplatform is constructed to release and switch ROS into reactive nitrogen species (RNS) for repressing hypoxic breast tumor. Systematic explorations validate that the nanoplatforms can attain continuous photocontrolled O2 release, alleviate hypoxia, and elevate ROS level. More significantly, the entrapped PDE5 inhibitor (PDE5‐i) in this nanoplatform can be enzymatically decomposed into nitric oxide that further combines with ROS to generate RNS, enabling the persistent antitumor effect since RNS features longer lifetime than ROS. Intriguingly, ROS conversion into RNS can help ROS to evade the hypoxia‐induced resistance to ROS‐based antitumor. Eventually, RNS production unlocks robust antitumor performances along with ROS elevation and hypoxia mitigation. Moreover, this extraordinary conversion from ROS into RNS also can act as a general method to solve the short lifetime of ROS. [ABSTRACT FROM AUTHOR]