neutrophils in the ulcer area can produce excessive reactive oxygen species (ROS) which on one hand injury the epithelial cells to impede the wound recovery, and on the other hand block the supply of oxygen and nutrition to the ulcer area to hinder the angiogenesis. [2] In addition, the high level ROS can induce excessive inflammatory response of the macrophages, enhancing the wound vulnerability that further delays the recovery of DUs. [3] Moreover, the long-term open ulcers are more susceptible to pathogen infection, partly due to high local glucose level. [4] The infectious microorganisms can not only enhance the inflammatory response, interfere with the angiogenesis and epithelial proliferation, but also boost the generation of ROS in the ulcer areas. [5] The vicious circle of "excessive ROS-blocking the wound healingpromoting pathogenic infection-activating the generation of ROS" leads to the deterioration of DUs. In the absence of prompt and effective treatments, DUs may eventually deteriorate into lower limb amputation, giving rise to great physical and psychological trauma to the diabetic patients. [6] Thus, it is imperative to explore effective therapy for treating the early stage DUs to improve the life quality of the patients. [7] Diabetic ulcers (DUs) appearing as chronic wounds are difficult to heal due to the oxidative stress in the wound microenvironment and their high susceptibility to bacterial infection. A routine treatment combining surgical debridement with anti-infection therapy is widely used for treating DUs in the clinic, but hardly offers a satisfying wound healing outcome. It is known that a longterm antibiotic treatment may also lead to the drug resistance of pathogens. To address these challenges, new strategies combining both reactive oxygen species (ROS) scavenging and bacterial sterilization have been proposed for fighting against DUs. Following this idea, oxygen deficient molybdenum-based nanodots (MoO 3−X ) for healing the DUs are reported. The ROS scavenging ability of MoO 3−X nanodots is investigated and the antibacterial property of the nanodots is also demonstrated. The systematic cell and animal experimental results indicate that the MoO 3−X nanodots can effectively reduce inflammation, promote epithelial cell regeneration, accelerate angiogenesis, and facilitate DUs recovery. Most importantly, they present excellent capacity to diminish infection of methicillin-resistant Staphylococcus aureus, manifesting the potent application prospect of MoO 3−X nanodots for diabetic wound therapy.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202107137.

Background Fluorescence imaging as the beacon for optical navigation has wildly developed in preclinical studies due to its prominent advantages, including noninvasiveness and superior temporal resolution. However, the traditional optical methods based on ultraviolet (UV, 200–400 nm) and visible light (Vis, 400–650 nm) limited by their low penetration, signal-to-noise ratio, and high background auto-fluorescence interference. Therefore, the development of near-infrared-II (NIR-II 1000–1700 nm) nanoprobe attracted significant attentions toward in vivo imaging. Regrettably, most of the NIR-II fluorescence probes, especially for inorganic NPs, were hardly excreted from the reticuloendothelial system (RES), yielding the anonymous long-term circulatory safety issue. Results Here, we develop a facile strategy for the fabrication of Nd3+-doped rare-earth core–shell nanoparticles (Nd-RENPs), NaGdF4:5%Nd@NaLuF4, with strong emission in the NIR-II window. What’s more, the Nd-RENPs could be quickly eliminated from the hepatobiliary pathway, reducing the potential risk with the long-term retention in the RES. Further, the Nd-RENPs are successfully utilized for NIR-II in vivo imaging and magnetic resonance imaging (MRI) contrast agents, enabling the precise detection of breast cancer. Conclusions The rationally designed Nd-RENPs nanoprobes manifest rapid-clearance property revealing the potential application toward the noninvasive preoperative imaging of tumor lesions and real-time intra-operative supervision. Graphical abstract

The precise diagnosis of early lymphatic metastasis can be achieved with the assistance of Gd:Nd-RENPs.