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Ultraviolet A (UVA) irradiation can induce cellular senescence and cause skin photoaging, which is mainly driven by the excessive production of reactive oxygen species (ROS). Emerging studies have focused on new strategies for the prevention of skin photoaging. Ultrasmall Prussian blue nanoparticles (USPBNPs) demonstrate an intensive ability to scavenge ROS as nanozymes and exhibit great potential in the treatment of ROS-related diseases. Our goal was to investigate the anti-senescent role of USPBNPs against UVA-induced premature senescence in human dermal fibroblasts (HDFs). Our results showed that the activation of senescence-associated β-galactosidase (SA-β-gal) and the arrest of the cell cycle induced by UVA radiation in HDFs were significantly inhibited by pretreatment of USPBNPs (1 μg ml -1 ). Furthermore, USPBNPs downregulated the expression of DNA damage marker γH2AX and inhibited the secretion of senescence-associated secretory phenotypes (SASP) including IL-6, TNF-α and matrix metalloproteinases (MMPs). In addition, we found that the antiphotoaging effect of USPBNPs involved the scavenging of ROS as well as the inhibition of the ERK/AP-1 pathway. In conclusion, USPBNPs exhibited great potential to become novel anti-photoaging agents by alleviating UVA-induced cellular senescence and thus delaying the process of skin photoaging.

Iron based nanomedicine (IBNM) has been one powerful diagnostic tool as a magnetic resonance imaging (MRI) contrast agent (CA) in the clinic for years. Conventional IBNMs are generally employed as T 2 -MRI CAs, but most of them are constrained in clinical indication expansion by magnetic susceptibility artifacts. In comparison, extremely small iron oxide (ESIO) with a core size less than 5 nm has demonstrated the T 1 -MRI effect, which provides prospects for a Gd-based agent alternative. Nevertheless, currently developed ESIOs for T 1 -MRI CAs always require harsh conditions such as a high temperature and high boiling point reagent. Moreover, very few of the currently developed ESIOs meet the stringent pharmaceutical standard. Herein, on the basis of a crystal nuclear precipitation-dissolution equilibrium mechanism and outer/inner sphere T 1 -MRI theory, monodisperse ESIOs with an average size of 3.43 nm (polydispersity index of 0.104) are fabricated using a moderate cooling procedure with mild coprecipitation reaction conditions. The as-synthesized ESIOs display around 3-fold higher T 1 MRI signal intensity than that of commercial Ferumoxytol (FMT), comparable to that of Gd-based CAs in vitro. Additionally, the T 1 -MRI performance of the ESIOs is pH dependent and delivers bright signal augmentation. Eventually, the internalization into mesenchymal stem cells of the ESIO is realized in the absence of a transferring agent. Considering the identical structure and composition of the ESIOs as compared to that of FMT, they could meet the pharmaceutical criteria, thus providing great potential as T 1 -MRI Cas, for instance as stem cell tracers.

Ferumoxytol, which is originally intended for MRI and anemia treatment, is currently the only inorganic nanodrug approved by FDA for clinical application in vivo. Common ferumoxytol seems incapable of meeting the requirements for diverse applications. Thus, the development of a novel strategy based on co-precipitation to produce ferumoxytol with high quality is an imminent task. Herein, we proposed a physically assisted strategy, namely hydrocooling and magnetically internal heating co-precipitation, to optimize the properties of ferumoxytol and thus significantly enhance its magnetic performance. Magnetization of the newly developed ferumoxytol can reach 104-105 emu g-1 Fe, which is the highest value among the reported results. It has been found that the crystalline structures of the newly developed ferumoxytol have been greatly improved on the basis of pharmaceutical quality criteria.