Inspired by the adhesion behaviors of mussels, we synthesized a chitooligosaccharide (COS) based multidentate ligand (ML) for preparing robust biocompatible magnetic iron oxide nanoparticles (IONPs). The COS was modified with mussel adhesive protein (MAP) mimetic multiple catechol groups and branched poly(ethylene glycol) moieties, which can not only strongly bind to IONPs through multiple catechol groups, but also afford IONPs with good colloidal stability and biocompatibility due to PEG integrated into the COS coating. The resultant ML-stabilized IONPs consist of single nanoparticles coated with ML shells and exhibited high dispersion stability in aqueous solution for a wide range of pH and concentrated salt solutions. The potential of ML-stabilized IONPs as contrast agents for T 2 -weighted magnetic resonance imaging was demonstrated by conducting in vivo imaging and relaxivity measurements. The ML-stabilized IONPs are therefore expected to be useful for magnetic resonance imaging under physiological conditions. Scheme 1 (a) Stabilization and functionalization of hydrophobic IONPs with a COS based multidentate ligand (ML). (b) Synthetic procedure for ML.

Empathy, crucial to harmonious interpersonal relationships and moral development, has both affective and cognitive components. Previous studies found that toddlers' temperamental inhibition may influence their empathy, but mainly focused on emotional response to others' distress. Little is known about whether inhibited children's poor empathy is due to high reactivity and social withdrawal when sharing others' affective states, such as distress (affective empathy), or to a difficulty in comprehending and inferring others' perspective (cognitive empathy). The current study investigated the role of behavioral inhibition (BI) in affective empathy (response to pain simulation) and cognitive empathy (performance in perspective-taking task) among 163 Chinese toddlers and tested in both only and non-only children. Correlation analyses showed that BI was only negatively associated with affective empathy. The relation between BI and cognitive empathy was moderated by self-regulation and inhibited children who were low in selfregulation presented low cognitive empathy. Additionally, only children presented advanced cognitive empathy but poorer affective empathy than non-only children. These findings imply different roles of BI in affective versus cognitive empathy in early childhood. Although highly inhibited children rarely show positive social expression toward others' distress, caution is needed in inferring that they lack a capacity for cognitive empathy.

Elemental sulfur is the oldest known antimicrobial agent. However, conventional sulfur in the clinic suffers from poor aqueous solubility and limited antibacterial activity, greatly hindering its practical use. Herein, we report a reform strategy coupling dimension engineering with chirality transfer to convert conventional 3D sulfur particles into chiral 2D sulfur nanosheets (S-NSs), which exhibit 50-fold improvement of antibacterial capability and dualselective inhibition against Gram-positive bacteria. Benefiting from the inherent selectivity of S-NSs and chirality selectivity from decorated Dhistidine, the obtained chiral S-NSs are proven to precisely kill Gram-positive drug-resistant bacteria, while no obvious bacterial inhibition is observed for Gram-negative bacteria. Mechanism studies reveal that S-NSs produce numerous reactive oxygen specipoes and hydrogen sulfide after incubation with bacteria, thus causing bacterial membrane destruction, respiratory chain damage, and ATP production inhibition. Upon spraying chiral S-NSs dispersions onto MRSA-infected wounds, the skin healing process was greatly accelerated in 8 days due to metabolism inhibition and oxidative damage of bacteria, indicating the excellent treatment efficiency of MRSA-infected wounds. This work converts the traditional well-known sulfur into modern antibacterial agents with a superior Gram-selectivity bactericidal capability.

This review summarizes the synthesis, properties, classification, biological effects, and biomedical applications of emerging metallenes.