Real-time in situ magnetic measurement of the intracellular biodegradation of iron oxide nanoparticles in a stem cell-spheroid tissue model

The use of magnetic nanoparticles in nanomedicine keeps expanding and,for most applications,the nanoparticles are internalized in cells then left within,bringing the need for accurate,fast,and easy to handle methodologies to assess their behavior in the cellular environment.Herein,a benchtop-size magnetic sensor is introduced to provide real-time precise measurement of nanoparticle magnetism within living cells.The values obtained with the sensor,of cells loaded with different doses of magnetic nanoparticles,are first compared to conventional vibrating sample magnetometry(VSM),and a strong correlation remarkably validates the use of the magnetic sensor as magnetometer to determine the nanoparticle cellular uptake.The sensor is then used to monitor the progressive intracellular degradation of the nanoparticles,over days.Importantly,this real-time in situ measure is performed on a stem cell-spheroid tissue model and can run continuously on a same spheroid,with cells kept alive within.Besides,such continuous magnetic measurement of cell magnetism at the tissue scale does not impact either tissue formation,vibility,or stem cell function,including differentiation and extracellular matrix production.

Design strategies towards transition metal single atom catalysts for the oxygen reduction reaction-A review

The electrochemical oxygen reduction reaction(ORR)is pivotal in energy conversion via a 4e-ORR pathway and green hydrogen peroxide production via 2e-ORR pathway.Transition metal single atom catalysts(TM SACs)have attracted intense attention in recent years for ORR due to their high activity and near maximum metal atom utilization.The future development of TM SACs for ORR requires improved understanding of reaction pathways,since currently the true origin of activity remains contentious owing to the lack of qualitative/quantitative information about active sites.Knowledge-guided design is imperative for the optimization of TM SACs performance in terms of activity and selectivity.This review focuses on the latest progress in the design of TM SACs for ORR,placing particular attention on efforts to elucidate reaction mechanisms.Experimental evidence based on in-situ/operando characterization measurements,along with theoretical predictions,are summarized to deepen understanding of the structure-performance relationships at both atomic and molecular level.Finally,some perspectives are offered relating to the fundamental science needed for TM SACs to find practical application in energy storage and conversion devices.We hope this review will inspire the development of new synthetic routes towards high-performance ORR electrocatalysts for the energy sector.