Development of exosome membrane materialsfused microbubbles for enhanced stability and efficient drug delivery of ultrasound contrast agent

Lipid-coated microbubbles are widely used as an ultrasound contrast agent,as well as drug delivery carriers.However,the two main limitations in ultrasound diagnosis and drug delivery using microbubbles are the short half-life in the blood system,and the difficulty of surface modification of microbubbles for active targeting.The exosome,a type of extracellular vesicle,has a preferentially targeting ability for its original cell.In this study,exosome-fused microbubbles(Exo-MBs)were developed by embedding the exosome membrane proteins into microbubbles.As a result,the stability of Exo-MBs is improved over the conventional microbubbles.On the same principle that under the exposure of ultrasound,microbubbles are cavitated and self-assembled into nano-sized particles,and Exo-MBs are self-assembled into exosome membrane proteins-embedded nanoparticles(Exo-NPs).The Exo-NPs showed favorable targeting properties to their original cells.A photosensitizer,chlorin e6,was loaded into Exo-MBs to evaluate therapeutic efficacy as a drug carrier.Much higher therapeutic efficacy of photodynamic therapy was confirmed,followed by cancer immunotherapy from immunogenic cell death.We have therefore developed a novel ultrasound image-guided drug delivery platform that overcomes the shortcomings of the conventional ultrasound contrast agent and is capable of simultaneous photodynamic therapy and cancer immunotherapy.

Super-resolution visible photoactivated atomic force microscopy

Imaging the intrinsic optical absorption properties of nanomaterials with optical microscopy(OM)is hindered by the optical diffraction limit and intrinsically poor sensitivity.Thus,expensive and destructive electron microscopy(EM)has been commonly used to examine the morphologies of nanostructures.Further,while nanoscale fluorescence OM has become crucial for investigating the morphologies and functions of intracellular specimens,this modality is not suitable for imaging optical absorption and requires the use of possibly undesirable exogenous fluorescent molecules for biological samples.Here we demonstrate super-resolution visible photoactivated atomic force microscopy(pAFM),which can sense intrinsic optical absorption with~8 nm resolution.Thus,the resolution can be improved down to~8 nm.This system can detect not only the first harmonic response,but also the higher harmonic response using the nonlinear effect.The thermoelastic effects induced by pulsed laser irradiation allow us to obtain visible pAFM images of single gold nanospheres,various nanowires,and biological cells,all with nanoscale resolution.Unlike expensive EM,the visible pAFM system can be simply implemented by adding an optical excitation sub-system to a commercial atomic force microscope.