Formation of biomimetic hierarchical nanostructure in homopolymers and block copolymer ternary blend particles

In order to mimic hierarchical nanostructures in nature,particles of polymer blends consisting of poly(4-butyltriphenylamine)(PBTPA),poly(methyl methacrylate)(PMMA)and PBTPA-block-PMMA were fabricated by a solvent evaporation method.Effects of the molecular weight and the chemical composition of PBTPA-b-PMMA,molecular weights of homopolymers,and the composition of the blend on the morphology were investigated.The polymer blend particle consisting of PBTPA and PMMA homopolymers exhibited thermodynamically favored core-shell structure,in which more hydrophilic PMMA-shell surrounded PBTPA-core.The addition of 10 wt%of PBTPA-b-PMMA caused the morphological transition from core-shell toJanus or inversed core-shell,in which PBTPA-shell surrounded PMMA-core,depending on the molecular weight of PBTPA segment in PBTPA-b-PMMA.When the molecular weight of PMMA segment was higher than that of PMMA homopolymer,watermelon-like particles in which small PBTPA domain less than 80 nm dispersed in the PMMA domain surrounded by PBTPA shell were observed.As the ratio of PBTPA-b-PMMA increased,the interface of the macrophase separation became obscure.At 50 wt%of the PBTPA-b-PMMA,only microphase separation was observed.The measurement of interfacial tension by pendant drop method demonstrated that PBTPA-b-PMMA lower the interfacial tension between PBTPA and the aqueous phase to the value similar to that of PMMA with the aqueous phase.

Inside-out assembly of viral antigens for the enhanced vaccination

Current attempts in vaccine delivery systems concentrate on replicating the natural dissemination of live pathogens,but neglect that pathogens evolve to evade the immune system rather than to provoke it.In the case of enveloped RNA viruses,it is the natural dissemination of nucleocapsid protein(NP,core antigen)and surface antigen that delays NP exposure to immune surveillance.Here,we report a multi-layered aluminum hydroxide-stabilized emulsion(MASE)to dictate the delivery sequence of the antigens.In this manner,the receptor-binding domain(RBD,surface antigen)of the spike protein was trapped inside the nanocavity,while NP was absorbed on the outside of the droplets,enabling the burst release of NP before RBD.Compared with the natural packaging strategy,the inside-out strategy induced potent type I interferon-mediated innate immune responses and triggered an immune-potentiated environment in advance,which subsequently boosted CD40+DC activations and the engagement of the lymph nodes.In both H1N1 influenza and SARS-CoV-2 vaccines,rMASE significantly increased antigen-specific antibody secretion,memory T cell engagement,and Th1-biased immune response,which diminished viral loads after lethal challenge.By simply reversing the delivery sequence of the surface antigen and core antigen,the inside-out strategy may offer major implications for enhanced vaccinations against the enveloped RNA virus.

A plant growth chamber system equipped with aerosol generators for studying aerosol-vegetation interactions

Understanding aerosol-vegetation interactions is vital in ecosystems.However,the interactions remain elusive partly due to the lack of suitable plant growth chamber systems.Particularly,deposition of submicron particles on leaf surfaces is challenging due to its low deposition velocities compared to larger particles.In this work,we present a plant-growth chamber that was used to study the effect of sub-micron black carbon(BC)particles on the growth and photosynthesis of plants.The chamber system simultaneously enables the growth of multiple plants in pots and the deposition of submicron particles onto them.Two spraying methods assisted by ultrasonic and electrostatic forces were employed as aerosol generators to realize the particle deposition.The flow regime inside the chamber was numeri-cally calculated to predict the transportation of aerosol particles,suggesting the optimal operating conditions of the chamber.The gas-phase particle size distribution measurements showed that gener-ated BC particles were suspended in submicron diameter ranges.The aerosol generators were examined in the chamber using three conductor and insulator substrates as a model of plant leaves.Microscope observations and spectroscopic analysis ascertained that submicron BC particles generated from our generators were deposited on all substrate surfaces.Using the developed chamber system,systematic studies can be performed to advance the fundamental understanding of aerosol-vegetation interactions.