Biofunctionalized Janus particles with tailored surface chemistry are gathering interest for applications as catalysts, multifunctional cell surface targets, nanomotors, and drug delivery systems. The dual nature of the surface chemistry of Janus particles can be exploited to immobilize drugs, cell surface targets, and/or other functional molecules on both sides of the particle surface. In this study, a model system is established for the scalable preparation of nanoscale Janus particles with dual protein functionalization with the proteins ferritin and streptavidin. 80 nm silica nanoparticles (SiNPs) modified with azidosilane are used to prepare Pickering emulsions with molten wax as the droplet phase. The azide‐functionalized SiNPs on the Pickering emulsion droplets are further subjected to face‐selective silanization with biotin‐polyethylene glycol ethoxy silane. Afterward, ferritin is grafted on the azide‐functionalized side via a click‐reaction and the biotin groups are conjugated with streptavidin which is labeled with ultrasmall gold nanoparticles. In order to elucidate the advantages and limits of this approach, a detailed characterization is performed of the particles at every process step. The results show that this method represents a scalable platform for the versatile preparation of nanoscale Janus nanoparticles that can potentially be used with a wide variety of proteins.

This study presents a scalable method for designing magnetic Janus nanoparticles, which are capable of performing bacterial capture, while preventing agglomeration between bacterial cells. To this end, we prepared silica-coated magnetite Janus nanoparticles functionalized with a bacteria-specific antibody on one side and polyethylene glycol chains on the other, using the established wax-in-water emulsion strategy. These magnetic Janus nanoparticles specifically interact with one type of bacteria from a mixture of bacteria via specific antigen–antibody interactions. Contrarily to bacterial capture with isotropically functionalized particles, the bacterial suspensions remain free from cell–nanoparticle–cell agglomerates, owing to the passivation coating with polyethylene glycol chains attached to the half of the magnetic nanoparticles pointing away from the bacterial surface after capture. The selective magnetic capture of Escherichia coli cells was achieved from a mixture with Staphylococcus simulans without compromising bacterial viability and with an efficiency over 80%. This approach is a promising method for rapid and agglomeration-free separation of live bacteria for identification, enrichment, and cell counting of bacteria from biological samples.

DSPE/PEG-coated Janus nanoparticles firmly anchor onto cell surfaces by a process that involves incomplete macropinocytosis.

Tyrphostin 23 (T23) is a well-known inhibitor of protein tyrosine kinases. To investigate potential acute effects of T23 on the viability and the glucose metabolism of brain cells, we exposed cultured primary rat astrocytes to T23 for up to 4 h. While the viability and the morphology of the cultured astrocytes were not acutely affected by the presence of T23 in concentrations of up to 300 µM, this compound caused a rapid, time- and concentration-dependent increase in glucose consumption and lactate release. Maximal effects on glycolytic flux were found for incubations with 100 µM T23 for 2 h which doubled both glucose consumption and lactate production. The stimulation of glycolytic flux by T23 was reversible, completely abolished upon removal of the compound and not found in presence of other known inhibitors of endocytosis. Structurally related compounds such as tyrphostin 25 and catechol or modulators of AMP kinase activity did neither affect the basal nor the T23-stimulated lactate production by astrocytes. In contrast, the presence of the phosphatase inhibitor vanadate completely abolished the stimulation by T23 of astrocytic lactate production in a concentration-dependent manner. These data suggest that T23-sensitive phosphorylation/dephosphorylation events are involved in the regulation of astrocytic glycolysis.

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