Nanoparticle-sensitized photoporation enables inflammasome activation studies in targeted single cells

Inflammasomes are multi-protein complexes that guard against cellular stress and microbial infections. Inflammasome activation studies frequently require delivery of pathogen-derived virulence factors into the cytosol of macrophages and other innate immune cells. This is a challenging requirement since primary macrophages are difficult-to-transfect, especially when it comes to the intracellular delivery of proteins. Here, we report on the use of nanoparticle-sensitized photoporation as a promising upcoming intracellular delivery technology for delivering proteins of various molecular weights into the cytosol of primary macrophages. While 60-70 nm gold nanoparticles are the most commonly used sensitizing nanoparticles for photoporation, here we find that 0.5 μm iron oxide nanoparticles perform markedly better on primary macrophages. We demonstrate that LFn-FlaA or lipopolysaccharides can be delivered in primary macrophages resulting in activation of the NLRC4 or the non-canonical inflammasome, respectively. We furthermore show that photoporation can be used for targeted delivery of these toxins into selected cells, opening up the possibility to study the interaction between inflammasome activated cells and surrounding healthy cells. Taken together, these results show that nanoparticle-sensitized photoporation is very well suited to deliver pathogenic virulence factors in primary macrophages, thus constituting an effective new enabling technology for inflammasome activation studies.