Commonly used sample introduction systems for inductively coupled plasma mass spectrometry (ICP-MS) are generally not well-suited for single particle ICP-MS (spICP-MS) applications due to their high sample requirements and low efficiency. In this study, the first completely 3D-printed, polymer SIS was developed to facilitate spICP-MS analysis. The system is based on a microconcentric pneumatic nebulizer and a single-pass spray chamber with an additional sheath gas flow to further facilitate the transport of larger droplets or particles. The geometry of the system was optimized using numerical simulations. Its aerosol characteristics and operational conditions were studied via optical particle counting and a course of spICP-MS measurements, involving nanodispersions and cell suspensions. In a comparison of the performance of the new and the standard (quartz microconcentric nebulizer plus a double-pass spray chamber) systems, it was found that the new sample introduction system has four times higher particle detection efficiency, significantly better signal-to-noise ratio, provides ca. 20% lower size detection limit, and allows an extension of the upper limit of transportable particle diameters to about 25 µm.

Photosynthetic microorganisms enable the conversion of sunlight into electricity via exoelectrogenesis - the export of electrons to the extracellular environment. However, current strategies to enhance this process often rely on nutrient deprivation, such as iron limitation, which inevitably compromises the photosynthetic apparatus and arrests cell growth. Here, we investigate the physiological basis of the inherently enhanced exoelectrogenesis in the green microalga Parachlorella kessleri MACC-38 - a strain that exhibits tenfold higher electric current production than the model alga Chlamydomonas reinhardtii without requiring stress treatments. We propose that upon exposure to ferricyanide as an extracellular electron sink, the oxidative pentose phosphate pathway (OPPP) is upregulated - specifically via glucose-6-phosphate dehydrogenase - to supply NADPH as the primary reducing power for exoelectrogenesis. Furthermore, we suggest that while the OPPP supports electron export, it simultaneously induces a transient over-reduction of the photosynthetic electron transport chain. Our data indicates that chlororespiration, mediated by the plastid terminal oxidase (PTOX), is essential to maintain redox homeostasis by re-oxidizing the plastoquinone pool, while sustaining exoelectrogenesis. These results may find application in the rational design of highly exoelectrogenic microorganisms with synthetic biology tools for sustainable, high-efficiency biophotovoltaic systems.