3-D printed aseptic injection system for capillary electrophoresis

Capillary electrophoresis (CE) is a powerful tool to separate complex mixtures which includes mixtures of intact and viable organisms, a promising new area to improve analysis of microbiomes. CE requires an injection block or autosampler to load samples for separation. Neither of these sample introduction systems offer ease-of-use and cost efficiency with aseptic injection for analysis of microbiota. We developed a manual injection block to facilitate sterile analysis of organisms via CE. The system replaces traditional clamped blocks with an internally threaded collar. The capillary and electrode are recessed within the collar, preventing external contamination while preserving means to sterilize between analyses. A cylindrical vial holder is externally threaded and accommodates an autoclavable 200 μL polypropylene tube for sample, background electrolyte, and wash solutions. We evaluated performance of the new injector using capillary zone electrophoresis (CZE) on a CE system with laser-induced fluorescence detection of fluorescein and subsequent injection of viable Escherichia coli. Analyses of fluorescence produce a linear response across at least four orders of magnitude for hydrodynamically injected samples with LLOD of 6 pM and electrokinetically injected samples with LLOD of 8 pM. Performance for organismal separations coupled with automated fraction collection was evaluated using a standard laboratory strain of E. coli. We demonstrate four-fold improvement in zone width of E. coli using the new injector. Migration times for E. coli were comparable to previous designs; 133.7 ± 2.8 s and 129.8 ± 2.8 s, respectively.