Making thousands of photo’s of microorganisms in minutes with nanosecond exposure time is a challenge. CytoSense offers an unconventional combination of high resolution imaging in a wide flowcell. No changing of flow cells or lenses to switch from small to larger particles is required. Special aplanatic18 x magnification (0.4NA) lenses yield an in-focus aberration free optical resolution (≤1µm) better than alternative 20x systems, as shown by doublets of microspheres of 0.93 µm.
Details of cells, such as spines of Desmodesmium, or groove and pore patterns in diatoms are visible, with good resolution over the whole field-of-view. This allows imaging of larger particles like diatoms, chains, colonies and microzooplankton with fine detail of their in-focus parts.
The flow cell is wide enough (> 1 mm2) to allow unhampered entry of larger particles, whith a camera sensor covering a large area of the flowcell.
Unmanipulated bright field imaging yields high resolution images. The intrisically narrow depth-of-focus reveals the 3D spatial structure of larger cells and organisms, like a cutaway picture. The CytoSense photo of the Tinitinnid shows the cell outline and peduncle clearly inside the cross section of the lorica. With images of multiple individuals collected, a more complete picture can be constructed, as shown with the Volvox colonies photo’s.
Plankton particles are low refractive index particles, meaning low contrast. The pigmented areas show up dark but other parts of the cells are difficult to see in normal bright field microscopy. CytoSense uses Köhler type oblique illumination to enhance contrast, as shown by the image of a Dolychospermium trichome with a surrounding mucilage sheath clearly visible.