Bio‐Engineering Yeast Cells Biolenses by Reshaping Intracellular Vacuoles

An intriguing field of research has recently emerged in which biological cells can be demonstrated to behave as photonics devices, such as optical microlenses. This research highlights yeast cells as promising candidates for engineering biolenses with customizable focal properties. Typically serving as positive biolenses due to their quasi-spherical shape and positive refractive index (RI) contrast, yeast cells can achieve a negative lensing effect by manipulating their intracellular content, without altering their overall morphology. In fact, it shows that exposure to hypotonic conditions induces the formation of a large, roundish vacuole with lower RI values with respect to the surrounding cytoplasm, thus altering the cell's optical properties. This behavior is investigated by using 3D RI tomograms obtained through a holo-tomographic phase imaging flow cytometry system, demonstrating that the anisotropic nature of yeast cells results in focal properties dependent on their specific orientations in respect to the incident light. Furthermore, Zemax OpticStudio is utilized to perform comprehensive assessments for optical design analysis of the obtained cell biolenses. The methods described here and the related results represent a pioneering investigation of biological cells' metamorphoses via intracellular content manipulation for biolens applications. Achieving tunable biolens effects in single cells by altering their internal structures is feasible. Particularly, hypotonic conditions prompt reshaping of intracellular vacuoles in yeast cells. Utilizing Tomographic Phase Imaging Flow Cytometry, 3D refractive index tomograms of suspended cells are captured, thus enabling in-depth characterizations. Following acquisition, the resulting focal properties are analyzed using digital holography and an optical simulation software. image