PT  - JOURNAL ARTICLE
AU  - Stephen Grant
AU  - Kyle Richford
AU  - Heidi Burdett
AU  - David McKee
AU  - Brian R. Patton
TI  - Low-cost, open-access refractive index mapping of algal cells using the transport of intensity equation
AID  - 10.1101/640755
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 640755
4099  - http://biorxiv.org/content/early/2019/05/17/640755.short
4100  - http://biorxiv.org/content/early/2019/05/17/640755.full
AB  - Phase contrast microscopy allows stain free imaging of transparent biological samples. One technique, using the transport of intensity equation (TIE), can be performed without dedicated hardware by simply processing pairs of images taken at known spacings within the sample. The resulting TIE images are quantitative phase maps of unstained biological samples. Therefore, spatially resolved refractive index information can also be determined.Using low-cost, open-source hardware, we applied the TIE to living algal cells to measure their refractive index. We obtained refractive index values that were repeatable within species and differed by distinct amounts depending on the species being measured. We suggest TIE imaging as a method of discrimination between different algal species and, potentially, non-biological materials, based on refractive index. Potential applications in biogeochemical modelling and climate sciences are suggested.