Scientists from Indian Institute of Science (IISc) and Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have demonstrated a new type of 3 dimensional imaging platform, called iLIFE, that provide detailed images of biological specimen flowing in a fluid.
iLIFE stands for integrated light-sheet imaging and flow based enquiry. Light-sheet microscopy is a technique used to image fast moving or imaging-sensitive biological samples. Here the biological sample is made to pass through a light-sheet—a literal sheet made of light, while a detector or a camera placed perpendicular to the sheet, records the cross sections of the biological sample as it moves through the light-sheet. The detector can then provide a complete 3D image of the sample by merging the cross sections together. This method also avoids any affects of the light on the specimen, by illuminating only a single plane of the specimen at a time.
For iLIFE, the scientists used a “diffraction-limited light-sheet, with a large field-of-view, to optically section the specimens flowing through the microfluidic channel”. They then optimized the parameters of set-up; like the intensity of the light used, width and thickness of the light-sheet, the width and flow rate of the microfluidic channel, and the exposure time and frame rate of the camera. Once the parameters were optimized, the setup could then be used to cross sectional imaging of the biological specimen as the moved through the optimized microfluidic channel, illuminated by a light-sheet. The cross sectional images are then used to create a complete 3D image reconstruction of the biological specimen. Next, a maximum likelihood technique was developed and optimized to the iLIFE imaging system, making it an efficient system at recording the samples as it flowed fast through the light sheet.
The system has already been used to screen and image biological specimen of varying sizes, including single cell organisms (like HeLa) and multi cellular organisms, like Caenorhabditis elegans, commonly called roundworm which can grow to a size of around 1 millimeter.
The authors foresee a range of 3D imaging applications for the iLIFE system in the future, in fields like structural biology and biophysics, with their demonstration being the first step.