Lensless On-chip Imaging of Cells Provides a New Tool for High-throughput Cell-Biology and Medical Diagnostics

Summary

Lensfree on-chip imaging and characterization of cells is illustrated. This on-chip cell imaging approach provides a compact and cost-effective tool for medical diagnostics and high-throughput cell biology applications, making it especially suitable for resource poor settings.

Abstract

Conventional optical microscopes image cells by use of objective lenses that work together with other lenses and optical components. While quite effective, this classical approach has certain limitations for miniaturization of the imaging platform to make it compatible with the advanced state of the art in microfluidics. In this report, we introduce experimental details of a lensless on-chip imaging concept termed LUCAS (Lensless Ultra-wide field-of-view Cell monitoring Array platform based on Shadow imaging) that does not require any microscope objectives or other bulky optical components to image a heterogeneous cell solution over an ultra-wide field of view that can span as large as ~18 cm². Moreover, unlike conventional microscopes, LUCAS can image a heterogeneous cell solution of interest over a depth-of-field of ~5 mm without the need for refocusing which corresponds to up to ~9 mL sample volume. This imaging platform records the shadows (i.e., lensless digital holograms) of each cell of interest within its field of view, and automated digital processing of these cell shadows can determine the type, the count and the relative positions of cells within the solution. Because it does not require any bulky optical components or mechanical scanning stages it offers a significantly miniaturized platform that at the same time reduces the cost, which is quite important for especially point of care diagnostic tools. Furthermore, the imaging throughput of this platform is orders of magnitude better than conventional optical microscopes, which could be exceedingly valuable for high-throughput cell-biology experiments.

Protocol

Here we discuss the experimental procedures that are involved in LUCAS [1-3]. To illustrate the proof of concept of LUCAS we will describe the imaging process for a whole blood sample.

A. Imaging Set-up

The LUCAS Imaging platform exhibits significant advantages to provide a cost-effective and compact alternative to existing point-of-care cytometry and medical diagnostic tools, especially for resource-limited settings. Rather than detecting the image of the cells, LUCAS instead captures digital holograms of the cells that are created by the interference of the scattered light from each cell with the background light....

Discussion

We have illustrated that the LUCAS platform can accurately count and identify various micro-objects/cells on a chip based on their holographic signatures, and provides a promising tool for point-of-care medical diagnostics and high-throughput cell-biology. In order to accurately process the recorded holographic patterns, we implemented a custom-developed LUCAS decision software. This algorithm, which uses a statistical diffraction image database created by training of LUCAS images, identifies various features of cells wi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Charged couple device (CCD)	KODAK	KAI-11002
Charged couple device (CCD)	KODAK	KAF-39000
Complementary Metal-Oxide-Semiconductor (CMOS)	Micron	MT9P031
Xenon Lamp	Newport Corp.	Cornerstone T260
Vacuum pen	Edmund Scientific	NT57-636
5, 10, and 20 μm Microbeads	Thermo Fisher Scientific, Inc.	4000 Series
RPMI	Fisher Scientific	1640
Pure Eosin Y	Acros Organics	MW=691.85
New Methylene Blue(NMB) Dye	Acros Organics	MW=347.90
Potassium Oxalate Monohydrate	Acros Organics	99.0% Reagent ACS