Dual-modality digital holographic and polarization microscope to quantify phase and birefringence signals in biospecimens with a complex microstructure

Abstract

Optical phase and birefringence signals occur in cells and thin, semi-transparent biomaterials. A dual-modality quantitative phase and polarization microscope was designed to study the interaction of cells with extracellular matrix networks and to relate optical pathlength and birefringence signals within structurally anisotropic biomaterial constructs. The design was based on an existing, custom-built digital holographic microscope, to which was added a polarization microscope utilizing liquid crystal variable retarders. Phase and birefringence channels were calibrated, and data was acquired sequentially from cell-seeded collagen hydrogels and electrofabricated chitosan membranes. Computed phase height and retardance from standard targets were accurate within 99.7% and 99.8%, respectively. Phase height and retardance channel background standard deviations were 35 nm and 0.6 nm, respectively. Human fibroblasts, visible in the phase channel, aligned with collagen network microstructure, with retardance and azimuth visible in the polarization channel. Electrofabricated chitosan membranes formed in 40 µm tall microfluidic channels possessed optical retardance ranging from 7 to 11 nm, and phase height from 37 to 39 µm. These results demonstrate co-registered dual-channel acquisition of phase and birefringence parameter maps from microstructurally-complex biospecimens using a novel imaging system combining digital holographic microscopy with voltage-controlled polarization microscopy.

Programmable Physical Properties of Freestanding Chitosan Membranes Electrofabricated in Microfluidics

“…The interfacial electrofabrication of chitosan membrane(s) was conducted following previous works with modifications [ 35 , 44 , 45 ]. Two (for single-aperture PDMS device) or three (for three-channel PDMS device) metal couplers (22 ga × 0.3 inch, Instech Laboratories, Inc., Plymouth Meeting, PA, USA) were used as both capillary connectors and distal electrodes for the interfacial electrofabrication.…”

Accurate phase reconstruction in digital holography microscopy using Fresnel biprism

“…Digital holographic microscopy (DHM) has witnessed widespread applications in different application areas, delivering remarkable advantages in high-resolution and non-invasive imaging of cells and tissues, 1, 2 disease diagnoses, 3,4 polarimetric study, 5,6 surface topography, 7,8 etc. DHM is based on the principle of optical interferometry, which involves the digital recording of the interference pattern formed by the interaction of scattered light from the sample, known as the object beam, with a well-defined reference beam, using a digital image sensor.…”

pyDHM: A Python library for applications in digital holographic microscopy

“…Digital holographic microscopes (DHMs) have been widely applied in material and biological applications. For instance, among many biological and biomedical applications [ 1 – 4 ], DHM systems are used for analyzing cells and tissues [ 4 – 8 ], as well as disease diagnosis and screening [ 4 , 9 – 11 ] and assessing the polarimetric properties of biomedical samples[ 12 , 13 ]. In material science, DHM systems have been used to measure MEMs [ 14 – 19 ], detect and characterize defects [ 20 ], as well as to characterize surface topography [ 21 – 23 ].…”