multimodal-quantitative-phase-imaging-with-digital-holographic

Multimodal Quantitative Phase Imaging with Digital Holographic Microscopy Accurately Assesses Intestinal Inflammation and Epithelial Wound Healing

The incidence of inflammatory bowel disease, i.e., Crohn&#39;s disease and Ulcerative colitis, has significantly increased over the last decade. The ...

University of Münster

Digital holographic microscopy (DHM) enables a quantitative multifocus phase contrast imaging that has been found suitable for technical inspection and quantitative live cell imaging. The combination of DHM with fast and robust autofocus algorithms enables subsequent automated focus realignment by numerical propagation of the digital holographically reconstructed object wave. In combination with a calibrated optical imaging system, the obtained propagation data quantify axial displacements of the investigated sample. The evaluation of quantitative DHM phase contrast images also enables an effective determination of lateral cell displacements. Thus, 3-D displacement data are provided. Results from investigations on sedimenting red blood cells and HT-1080 fibrosarcoma cells in a collagen tissue model demonstrate that DHM enables marker-free automated quantitative dynamic 3-D cell tracking without mechanical focus adjustment.

Automated three-dimensional tracking of living cells by digital holographic microscopy.

Digital holographic microscopy (DHM) enables quantitative multifocus phase contrast imaging for nondestructive technical inspection and live cell analysis. Time-lapse investigations on human brain microvascular endothelial cells demonstrate the use of DHM for label-free dynamic quantitative monitoring of cell division of mother cells into daughter cells. Cytokinetic DHM analysis provides future applications in toxicology and cancer research.

Label-free quantitative cell division monitoring of endothelial cells by digital holographic microscopy.

The intracellular refractive index is an important parameter that describes the optical density of the cytoplasm and the concentration of the intracellular solutes. The refractive index of adherently grown cells is difficult to access. We present a method in which silica microspheres in living cells are used to determine the cytoplasm refractive index with quantitative phase microscopy. The reliability of our approach for refractive index retrieval is shown by data from a comparative study on osmotically stimulated adherent and suspended human pancreatic tumor cells. Results from adherent human fibro sarcoma cells demonstrate the capability of the method for sensing of dynamic refractive index changes and its usage with microfluidics.

Sensing dynamic cytoplasm refractive index changes of adherent cells with quantitative phase microscopy using incorporated microspheres as optical probes.

Inflammatory bowel diseases including Crohn's disease and ulcerative colitis resemble a large burden for patients due to the chronic course of disease. Therefore, there is an urgent need to explore new potential drugs and to develop new treatment options. Usually, evaluation of therapeutic potential is performed in murine models of colitis with the challenge of a valid assessment of the ongoing inflammation and the therapeutic response. Digital holographic microscopy (DHM) enables stain-free quantitative phase contrast imaging and provides tissue density assessment by measuring optical path length delay and accordingly refractive index. Dextran sodium sulphate induced colitis was performed in C57Bl/6 wildtype mice and colonic sections were examined by histological analyses and by DHM. This study proves the average refractive index to be an accurate marker to distinguish between different layers of the intestinal wall, such that the stroma is characterized by the highest value and the submucosa by the lowest. Furthermore, DHM allows a reliable detection of inflamed colonic segments (P < 0.001) with a strong correlation between the severity of inflammation and the refractive index, especially in the submucosa (R(2) = 0.639). In conclusion, this approach opens a novel diagnostic option for optical quantification of inflammation in murine models of colitis. Our results pave the way to further studies to elucidate the translational potential of DHM for the clinical management of patients with inflammatory bowel diseases.

Digital holographic microscopy quantifies the degree of inflammation in experimental colitis.

Impaired epithelial wound healing has significant pathophysiological implications in several conditions including gastrointestinal ulcers, anastomotic leakage and venous or diabetic skin ulcers. Promising drug candidates for accelerating wound closure are commonly evaluated in in vitro wound assays. However, staining procedures and discontinuous monitoring are major drawbacks hampering accurate assessment of wound assays. We therefore investigated digital holographic microscopy (DHM) to appropriately monitor wound healing in vitro and secondly, to provide multimodal quantitative information on morphological and functional cell alterations as well as on motility changes upon cytokine stimulation. Wound closure as reflected by proliferation and migration of Caco-2 cells in wound healing assays was studied and assessed in time-lapse series for 40 h in the presence of stimulating epidermal growth factor (EGF) and inhibiting mitomycin c. Therefore, digital holograms were recorded continuously every thirty minutes. Morphological changes including cell thickness, dry mass and tissue density were analyzed by data from quantitative digital holographic phase microscopy. Stimulation of Caco-2 cells with EGF or mitomycin c resulted in significant morphological changes during wound healing compared to control cells. In conclusion, DHM allows accurate, stain-free and continuous multimodal quantitative monitoring of wound healing in vitro and could be a promising new technique for assessment of wound healing.

Quantitative stain-free and continuous multimodal monitoring of wound healing in vitro with digital holographic microscopy.

Self-interference digital holographic microscopy (DHM) has been found particular suitable for simplified quantitative phase imaging of living cells. However, a main drawback of the self-interference DHM principle are scattering patterns that are induced by the coherent nature of the laser light which affect the resolution for detection of optical path length changes. We present a simple and efficient technique for the reduction of coherent disturbances in quantitative phase images. Therefore, amplitude and phase of the sample illumination are modulated by an electrically focus tunable lens. The proposed method is in particular convenient with the self-interference DHM concept. Results from the characterization of the method show that a reduction of coherence induced disturbances up to 70 percent can be achieved. Finally, the performance for enhanced quantitative imaging of living cells is demonstrated.

Article	Year
Automated three-dimensional tracking of living cells by digital holographic microscopy. Journal of biomedical optics\| PubMed ID: 19256706	2009
Label-free quantitative cell division monitoring of endothelial cells by digital holographic microscopy. Journal of biomedical optics\| PubMed ID: 20615011	2010
Sensing dynamic cytoplasm refractive index changes of adherent cells with quantitative phase microscopy using incorporated microspheres as optical probes. Journal of biomedical optics\| PubMed ID: 23085920	2012
Digital holographic microscopy quantifies the degree of inflammation in experimental colitis. Integrative biology : quantitative biosciences from nano to macro\| PubMed ID: 23328993	2013
Quantitative stain-free and continuous multimodal monitoring of wound healing in vitro with digital holographic microscopy. PloS one\| PubMed ID: 25251440	2014
Enhanced quantitative phase imaging in self-interference digital holographic microscopy using an electrically focus tunable lens. Biomedical optics express\| PubMed ID: 25574433	2014

Steffi Ketelhut

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