Name: correlative light- and electron microscopy using quantum dot nanoparticles
Uploaded: 2016-08-07T14:00:00
Description: Watch this Scientific Journal Video about Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles at JoVE.com

The authors wish to acknowledge the support of Xiao Juan Wu (Immunohistochemistry Laboratory) and the Department of Anatomical Pathology, Sydney South West Pathology Service (SSWPS), NSW Health Pathology, Liverpool, New South Wales, Australia.

1. Tissue Dissection and Fixation
<ol>
	<li>Tissue Dissection
	<ol>
		<li>Dissect tissue pieces from a surgically resected tumor specimen or tissue biopsy. 
		Note: The tissue used in this study was routinely fixed in formalin but fresh tissue is also suitable. We selected an area confirmed and reported by an anatomical pathologist to contain somatostatinoma tumor after routine histological staining and anti-somatostatin immunostaining (not shown).</li>
		<li>Use tissue pieces no larger than appro...

<ol>
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This study has demonstrated the potential utility of QDs as universal probes for CLEM studies. The 585 nm QD nanoparticles used showed bright and stable fluorescence when viewed by widefield light microscopy and were readily observed by TEM. A previous study by one of the present authors has shown QDs also to be suitable for super-resolution light microscopy7. Their photostability was particularly useful for extended viewing periods and long imaging exposures. QDs can also be used for multiplex immunohistochem...

Correlative light- and electron microscopy (CLEM) is a powerful approach for the analysis of transient dynamic events1, rare events2, 3 and complex systems4. There are many different technical permutations available5 depending on the question being asked however a common requirement is that the same structure in a single sample6 is imaged by multiple microscopy modalities. Our particular approach to CLEM was developed for the study of archival human pathology tissue and the case used here has been well characterized and published previously7. The aim was firstly, to maximize the analytical data from a single biopsy or surgical sample and secondly, to use fluorescence light microscopy to help clarify the context of the immunocytochemical labeling pattern seen at the ultrastructural level.
Quantum dot nanocrystals (QDs) offer the potential of a universal marker system able to be viewed by both, fluorescence light microscopy and electron microscopy8, 9, 10. Their crystalline core structure allows QDs of different sizes to generate a wide range of fluorescence emission peaks when excited by light at wavelengths far from their emission spectra11. Their atomic weight is sufficient to yield electron density that is detectable by transmission electron microscopy, scanning transmission electron microscopy (STEM) or field emission scanning electron microscopy. They are particularly suited to immunocytochemical studies as even single QDs may be observed giving an ultimate sensitivity of one QD per target molecule12. Furthermore, depending on the QD used they can possess an individual elemental signature suitable for mapping.
Human pathology samples offer significant benefits for translational biomedical research. Surgical tissue and biopsy samples are routinely submitted for biobanking and with appropriate ethics clearances can be accessed for research studies. Human tissue does not have issues of relevance or interpretation that can occur in animal or in vitro models of disease. However, specimen preparation of pathology samples often is not optimal. There can be delay in tissue being placed in fixative, inappropriate fixative used such as formalin rather than glutaraldehyde for TEM and inappropriate sampling. CLEM methods have the potential to optimize the diagnostic and prognostic information available from a single human sample. However, some newly developed correlative approaches such as those employing mini Singlet Oxygen Generator (miniSOG) are not available for use in pathology due to the need for the tag to be genetically encoded into the cell of interest13. For this reason we have explored the utility of QD labeling of routinely prepared TEM tissue for correlative immunocytochemical studies. QDs applied to etched epoxy or acrylic resin sections from lightly aldehyde fixed biopsy and tissue samples offer the possibility of obtaining correlative fluorescence light microscopy and TEM data from a single sample.

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			<td height="21" style="height:21px;width:255px;">Qdot 585 Streptavidin Conjugate&#160;</td>
			<td style="width:117px;">Invitrogen</td>
			<td style="width:119px;">Q10113MP</td>
			<td></td>
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			<td height="42" style="height:42px;width:255px;">Biotinylated goat anti-rabbit IgG antibody</td>
			<td style="width:117px;">Sigma</td>
			<td style="width:119px;">B7389-1ML</td>
			<td></td>
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			<td height="21" style="height:21px;width:255px;">Glutaraldehyde 50%</td>
			<td style="width:117px;">EMS</td>
			<td style="width:119px;">16320</td>
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			<td height="21" style="height:21px;width:255px;">PBS &#34;Dulbecco A&#34;</td>
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			<td height="21" style="height:21px;width:255px;">Transmission electron microscope</td>
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			<td></td>
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			<td height="21" style="height:21px;width:255px;">Fluorescence light microscope</td>
			<td style="width:117px;">Carl Zeiss</td>
			<td style="width:119px;">Axioscope A1</td>
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			<td height="42" style="height:42px;width:255px;">TEM camera control software</td>
			<td style="width:117px;">Soft Imaging System</td>
			<td style="width:119px;">AnalySIS</td>
			<td>Version 3.0</td>
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</table>

correlative light- and electron microscopy using quantum dot nanoparticles

A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using widefield fluorescence light microscopy and transmission electron microscopy (TEM). To demonstrate the protocol we have immunolabeled ultrathin epoxy sections of human somatostatinoma tumor using a primary antibody to somatostatin, followed by a biotinylated secondary antibody and visualization with streptavidin conjugated 585 nm cadmium-selenium (CdSe) quantum dots (QDs). The sections are mounted on a TEM specimen grid then placed on a glass slide for observation by widefield fluorescence light microscopy. Light microscopy reveals 585 nm QD labeling as bright orange fluorescence forming a granular pattern within the tumor cell cytoplasm. At low to mid-range magnification by light microscopy the labeling pattern can be easily recognized and the level of non-specific or background labeling assessed. This is a critical step for subsequent interpretation of the immunolabeling pattern by TEM and evaluation of the morphological context. The same section is then blotted dry and viewed by TEM. QD probes are seen to be attached to amorphous material contained in individual secretory granules. Images are acquired from the same region of interest (ROI) seen by light microscopy for correlative analysis. Corresponding images from each modality may then be blended to overlay fluorescence data on TEM ultrastructure of the corresponding region.

The somatostatinoma tumor specimen used for this study comprised tumor cells forming ductal structures mixed with collagenous stomal tissue. By fluorescence light microscopy, individual tumor cells that contained abundant secretory granules showed positive labeling for the somatostatin hormone. Nuclei appeared as dark holes with minimal non-specific labeling detectable (Figure 1). At low magnifications, variably intense granular orange fluorescence was seen in the cytopla...

Watch this Scientific Journal Video about Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles at JoVE.com

Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles

A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of epoxy embedded human pathology tissue. We employ commercial antibody fragment conjugated QDs that are visualized by widefield fluorescence light microscopy and transmission electron microscopy.

A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using ...

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