Name: Quality Check (QC) of the TCPP Beads by Flow Cytometry
Uploaded: 2023-03-24T12:55:00
Description: Watch this Scientific Journal Video about Quality Check QC of the TCPP Beads by Flow Cytometry at JoVE.com

quality check (qc) of the tcpp beads by flow cytometry

Porphyrin-Modified Beads in Flow Cytometry

Porphyrins have been of interest for many years in the biomedical field owing to their fluorescence and tumor-targeting properties1,2,3. Therapeutic applications such as photodynamic therapy (PDT) and sonodynamic therapy (SDT) entail the systemic administration of a porphyrin to a cancer patient, the accumulation of the drug in the tumor, and the localized exposure of the tumor to a laser light of a specific wavelength or ultrasound. The exposure to laser light or ultrasound leads to the generation of reactive oxygen species by the porphyrin and subsequent cell death4,5. In photodynamic diagnosis (PDD), porphyrin fluorescence is used to distinguish cancer cells from normal cells6. In this context, protoporphyrin IX, a natural fluorescent porphyrin that accumulates in tumors upon the systemic or local injection of its precursor, 5-aminolevulinic acid (5-ALA), is used to identify gastrointestinal stromal tumors, bladder cancer, and brain cancer7,8. More recently, 5-ALA treatment was explored as an approach to detect minimal residual disease in multiple myeloma9. Our laboratory has been using the tetraaryl porphyrin TCPP (5,10,15,20-tetrakis-(4-carboxyphenyl)-21,23H-porphine) for its ability to selectively stain lung cancer cells and cancer-associated cells in human sputum samples, which is a property that has been exploited in slide-based and flow cytometric diagnostic assays10.
Some porphyrins are bifunctional in that they can be used as therapeutic and diagnostic agents2,11. In biomedical research, such bifunctional porphyrins are used to evaluate how their ability to selectively target and kill cancer cells is a function of their structure as well as how it is affected by the presence of other compounds12,13,14,15,16. Both the cellular uptake of porphyrins and their cytotoxicity can be measured on a flow cytometric platform in a high-throughput manner. The absorption and emission spectra of fluorescent porphyrins are complex, but most flow cytometric platforms are equipped to correctly identify them. The absorption spectrum of fluorescent porphyrins is characterized by a strong absorption band in the 380-500 nm range, known as the Soret band. Two to four weaker absorption bands are generally observed in the 500-750 nm range (Q bands)17. A blue&#160;488 nm laser, present in most flow cytometers, or a violet laser (405 nm) can generate light of the appropriate wavelength to excite porphyrins. The emission spectra of porphyrins typically display peaks in the 600-800 nm range18, which results in very little spectral overlap with fluorescein isothiocyanate or phycoerythrin (PE) fluorophores but considerable overlap with other often-used fluorophores, such as allophycocyanin (APC), as well as tandem fluorophores, such as PE-Cy5 and others. Therefore, when using porphyrins in multi-color flow cytometry assays, single-fluorophore controls are essential to adequately correct the spillover of fluorescence in channels other than the one designated to measure the porphyrin&#39;s fluorescence.
Ideally, the single-fluorophore controls used to calculate the spillover matrix for a panel of fluorophores (also called &#34;compensation controls&#34;) should consist of the same cell type(s) as the sample. However, using the sample for this purpose is not optimal if there is very little sample to begin with or if the target population within the sample is very small&#160;(for example, if one wants to look at minimal residual disease or cancer cells at the early stages of the disease). A useful alternative to cells is beads coupled with the same fluorophore that is used to analyze the sample. Many such beads are commercially available; these beads are either prelabeled with the desired fluorophore (prelabeled fluorophore-specific beads)19,20, or a fluorescently labeled antibody can be attached to them (antibody capture beads)20,21. While commercial compensation beads are available for many fluorophores, such beads are unavailable for porphyrins, despite their increasing use in basic and clinical research.
In addition to sample preservation and appropriately sized positive versus negative populations, the other advantages of using beads as compensation controls are the ease of preparation, low background fluorescence, and excellent stability over time22. The potential disadvantage of using beads as a compensation control is that the emission spectrum of the fluorescent antibody captured on beads may differ from that of the same antibody used to label the cells. This may be of specific importance when using a spectral flow cytometer20. Therefore, the development of beads as a compensation control needs to be performed on the flow cytometer that will be used for the assay for which the beads are developed. Moreover, the development of the beads needs to include a comparison with cells labeled with the same fluorescent staining reagent.
Here, we describe the preparation of TCPP amine-functionalized polystyrene compensation beads, whose median fluorescence intensity in the detection channel was comparable to that of TCPP-labeled cells in sputum, and their use as compensation controls for flow cytometry. The autofluorescence of equivalent, non-functionalized beads was sufficiently low for their use as negative fluorescence compensation controls. In addition, these beads demonstrated stability in storage for nearly 1 year.

Author Spotlight: Porphyrin-Modified Beads for Use as Compensation Controls in Flow Cytometry  

Porphyrin-Modified Beads for Use as Compensation Controls in Flow Cytometry

We developed polystyrene beads modified with the porphyrin TCPP as compensation controls and multicolor flow cytometry. The beads used in this protocol have fluorescence intensity comparable to TCPP stain cells and still passed through the flow cytometer. We accomplished that and are currently working on better methods to remove the particulate byproduct.Porphyrin-modified compensation beads were preferable to TCPP stained cells as compensation controls. These speeds were stable over months without significant loss of fluorescence. Porphyrins are known to stain cancer cells selectively.The research combines the selectivity of porphyrins with quantitative flow cytometry as a powerful platform for high-throughput analysis of human samples.

Watch this Scientific Journal Video about Quality Check QC of the TCPP Beads by Flow Cytometry at JoVE.com

Quality Check (QC) of the TCPP Beads by Flow Cytometry  

Begin the quality check of the beads labeled as meso-tetra 4-carboxyphenyl porphine or TCPP beads in the flow cytometer by running and collecting 10, 000 events of the rainbow beads. Then perform a rinse with water and collect 10, 000 events of the TCPP negative beads. After rinsing with water again, collect 10, 000 events of the TCPP positive beads.Then perform a one minute water rinse before appropriate cleaning and shut down the flow cytometer. A representative outcome of the TCPP bead labeling process determined by flow cytometry is shown here with a standardized profile of rainbow beads. These beads serve as quality checks for standardizing the laser voltages to detect TCPP.The light scatter profile of amine functionalized polystyrene TCPP labeled beads was observed. The light scatter profile of non-functionalized beads was used as a negative bead control to calculate the compensation matrix. The population indicated by the red rectangle in the TCPP labeled beads was absent in the unlabeled bead suspension representing that the TCPP related particulates were not formed in the absence of TCPP and EDC.The fluorescence intensity of the labeled beads selected by the black gate was several logs higher than that of the unlabeled beads.

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Chemistry

Flow cytometry can rapidly characterize and quantify diverse cell populations based on fluorescence measurements. The cells are first stained with one or ...