New tools in cytometry

Shedding Light on Intracellular Proteins using Flow Cytometry

Intracellular protein abundance is routinely measured in mammalian cells using population-based techniques such as western blotting which fail to capture single cell protein levels or using fluorescence microscopy which is although suitable for single cell protein detection but not for rapid analysis of large no. of cells. Flow cytometry offers rapid, high-throughput, multiparameter-based analysis of intracellular protein expression in statistically significant no. of cells at single cell resolution. In past few decades, customized assays have been developed for flow cytometric detection of specific intracellular proteins. This review discusses the scope of flow cytometry for intracellular protein detection in mammalian cells along with specific applications. Technological advancements to overcome the limitations of traditional flow cytometry for the same are also discussed.

Flow Cytometric and Immunohistochemical Follow-Up of Spermatogonial Lineage Commitment

Flow cytometry and immunohistochemistry techniques both determine the target protein by immunolabeling. Flow cytometric analysis quantifies total number of fluorescent labeled cells and qualify sup-populations according to size and granularity. Immunohistochemistry is able to map immune-labeled cells and extracellular matrix components under light and electron microscope by enzyme or fluorescent molecules. Real-time identification, in-time classification, and final plotting of spermatogonial lineage are of crucial importance for monitoring the fertility potential of spermatogonial stem cell microenvironment and predicting progress of spermatogenesis. Here we define the evaluation of mouse male germ cell microenvironment at single cell and whole tissue section levels by using flow cytometric and immunohistochemical approaches.

A Guide to Flow Cytometry: Components, Basic Principles, Experimental Design, and Cancer Research Applications

Flow cytometry (FCM) is a state-of-the-art technique for the qualitative and quantitative assessment of cells and other particles' physical and biological properties. These cells are suspended within a high-velocity fluid stream and pass through a laser beam in single file. The main principle of the FCM instrument is the light scattering and fluorescence emission upon the interaction of the fluorescent particle with the laser beam. It also allows for the physical sorting of particles depending on different parameters. A flow cytometer comprises different components, including fluidic, optics, and electronics systems. This article briefly explains the mechanism of all components of a flow cytometer to clarify the FCM technique's general principles, provides some useful guidelines for the proper design of FCM panels, and highlights some general applications and important applications in cancer research. © 2023 Wiley Periodicals LLC.

In Vitro Exploration of Probiotic Bacteria Interactions with Candida Using Culture Techniques to Model Dysbiotic Conditions in Colonized Tissues

Candida albicans overgrowth at various mucosal sites is an ongoing and complex clinical concern involving interactions with indigenous microbiota and therapeutic or preventive measures superimposed on the pathogen-microbiome interaction. In this paper we describe the use of quantitative flow cytometry (specific to the cytometer’s sample introduction mechanism) to explore the in vitro interaction between Candida albicans, probiotic lactobacilli and a topical vaginal therapeutic. Our central hypothesis was cytometric measurements of co-cultures of yeast and bacteria could provide a useful method for exploring the dynamics of different microbial species in culture, with and without inhibitors. Two commercial products were used as exemplars for this research, a vaginal antimicrobial gel and two species of probiotic lactobacillus intended or oral administration with crystalline bovine lactoferrin to augment the vaginal gel. The cytometer forward channel height parameter distinguished yeast from bacteria in co-culture experiments in the presence of a vaginal therapeutic gel or components of its formulation including EDTA, glycogen, polydextrose as well as the host defense factor, lactoferrin. Flow cytometry showed lactobacilli influenced yeast counts in co-culture, with the technique lending itself to wide-ranging test conditions including organisms, media composition and screening of various antimicrobials. Key findings: The proprietary vaginal gel augmented the effect of lactobacilli, as did EDTA and lactoferrin. Prebiotic compounds also enhanced Candida inhibition by lactobacilli. Propidium iodide (Fluorescence channel 3) discriminated between necrotic and non-necrotic yeast and bacteria in co-cultures under various culture conditions. This research demonstrates the value of flow cytometry to evaluate the population dynamics of yeast and bacteria in co-culture using a proprietary product and its components. We discuss both the limitations of the current study and describe how methods employed here would be transferrable to the investigation of organisms present in defined cultures or at body sites colonized by fungal species and the effects of therapeutics or probiotics on Candida.

Flow cytometry: principles, applications and recent advances

Flow cytometry (FCM) is a sophisticated technique that works on the principle of light scattering and fluorescence emission by the specific fluorescent probe-labeled cells as they pass through a laser beam. It offers several unique advantages as it allows fast, relatively quantitative, multiparametric analysis of cell populations at the single cell level. In addition, it also enables physical sorting of the cells to separate the subpopulations based on different parameters. In this constantly evolving field, innovative technologies such as imaging FCM, mass cytometry and Raman FCM are being developed in order to address limitations of traditional FCM. This review explains the general principles, main applications and recent advances in the field of FCM.

In flow metal-enhanced fluorescence for biolabelling and biodetection

Escherichia coli bacteria were determined by in flow cytometry with laser excitation and fluorescence detection applying ultraluminescent core-shell nanoparticles based on Metal Enhanced Fluorescence (MEF). Core-shell nanoparticles consisted of a 40 nm core modified with a silica spacer grafted with Rhodamine B (RhB). The electromagnetic field in the near field of the core surface enhanced the fluorescence of RhB by plasmonic and fluorophore coupling. The hydrophilic silica spacer allowed the non-covalent interaction with the polar E. coli surface and thus ultraluminescent bacteria biolabelling was developed. Clearly, well defined and bright bacteria imaging was recorded by Laser Fluorescence Microscopy based on the non-covalent deposition of the ultraluminescent nano-emitters. Using these nano-labellers, it was possible to detect labelled E. coli by in flow cytometry. Higher values of Side-scattered light (SSC) and Forward-scattered light (FSC), and number of fluorescent event detections, were observed for labelled bacteria compared to those non-labelled. The sensitivity of the methodology was evaluated by varying bacteria concentration and acceptable analytical figures of merit were determined. Applying this methodology we could quantify E. coli from a synthetic real sample of fortified water. Similar results were obtained by bacteria counting with Laser Fluorescence Microscopy and with a cell-bacteria counter.

Leveraging advances in biology to design biomaterials

Biomaterials have dramatically increased in functionality and complexity, allowing unprecedented control over the cells that interact with them. From these engineering advances arises the prospect of improved biomaterial-based therapies, yet practical constraints favour simplicity. Tools from the biology community are enabling high-resolution and high-throughput bioassays that, if incorporated into a biomaterial design framework, could help achieve unprecedented functionality while minimizing the complexity of designs by identifying the most important material parameters and biological outputs. However, to avoid data explosions and to effectively match the information content of an assay with the goal of the experiment, material screens and bioassays must be arranged in specific ways. By borrowing methods to design experiments and workflows from the bioprocess engineering community, we outline a framework for the incorporation of next-generation bioassays into biomaterials design to effectively optimize function while minimizing complexity. This framework can inspire biomaterials designs that maximize functionality and translatability.

Analysis of polyethylene glycol (PEG) fusion in cultured neuroblastoma cells via flow cytometry: Techniques & optimization

Polyethylene glycol (PEG) has long been used as a membrane fusogen, but recently it has been adopted as a technique for peripheral nerve repair. Vertebrate models using PEG fusion have shown improved outcomes when PEG is applied during repair of severed peripheral nerves. The cellular mechanism of PEG fusion in the peripheral nerve repair model has not previously been assessed via flow cytometry. PEG fusion was assessed in this experiment by dying B35 rat neuroblastoma cells with different color fluorescent labels. The different color cells were combined and PEG was applied in concentrations of 50%, 75% and 100%. The amount of cell fusion was assessed via flow cytometry as the percentage of double positive cells. Results showed increasing fusion and decreasing viability with increasing concentrations of PEG.