Fluorescent products have many useful functions in biological studies. The following is a summary of the potential uses.
1. Permeability Studies
Biological permeability is the passage of substances through a biological membrane or a barrier which can either be selectively or indiscriminately permeable. The permeability is affected by substance properties such as a polarity, hydrophobicity, charge, size, and shape (1). The properties of the membrane or barrier itself are also important. Fluorescent dextran derivatives or other polysaccharides of various sizes can be used for permeability and transport studies in cells, tissues, and animals. Fluorescent measurements can also provide qualitative data in real time with use of intravital fluorescence microscopy. More specifically, they are ideal for many types of studies such as vascular permeability (2,3), glomerular filtration (4–6), and evaluating the blood-brain barrier (7), internal tissue (14,15), neural stem cells (16), renal tissue (17), keratin permeability (8), and the epithelial (9–11) and mucosal (12,13) layers. In addition, fluorescent dextran derivatives have been used to study microcirculation, the smallest level of blood circulation in the micro vessels present in all organ tissues (21), for applications such as leukocyte adhesion, macromolecular leakage (22), and intestinal mucosal microcirculation (23). Polysaccharides conjugated with carboxymethyl (CM)-or diethylaminomethyl (DEAE)-groups are useful for studying the effects of charge on permeability (18–20).
2. Sugar Metabolic Studies
In nature, trehalose can be found in animals, plants, and microorganisms. Fluorescein isothiocyanate trehalose (FITC-Trehalose), which is a fluorescent derivative of trehalose, proves to be a useful functional and imaging probe in studies of trehalose uptake by culture cells (1) or bacteria (2), and sugar metabolization in bacteria (3).
3. pH Visualizations
Fluorescent dyes have the ability of changing color in response to pH-changes, utilized for measuring pH in living cells. Changes in cellular pH can reflect a range of physiological processes, including muscle contraction, endocytosis, cell proliferation, apoptosis, and ion transport (1). Compared to microelectrode techniques, fluorescent pH-indicators also have greater spatial sampling capability (1). Fluorescent pH-indicators can be coupled with macromolecules, such as dextran. The advantage of using fluorescent dextran derivatives is that the molecules can be accumulated into specific intracellular compartments and don’t bind to cellular proteins (2). Dextran derivatives involving dye-entities like FITC, TRITC or Texas Red™ (3) can be combined in a single dextran in order to achieve more accurate results for a more information-dence readout.
Dextran derivatives can be incorporated in hydrogels which can be considered matrices for the controlled release of drug molecules. Ongoing research aimed at improving the fabrication efficiency as well as the drug delivery capability of various anti-cancer drugs can utilize dextran derivatives as they exhibit high hydrogel formation capacity, low toxicity combined with high biocompatibility, and biodegradability (1). Fluorescent dextran derivatives, blue dextran, and other polysaccharides have been used for studying drug delivery with hydrogel scaffolds (2), drug release with microneedles arrays (3,4), drug loading features of nano-erythrocytes (5), and biphasic pulsatile drug release (6).
5. Matrix Preparation
CM-dextran and CM-polysucrose can be used as a matrix component in order to prepare surfaces for cell adherence and culture in studies of magnetic nanoparticles targeted to cancer cells (1) and P-selectin (2), electrochemical immunoassays (3), regulation of scaffold cell adhesion (4) and enzyme immobilization (5), and more. CM-dextran can also be used for the construction of polymer membranes. Phenyl-dextran can use for coating medical devices to impart a more hydrophilic character.