FITC-dextran

Fig. 16 Contours of fluorescent intensity in frozen sections of the rabbit eye following 15 pL injection of marker solution in the central vitreous cavity injection was conducted through the superior rectus muscle 15 hours following injection of 0.2% sodium fluorescein 14 days following injection of 0.1% FITC-dextran, molecular weight 66,000. (From Ref. 230.)... 

Figure 4 Anti-angiogenic activity of 1 and 3. (A) Angiographic images of the developmental CAM (EDD 9) treated with 0.9% NaCl (control) and 1 and 3 (150 pM/day). The vasculature is visualized by FITC-dextran fluorescence angiography (25 mg/kg, 20 kDa, XCK = 470 nm, Xem = 520 nm).

Morimoto et al. [33] demonstrated that the ocular absorption of hydrophilic compounds over a wide range of molecular weights could be increased by 2 and 10 mM sodium taurocholate and sodium taurodeoxycholate in a dose-dependent manner. The compounds were glutathione (307 Da), 6-carboxyfluorescein (376 Da), FTTC-dextran (4 kDa), and insulin (5.7 kDa). Of the two bile salts, sodium taurodeoxycholate was more effective. At 10 mM, this bile salt increased the permeability of 6-carboxyfluorescein from 0.02% to 11%, glutathione from 0.08% to 6%, FITC-dextran from 0% to 0.07%, and insulin from 0.06% to 3.8%. Sodium taurocholate, on the other hand, increased the permeability to 0.13%, 0.38%, 0.0011%, and 0.14%, respectively. Taurodeoxycholate was more effective than taurocholate in the nasal epithelium as well [202], This difference in activities can possibly be attributed to their micelle-forming capability, which is higher for taurodeoxycholate, a dihydroxy bile salt [190],... 

Jiang and Zhu (2000) and Qiu and Zhu (2001) have reported the fabrication of multilayered devices composed of stacks of compression-molded disks of alternating compositions. One type of disk is either P(SA-EG) or P[SA-co-TMAgly)-Z>-EG] and the other is a pH-sensitive, protein-loaded blend of, for example, poly(methacrylic acid) and polyethoxazoline. The release of model proteins, myoglobin, bovine serum albumin, and FITC-dextran, and compounds such as brilliant blue have been studied and pulsatile release profiles have been demonstrated (Jiang and Zhu, 2000 Qiu and Zhu, 2001). 

However, caution must be exercised in the use of Caco-2 monolayers to study paracellular transport. Tanaka et al.82 found that the TEER values of Caco-2 monolayers (468 Q cm2) were higher than those of rat jejunum (37 Q cm2) and colon (83 Q cm2). Consistent with higher TEER values, the Papp of the paracellular permeability marker FITC-dextran (MW = 4000) in Caco-2 monolayers, rat jejunum, and rat colon were 0.22,2, and 0.95 X 10 5 cm/min,... 

Liposomes (without peptide) were labelled with rhodamine-PE in the lipid bilayer and in the inner compartment using FITC-dextrane 9000 and incubated with DCs for one hour. Figure 3 shows clearly that only in the case of AVE 3 and AVE 43 could a significant uptake be observed. The fluorescence inside the DCs is in the case of AVE 3 homogenously distributed in the cytosol, whereas in the case of AVE 43 the liposomes seem to be caught in granular structures, presumably endosomes. The PS causes the liposomes... 

Cholera Toxin Subunit B. a marker for caveolae-dependent endocytosis. partly co-localizes with liposomal FITC>dextran indicating that pH-sensitive liposomes are taken up-at least to a certain extend— via caveotae pathway... 

Trypan blue (0.4%), a substance that is usually applied to identify dead cells, can be used as a quencher for some of the external dextran conjugates [fluorescein isothiocyanate (FITC)-dextran] (72,129). 

The quantification of fluorescent particles in cellular systems is difficult because several aspects such as autofluorescence, bleaching (see below), and quenching hamper analysis. Keep in mind that many fluorophores show a pH-dependent change in emission spectrum and intensity fluorescein-labeled dextrans (FITC-dextran) and calcein are strongly quenched upon acidification. If available, one should read the fluorescence intensity at its isosbestic point, where the intensity is not pH dependent. 

A significant size exclusion phenomenon was observed for the IPN membranes. Theophylline R =1.3 A), proxyphylline = 2.3 A), ox-prenolol HCl R = 2.6 A), and FITC-Dextran R = 49 A) were used as model drugs in the diffusion study where R denotes the hydrodynamic radius of the solute. The solute size, membrane mesh size, pH, temperature, and the affinity of the solute with the membrane can affect the permeation of the solute. 

Shown in Figure 6 is a plot for the permeation of the four different model drugs through a PMAA/PNIPAAm IPN membrane containing 70 mol% of PNIPAAm in pH 7.4 buffer solution. As mentioned, the slope of each linear curve represents the permeability of each solute. As expected, higher permeability was observed for smaller model drug. From theophylline to FITC-Dextran, the permeability decreases, which is an indication of the size exclusion behavior in the IPN membrane at the same gel swollen state, the IPNs show higher permeability for the smaller solutes. 

Figure 6 Solute permeation of theophylline (O), proxyphylline ( ), oxprenolol HCl (A), and FITC-Dextran (V) through PMAA/PNIPAAm IPN. The slope represents the permeability of each solute.

Figure 11.3 DNA size dependence of relative diffusion coefficients in cytoplasm (Dcyto/Dw) and nucleus (Dnuc/Dw). Apparent diffiisional coefficients in the cytoplasm (Dcyt) relative to aqueous solution (Dw) were determined from 50% recovery times (t1/2) using an experimentally determined calibration relation of t1/2 versus D as described in Kao et al., 1993. Each point is the mean SE for 5-15 independent measurements for DNA diffusion in cytoplasm (open circles) or nucleus (filled circles). For comparison, I )/l )w values for microinjected FITC-dextrans are shown. Reproduced with permission from Lukacs etal., 2000.

Tokudome, Y., and K. Sugibayashi. 2003. The effects of calcium chloride and sodium chloride on the electroporation-mediated skin permeation of fluorescein isothiocyanate (FITC)-dextrans in vitro. Biol Pharm Bull 26 1508. 

Pitkanen et al. [51] reported the isolated bovine RPE-choroid was up to 20 times more permeable to lipophilic than hydrophilic beta-blockers. Furthermore, the in vitro permeability of bovine RPE-choroid to hydrophilic compounds and macromolecules was 10 to 100 times less compared to sclera, whereas the permeability for lipophilic molecules was in the same range for both tissues. The isolated bovine RPE-choroid also exhibited differential permeation by molecular weight and Stokes radius. The permeation rate of 4, 10, and 20 kDa FITC dextrans was moderate compared to a good permeation rate for the 376 Da carboxyfluor-escein and a poor penetration rate for 40 and 80 kDa FITC-dextrans. The permeability to carboxyfluorescein was 35 times more than to 80 kDa FITC-dextran [51]. In a study on the permeability of the human ciliary epithelium to a horseradish peroxidase, Tonjum and Pedersen [52] reported that ciliary and iridial epithelium contained a system of paracellular zonulae occludentes. Peroxidase was applied on the stromal side of ciliary body and iris specimens obtained from freshly enucleated eyes. The 40 kDa peroxidase was blocked apically in the lateral intercellular spaces of the CNPE whereas in the iris the progression of peroxidase was blocked apically in the lateral intercellular spaces of the IPE. Freddo [53] studied the intercellular junctions in the posterior IPE cells of the rhesus monkey by electron microscopy, freeze-fracture, and horseradish peroxidase. Intravenously injected horseradish... 

Sasaki, H., et al. 1995. Ocular permeability of FITC-dextran with absorption promoter for ocular delivery of peptide drug. J Drug Target 3 129. 

In addition to the corneal route, topically applied ocular drugs may be absorbed via a noncorneal absorption route that involves drug transport across the bulbar conjunctiva and underlying sclera into the uveal tract and vitreous humor.65 The intercellular spaces of the conjunctival epithelium are wider than those of the corneal epithelium. As a result, the conjunctiva has higher permeability than the cornea to agents such as mannitol, inulin, and FITC-dextran.86 The penetration of peptides, however, is limited by enzymatic degradation.87 The limit of molecular size for conjunctival penetration is between 20,000 and 40,000 Da. Vitreous can act as an aqueous and unstirred diffusion barrier to drug permeation.64... 

More often, carbamates of dextran are prepared by one-step conversion of the polysaccharide with isocyanates or isothiocyanates. This path is especially useful for the conjugation of fluorescent dyes. Fluorescent-marked dextrans are commercial products today. Fluorescent dextran derivatives with different molecular weights and substituents are available as invaluable tracers for studies on microcirculation and vascular permeability in health and disease [8]. Fluorescein isothiocyanate (FITC) dextran (actually the thiocarba-mate) has been well established in this area of research since the 1970s [358]. The isothiocyanate of fluorescein is covalently bound to dextran leading to... 

Fig. 53 Preparation of fluorescein-labelled dextran (FITC dextran) by the isothiocyanate technique [359]...

At P17, the pups are euthanized and their eyes enucleated and fixed for embedding and sectioning. Representative pups from each group are anesthetized and perfused through the left ventricle with 4% paraformaldehyde in 0.1 M sodium phosphate (pH 7.4) containing FITC-dextran for visualizing the retinal vasculature (see later). 

Fluorescein isothiocyanate-dextrans (FITC-dextrans), 167 kDa (Synopharm GmbH Co KG, Barsbiittel, Germany). 

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