Encapsulation of Dyes

The labeling of nanoparticles with fluorescent dyes allows one to use them as markers in biomedical appUcations. One possibility is to immobilize the fluorescent dyes physically or chemically on the particle s surface (e.g. FITC-dextran [29]). However, either desorption can occur, or the surface is changed that much that the biological response (cell uptake, toxicity) is significantly modified or even totally hindered. Therefore, an incorporation of hydrophobic dyes into the polymeric nanoparticles leads to marker systems where only the polymer and the highly variable surface functionaUty are the relevant factors for particle-cell interactions. 

Carboxy- and amino-functionaUzed polystyrene nanoparticles have been synthesized by the miniemulsion process using styrene and the functional monomers acrylic acid (AA) or 2-aminoethyl methacrylate hydrochloride (AEMH) as functional comonomers [30,31]. By changing the amount of the comonomer, different surface densities of the charged groups could be realized. Since a fluorescent dye was incorporated inside the nanoparticles, the uptake behavior of different cell Unes could be determined as a function of the surface functionalization [30,31]. It was found that, in general, the uptake of the nanoparticles into the cells increases with increasing functionality on the particle s surface. For HeLa cells, for example, the internalized particle amount was up to sixfold better for carboxy-functionaUzed polystyrene (PS) nanoparticles than for non-functionalized PS particles. For amino functionalized PS nanoparticles, an up to 50-fold enhanced uptake could be detected. In order to investigate the actual uptake pathway into HeLa cells, positively 

In addition to the above-mentioned experiments using PS-based nanoparticles, the hydrophobic fluorescent dye A-(2,6-diisopropylphenyl)perylene-3,4-dicarbonacidimide (PMI) could also be successfully incorporated in phosphate-functionalized poly(methylmethacrylate) (PMMA) and PS [33], polyisoprene (PI), PS-co-PI [34], PBCA [35, 36] and polylactide (PLLA), or poly(e-caprolactone) (PCL) nanoparticles [37] in order to study the cellular response to these polymeric nanoparticles. For qualitative investigations, confocal microscopy can be used the quantitative measurements can be realized by a fluorescent activated cell sorter (FACS). 

It was shown that the uptake behavior is greatly affected by the type of the polymer (see Fig. 5). In the case of polyisoprene, the uptake of non-functionalized nanoparticles without any transfection agents into different adherent (HeLa) and also suspension (Jurkat) cell lines is extremely fast compared to other polymeric particles and, moreover, leads to high particle loading of the cells. The internalized 

It could be shown that PBCA particles are also internalized by HeLa, Jurkat, and mesenchymal stem cells (MSCs) however, the cellular uptake kinetics are different for HeLa and Jurkat cells (see Fig. 6) [35, 36]. While the particle size has a significant impact on particle uptake in HeLa cells, Jurkat cells are more sensitive towards surface functionalization. Especially the methoxypolyfethylene glycol) (MePEG)-fimctionalized particles are internalized to a lesser extent than the rest of the investigated particles (non-functionalized, phenylalanine-functionalized). 

---

M. Wark, M. Ganschow, Y. Rohlfing, G. Schulz-Ekloff, and D. Wohrle, Methods of Synthesis for the Encapsulation of Dye Molecules in Molecular Sieves. Stud. Surf. Sci. Catal., 2001,135,180. 

Y.M. Jin and H. Chon, A Novel Method for Encapsulation of Dyes into AIPO4-8 Molecular Sieve. Chem. Commun., 1996, 135-136. 

Methods of synthesis for the encapsulation of dye molecules in molecular sieves... 

It s worth mentioning that, encapsulation of dyes in dendrimers can be used for dye extraction. The used dendrimers were soluble in dichloromethane while insoluble in water. As eosin is colored in aqueous solution at pH > 5, mixing the colored aqueous solution of eosin with dendrimer (2D-5D) containing dichloromethane results in phase transfer of eosin from aqueous to dichloromethane phase through dye encapsulation in dendrimer. This can be detected visually and quantitatively by measuring the absorbance changes at the wavelength of maximum of eosin absorption spectrum in water = 515 nm). 

Feng CL, Caminade AM, Majoral JP (2010) Selective encapsulation of dye molecules in microcapsules by DNA hybridization. J Mat Chem 20 1438-1441... 

Another important apphcation for 4-/ f2 -octylphenol is ia the production of phenoHc resias. Novolak resias based oa 4-/ f2 -octylpheaol are widely used ia the tire iadustry as tackifiers. The tackiaess of these resias biads the many parts of an automobile tire prior to final vulcanization. A specialty use for novolak resias based oa 4-/ f2 -octylpheaol is the productioa of a ziacated resia, which is formulated as a dispersioa ia water and coated onto paper ia combination with eacapsulated leuco dyes to yield carbonless copy paper (see Microencapsulation). Pressure from writing bursts the encapsulated leuco dye, which is converted from its colorless form to its colored form by the ncated resin (53). Novolak resias based oa 4-/ f2 -octylpheaol are also used ia the productioa of specialty printing inks. 

Chloriaated paraffias and modified types are used as solvents ia carbonless copyiag paper production based on the encapsulation of a solution of reactive dyes. Chloriaated paraffias fiiUfill the technical requirements for a solvent including excellent solvency for the dyes they do not react with the dyes nor encapsulation material, are immiscible with water, and have low volatihty and low odor. 

In 2000, the first example of ELP diblock copolymers for reversible stimulus-responsive self-assembly of nanoparticles was reported and their potential use in controlled delivery and release was suggested [87]. Later, these type of diblock copolypeptides were also covalently crossUnked through disulfide bond formation after self-assembly into micellar nanoparticles. In addition, the encapsulation of l-anilinonaphthalene-8-sulfonic acid, a hydrophobic fluorescent dye that fluoresces in hydrophobic enviromnent, was used to investigate the capacity of the micelle for hydrophobic drugs [88]. Fujita et al. replaced the hydrophilic ELP block by a polyaspartic acid chain (D ). They created a set of block copolymers with varying... 

In summary, the encapsulation of cyanine dyes in CB7 causes either an increase or a decrease in quantum yields and brightness but in general increases photostability. Enhancements in fluorescence intensity by about one order of magnitude or more were observed [46]. These fluorescence property changes are utilized for the development of sensors, where the fluorescent dye may serve as a probe to signal the binding of an analyte. No reports were found on the encapsulation of squaraines in CBs. 

Some of the spectral properties of squaraine rotaxanes are given in Table 5. It can be seen that encapsulation of squaraines 22a-22d with heterocyclic end-groups in a tetralactam macrocycle results in a small blue-shift of the absorption and emission maxima while the encapsulation of squaraines 22e and 21a leads to red-shifted rotaxanes [60]. Importantly, encapsulation in a tetralactam macrocycle has a positive effect not only on the photostability (Figs. 9 and 10) of these dyes but also on the quantum yields (<2>F) and fluorescence lifetimes (Tmean)- Embedding of any type squaraines in tetralactam rotaxane system increases [Pg.175]

Koner AL, Nau WM (2007) Cucurbituril encapsulation of fluorescent dyes. Supramol Chem 19 55-66... 

Amorphous silica is an optically transparent, biocompatible [37] and nontoxic [38] matrix that permits the encapsulation of the dyes without affecting... 

Fig. 4 Schematic illustration of synthesis of multifunctional nanoparticles starting from a w/o microemulsion, b solubilization of fluorescent dye in the microemulsion core, c formation of silica nanoparticle and encapsulation of fluorescent dye, d condensation of silane ligand and chelation of Gd(lll), e post coating with silica, and f extraction of nanoparticles...

Fig. 8.4 Encapsulation of anionic dye mole- printboard (schematic only 23 of the 64 ter-cules (green) by the dendrimer bound supra- minal adamantyl groups are shown and the molecularly to the surface of the molecular branches are symbolised)...

Sun et al. [59] used NCE-LIF to evaluate a derivatization method mediated by liposome for single cell analysis. According to these workers single cell analysis revealed that liposome-membrane fusion occurred after entrance of liposomes into the cells, with release of encapsulated fluorescence dyes and labeling of intracellular species. 

---