Fluorescent drug delivery

Host-guest systems made from dendritic materials have potential in the areas of membrane transport and drug delivery [68, 84, 85]. In a recent report [136] Tomalia and coworkers investigated structural aspects of a series of PAM AM bolaamphiphiles (e.g., 50) with a hydrophobic diamino do decane core unit. Fluorescence emission of added dye (nile red) was significantly enhanced in an aqueous medium in the presence of 50 unlike the cases when 51 and 52 were added (Fig. 23). Addition of anion surfactants to this mixture generated supramolecular assemblies which enhanced their ability (ca.by 10-fold) to accommodate nile red (53). Further increase in emission was noted by decreasing the pH from the normal value of 11 for PAMAM dendrimers to 7. At lower pH values the... 

Fig. 12 CNTs act as a vector for drug delivery into living cells. After incubation of HeLa cells with AlexaFluor594-labeled SWNTs for 12 h at 37 °C, living cells were observed under confocal fluorescence microscope for a CNT uptake study, (a) Images show dual confocal detection of AlexaFluor594-SWNT (red) internalized into cells with the membrane stained by AlexaFluor488 (green), (b) Series of images of different z-focal scanning planes down through cells. (Adapted from [61])...

The same group reported the simultaneous radiolabeling (with DOTA-anchored 4Cu) and fluorescence studies, coupled with biodistribution in vivo and in vitro (92). It is believed that appropriately functionalized SWNTs can efficiently reach tumor tissues in mice with no apparent toxicity (159). Furthermore, water-solubilised carbon nanotubes are nontoxic when taken up by cells even in high concentration (92). These studies have been complemented by the recent PET imaging of water-soluble 86Y labelled carbon nanotubes in vivo (mice) (160,161), to explore the potential usefulness of carbon nanocarriers as scaffolds for drug delivery. The tissue biodistribution and pharmacokinetics of model DOTA functionalized nanotubes have been explored in vivo (mouse model). MicroPET images indicated accumulation of activity mainly in the kidney, liver, spleen, and to a much less... 

Zhu H, McShane MJ (2005) Loading of hydrophobic materials into polymer particles implications for fluorescent nanosensors and drug delivery. J Am Chem Soc 127 13448-13449... 

All in all, uptake studies with targeted systems carrying a pH-dependent fluorescent label in conjunction with monensin treatment at the end of the incubation period offer the possibility to discriminate between different intracellular trafficking pathways. At 37°C, an increasing fluorescence emission upon addition of monensin points toward accumulation of the targeted drug delivery system within acidic compartments of the cell, such as lysosomes. 

Watson, P., Jones, A.T., Stephens, D.J., Intracellular trafficking pathways and drug delivery Fluorescence imaging of living and fixed cells. Adv Drug Deliv Rev 57, 43-61 (2005). 

Organizational characteristics of surface-active molecules have been studied by several researchers due to their applications in many areas such as personal care, polymerization, catalysis, drug delivery, separation and purification, enhanced oil recovery and lubrication. The structure of supramolecular organized assemblies formed in different solvents, when a critical concentration is exceeded, determines their properties such as solubilization [1-3], catalysis [1,4-6], adsorption [7-11] and flocculation [12,13]. As such, many techniques have been used to determine their structural properties. In this paper, the results obtained using fluorescence probing for properties of assemblies in solution and at solid-liquid interfaces are discussed in detail after a brief review of relevant assemblies formed by them. 

The experiments reviewed in Section 13.1 demonstrated in detail that LCM can be labeled with lipophilic fluorescent dye and still retain their tumor-targeting properties. Furthermore, these lipophilic-dye-labeled LCM were shown to become internalized by tumor cells both in vitro and in vivo. This tumor-targeting ability of dye-labeled LCM, and their in vivo persistence at the tumor site and/or within the tumor cell for many minutes, suggested a potential use of LCM as a targeted drug-delivery agent or vehicle (ref. 532). Thus, a search was started for lipophilic anticancer drugs (preferably already FDA-approved for clinical use) that could be incorporated into the LCM and carried specifically to the tumor site. 

Peptide amphiphiles may also be used for drug delivery. For example, Marini used fluorescently labeled peptide amphiphiles that were functionalized with the cyclo-RGD ligand and found that these structures were internalized by cells (Marini et al., 2002). 

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