Therapeutic agents targeted delivery

Targeted delivery has also been used to investigate the structure of carbohydrates needed to obtain discrimination of cellular uptake between liver and tumor cells [184], A study was performed by doubly modifying BSA with both a fluorophore (via Lys isothiocyanate derivatization) and different fucose derivatives (via Tyr diazotization). Similar studies have used EDC-mediated coupling to also attach therapeutic agents for delivery to human embryonal carcinoma cells [185]. 

Some of their derivatives have been used as antiviral drugs. Due to their flexible chemistry, they can be exploited to design drug delivery systems and in molecular nanotechnology. In such systems, they can act as a central lipophilic core and different parts like targeting segments, linkers, spacers, or therapeutic agents can be attached to the said central nucleus. Their central core can be functionalized by peptidic and nucleic acid sequences and also by numerous important biomolecules. 

The conventional concentration of benzalkonium chloride in eyedrops is 0.01%, with a range of 0.004-0.02% [111]. While uptake of benzalkonium chloride itself into ocular tissues is limited [113], even lower concentrations of benzalkonium chloride have been reported to enhance corneal penetration of other compounds including therapeutic agents [93,112,114]. The differential effect of this preservative on the cornea compared to the conjunctiva can be exploited to target a drug for corneal absorption and delivery to the posterior segment of the eye [115]. Its use has been proposed as a means of delivering systemic doses by an ocular route of administration [116]. 

The potential of the chemically modified nucleic acid molecules has been proven by in vitro studies however, the in vivo therapeutic applicability of these molecules seems to be unsatisfactory because of their possible toxic effects (largely unknown) and adverse bioavailability. In this view, both antisense and transfection technologies require reliable and efficient systems for their delivery into target cells. On the basis of this consideration, the development of an efficient nucleic acid delivery system represents one of the key steps for these therapeutic agents, which are necessary for a practical clinical utilization of natural or unnatural oligonucleotides. 

Fig. 34. Model of a functionalised (internally or externally) SWNT, which may be closed, open and/or corked reversibly or permanently after filling. Potentially the inner cavity may be filled with a (radio)-imaging agent (for PET/SPECT and/or MRI) or a (radio)therapeutic agent. Such functionalized SWNTs may conceivably act as probe prototype for multimodal imaging/therapy and targeted drug delivery (155).

The interaction of ultrasound waves with microbubbles allows a drug (including genetic material for gene therapy [10]) to be released from the particles selectively at the desired insonified areas of the body, thus allowing targeted delivery of therapeutic agents. Currently, this approach is still far from clinical application. 

Gene therapy constitutes a novel form of drug delivery.51 To employ their full potential as therapeutic agents, genes have to be delivered in a very specific and efficient way to their cellular targets. In the field of gene therapy, the problems and high risks associated with the use of virus particles for efficient delivery of... 

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