Laser-targeted drug delivery

METHODOLOGY OF LASER-TARGETED DRUG DELIVERY Principle of Laser-Targeted Drug Delivery 

The pharmacokinetic behavior of the liposomes was studied in vivo. Five rats were injected with dye encapsulated in liposomes, and blood samples were collected every 

A fundus camera was modified to provide video angiograms and to deliver one laser beam used to release the content of the liposomes and another laser beam to activate the photosensitizer. The first laser was also used to illuminate the fundus. The output of the charge-coupled device (CCD) camera was fed into a video image enhancer and recorded on magnetic tapes with a high-frequency video recorder. Later, the tape was played back, and video sequences were digitized with a frame grabber for subsequent analysis. 

An argon laser (filtered to deliver only at 488 nm) was used to release the liposomes content for purposes of angiography. The power of the laser was increased gradually until a bright fluorescent bolus was observed. Typically, this was achieved with a power of 16mW applied on a 600-pm spot for a duration of 200 msec. In the case of photo-occlusion (described later), a diode laser emitting at 675 nm was used to activate the photosensitizer. The delivery of both laser beams was controlled by shutters activated by a computer. 

The instrument has been developed further to be applicable in Phase I and II clinical trials. The optics have been specifically designed to yield a compact optical head. The illumination for angiography is provided by light-emitting diodes, and the lasers for release and activation consist of diode lasers incorporated into the 

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Figure 1 Principle of LTD. Schematic representation of heat and dye distribution during laser-targeted drug delivery following a laser pulse in an eye with CNV. The energy deposited in the tissues causes heating, as illustrated by the oval. The bolus of dye released in the CNV vessels is retained longer than that in the choriocapillaris because of slower flow within the CNV. The CNV and the tissues in its immediate vicinity reach the releasing temperature of the liposomes, but the retinal vessels do not. Abbreviations. LTD, laser-targeted delivery CNV, choroidal neovascularization. Source From Ref. 4, Figure 1.

Laser-Targeted Drug Delivery to Retinal Tissues... 

FIGURE 15.16 Photomechanical wave delivery devices. A drug reservoir backed with a laser target material (e.g., black polystyrene) is placed on the skin. Laser-induced photomechanical waves are supposed to increase the permeability of the stratum comeum allowing the facilitated passage of drug molecules from the reservoir into the skin. (From Cross, S.E. and Roberts, M.S., Curr. Drug Deliv., 1, 81, 2004. With permission.)... 

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