As you probably know, researchers have been working for a while to find more efficient ways to deliver anti-cancer drugs directly to their targets. But instead of finding a new drug carrier, why not focusing on a drug that knows its path to the target and which delivers itself to the tumor? This is what University at Buffalo (UB) scientists have done by developing a solution in which the delivery system is the drug itself by using nanocrystals of a hydrophobic drug. But this research work needs to be confirmed before this drug can be approved by the medical regulators. And it will take time...
This project has been led by Paras Prasad, the executive director of the Institute for Lasers, Photonics and Biophotonics, who also is a Professor of Biophysical Sciences at Roswell Park Cancer Institute (RPCI), and his colleagues.
So what have they found?
The system involves the use of nanocrystals measuring about 100 nanometers of pure HPPH, a photosensitizer currently in Phase I/II human clinical trials at RPCI for treating various types of cancer. The UB researchers found that the nanocrystals of HPPH were taken up by tumors in vivo, with efficacy comparable to conventional, surfactant-based delivery systems. A patent has been filed on this work.
But what exactly is HPPH? And how does it work?
 On the left is a "confocal fluorescence image of tumor cells treated with HPPH-doped nanoparticles developed at UB" (Credit: Paras Prasad). This picture comes from an article published by the UB Reporter, UB scientists develop non-release nanoparticle to deliver photodynamic cancer therapy" (July 3, 2003).
According to the National Cancer Institute in its dictionary of cancer terms, HPPH -- also known as 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a -- is "drug that is used in photodynamic therapy that is absorbed by tumor cells; when exposed to light, it becomes active and kills the cancer cells."
In its Drug Dictionary, the National Cancer Institute gives more details about HPPH. Just visit this page and scroll near the middle. You'll see that "upon intravenous administration, HPPH selectively accumulates in the cytoplasm of cancer or pre-cancerous cells. Photodynamic reaction between HPPH and oxygen occurs when laser light is applied. As a result, reactants from the photodynamic reaction trigger serial cytotoxic events, thereby killing tumor cells."
 On the left, this newer "confocal microscope image shows uptake of the nanocrystals by cancer cells, a technique developed by researchers at UB and RPCI" (Credit: Paras Prasad). Here is a link to a larger version.
This research work has been published online in advance of its print publication by Molecular Pharmaceutics under the name "New Method for Delivering a Hydrophobic Drug for Photodynamic Therapy Using Pure Nanocrystal Form of the Drug" on February 1, 2007. Here is a link to the abstract. You can find some comments about this paper -- and a related one -- issued by the National Cancer Institute under the name "Nanoparticles advance photodynamic therapy to kill tumor cells" (via News-Medical.Net, February 20, 2007).
Sources: University of Buffalo news release, March 7, 2007; and various websites
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