What Are They?
Liquid crystals are materials that flow like a liquid, all the while maintaining an ordered structure, somewhat like a crystal. While their use in electronics is well known (i.e. LCD TV screens), certain types of liquid crystals are also very useful in nanomedicine as tools for drug delivery. This is because of the enhanced ability of these nanoparticles to penetrate the skin or other tissues, and their capacity for timed release of their "payload".
The liquid crystals used for pharmaceutical purposes have been modeled after those already existing in biological systems. Examples of naturally occurring liquid crystals are the lyotrophic molecules that make up our cells and tissues, and are essential for life including phospholipid membranes, DNA and cholesterol.
Some liquid crystal pharmaceuticals (LCPs) have proven effective for treatment of viral diseases like herpes (HSV) as well as fighting tumors as in bladder and prostate cancer. LCPs have shown promise especially for transdermal applications and because of their ability to target inflamed tissue. An example of a liquid crystal pharmaceutical is the LCP-based anti-tumor drug called Tolecine. Tolecine has antibacterial and antiviral properties and prevents abnormal tumor proliferation. Tolecine is sometimes combined with another LCP called Apatone. The combined formulation is produced using technology that utilizes the properties of lyotropic liquid crystals, or organic liquid crystals.
Are LCPs Safe?
It is generally believed that LCPs are relatively safe for use as drugs, since studies so far indicate they have very low toxicity. Liposomes are safe enough to be commonly used for cosmetic purposes. Apatone is made from two non-toxic compounds, a liquid crystal compound and a the sugar glucose, and active ingredients, Vitamins C and K. Because of the glucose, Apatone easily enters cells. Once inside, the active ingredients generate free radicals. The oxidative stress results in weakening of target cells from the inside, and prevents the anti-inflamatary response that protects them from chemotherapy drugs. The production of free radicals is a concentration driven intracellular reaction that only takes place in cells with sufficient sugar concentrations (such as cancer cells). The reaction is quick and does not produce any toxic by-products that might harm adjacent healthy cells. Apatone is so effective, it was granted orphan drug status by the FDA in 2007.