Monday, March 19, 2012

Biological glue is universal drug carrier and band-aid

With the help of chemical engineering, scientists were able to create a form of biological glue that sticks to the outer layer of a cell. By sticking cells together, the substance ought to be effective in stopping bleeding, but can also be used to deliver drugs directly to cells that require them. The scientists who developed the glue reckon it can be applied in many different situations.

Cellular structures are protected by an outer layer. It consists of a so-called lipid bilayer covered by a wide variety of molecules. Many receptors are built in the cellular surface, in order to receive and process signals coming from neighbouring cells or elsewhere in the body. Membranes also contain a substance called phosphatidyl choline (PC), a molecule that provides electrical charge. Scientists from the University of British Columbia in Vancouver made handy use of this cellular feature by engineering a molecule that reverses the electrical charge, or polarity of PC. This molecule, called CP, binds to PC on the cell membrane because their opposing charges attract each other.
A cellular membrane with two layers of lipids (orange dots). Various other molecules are built in, including transport channels and protruding molecular chains.  In reality, the membrane surface is completely covered with a huge variety of molecules.
A dose of CP-covered molecules is able to make cells stick to each other, as was shown by administering them to blood cells. By glueing cells together, a CP-based therapy has the ability to stop bleeding: not only externally, but also internal bleeding, which is often far more dangerous. The researchers also managed to show the binding process was reversible. Naturally, this comes in handy for when things get too sticky.

Drug delivery
For many diseases we would like to deliver drugs specifically to a group of cells. Cancer therapy benefits greatly from targeting: current chemotherapeutic drugs are highly toxic and not very specific, leading to severe side effects. By coupling a CP molecule with a chemotherapeutic, it may be possible to target cancer cells more precisely. Additionally, other diseases in which a specific cell type is damaged or infected could benefit from a CP-based therapy if we succeed in using it for drug targeting.

CP groups can be added to various polymers to create a functional molecule. This can be done for cancer drugs, as explained, but it is also possible to create a large polymer sheet that functions as an internal band-aid. Because different shapes and structures can be made and consequently covered with CP molecules, one can imagine a lot more medical applications which use the cell membrane as an attracting force. 

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