End-of-Grant promo, Gamma sterilization, and Carbonate buffer technical notes

The PolySciTech division of Akina, Inc. (www.polyscitech.com) provides a wide array of biodegradable polymers and other research supplies. March ends the fiscal quarter for several institutions and grants which is why we are having a special end-of-quarter promotion. Orders between $100-250 receive a free drink-coozy, orders $250-500 receive a free string-backpack and orders >$500 receive a free PolySciTech T-shirt. As manager of Akina, I receive technical questions and sometimes I receive the same ones quite often. Often, I receive questions about gamma sterilizing our products. Our experience has been, however, that it is common for ionizing radiation techniques such as this to cause some degradation and cross-linking of polyesters which can change their mechanical properties (tend to become brittle) and their solubility properties (may become insoluble). This is similar to literature reports for the effects of radiation on polymers (http://link.springer.com/article/10.1023/A:1016256903322, http://www.sciencedirect.com/science/article/pii/0032386183901982). One way to reduce this damage is to perform the radiation dosing in an inert gas (argon or nitrogen). We've found this reduces some of the reactions which require the participation of atmospheric oxygen, humidity, or other gasses. Alternatively, depending on your application, it may be worthwhile to investigate alternate sterilization techniques such as ethylene oxide exposure. Another issue which has recently come up is the dissolution of thermogelling polymers (PLGA-PEG-PLGA, PLCL-PEG-PLCL) in specific buffers. Thermogel polymers of this category represent a balance between the hydrophilic attractions of the PEG block to water molecules and the hydrophobic attractions of the polyester blocks to each other. Species dissolved in the water which interfere with the water attractions can affect the performance of these thermogels. Although these work well in water, phosphate and several other buffers, they do not work well in carbonate buffers. Likely, this is due to the effects of carbonate species on water’s hydrogen bonding properties (http://pubs.acs.org/doi/abs/10.1021/jp809069g). Poor solubility of these thermogels has been reported in carbonate buffers and avoidance of carbonate buffer is suggested for these materials.