Polyorthoesters form a very important class of bioresorbable polymers. We call them Orthomer™. Polyorthoesters are of growing interest for controlled drug and gene delivery applications. They tend to degrade predominantly through surface erosion unlike most polyesters such as PLA and PLGA that degrade predominantly through bulk erosion. The polymers are stable at alkaline and neutral conditions, but rapidly hydrolyze at acidic conditions, of which the overall rate of it we can control through compositional tuning.
Polyorthoesters are normally low in molecular weight making them interesting for injectable formulations creating soft gels in vivo. However, solid polymers, with higher molecular weight, can be made as well and we know how to do that. Such higher molecular weight polyorthoesters are highly interesting for microsphere and microrod solid controlled release depots as well as for in situ forming solid depots through the use of a biocompatible carrier.
We have years of experience in synthesizing polyorthoesters with variations in composition and molecular weights. The basic monomer or building block is always DETOSU for the ortho ester part. Popular comonomers are TEG, PEG and aliphatic or cyclic diols either or not combined with lactic acid or glycolic acid. The latter acids will accelerate the overall hydrolysis rate of the so obtained orthoester copolymers.
Very interestingly, polyorthoesters can be made with glass transition temperatures significantly higher than those for classical PLA and PLGA. Where for PLA and PLGA the glass transition temperatures are limited to 50-60°C we can obtain polyorthoesters with glass transition temperatures in the range of 80 - 100°C. These higher Tg's are very useful in reducing burst release and controlling the overall release of drugs. The higher Tg's are in particular useul to control the release of small(er) molecular weight drugs where other bioresorbable polymers may not be so successful.
We fully customize Orthomer™ orthoester copolymers to your requirements.
Orthomer™ is a registered trademark of PolyVation.
Important note: if you are interested in polyorthoesters please contact us directly. We do not work through distributors unless we explicitly let you know. Furthermore, we recently entered into an exclusive business development partnership with a global materials company to accelerate your product development and advancing product opportunities using polyorthoesters in the pharmaceutical space. The relationship is not made public yet.