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A polymer enabling better acceptance of implants

Drug delivery devices like implants offer several advantages over pills or injections, but often result in immune responses that hinder their performance. A group of researchers led by Professor Bikramjit Basu and Prof. Giridhar Madras from the Indian Institute of Science (IISc), Bangalore, have developed a biodegradable polymer that delivers an anti-inflammatory agent, to allow better acceptance of biomedical implants by the body.

The study was published during December 2014 in the journal Biomacromolecules.

Implantable devices facilitate drug delivery at specific regions of the body where they are required. This local delivery provides an advantage of using lower doses of the drug and thereby reduces potential side effects. The novel biodegradable salicylic acid based polyester (SAP) is designed to slowly deliver salicylic acid (a Non-Steroidal Anti-Inflammatory Drug- NSAID)for a prolonged period of time

“Other salicylic acid releasing polymers belong to the class of poly(anhydride-esters) and are linear or have salicylic acid conjugated to a linear chain. Anhydride linkages in these polymers are very labile and, therefore, unstable. SAP synthesized by us is cross-linked. Ester linkages are known to be stable compared to anhydride linkages, and hence sustained release is possible. This difference in the chemical structure is the main reason for the long term, sustained release that is possible over a prolonged period of time with our polymer”, said primary author and PhD student Yashoda Chandorkar, , Materials Research Centre, IISc.

Implantation of SAP under the skin of mice reduced the foreign body response and the formation of an undesirable coating around it. This coating/fibrous capsule prevents effective communication between the implant and the body

 “Commonly used biodegradable polymers—such as poly(lactic acid-co-glycolic acid) (PLGA)—have noxious degradation products, which are undesirable for an ideal system” said Chandorkar.

Comparison of SAP with PLGA, following implantation in mice for 2, 4, and 16 weeks, showed that fibrous capsule surrounding the PLGA implant was denser. However, the SAP implant was surrounded by normal tissue-like structure. Moreover, 96% of PLGA versus ~8% SAP degraded by 16 weeks. This slow degradation results in the sustained release of salicylic acid.

“One of our long term aims is to enable the release of different drugs along with salicylic acid as an anti-inflammatory agent. This would involve strategies to load the drug in the polymer, which need to be explored further”.

About the authors

Yashoda Chandorkar and Nitu Bhaskar are with the Laboratory for Biomaterials, Materials Research Centre, IISc. Giridhar Madras is a Professor at the Department of Chemical Engineering, IISc. Bikramjit Basu is a Professor with Materials Research Centre and the Bio-Engineering Program, IISc

Website: https://sites.google.com/site/bikramiisc/

Tel.: +91 80 2293 3256; Email: yashoda1@gmail.comand bikram@mrc.iisc.ernet.in

Yashoda Chandorkar, Nitu Bhaskar, Giridhar Madras, and Bikramjit Basu. Long Term, Sustained Release of Salicylic Acid from Crosslinked, Biodegradable Polyesters induces Reduced Foreign Body Response in Mice. Biomacromolecules. http://pubs.acs.org/doi/abs/10.1021/bm5017282