Biomaterials

Seeping into Cartilage

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Science  15 Feb 2008:
Vol. 319, Issue 5865, pp. 878
DOI: 10.1126/science.319.5865.878c

Polymer nanoparticles have been explored for more accurate delivery of drugs to improve efficacy and reduce toxicity within the body. For tissues lacking vasculature, such as articular cartilage, the challenge is to get the drug through the dense extracellular matrix (ECM) via a localized injection without removal in the synovial fluid. Rothenfluh et al. synthesized poly(propylene sulfide) (PPS) particles, ranging in size from 20 to 200 nm, that could potentially be used to deliver hydrophobic drugs such as aggrecanase inhibitors used to treat osteoarthritis. The PPS particles were decorated with a peptide sequence obtained from a five-generation phage panning process, where cloning enhances the population of sequences that best bind to a target tissue. For the best sequence obtained, binding tests with the target peptide and a related scrambled sequence showed that binding was sequence-specific to collagen II α1. Not only were the smallest particles able to enter the ECM, but the targeting peptide then caused them to bind to the collagen matrix, thus turning a barrier into a reservoir that persisted for more than 96 hours. — MSL

Nat. Mater. 7, 10.1038/nmat2116 (2008).

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