An all-in-one approach to prepare tumour-targeting polymer spheres has been developed by Korean scientists.

Polymeric micelles made from protein-polymer hybrid materials show great promise for drug delivery as the hollow spheres can surround and protect the therapeutic compounds until they reach their target. Typically, the micelles are self-assembled in solution, but they need to then be functionalised with specific ligands to improve their delivery efficiency, making the process lengthy and complicated.

A modified PHA synthase forms micelles with its PHA product

Now, Young-Rok Kim and co-workers from Kyung Hee University, Yongin, have developed a single-step procedure for synthesising nanocarriers that target cancer cells. They achieved this by exploiting a key feature of the enzyme PHA synthase, which catalyses polyhydroxyalkanoate (PHA) biosynthesis. 'PHA synthesised by PHA synthase remains covalently attached to the enzyme,' explains Kim. 'I thought that this could be an excellent way of synthesising a protein-polymer hybrid.' The group modified the PHA synthase with an additional amino acid sequence that targets tumours by recognising integrin, a cancer-specific marker. They found that the resulting micelles bound effectively to breast cancer cells. 

Vladimir Torchilin, director of the Center for Pharmaceutical Biotechnology and Nanomedicine at Northeastern University, Boston, US, says Kim's method 'is an interesting idea'. However, he warns that 'the problems with more traditional approaches are not that serious,' so the approach may not supplant current methods.

Kim agrees that traditional approaches might be better for functionalising nanocarriers with relatively simple ligands, but adds that 'our approach is suitable for introducing more elaborate functionalities to the nanocarrier, which is hard to achieve with current methods. I believe this will provide much more freedom in designing new macromolecular architectures with precise biological functionality.'

Bailey Fallon

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