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Hyperbranched Polydisulfide


Disulfide containing polymers have been extensively studied as responsive materials for biomedical applications such as drug delivery, gene delivery, bio-sensing and receptor-mediated cellular uptake due to the possibility of cleaving the disulfide linkage by glutathione (GSH), a tri-peptide over expressed in cancer cells. While linear and branched polymers containing disulfide groups have been studied and more recently polydisulfides (PDS) have come to the fore, hyperbranched polydisulfides (HBPDS) were not known. This manuscript for the first time reports a generally applicable methodology for synthesis of HBPDS by A2 + B3 condensation approach. The B3 monomer contains three pyridyl-disulfide (Py-Ds) groups while a di-thiol compound serves as the A2 monomer. Polycondensation reaction under a very mild reaction condition produces HBPDS (Mw = 14300 gmol-1, Ð = 1.9) with a very high degree of branching (DB) value of 0.8 and more than twenty highly reactive Py-Ds groups present at the terminal or linear unit of a polymer on an average. The reactive Py-Ds groups can be completely replaced by post-polymerization functionalization using a hydrophilic thiol resulting in bio-reducible amphiphilic HBPDS. It produces micellar aggregates in water with hydrodynamic diameter ~ 80 nm, low critical aggregation concentration (7.0 µM) and high dye (Nile red) loading content. Exchange dynamics of these micellar aggregates, studied by fluorescence resonance energy transfer (FRET), reveals practically no inter-micellar exchange after 6h indicating very high non-covalent encapsulation stability. On the other hand, in presence of glutathione, the PDS backbone can be degraded resulting in efficient triggered release of the encapsulated dye. Dye release kinetics strongly depends on the GSH concentration and interestingly with a fixed concentration of glutathione the release kinetics appears to be much faster for the hyperbranched PDS micelle compared to its linear analogue. MTT assay with two representative cell lines indicates that the amphiphilic HBPDS is biocompatible upto 500 µg/ mL which is further supported by hemolysis assay showing merely 6.0 % hemolysis up to a polymer concentration of 500 µg/mL.

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Publication details

The article was received on 05 Nov 2019, accepted on 03 Dec 2019 and first published on 04 Dec 2019

Article type: Paper
DOI: 10.1039/C9PY01675A
Polym. Chem., 2019, Accepted Manuscript

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    Hyperbranched Polydisulfide

    R. Bej, P. Rajdev, R. Barman and S. Ghosh, Polym. Chem., 2019, Accepted Manuscript , DOI: 10.1039/C9PY01675A

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