Functionalisation of polymers with palladium nanomaterials for applications in bioorthogonal catalysis

The ongoing search for novel drug delivery to a target site has led to increased interest in using bioorthogonal organometallic chemistry for localised prodrug activation. Anticancer prodrugs containing a palladium-cleavable propargyl protecting group have been developed, necessitating a suitable method to deliver the palladium nanoparticle (PdNP) catalyst to a desired location. PdNP-immobilisation within a non-degradable, biocompatible polymer matrix enables implantation of the catalyst, e.g. intratumourally, and subsequent systemic administration of a harmless Pd-sensitive prodrug will locally generate therapeutic concentrations of drug.

Polymer systems based on poly(2-hydroxyethyl methacrylate) have been functionalised with PdNPs in varying shapes and sizes – spherical, cubic and sheets. The entrapped nanomaterials were characterised using electron microscopy techniques. Catalytic efficiency of each of these composite materials was evaluated by incubation with the Pd-sensitive fluorogenic compound, propargylated Resorufin (Pro-Res), and measuring the resultant increase in solution fluorescence intensity.

The entrapped PdNPs all performed the catalytic depropargylation of the prodye, Pro-Res, showing that the development of catalytic polymer composite materials was a success. The polymer materials within which the PdNPs are entrapped also absorbed an amount of dye from the system, giving rise to the possibility of these materials being used as dual action, prodrug activating and drug storage and elution devices.