Bright insights into palladium-triggered local chemotherapy

We report fundamental insights into the validity, reliability and clinical feasibility of using heterogeneous Pd catalysts as implantable devices to accurately activate chemotherapy within a tumour.


Synthesis of Pd-labile masking groups
Synthesis of propargyloxybenzyl alcohol derivatives. Potassium carbonate (4.7 g) was added to a solution of o-hydroxybenzyl alcohol or p-hydroxybenzyl alcohol (2.5 g) dissolved in acetonitrile (50 mL).
After stirring at room temperature for 1 h, the mixture was treated dropwise with propargyl bromide (2.93 mL as 80 % (v/v) in toluene) and heated to reflux for 48 h. The solution was then filtered, concentrated in vacuo, and the crude was purified via flash chromatography (30 % ethyl acetate in hexane).
p-Propargyloxybenzyl alcohol. The synthetic method described using phydroxybenzyl alcohol gave a viscous bright yellow liquid (3.7 g, 99 %). Rf (2 x 50 mL) and brine (2 x 50 mL), dried over MgSO4 and re-concentrated in vacuo, and the crude was purified via flash chromatography (50 % DCM in hexane). anhydrous DMF (2 mL) was flushed with nitrogen after stirring for 10 min, then syringed into a flask containing a solution of doxorubicin HCl (20 mg) and triethylamine (7.5 μL) in anhydrous DMF under nitrogen at room temperature. The reaction was monitored by TLC (10 % methanol in DCM) to observe complete consumption of doxorubicin. After 20 h, the reaction was diluted with H2O (50 mL) and extracted with ethyl acetate (4 x 50 mL). The combined organic extracts were concentrated down to a volume of ~100 mL, then washed successively with saturated NaHCO3 (2 x 50 mL), H2O (2 x 50 mL) and brine (2 x 50 mL), dried over MgSO4, concentrated in vacuo with the water bath kept below 40 °C and the crude was purified via flash chromatography (0 2 % methanol in DCM).  nm gold palladium and viewed using a Hitachi S-4700 scanning electron microscope.

Inductively Coupled Plasma-Optical Emission spectrometry
The proportion of Pd element in the Pd-devices was determined by inductively coupled plasma-optical emission spectrometry at the School of Chemistry of the University of Edinburgh. A small amount of material (1-3 mg) was solubilized in a 10% HNO3 aqueous solution (1 mL) and heated at 80 °C overnight. The resulting mixture was diluted x5 in distilled water and Pd content measured in a Perkin Elmer Optima 5300 DV ICP-OES spectrometer using commercial Pd sample as standard.

Cell culture
Cell lines were grown in culture media supplemented with 10 % Fetal Bovine Serum (FBS) and 2 mM L-glutamine, then incubated in a tissue culture incubator at 37 °C and 5 % CO2. Human prostate cancer DU145 cells (a gift from Prof Neil Carragher) and human glioblastoma multiforme U87 cells (a gift from Dr Noor Gamon) were cultured in Dulbecco's modified Eagle's media (DMEM).

Cytotoxicity study: drug vs prodrug
Cells were seeded in a 96 well plate format at 2000 cells/well and incubated for 48 h before treatment. curves fitted with GraphPad Prism 5 using a sigmoidal variable slope curve. Zebrafish (AB line) were raised and maintained as previously described [2]. Embryos were generated by natural pair-wise mating and were kept and handled for all experiments in E3 medium (5 mM NaCl,

In vivo intratumoural ultrasound-guided implantation of Pd-devices
Mice identified as having produced tumours from initial cancer cell culture implantation were