Freshly prepared aqueous solution of gold (III) chloride trihydrate (0.25 mM, 400 mL) was placed in a 500 mL two-necked round-bottomed flask and NaOH (1 mM, 50 mL) was then added directly into the solution. The mixture was stirred for 30 mins and then heated to reflux in a 130 °C oil bath under magnetic stirring. After the solution was started to reflux, trisodium citrate solution (166 mM, 6 mL) was then quickly added. The solution colour gradually changed from yellow to light red in 15 mins. The reaction was refluxed for another 1 hr to complete the synthesis. The solution was then taken out of the oil bath, and kept stirring for 1 hr till it was cooled down to RT. This produced 27 nm GNPs (G27) stock which was transferred to a clean glass container and stored at RT till use. (dt, 1H, J=12.9, 6.9 Hz), 1.78 -1.54 (m, 4H), 1.42 (q, 1H, J=7.6 Hz); Preparation of Gx-DiMan. Twenty mL each of the citrate stabilised G13 or G27 stock solutions were directly added with the required amount of LA-EG4-DiMan ligand stock solution (in water) at a GNP: ligand molar ratio of 1:3 000 for G13 or 1:10 000 for G27. The resulting solutions were stirred at RT in the dark overnight to promote ligand exchange via gold-thiol self-assembly. After that the resulting mixtures were divided into 1.5 mL portions into eppendorf tubes and centrifuged at 17 000 x g for 30 mins for G13-conjugates or 6 000 x g for 15 mins for G27-conjugates to remove any unbound free ligands. After careful withdrawn of supernatant, the GNP residues were washed with pure water (3 x 500 μL) followed by centrifugation three times to remove any unbound free ligands. For G27, the eppendorf tubes were pre-washed with 0.025% Tween-20 aqueous solution before being used in Gx-