Synthesis of vincristine-mediated gold nanoparticles and evaluation of their anticancer potential against human colon cancer cells (Colo-205)

Gold nanoparticles (AuNPs) are widely studied as carriers for chemotherapeutic drugs, but drug-loaded AuNPs are usually prepared in several steps that need separate reducing agents, stabilizers and linker chemistry. Here we report a one-pot, sunlight-assisted synthesis in which a commercial vincristine sulphate (VCR) injectable formulation acted as the reducing and capping agent, giving VCR-associated AuNPs (VCR-AuNPs) within 5 min without any other reagent. The particles showed a surface plasmon resonance band at 541 nm (citrate-capped AuNPs, 507 nm), and XRD and SAED confirmed face-centred cubic gold (lattice parameter 4.07 Å). TEM showed mainly quasi-spherical particles with a minor fraction of triangular and hexagonal plates (mean core size 18.2 ± 4.7 nm), while nanoparticle tracking analysis gave a modal hydrodynamic diameter of 27 nm together with smaller populations of larger particles. FTIR indicated that hydroxyl, amine and carbonyl groups of VCR are involved at the particle surface, and HPLC of the supernatant showed that 32.7% of the initial VCR was removed from solution during synthesis. VCR-AuNPs scavenged 50.7 ± 1.2% of DPPH radicals at 10 µg/mL compared with 31.8 ± 0.7% for free VCR (p < 0.001), whereas drug-free citrate-capped AuNPs scavenged at most 34.0 ± 0.8% up to 80 µg/mL. In the sulforhodamine B assay against Colo-205 human colon cancer cells, VCR-AuNPs inhibited growth as effectively as free VCR (24.0 ± 18.6% and 14.5 ± 6.9% of control growth at 10 µg/mL; GI 50 < 10 µg/mL for both; p = 0.56), showing that the drug keeps its antiproliferative activity after particle formation, whereas citrate-capped AuNPs were inactive (GI 50 > 80 µg/mL). The method offers a simple route to drug-bearing AuNPs; the reduction mechanism, the photostability of the drug and in vivo performance still need to be established.