Bioconjugation of gold nanoparticles obtained by laser ablation in liquid solution for temperature controlled cell uptake and photothermal therapy

Gold nanoparticles (AuNP) obtained by laser ablation synthesis in liquid solution (LASiS) can be easily functionalized and bioconjugated. Stable AuNP solutions can be obtained by LASiS in water or in organic solvents, without any ligands or chemicals. Hence, nanoparticles surface is usually free and functionalization with a wide range of organic- and bio-molecules occurs in one step. Moreover AuNP multi-bio-conjugation can easily be obtained without place exchange reactions and real time monitoring of the surface coverage is possible by UV-Vis spectroscopy.[1-3] The size of AuNP obtained by LASiS can be further manipulated by chemical free laser techniques inspired by top down and bottom up approaches. Gold nanoparticles with average radii of 4.5 nm were obtained in this way, which allowed the sensing of AuNP bioconjugation with bovine serum albumin (BSA) down to 10:1 AuNP:BSA.[4] Thermosensitive gold nanoparticles have been obtained by surface conjugation of thiolated thermo-responsive poly-N-isopropylacrylamide. The polymer coated AuNP showed temperature controlled cell uptake. In human breast adenocarcinoma MCF7 cells, an 86 fold increase in the AuNP cell uptake was found by switching the temperature from 34°C to 40°C.[5] Irradiation experiments with 532 nm (9 ns) laser pulses fostered the death of cells preliminarily incubated with polymer coated AuNP at 40°C. These results provide new perspectives for the photothermal therapy of cancerous tissues by using cancer selective plasmonic nanostructures.[5]