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

Surface accessibility to functionalization or bioconjugation are key points for gold nanoparticles (AuNP) applications. Often, synthesis methods based on chemical reduction require long and expensive processes to obtain the desired AuNP functionalization. An alternative is represented by laser ablation synthesis of metal nanoparticles in liquid solution (LASiS).[1-3] LASiS provides stable colloidal solutions in water or in organic solvents, without any ligands or chemicals. Therefore AuNP surface is usually free and functionalization with a wide range of organic and bio-molecules occurs in one step. Also AuNP multi-conjugation can easily be obtained. Moreover the 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 a chemical free laser techniques inspired by top down and bottom up approaches. Gold nanoparticles (AuNP) 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 a ratio of 10:1 for AuNP:BSA.[4] The conjugation of AuNP with the thermo-responsive polymer poly-N-isopropylacrylamide was exploited for the temperature controlled cellular uptake of AuNP. An 86 fold increase in the AuNP loading was found by switching the temperature from 34°C to 40°C in human breast adenocarcinoma MCF7 cells. Irradiation experiments with 532 nm (9 ns) laser pulses produced the preferential death of AuNP loaded cells, indicating a new strategy for the photothermal therapy of cancerous tissues combined with temperature responsive plasmonic nanostructures.[5]