Laser-driven synthesis of nanoparticles for therapeutic applications

A nanosecond (ns) laser performed similar experiments using fluences in the range of 1.2-15 kJ/cm2 producing AuNP and TiO2NP. Cytotoxicity tests were performed with both species of NP up to concentrations of 40 µg/ml which were synthesised via ns laser ablation. Tests were performed on L929 fibroblast, RAW 264.7 macrophages, and antibacterial tests with S. aureus and E. coli bacteria.<br>The ultra-fast laser demonstrated good size controllability of nanoparticles with modal diameters ranging from 5-8 nm depending on laser fluence, with Gaussian size distributions <0.3 Polydispersity index (PDI).

At fluences > 90 J/cm2, a second peak emerging from the size distribution at 10-15 nm. The concentration was estimated around 68-84 µg/ml and zeta-potential (ζ) measured to be -22.2±0.4 mV. Synthesis with the ns laser of AuNP and TiO2NP gave TEM modal diameters at 8 nm and 13 nm, and hydrodynamic diameters around 130 nm and 370 nm respectively, with <0.3 PDI, and ζ around -20 mV.

UV-Vis spectroscopy estimated AuNP diameters of 3.6 nm-9 nm. Cytotoxicity tests on L929 fibroblasts proved AuNP cyto-compatibility, and TiO2NP were cytotoxic above 35 µg/ml but cyto-compatible for RAW 264.7 macrophages. Anti-bacterial tests with AuNP had a 3 log reduction with increasing concentration and TiO2NP showed a 3-4 log reduction of CFU/ml from 5-40 µg/ml.

Furthermore, a comparative study with commercially produced TiO2NP showed laser synthesised NP with stronger anti-bacterial properties.<br>Synthesis of NP through laser ablation can reliably produce NP with narrow size distributions and good size controllability was found with ultra-fast laser. ζ around ±20 mV demonstrates a stable solution contrary to coagulation evidence. The cyto-compatibility, particularly AuNP, show promise for implementation into clinical applications.

Future work into NP laser synthesis of other nano-shapes, species, and functionalisation will push this research further.<br><br><br>