|Ph.D Student||Bisker Gili|
|Subject||Nanomanipulations of Biomolecular Targets Using Femtosecond|
Laser Pulses and Gold Nanoparticles
|Department||Department of Nanoscience and Nanotechnology||Supervisor||Professor Dvir Yelin|
|Full Thesis text|
Gold nanoparticles play an important role in recent biomedical research and applications due to their unique optical properties. When resonantly illuminated by intense short laser pulses, noble metal nanoparticles can directly affect their nearby environment through a variety of physical mechanisms, including near field enhancement, local heating, generation of acoustic shock waves, and formation of cavitation bubbles.
We present a theoretical study of the relative effects of various experimental parameters, including pulse duration, irradiance and wavelength, and particle’s substance, size and shape. We show that spatially confined, local nanometric interactions between a particle and its near surroundings are feasible using 50 nm gold and silver nanospheres illuminated by laser pulses shorter than 70 fs and 90 fs, respectively, with no particle melting and minimal collateral damage. The results of this work could be useful for researchers in various fields, who aim at manipulating matter on the smallest possible scales.
We experimentally demonstrate a laser-driven chemical process for a controlled conjugation of gold nanoparticles to different fluorescent proteins. The process is enabled by illuminating PEG-coated nanoparticles with intense single femtosecond pulses at wavelengths that are tuned to their plasmonic resonance, while monitoring the fluorescent signal of the proteins. The resonant irradiation induces gold-sulfur bond breaking and cause the removal of the original PEG layer, enabling the adsorption of the fluorescent proteins onto the nanoparticles' surface. Possible applications of the resulting conjugates include controlled delivery of fluorescent markers and local sensing of biochemical processes.
The ability of laser pulses to effectively release coating molecules from gold nanoparticles is utilized for optically controlled drug release. Releasing drug molecules at their targets with high spatial and temporal accuracy could aid numerous clinical applications which require low systemic damage and low side effects. Nano-carriers of drugs are an attractive solution for such task, allowing specific accumulation in tumors and gradual release of their payload. We utilize gold nanospheres conjugated to Rituximab, an anti-CD20 monoclonal antibody-based drug, for carrying and releasing the drug upon irradiation of specifically tailored femtosecond pulses. The released anti-CD20 molecules retain their functionality and ability of triggering the complement-dependent cytotoxicity mechanism. This effect comes in addition to cell necrosis caused by the plasmonic nanometric shock waves emanating from the nanospheres and rupturing the plasma membranes. Main advantages of the presented technique include high spatial and temporal resolution, low toxicity and high repeatability and consistency due to the morphological stability of the nanospheres.