Pluronic-Nanogold hybrids: synthesis and tagging with photosensitizing molecules.

The design of polymeric-metal hybrid nanocomposites with multiple functionalities, i.e. from enabling detection and imaging to assisting diagnosis and therapy, is becoming an important research topic in nanomedicine. In this work, Pluronic-Nanogold hybrid nanoparticles (Au-PF127) were successfully prepared in aqueous solution in a single step reaction using Pluronic F127 block copolymer as both reducing and stabilizing agent. The ability of polymer to control the nanoparticle formation and stabilization was systematically investigated by several characterization techniques: UV-Vis absorption, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential measurements. It was found that polymer concentrations higher than critical micelle concentration (CMC) provide stable nanoparticles even in high molarity NaCl solution. In view of biomedical applications, as prepared Au-PF127 nanoparticles were modified with Methylene Blue (MB) phenothiazinium based photosensitizing drug. Combined surface enhanced Raman scattering (SERS) and fluorescence detection of MB embedded within the polymer shell has revealed the dual functionality of MB-encoded Pluronic-Nanogold hybrids (Au-PF127-MB) to operate under biological conditions as both effective drug carriers and sensitive optical probes.

Chitosan-coated triangular silver nanoparticles as a novel class of biocompatible, highly effective photothermal transducers for in vitro cancer cell therapy.

One of the relevant directions that nanotechnology is taking nowadays is connected with nanomedicine and specifically related to the use of light and nanoparticles in early diagnosis and effective therapeutics of cancer. Noble-metal nanoparticles can act under laser irradiation as effective photothermal transducers for triggering localized hyperthermia of tumors. In this work we report the performance of newly synthesized chitosan-coated silver nanotriangles (Chit-AgNTs) with strong resonances in near-infrared (NIR) to operate as photothermal agents against a line of human non-small lung cancer cells (NCI-H460). The hyperthermia experiments were conducted by excitation of nanoparticles-loaded cells at 800 nm wavelength from a Ti:Sapphire laser. We found that the rate of cell mortality in the presence of Chit-AgNTs is higher than in the presence of thiolated poly(ethylene) glycol capped gold nanorods (PEG-AuNRs) - a common hyperthermia agent used as reference-, while no destructive effects were noticed on the control sample (cells without nanoparticles) under identical irradiation conditions. Additionally, we conducted cytotoxicity assays and found Chit-AgNTs to be efficiently uptaken by the cells while exhibiting good biocompatibility for healthy human embryonic cells (HEK), which is essential for any in vivo applications. Our results reveal a novel class of biocompatible plasmonic nanoparticles with high potential to be implemented as effective phototherapeutic agents in the battle against cancer.

Detoxification of gold nanorods by conjugation with thiolated poly(ethylene glycol) and their assessment as SERS-active carriers of Raman tags.

We present an effective, low cost protocol to reduce the toxicity of gold nanorods induced by the presence of cetyltrimethylammonium bromide (CTAB) on their lateral surface as a result of the synthesis process. Here, we use thiolated methoxy-poly(ethylene) glycol (mPEG-SH) polymer to displace most of the CTAB bilayer cap from the particle surface. The detoxification process, chemical and structural stability of as-prepared mPEG-SH-conjugated gold nanorods were characterized using a number of techniques including localized surface plasmon resonance (LSPR), transmission electron microscopy (TEM) and surface-enhanced Raman spectroscopy (SERS). In view of future applications as near-infrared (NIR) nanoheaters in localized photothermal therapy of cancer, we investigated the thermal behaviour of mPEG-SH-conjugated gold nanorods above room temperature. We found a critical temperature at around 40 degrees C at which the adsorbed polymer layer is susceptible to undergo conformational changes. Additionally, we believe that such plasmonic nanoprobes could act as SERS-active carriers of Raman tags for application in cellular imaging. In this sense we successfully tested them as effective SERS substrates at 785 nm laser line with p-aminothiophenol (pATP) as a tag molecule.

An ethylene-glycol decorated ruthenium(ii) complex for two-photon photodynamic therapy.

A novel water-soluble Ru(ii) complex has been prepared, which represents a promising new class of selective two-photon sensitizers for use in photodynamic therapy within a confined space.