Platinum nanoparticles: a non-toxic, effective and thermally stable alternative plasmonic material for cancer therapy and bioengineering

Abstract

Absorption of near infrared (NIR) light by metallic nanoparticles can cause extreme heating and is of interest for instance in cancer treatment since NIR light has a relatively large penetration depth into biological tissue. Here, we quantify the extraordinary thermoplasmonic properties of platinum nanoparticles and demonstrate their efficiency in photothermal cancer therapy. Although platinum nanoparticles are extensively used for catalysis, they are much overlooked in a biological context. Via direct measurements based on a biological matrix we show that individual irradiated platinum nanoparticles with diameters of 50-70 nm can easily reach surface temperatures up to 900 K. In contrast to gold nanoshells, which are often used for photothermal purposes, we demonstrate that the platinum particles remain stable at these extreme temperatures. The experiments are paralleled by finite element modeling confirming the experimental results and establishing a theoretical understanding of the particles' thermoplasmonic properties. At extreme temperatures it is likely that a vapor layer will form around the plasmonic particle, and we show this scenario to be consistent with direct measurements and simulations. Viability studies demonstrate that platinum nanoparticles themselves are non-toxic at therapeutically relevant concentrations, however, upon laser irradiation we show that they efficiently kill human cancer cells. Therefore, platinum nanoparticles are highly promising candidates for thermoplasmonic applications in the life sciences, in nano-medicine, and for bio-medical engineering.

Optical trapping reveals differences in dielectric and optical properties of copper nanoparticles compared to their oxides and ferrites

“…To calculate C scat and C abs for the massive CuNPs, we used finite element modeling (FEM) implemented in COMSOL software to solve the scattering problem in the frequency domain by numerically solving Maxwell's equations within a discretized space. This procedure has previously been employed to calculate optical properties of metallic nanoparticles and has been shown to provide results reproducing direct experimental measurements 20,21 . We used tetrahedral meshes with a mesh size of 1/10 of the particle diameter.…”

“…To estimate the temperature increase of an optically trapped CuNP we used FEM to theoretically predict its plasmonic heating in the laser trap. The temperature of an optically trapped plasmonic nanoparticle equilibrates within nanoseconds 21 , hence, at the timescales here considered, the temperature can be assumed constant across the particle and decays with distance to the particle's surface, r, as 28,31…”

“…Optical tweezers are a well-known tool by which nano-or micro-scopic particles can be manipulated and accurately positioned using a highly focused laser beam 14 . Not only dielectric particles but also plasmonic nanoparticles made of gold, silver or platinum have been reported individually optically trapped using a tightly focused Gaussian laser beam, one of the simplest implementations of optical tweezers [15][16][17][18] , and their interaction with electromagnetic field, including the absorption and scattering of the particles, is relatively well understood [19][20][21][22][23] . For copper, however, only larger particles, 1-20 µm, have been reportedly trapped 24 , and a quantitative description of the interaction between CuNPs and the electromagnetic field is still lacking.…”

Plasmonic Material Engineering for Targeted Therapeutics

“…Several inorganic particles made from materials like Ag, Pt, Pd, Li, Na, Al, or other alternative plasmonic materials are currently being tested for their photothermal properties and do hold potential for future use with NIR light. [ 45–47 ]…”

The Use of a Biopolymer Conjugate for an Eco-Friendly One-Pot Synthesis of Palladium-Platinum Alloys

“…Moreover, the nanoparticles are often easily recovered from the reaction medium, and they possess steric environments within their active sites, both features that can positively influence the catalytic activity [32]. Among the noble metals, both palladium (Pd) and platinum (Pt) are well known for their unique characteristics, and both are used successfully in different scientific fields, including catalysis [33][34][35][36][37][38]. Due to the fact they have similar face-centred cubic (fcc) crystal structures and a high lattice match (lattice mismatch of 0.77%), palladium and platinum are highly miscible [39,40].…”