An Efficient Method Based on the Photothermal Effect for the Release of Molecules from Metal Nanoparticle Surfaces

Abstract

New methods for the spatially and temporally controlled delivery of chemical and/or biochemical species using lowenergy visible light offers greater opportunities in photodynamic therapy, [1] chemical synthesis, [2] and photolithography. [3] The fact that designer metal nanoparticles absorb light of specific frequencies (at their plasmon resonance) and efficiently convert it into heat (through the photothermal effect) is a particularly appealing phenomenon that has been effectively used to trigger cell death [4] and melt ice [5] within the vicinity of the nanoparticles. However, to date, the heat generated when visible light is absorbed by such structures has not been used to initiate delivery events. This is surprising, as this technique would provide a convenient and general method to break chemical bonds and release biologically relevant payloads from the nanoparticle surfaces. Both detrimental (poisonous) and beneficial (therapeutic) agents could be released on command by using such a universal method.We recently set out to develop a new method to harness the local heat that dissipates from the nanoparticles when they are stimulated with visible light, in order to trigger thermally activated bond-breaking reactions close to the nanoparticle surfaces without significantly increasing the temperature of the surrounding environment. This approach has a benefit over others in that specific agents can be delivered to a cell without damaging it. Herein, we describe how we can trigger the release of a fluorescent dye from coreshell nanoparticles as the first illustration of a generalized approach to photothermal release.We chose the retro-Diels-Alder reaction to demonstrate our new release method because the temperature at which it is activated can be easily tuned by modifying the structure of the two chemical components (the diene and dienophile). [6] This cycloaddition reaction is particularly well-suited for surface-localized chemistry and has been used to selectively decorate [7] and control nanoparticle aggregation [8] by directly applying heat to suspensions of nanoparticles. The photothermal effect has yet to be taken advantage of in this context. We identified a specific retro-Diels-Alder reaction (shown in the substructure in Figure 1 a). Our choice was based on the fact that the bond-breaking reaction of 7-oxa-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic imide to release a furan and a maleimide component barely occurs at room temperature but proceeds above 60 8C. Model studies on both the endo and exo isomers of the depicted bicyclic system suggest that, as expected, the use of the former isomer is advantageous [9][10][11] since is cleanly converts into its two components at Figure 1. a) Release of the fluorescein dye from the surface of a silicagold core-shell nanoparticle by using the photothermal effect to induce the retro-Diels-Alder reaction of an anchored 7-oxa-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic imide derivative. UV/Vis absorption spectra of aqueous dispersions with TEM images of each type of pa...

Near-Infrared Photothermal Release of siRNA from the Surface of Colloidal Gold–Silver–Gold Core–Shell–Shell Nanoparticles Studied with Second-Harmonic Generation

“…5,6 Recent investigations described the use of retro-Diels–Alder-based chemistry to induce thermal cleavage using a furan and maleimide cycloadduct group to tether a fluorophore to gold nanoshell surfaces. 7 Cleavage at 60 °C was demonstrated with water bath experiments, and additional studies reported success with similar linker mimics. 8 Here we report the synthesis of gold–silver–gold core–shell– shell (CSS) nanoparticles linked to a siRNA mimic of miRNA148b using a furan–maleimide-based Diels–Alder adduct for photothermal release studies under near-infrared irradiation monitored in real time using second-harmonic generation spectroscopy.…”

Comparison of thermally actuated retro-diels-alder release groups for nanoparticle based nucleic acid delivery

“…At higher temperatures the cyloaddition reactions undergo reverse reaction pathways, referred to as the retro-Diels-Alder (rDA) reaction, to reproduce their diene and dienophile counterparts [20] [21] [22]. In Bakhtiari et al [23], it was demonstrated that the cycloadduct between a furan and maleimide could be synthesized at room temperature over seven days, with the rDA reaction observed to occur at temperatures 60 °C and above. Using gold nanoparticles modified with fluorescein-tagged furan-maleimide linkers and irradiated at their plasmonic wavelength of 532 nm, an increase in solution fluorescence was observed due to localized plasmon-phonon heat generation, triggering the rDA reaction and releasing the markers.…”

“…The Diels-Alder forward reaction can be facilitated via an electron-enriched diene with an electron-poor dienophile, substituted with electron-donating and electron-withdrawing groups, respectively [27]. In the current study, we aim to build on the chemistry investigated previously [23], in which the bond breaking of 7-oxa-bicyclo-[2.2.1]hept-5-ene-2,3-dicarboxylic imide was studied, and explore the bicyclic reactions of alternate dienes. With distinct temperature ranges achieved in which to initiate the rDA reaction, multiplex delivery applications can be realized.…”

Nanogold Flower‐Inspired Nanoarchitectonics Enables Enhanced Light‐to‐Heat Conversion Ability for Rapid and Targeted Chemo‐Photothermal Therapy of a Tumor

“…They were able to generate heat in surrounding areas and be widely used in drug delivery, cancer diagnosis and treatment, as well as sensors . Further, an improved biocompatibility and versatile surface functionalizations were obtained when specific‐shaped gold nanoparticles were immobilized on the surfaces of nano graphene oxide . Nanoscale graphene oxide has been widely employed to construct multifunctional nanocarriers for high capacity of anticancer drug loading .…”