Biofriendly Route to Near-Infrared-Active Gold Nanotriangles and Nanoflowers through Nitric Oxide Photorelease for Photothermal Applications

Abstract

The development of ecofriendly synthetic protocols for the fabrication of nonspherical gold (Au) nanoobjects with localized surface plasmon resonance (LSPR) falling in the near-infrared (NIR) region is one challenging topic in modern materials science. Among others, such metallic nanostructures have intriguing applications in nanomedicine because of their photothermal properties activated by light excitation in the so-called therapeutic window (λmax = 650–1300 nm). Here we report an unprecedented, simple, and “green” methodology to prepare water-dispersible Au nanotriangles and nanoflowers with NIR LSPR (λmax = 850–1250 nm). They are obtained in a single step at room temperature and in a few minutes by using one of the most biologically relevant molecules, nitric oxide (NO), generated by visible-light irradiation of a tailored β-cyclodextrin-branched polymer, without the need of preformed seeds, external reducing and sacrificial agents, conventional surfactants, and stabilizing ligands. Biocompatibility and effective photothermal applications of these metallic nanostructures are demonstrated by a photothermally activated enzymatic reaction and photothermal-induced sarcoma cancer cell mortality using 808 nm light. This approach may pave the way for completely unexplored, facile, and bio/ecofriendly synthetic protocols based on the photogeneration of NO through biocompatible polymeric scaffolds, for the preparation of Au nanostructures directed toward bioapplications.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

“… 1081 Additionally, self-assembled NO-releasing amphiphiles based on N -nitrosamine moieties have been used to achieve NO delivery with polymersomes. 1331 Another common strategy is to combine polymers with NIR-active nanoparticles 1322 , 1332 and upconverting nanoparticles. 1258 , 1323 , 1325 , 1333 Finally, Furukawa and co-workers introduced an alternative approach for NO release using a zeolitic imidazole framework with nitroimidazole ligands.…”

Cyclodextrin-Based Nanoplatforms for Tumor Phototherapy: An Update

“…In another report, a nitroaniline type NO generator-tethered β-CD was copolymerized with β-CD and epichlorohydrin. Under 420 nm light irradiation, the tethered NO generator can produce an NO capable of reducing Au 3+ to Au 0 to form gold nanotriangles or nanoflowers in situ [ 26 ]. This method provided a biofriendly synthesis route without gold seed, toxic reductant, and surfactant.…”

Carbon Dots as Promising Tools for Cancer Diagnosis and Therapy

“…Several nanomaterials can act as effective photothermal transducers due to their photothermal effect in the NIR region, better tumor accumulation (EPR effect), and photostability. The most used PTT nanoparticles are metallic NPs, including Gold nanorods, nanoshells, nanostars, nanocages, nano triangles, and nanoflowers [ 15 , 119 ]. Recently, CDs have also been used as photosensitizing agents since they can provoke substantial temperature variations under irradiation.…”