Single-Step Photochemical Formation of Near-Infrared-Absorbing Gold Nanomosaic within PNIPAm Microgels: Candidates for Photothermal Drug Delivery

Abstract

<jats:p>This work demonstrates the dynamic potential for tailoring the surface plasmon resonance (SPR), size, and shapes of gold nanoparticles (AuNPs) starting from an Au(I) precursor, chloro(dimethyl sulfide)gold (I) (Au(Me2S)Cl), in lieu of the conventional Au(III) precursor hydrogen tetrachloroaurate (III) hydrate (HAuCl4). Our approach presents a one-step method that permits regulation of an Au(I) precursor to form either visible-absorbing gold nanospheres or near-infrared-window (NIRW)-absorbing anisotropic AuNPs. A collection of shapes is obtained for the NIR-absorbing AuNPs herein, giving rise to spontaneously formed nanomosaic (NIR-absorbing anisotropic gold nanomosaic, NIRAuNM) without a dominant geometry for the tesserae elements that comprise the mosaic. Nonetheless, NIRAuNM exhibited high stability; one test sample remains stable with the same SPR absorption profile 7 years post-synthesis thus far. These NIRAuNM are generated within thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) microgels, without the addition of any growth-assisting surfactants or reducing agents. Our directed-selection methodology is based on the photochemical reduction of a light-, heat-, and water-sensitive Au(I) precursor via a disproportionation mechanism. The NIRAuNM stabilized within the thermoresponsive microgels demonstrates a light-activated size decrease of the microgels. On irradiation with a NIR lamp source, the percent decrease in the size of the microgels loaded with NIRAuNM is at least five times greater compared to the control microgels. The concept of photothermal shrinkage of hybrid microgels is further demonstrated by the release of a model luminescent dye, as a drug release model. The absorbance and emission of the model dye released from the hybrid microgels are over an order of magnitude higher compared to the absorbance and emission of the dye released from the unloaded-control microgels.</jats:p>

Surface‐Bound Microgels for Separation, Sensing, and Biomedical Applications

“…Marpu et al followed this work by developing a single-step method for synthesizing thermosensitive P(NIPAm-co-allylamine) microgels integrating AuNPs of various sizes, shapes, and plasmon resonance. [214] The hybrid microgels offer a tunable light-responsive platform for drug delivery via "squeeze out" mechanism.…”

Special Issue: Application of Nanomaterials in Biomedical Imaging and Cancer Therapy

“…The in vitro results demonstrated that the combination of pulse wave laser illumination of nanorods could produce about a 93% reduction in cell viability, compared with control exposures. In studying drug delivery, Marpu et al proposed a one-step method for the photochemical formation of NIR-absorbing gold nanomosaic using thermoresponsive poly(N-isopropylacrylamide) microgels [ 9 ]. This nanomosaic was generated based on photochemical reduction of a gold precursor, without reducing agent or growth-assisting surfactants.…”

Two Sides of the Same Coin: Light as a Tool to Control and Map Microsphere Design

“…As the application of polymer particles continues to expandalready including analytical, chromatographic, photonics, coatings, and biomedical applications − the ability to control their synthesis and properties becomes increasingly valuable. It is often desirable to be able to tune the particle size, shape, composition, functionality, and porosity to suit the intended application. − In particular, photochemistry has emerged as a heavily exploited tool in polymer and materials applications, including particle synthesis. − Importantly, photochemistry enables finer control and milder conditions compared to traditional methods of particle synthesis, where elevated temperatures, radical reactions, extended reactions times, additives, and limited functionality are commonplace.…”