A Simple and Versatile Pathway for the Synthesis of Visible Light Photoreactive Nanoparticles

Abstract

This work pioneers the design of visible (415 nm) and UV-B light (300 nm) reactive nanoparticles via radical polymerization in aqueous heterogeneous media based on methyl methacrylate (MMA) and unique acrylates bearing tetrazole functionalities in a simple and straightforward two step reaction. Stable colloidal nanoparticles with an average diameter of 150 nm and inherent tetrazole functionality (varying from 2.5 to 10 wt% relative to MMA) are prepared via one-pot miniemulsion polymerization. In a subsequent step, fluorescent pyrazoline moieties serving as linkage points are generated on the nanoparticles by either photoinduced nitrile imine-mediated tetra zole-ene cycloaddition (NITEC) or nitrile imine carboxylic acid ligation (NICAL) in water, thus enabling the particles as fluorescent tracers. Through in-depth molecular surface analysis, it is demonstrated that the photoreactive nanoparticles undergo ligation to a variety of substrates bearing functionalities including maleimides, acrylates, or carboxylic acids, illustrating the versatility of the particle modification process. Critically, the unique ability of the photoreactive nanoparticles to be activated with visible light allows for their decoration with UV light-sensitive molecules. Herein, the ligation of folic acid-a vitamin prone to degradation under UV light-to the photoreactive nanoparticles using visible light is exemplified, demonstrating the synthetic power of our photoreactive fluorescent nanoparticle platform technology.

Chemiluminescent Read-Out of Degradable Fluorescent Polymer Particles

“…We subsequently evaluated the fluorescence of the particles and observed that the highest value is reached for 15 min of irradiation (Figure A, I max ). The subsequent decrease in fluorescence is most likely because of rearomatization of the pyrazoline (nonfluorescent adduct), as already described in literature. , Consequently, the CL output shows a similar trend as the light intensity is dependent on the fluorescent pyrazoline concentration (Figure B). SEM images after 15 min of irradiation showed polydisperse particles with small nuclei in the background, suggesting that the nucleation period is incomplete (Figures Cand S8).…”

Green-light induced cycloadditions

“…1 First described by Huisgen and Sustmann, 19 it has since been employed for a variety of applications, including protein labelling, 20 nucleic acid modification, 21 polymer ligation, 22 hydrogel assembly, 23 and modification of nanoparticles and microspheres. 24,25 In recent years, researchers have worked on extending the absorption profile of these compounds from UVB into the visible light regime, mostly by introducing substituents or extended conjugated chromophores at the N-phenyl ring. 22,26,27 However, to our knowledge, no NITEC reaction so far has been carried out with wavelengths longer than 420 nm in a one photon process.…”

Access to Photoreactive Core‐Shell Nanomaterials by Photoinitiated Polymerization‐Induced Self‐Assembly

“…This reaction has been termed nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC) . The Tet compounds have been used in a number of chemical, biological, and materials applications . Importantly, they offer the inherent possibility to fine‐tune the activation wavelength by varying the structure of the aryl moieties .…”