Thiol-Functional Polymer Nanoparticles via Aerosol Photopolymerization

Abstract

Spherical, individual polymer nanoparticles with functional –SH groups were synthesized via aerosol photopolymerization (APP) employing radically initiated thiol-ene chemistry. A series of various thiol and alkene monomer combinations were investigated based on di-, tri-, and tetrafunctional thiols with difunctional allyl and vinyl ethers, and di- and trifunctional acrylates. Only thiol and alkene monomer combinations able to build cross-linked poly(thio-ether) networks were compatible with APP, which requires fast polymerization of the generated droplet aerosol during the photoreactor passage within a residence time of half-minute. Higher monomer functionalities and equal overall stoichiometry of functional groups resulted in the best nanoparticles being spherical and individual, proven by scanning electron microscopy (SEM). The presence of reactive –SH groups in the synthesized nanoparticles as a basis for post-polymerization modifications was verified by Ellman’s test.

Synthesis of Spherical Nanoparticle Hybrids via Aerosol Thiol-Ene Photopolymerization and Their Bioconjugation

“…The spray solution placed inside the aerosol generation unit (ATM 220, Topas GmbH, Dresden, Germany) is atomized under the stream of pressurized nitrogen, forming a droplet aerosol, which, subsequently, passes to the photoreactor unit. In the photoreactor, droplets polymerize under the irradiation of UV-fluorescence lamps (λ max = 312 nm, T-15.C, Vilber Lourmat, incident irradiance E = 15.4 mW/cm 2 (measured via UV-Pad-E from Opsytec Dr. Gröbel GmbH)) to form polymer nanoparticles, which are collected on 0.1 µm pore size Durapore ® hydrophilic membrane filter (Millipore, Mersck KGaA, Darmstadt Germany) [ 18 ]. During the process, while the volatile solvent in the spray solution is partially evaporated, every 30 min after the start of the reaction, the solvent is added to compensate for the evaporated amount.…”

“…The nanoparticles obtained via aerosol photopolymerization were tested for the presence of reactive -SH groups using Ellman’s reaction [ 18 ]. The solution of DTNB in phosphate-buffered saline (PBS) was prepared and added to the dispersion of nanoparticles.…”

“…In our recent paper [ 18 ], we investigated several thiol-ene monomer combinations that worked well in combination with aerosol photopolymerization to form spherical individual nanoparticles with reactive -SH groups [ 18 ]. In the present study, we aim to establish a working combination to produce spherical individual polymer nanoparticles that contain individual silver nanospheres inside.…”

Immobilization of β-Galactosidase by Encapsulation of Enzyme-Conjugated Polymer Nanoparticles Inside Hydrogel Microparticles

“…In other methods, e.g., emulsion polymerization, additional separation procedures are required to obtain pure nanoparticles for enzyme conjugation. The combination of aerosol photopolymerization with thiol-ene monomers ensures the synthesis of spherical cross-linked polymer nanoparticles with reactive -SH groups ( Suvarli et al, 2021b ) that are not present on other types of nanoparticles such as silicon or gold nanoparticles. A two-step bioconjugation process that can bind various biomolecules onto -SH groups of polymer nanoparticles via thiol-ene “click” reactions was previously introduced ( Suvarli et al, 2021a ).…”

“…Polymer nanoparticles were synthesized via aerosol thiol-ene photopolymerization ( Suvarli et al, 2021a ). The accessible -SH groups on the surface of these polymer nanoparticles offer an effective way of bioconjugation through a thiol-ene “click” reaction with maleimide-biotin and subsequent addition of streptavidin derivatives ( Suvarli et al, 2021a ; Suvarli et al, 2021b ). An affinity binding immobilization technique was applied with biotin-conjugated nanoparticles and a commercially available streptavidin-β-galactosidase.…”