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Radiolytic synthesis of gold nanoparticles in HEMA-based hydrogels : potentialities for imaging nanocomposites

Dziarabina Katsiaryna, Pinaeva Uliana, Kadłubowski Sławomir, Ulański Piotr, Coqueret Xavier

Nukleonika

2021

Vol. 66, No. 4

165--177

This article reports on the radiolytic synthesis of nanocomposites containing gold nanoparticles (AuNPs) within two types of hydrogels based on 2-hydroxyethyl methacrylate (HEMA): (i) plain networks with various contents in ethylene glycol dimethacrylate (EGDMA), as a cross-linker and (ii) stimuli-responsive (SR) networks prepared from these monomers copolymerized with [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MADQUAT) to confer pH-switchable swelling. Hydrogels were prepared by photopolymerization with well-defi ned composition and a high degree of monomer conversion using two experimental procedures, as xerogels or in aqueous solution. Besides MADQUAT, acrylic acid (AA) or N-isopropylacrylamide have been tested as copolymers, yielding pH- or temperature-sensitive hydrogels, respectively. Isothermal swelling in water was affected by monomer composition. Electron beam (EB) irradiation at doses up to 100 kGy of poly(HEMA) xerogels and water-swollen networks prepared with 0.5 wt% of EGDMA had a moderate impact on swelling characteristics and thermomechanical properties of the plain materials, whereas small amounts of extractables were formed. Poly(HEMA)-based nanocomposites containing AuNPs were successfully obtained by EB irradiation of samples swollen by aqueous solutions of Au(III). The effects of dose and cross-linking density on the formation of AuNPs were monitored by UV-visible spectroscopy. Irradiation at well-defined temperatures of the Au(III)-loaded SR hydrogels induced the formation of nanoparticles with size-dependent features, whereas the efficiency of Au(III) reduction at 10 kGy was not significantly affected by the network structure. EB-induced reduction of Au(III) in poly(HEMA) hydrogels using a lead mask to generate well-defined patterns yielded coloured and long-lasting images in the zones where the nanocomposite was formed.

Radiation synthesis of poly(acrylic acid) nanogels for drug delivery applications – post-synthesis product colloidal stability

Rurarz Beata P., Gibka Natalia, Bukowczyk Małgorzata, Kadłubowski Sławomir, Ulański Piotr

Nukleonika

2021

Vol. 66, No. 4

179--186

Synthesis of polymer nanogels (NGs) for biomedical applications is considered to be a very promising application in radiation engineering. Under high-dose pulse irradiation of dilute aqueous polymer solution, reactive species generated by water radiolysis can create multiple radicals on each macromolecule and consequently induce intramolecular cross-linking of polymer chains, resulting in NG formation. The obtained products are free from harmful monomers, initiators, and cross-linking agents, which makes them potentially applicable for drug delivery applications. One of the biggest challenges in handling and use of nanoparticles, however, is the colloidal stability, when aqueous suspensions are stored for prolonged periods. Therefore, development of the best protocols for the particular nanocarrier storage is key. To address this need, we have performed the prospective study in which we systematically assessed the influence of various processing and storage scenarios feasible in our lab, on the colloidal stability of the radiation-synthesized poly(acrylic acid) (PAA) NG particles in suspension. This allowed us to choose the optimal way of handling the product after its synthesis. We confirmed that none of the strategies we used and tested are substantially detrimental to our product. Filtration with 0.2-m filters was proven sufficient for sample purification and prolonged storage in aqueous suspension did not exert a negative effect on the colloidal stability of particles suspension. We have also demonstrated that lyoprotectant- -free lyophilization was suitable for our polymer nanoparticles. This is an important fact for further application of particles as nanocarriers for biologically active compounds such as targeting ligands or therapeutic moieties.