Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso Application of radiation for the synthesis of poly(n-vinyl pyrrolidone) nanogels with controlled sizes from aqueous solutions S. Duygu Sütekin, Olgun Güven ⁎ Department of Chemistry, Hacettepe University, Beytepe, Ankara 06800, Turkey HIGHLIGHTS • PVP nanogels were prepared by Gamma and E-Beam irradiation of di- lute aqueous solutions. • Interdependence of PVP solution- and irradiation source-based parameters investigated. • PVP nanogels with sizes controllable in 30–250 nm range were produced. • Full characterization of nanogels was made by DLS, SEM, AFM and GPC. • As synthesized PVP nanogels were found to be stable for 2 years in re- frigerated solution. GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Nanogel Size Control Poly(N-vinyl pyrrolidone) Radiation induced crosslinking E-beam Gamma ABSTRACT Controlling of sizes of nanogels is very important for any biomedical application. In the present study we report a facile and reproducible method of preparing biocompatible nanogels of poly(N-vinyl pyrrolidone) (PVP) which were synthesized by using either electron beam (e-beam) (NGEB) or gamma irradiation (NGG) of dilute aqueous solutions. Nanogels with different hydrodynamic sizes were obtained at the variance of the polymer molecular weight, concentration, type of radiation source hence dose rate and total absorbed dose. For the first time a comparative study of gamma and e-beam irradiation was made on the same polymer with the aim of controlling sizes of nanogels in the range of 30–250 nm. Moreover the stability of radiation-synthesized nanogels was fol- lowed up to 2 years in refrigerated solution and found to retain their original sizes and distributions enabling their long-term storage and use. The synthesized nanogels were characterized by using dynamic light scattering (DLS), gel permeation chromatography (GPC), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. This work provides a clue to the fundamental question of how to control sizes of nanogels without using any additives which are indispensable with the other techniques. The technique is applicable to any water soluble polymer. 1. Introduction Nano- and microgels can be visualized as coiled state of macro- molecules where a permanent network consisting of intramolecular crosslinks exists and molecules of a solvent filling the pores of this network to make it a gel. Contrary to precursor linear polymers, new properties arise from the fact that these structures are covalently crosslinked. Like their macroscopic counterparts hydrogels, they have the ability to swell in water and body-fluids with fast response to en- vironmental factors, such as ionic strength, pH, and temperature (Cardiel et al., 2014; Knipe et al., 2014; Vinogradov, 2010). However the main factors that directly determines properties of nanogels are https://doi.org/10.1016/j.apradiso.2018.12.028 Received 26 September 2017; Received in revised form 18 December 2018; Accepted 20 December 2018 ⁎ Corresponding author. E-mail address: guven@hacettepe.edu.tr (O. Güven). Applied Radiation and Isotopes 145 (2019) 161–169 Available online 22 December 2018 0969-8043/ © 2018 Elsevier Ltd. All rights reserved. T