Copolymers of acrylonitrile with quaternizable thiazole and triazole side-chain methacrylates as potent antimicrobial and hemocompatible systems Rubén Tejero a , Beatriz Gutiérrez a , Daniel López a,⇑ , Fátima López-Fabal b , José L. Gómez-Garcés b , Marta Fernández-García a,⇑ a Instituto de Ciencia y Tecnología de Polímeros (ICTP-CSIC), Juan de la Cierva 3, 28006 Madrid, Spain b Hospital Universitario de Móstoles, Río Júcar, s/n, 28935 Móstoles, Madrid, Spain article info Article history: Received 15 April 2015 Received in revised form 13 July 2015 Accepted 24 July 2015 Available online 26 July 2015 Keywords: Copolymerization Quaternization Antimicrobial Time-killing Cytotoxicity Acrylonitrile Thiazolium abstract A series of six copolymeric families, P(AN-co-MTAs) with various molar fractions of acrylonitrile (f AN ) and methacrylates (f MTA ) based on 1,3-thiazole and 1,2,3-triazole pendant groups with several spacers of dif- ferent length and nature (alkyl or succinic), have been synthesized by conventional radical polymeriza- tion. The molar fraction of acrylonitrile in the copolymers (F AN ) was determined by CHNS elemental analysis. The copolymers were also characterized by ATR-FTIR and molecular weights were determined by size exclusion chromatography (SEC). Due to the nucleophilic nature of the azole heterocycles the copolymers have been easily modified by N-alkylation reaction with butyl iodide leading to polyelec- trolytes of diverse amphiphilic balance, P(AN-co-MTAs-BuI). The degree of quaternization (DQ) was quan- titative in all instances and was determined by 1 H NMR spectroscopy. Dynamic light scattering (DLS) measurements were performed in order to determine the particle size and the charge density of the sys- tems. The antimicrobial activity of the copolymers was studied in terms of minimal inhibitory concentra- tion (MIC) against the Gram-positive bacteria Staphylococcus aureus, the Gram-negative Pseudomonas aeruginosa and the yeast Candida parapsilosis, as well as the cytotoxic activity toward human red blood cells (RBCs). These types of amphiphilic copolycations presented high selectivity (>300) maintaining moderate to good antimicrobial activity (MIC = 4–64 lg/mL) and being non-hemolytic even at high molar fractions of AN in the copolymers compared to PMTAs-BuI homopolymers. Moreover, two examples of acrylonitrile-enriched copolymers (F AN = 0.6) presented an excellent time-killing efficiency against microorganisms with 99.9% of killing ranging from 5 to 30 min. Besides, important changes in the mor- phology of the cell envelop of the microorganisms after treatment with P(AN-co-MTAs) were observed by Field Emission Scanning Electron Microscopy (FE-SEM) compared to untreated samples. These results indicate that these quaternized copolymers (QUATs) behave like the corresponding PMTAs-BuI homopolymers, being microbiostatic and also highly effective microbiocidal agents. Ó 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. 1. Introduction Today’s society’s major concerns are infectious diseases as well as health related problems. Antibiotics revolutionized in the last century are the great solution to these problems. However, due to their mechanisms of action, which do not physically damage the cell wall, but penetrate into the microorganism, these microor- ganisms can mutate [1]; arising resistance problems to antibiotics and then, their uncontrolled spreading. Although more-potent antibiotics are developed, antimicrobial polymeric materials and in particular cationic polymers present some advantages, including the ability to kill rapidly target cells, broad activity spectra, activity against some of the more serious antibiotic-resistant pathogens in clinics and the relative difficulty in selection of resistant mutants in vitro [2–5]. This is because the mechanism of action is quite dif- ferent. It is proposed that there are initial electrostatic interactions between the cationic polymer chains and negatively charged phospholipids within the cellular membrane of bacteria. Then, the penetration of the cationic part into the cell wall and the destructive interaction with the cytoplasmic membrane, lead to the leakage of intracellular components and, consequently, to the cell death [6–8]. http://dx.doi.org/10.1016/j.actbio.2015.07.037 1742-7061/Ó 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: daniel.l.g@csic.es (D. López), martafg@ictp.csic.es (M. Fernández-García). Acta Biomaterialia 25 (2015) 86–96 Contents lists available at ScienceDirect Acta Biomaterialia journal homepage: www.elsevier.com/locate/actabiomat