Thermo-Mechanical and Adhesive Properties of Polymeric Films Based on ZnAl-Hydrotalcite Composites for Active Wound Dressings Luana Perioli, 1 Andrea Dorigato , 2 Cinzia Pagano, 1 Matteo Leoni, 3 Alessandro Pegoretti 2 1 Department of Pharmaceutical Sciences, University of Perugia, Perugia 06123, Italy 2 Department of Industrial Engineering and INSTM Research Unit, University of Trento, Trento 38123, Italy 3 Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento 38123, Italy Composite films based on sodium carboxymethyl cellu- lose (Na-CMC) loaded with a ZnAl(OH) 2 CO 3 ÁyH 2 O hydrotal- cite (ZnAl-HTlc), were developed and characterized. The composites were mechanically more stable than the matrix alone: the noticeable enhancement of elastic mod- ulus, creep resistance and failure properties, all propor- tional to the filler content, came at the expenses of a certain embrittlement. The filler tended to aggregate in the composites and the size of the aggregates increased with ZnAl-HTlc amount. Contact angle measurements highlighted how ZnAl-HTlc introduction in the polymeric matrix could strongly modify the wettability conditions of the films increasing their hydrophilicity. Bioadhesion tests showed that the adhesion behavior of the composites decreased as ZnAl-HTlc amount increases, testifying the influence of the filler on the ability of the film to bind skin surface. Therefore, the developed films may find applica- tion as active wound dressings since ZnAl-HTlc can be easily intercalated with an active pharmaceutical ingredi- ent to be progressively released on the wound. POLYM. ENG. SCI., 00:000–000, 2018. V C 2018 Society of Plastics Engineers INTRODUCTION Polymers currently find many applications in the pharmaceuti- cal field as fillers, binders, disintegrant, gliding, swelling, suspend- ing, emulsifiers, flocculating agents, and so forth [1]. Polymers are usually employed for their biocompatibility, permeability, hydro- philicity, and low coefficient of friction [2]. Hydrophilic polymers are able to swell (up to 90%) in contact with water forming hydro- gels useful for different applications in drug delivery, stem cell engineering, immunomodulation, cellular and molecular therapies, wound healing [2, 3]. Among the numerous polymers available, sodium carboxymethyl cellulose (Na-CMC) is one of the election polymers used in pharmaceutical field because of its exceptional properties such as high viscosity, transparency, hydrophilicity, non- toxicity, biocompatibility, biodegradability, and good film forming ability. This latest feature has allowed the development of various cellulose-based devices. Chemically, Na-CMC consists of b-linked glucopyranose residues with different levels of Na-carboxymethyl (AOCH 2 COO 2 Na 1 ) substitution. As three hydroxyls are present per C 6 ring, the maximum degree of substitution is three [4]. In general, cellulose derivatives are environmentally friendly and therefore favorable in the health field, as they can be easily digested or metabolized by those microorganisms present in air, water and soil able to synthesize cellulose-specific enzymes [5]. All these properties make Na-CMC a suitable material for the development of wound dressings. The main limiting factor of Na- CMC for this application is represented by the low mechanical properties [6]: the integrity of the formulation could be impaired before, during and after the application. In this way, wound dress- ing effectiveness and patient compliance are compromised [7]. A possible solution to overcome these limits is to add nanoparticles (<10% w/w) to the polymer matrix, to form a nanocomposite. An improvement of the mechanical, thermal and gas barrier properties is expected [8, 9]. Among the large number of available fillers, layered double hydroxides (HTlcs) find interesting application in the pharmaceutical field. HTlcs, anionic clays or hydrotalcites (from the name of the most important mineral belonging to this family) have a general formula M(II) 1–x M(III) x (OH) 2 (A n– ) x/ n 3yH 2 O, where M(II) is a divalent cation, M(III) is a trivalent cat- ion and A n– is a n-valent interlayer anion specie. The interlayer anions can be easily exchanged for other inorganic or organic spe- cies, thus transforming the HTlc into drug carriers and drug-release materials both for oral and topical use [10–14]. Biohybrids of HTlc and biomolecules can be designed to carry or drop functional biomolecules in gene therapy and drug deliv- ery [15]. Many studies demonstrated their ability to form micro- and nanocomposites with improved mechanical properties [16, 17]. Nanocomposites based on Na-CMC and HTlcs have already been proposed in the literature, but only a few examples exist. Yadollahi et al. [18] observed that HTlc increases the mechanical properties of Na-CMC-based films. This gain can be attributed to the strong interfacial adhesion of HTlc with Na-CMC [19–21]. The aim of this work is to study the impact of the physical dis- persion of HTlc on the morphological and structural properties of composite films made of Na-CMC and ZnAl-(OH) 2 CO 3 ÁyH 2 O (ZnAl-HTlc). For shortness the composite films will be here called CMC-HTlc. The films were characterized from morphological (X- ray diffraction [XRD], contact angle measurements, field emission scanning electron microscope [FESEM]), thermal (differential scanning calorimetry [DSC]) and a mechanical (quasi-static tensile tests, creep and recovery tests) points of view. Bioadhesion tests were also performed. The developed CMC-HTlc composites could be used for patches that can simultaneously protect the skin and provide a controlled drug release. Drug loading and delivery prop- erties are promising and detailed studies are in progress. EXPERIMENTAL Materials A purified granular Na-CMC (BLANOSE Cellulose Gum), was supplied by Hercules Inc. (Wilmington, DE). On the basis Correspondence to: A. Dorigato; e-mail: andrea.dorigato@unitn.it DOI 10.1002/pen.24877 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2018 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—2018