Pulsatile protein release and protection using radiation-crosslinked polypeptide hydrogel delivery devices Caterina LoPresti a,1 , Valeria Vetri b,c , Mariaelena Ricca a , Vito Foderà b,c,2 , Giuseppe Tripodo d,3 , Giuseppe Spadaro a , Clelia Dispenza a,⇑ a Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Università di Palermo, Viale delle Scienze Ed. 6, 90100 Palermo, Italy b Dipartimento di Scienze Fisiche ed Astronomiche, Università di Palermo, Via Archirafi 36, 90123 Palermo, Italy c CNR – Istituto di Biofisica, U.O. Via U. La Malfa 153, 90146 Palermo, Italy d Dipartimento di Chimica e Tecnologie Farmaceutiche, Università di Palermo, Via Archirafi 32, 90123 Palermo, Italy article info Article history: Received 28 June 2010 Received in revised form 23 November 2010 Accepted 26 November 2010 Available online 30 November 2010 Keywords: Polyaspartamide High energy irradiation pH-responsive hydrogels Mechanical properties Protein release abstract In the recent years recombinant technology has identified numerous protein based therapeutics. Their effective delivery, though, can be challenging due to the poor stability of most proteins along their path- way to the target site in the body. Hydrogels have been identified as good candidates for protein encap- sulation and delivery thanks to both material and manufacturing process advantages. In this work we propose high energy irradiation as a synthetic methodology of choice to engineer hydrogel-based delivery devices for encapsulation and pulsatile release of proteins, triggered by pH, and for prevention of their denaturation when encapsulated. In particular, maleic anhydride functionalised poly(N-2- HydroxyEthyl)-DL-Aspartamide (PHEA-MA) hydrogels have been crosslinked without the use of toxic reagents or catalysts and in mild conditions via gamma irradiation. At the variance of the irradiation con- ditions, hydrogels with dramatically different crosslinked structure, thus rheological properties and swelling behaviour, have been obtained. The ability to swell and shrink cyclically upon repeated pH jumps and the absence of cytotoxicity have been demonstrated for all the hydrogels produced. Moreover some of the variants exhibited full degradability at 37 °C with degradation products that are not-toxic for the cell. Depending on the networks average mesh size, as derived by the treatment of rheological data with simple rubber elasticity equations, with respect to the characteristic dimension of the chosen model protein, substantial loading of the protein and its retention or release, controlled by pH, have been achieved. These results, coupled with the versatility of the synthetic platform, suggest the possibility to use these materials as components of intelligent/programmable devices specifically designed as to release theoretically any protein based therapeutic. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Peptide and protein therapeutics, now available in large quanti- ties and at a reasonable cost by the recent advances in biotechnol- ogies, are growing in importance and attracting increased interest because they are specifically effective at a comparably low dose [1]. Therapeutic proteins have posed though the challenge for their effective delivery due to their susceptibility to proteolytic degrada- tion and/or secondary and tertiary structure disruption in physio- logical fluids or harsh pH [2–4]. Furthermore, patient compliance is often reduced by their lack of immunogenicity [5–6]. In order to ensure proper pharmacokinetics and efficacy, polymeric delivery systems can be developed, thereby providing protection of the inherently delicate payload from degradation/aggregation, prevention of an (enhanced) immune response and site/temporal control of the release [7–9]. Hydrogels, in particular, are extensively studied and continu- ously optimised to engineer delivery devices of protein therapeutics, for their widely variable and easily adjustable permeabilities, their aqueous inner environment and hydrophilic surface, rubbery and soft consistency [10–12]. With respect to other polymeric pro-drugs and matrices, hydrogels can offer either relatively mild conditions of synthesis that are particularly important, when contemporary pro- tein encapsulation is desired, or mild protein encapsulation condi- tions, when drug loading is performed after crosslinking, thereby not impairing the structure and activity of the protein in either case. 1381-5148/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.reactfunctpolym.2010.11.030 ⇑ Corresponding author. Tel.: +39 091 6567210; fax: +39 091 6567280. E-mail address: dispenza@dicpm.unipa.it (C. Dispenza). 1 Present address: Merck Serono S.p.A., Pharmaceutical Dev. Biotech Products- Technical Operations via Luigi Einaudi 11-00012 Guidonia Montecelio (Roma) Italy. 2 Present address: Sector of Biological and Soft Systems, Dept. of Physics, Cavendish Laboratory University of Cambridge JJ Thomson Avenue, Cambridge CB3 0HE, UK. 3 Present address: Zentrum für Biomaterialentwicklung, Institut für Polymerfors- chung, GKSS Forschungszentrum Kantstr. 55, 14513 Teltow, Germany. Reactive & Functional Polymers 71 (2011) 155–167 Contents lists available at ScienceDirect Reactive & Functional Polymers journal homepage: www.elsevier.com/locate/react