An acid-labile temperature-responsive sol–gel reversible polymer for enhanced gene delivery to the myocardium and skeletal muscle cells Ran Namgung a , Sujin Nam a , Soo Kyung Kim a , Sejin Son a , Kaushik Singha a , Jin-Sook Kwon b , Youngkeun Ahn b , Myung Ho Jeong b , In-Kyu Park b, c, d , Vivek K. Garripelli e , Seongbong Jo e , Won Jong Kim a, * a Department of Chemistry, BK21 Program, Polymer Research Institute, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang 790-784, Republic of Korea b Heart Research Center, Chonnam National University Hospital, Gwangju 501-757, Republic of Korea c Department of Biomedical Sciences, BK21 Program, Chonnam National University Medical School, Gwangju 501-746, Republic of Korea d The BioImaging Research Center, GIST, Gwangju 500-712, Republic of Korea e Department of Pharmaceutics, School of Pharmacy, The University of Mississippi, University, MS 38677, USA article info Article history: Received 20 April 2009 Accepted 22 May 2009 Available online 23 June 2009 Keywords: Myocardium Skeletal muscle Gene delivery Acid-labile Non-ionic polymer abstract The work demonstrates the development of acid-labile temperature-responsive sol–gel reversible polymer for enhanced in vivo myocardium and skeletal muscle gene delivery. In this report, multi-block copolymers (MBCPs) synthesized from pluronic Ò and di-(ethylene glycol) divinyl ether (DEGDVE) were used as a delivery vehicle for controlled and sustained release of plasmid DNA (pDNA) in in vitro as well as in vivo experiments. The non-ionic MBCP/pDNA complex showed remarkable transfection efficiencies against the myocardium cells as well as muscle cells in vivo, which is otherwise very difficult to achieve by using cationic polymers. In in vitro experimental settings, this intelligent stimuli-responsive polymer is shown to improve the transfection efficiency of branched polyethylenimine (BPEI)/pDNA complex when used together. The effect of MBCP on the surface charge and particle size of its various complexes with pDNA and BPEI was also studied. The release profile of pDNA from the MBCP gel was investigated and pH of the degraded polymer was also monitored to ascertain its non-cytotoxicity arising due to the increased acidity as observed with other PLGA-based polymers. The rapid sol–gel transition of MBCP under thermal stimuli with concomitant release of pDNA under acidic stimulation has potential for site specific, efficient and controlled transfection of therapeutic gene. In short, MBCP provides the silver lining in combat against the hurdles encountered in transfection to myocardial or other muscle cells. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Generally, two different approaches have been utilized for the delivery of genes in gene therapy, namely the viral vectors and non- viral delivery systems mainly using cationic polymers [1–4] or lipids [5,6]. Viral vectors show excellent transfection efficiencies although their use in clinical applications are often limited by several drawbacks, including the potential of mutagenicity or oncogenesis, several host immune responses, and the high cost of production [7,8]. As an alternative, non-viral gene delivery has become a promising strategy, which has been successfully applied to many therapeutic and research purposes such as gene therapy and tissue engineering. However, the major disadvantage of these non-viral vectors is their low transfection efficiency compared to viral vectors. Enhancement of the low transfection efficiency can be achieved through inhibited degradation of DNA in serum condition, facilitated cellular uptake, and facile escape from endosomal entrapment. Incorporation of DNA in polymeric biomaterials can overcome some of these barriers for the efficient gene transfer by protection of DNA from enzymatic degradation, localization of therapeutic gene, and sustained and controlled delivery of genes to the local site. For controlled DNA release from polymeric biomaterials, DNA is entrapped within the polymers and released into the environment, typically occurring by a combined mechanism of diffusion and polymer degradation [9]. Moreover, sustained local gene delivery from polymeric biomaterials or matrix may enhance gene transfer by first protecting DNA and then maintaining the DNA at effective concentrations around specific site, extending the opportunity for internalization, followed by DNA release into the tissue over days to months. Several approaches have been employed for controlled DNA release based on polymeric biomaterials including DNA * Corresponding author. Tel.: þ82 54 279 2104; fax: þ82 54 279 3399. E-mail address: wjkim@postech.ac.kr (W.J. Kim). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2009.05.073 Biomaterials 30 (2009) 5225–5233