Integration of antimicrobial peptides with gold nanoparticles as unique non-viral vectors for gene delivery to mesenchymal stem cells with antibacterial activity Li-Hua Peng a, b, * , Yan-Fen Huang a , Chen-Zhen Zhang a , Jie Niu a , Ying Chen c , Yang Chu a , Zhi-Hong Jiang b , Jian-Qing Gao a, ** , Zheng-Wei Mao c, *** a Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, PR China b State Key Laboratory of Quality Research in Chinese Medicine, Macau University of Science and Technology, PR China c MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, PR China article info Article history: Received 17 February 2016 Received in revised form 3 June 2016 Accepted 23 June 2016 Available online 27 June 2016 Keywords: Gold nanoparticles Antimicrobial peptide integration Gene delivery Stem cell abstract Gold nanoparticles (AuNPs) have emerged as attractive non-viral gene vectors. However their application in regenerative medicine is still limited partially due to a lack of an intrinsic capacity to transfect difficult- to-transfect cells such as primary cells or stem cells. In current study, we report the synthesis of anti- microbial peptide conjugated cationic AuNPs (AuNPs@PEP) as highly efficient carriers for gene delivery to stem cells with antibacterial ability. The AuNPs@PEP integrate the advantages of cationic AuNPs and antibacterial peptides: the presence of cationic AuNPs can effectively condense DNA and the antimi- crobial peptides are essential for the cellular & nucleus entry enhancement to achieve high transfection efficiency and antibacterial ability. As a result, antimicrobial peptides conjugated AuNPs significantly promoted the gene transfection efficiency in rat mesenchymal stem cells than pristine AuNPs, with a similar extent to those expressed by TAT (a well-known cell-penetrating peptide) modified AuNPs. More interestingly, the combinational system has better antibacterial ability than free antimicrobial peptides in vitro and in vivo, possibly due to the high density of peptides on the surface of AuNPs. Finally we present the concept-proving results that AuPs@PEP can be used as a carrier for in vivo gene activation in tissue regeneration, suggesting its potential as a multifunctional system with both gene delivery and antibacterial abilities in clinic. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Gold nanoparticles (AuNPs) have emerged as attractive nonviral gene vectors in last decades, due to their ease of synthesis, tunable size and shape, flexible surface modification, and tunable optical and electronic properties [1e5]. For example, Mirkin et al. developed AuNPs-oligonucleotide nanoconjugates as effective intracellular gene regulation agents [6]. Several groups have demonstrated that polyethylenimine (PEI)-conjugated AuNPs are able to deliver plasmid DNAs (pDNAs) to various types of cells with comparable or even better efficiency to PEI molecules [7e10]. Wang et al. and Gunaratne et al. demonstrated that AuNPs are capable of delivering microRNAs and small interfering RNAs into cells and efficiently down-regulated target genes and modulated cell func- tions [11,12]. Although AuNPs based gene delivery vectors are effective for in vitro gene transfection, the efficiency is greatly reduced in vivo. It is well recognized that once the surface of NPs is covered by bio- molecules (proteins, sugars, lipids and so on), upon the contact with biological systems, it results in the formation of a protein “corona” that is strongly associated with the NPs' surface. This process defines how living organisms “see” the NPs in a biological * Corresponding author. Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, 866# Yuhangtang Road, Hangzhou, 310058, PR China. ** Corresponding author. Institute of Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, 866# Yuhangtang Road, Hangzhou, 310058, PR China. *** Corresponding author. MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang Uni- versity, 38# Zheda Road, Hangzhou, 310027, PR China. E-mail addresses: lhpeng@zju.edu.cn (L.-H. Peng), gaojianqing@zju.edu.cn (J.-Q. Gao), zwmao@zju.edu.cn (Z.-W. Mao). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials http://dx.doi.org/10.1016/j.biomaterials.2016.06.057 0142-9612/© 2016 Elsevier Ltd. All rights reserved. Biomaterials 103 (2016) 137e149