Amphiphilic core-shell nanoparticles with poly(ethylenimine) shells as potential gene delivery carriers.
ABSTRACT Spherical, well-defined core-shell nanoparticles that consist of poly(methyl methacrylate) (PMMA) cores and branched poly(ethylenimine) shells (PEI) were synthesized via a graft copolymerization of methyl methacrylate from branched PEI induced by a small amount of tert-butyl hydroperoxide. The PMMA-PEI core-shell nanoparticles were between 130 to170 nm in diameter and displayed zeta-potentials near +40 mV at pH 7 in 1 mM aqueous NaCl. Plasmid DNA (pDNA) was mixed with nanoparticles and formed complexes of approximately 120 nm in diameter and was highly monodispersed. The complexes were characterized with respect to their particle size, zeta-potential, surface morphology, and DNA integrity. The complexing ability of the nanoparticles was strongly dependent on the molecular weight of the PEI and the thickness of the PEI shells. The stability of the complexes was influenced by the loading ratio of the pDNA and the nanoparticles. The condensed pDNA in the complexes was significantly protected from enzymatic degradation by DNase I. Cytotoxity studies using MTT colorimetric assays suggested that the PMMA-PEI (25 kDa) core-shell nanoparticles were three times less toxic than the branched PEI (25 kDa). Their transfection efficiencies were also significantly higher. Thus, the PEI-based core-shell nanoparticles show considerable potential as carriers for gene delivery.
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ABSTRACT: A novel amphiphilic and cationic triblock copolymer consisting of monomethoxy poly(ethylene glycol), poly(epsilon-caprolactone) (PCL) and poly(2-aminoethyl ethylene phosphate) denoted as mPEG(45)-b-PCL(100)-b-PPEEA(12) was designed and synthesized for siRNA delivery. The copolymers were well characterized by (1)H NMR spectroscopy and gel permeation chromatography. Micelle nanoparticles' (MNPs) formation of this amphiphilic copolymer in aqueous solution was studied by dynamic light scattering, transmission electron microscopy and fluorescence technique. MNPs took uniform spherical morphology with zeta potential of around 45 mV and were stabilized by hydrophobic-hydrophobic interaction in the PCL core, exhibiting the critical micelle concentration at 2.7 x 10(-3) mg/mL. Such MNPs allowed siRNA loading post nanoparticle formation without change in uniformity. The average diameter of nanoparticles after siRNA binding ranged from 98 to 125 nm depending on N/P ratios. The siRNA loaded nanoparticles can be effectively internalized and subsequently release siRNA in HEK293 cells, resulting in significant gene knockdown activities, which was demonstrated by delivering two siRNAs targeting green fluorescence protein (GFP). It effectively silenced GFP expression in 40-70% GFP-expressed HEK293 cells and it was observed that higher N/P ratio resulted in more effective silence which was likely due to better cell internalization at higher N/P ratio. MTT assay demonstrated that neither MNPs themselves nor siRNA loaded MNPs showed cytotoxicity even at high concentrations. Such cationic MNPs made from biocompatible and biodegradable polymers are promising for siRNA delivery.Biomaterials 12/2008; 29(32):4348-55. DOI:10.1016/j.biomaterials.2008.07.036 · 8.31 Impact Factor
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ABSTRACT: Monosized cationic nanoparticles were produced by emulsifier-free emulsion polymerization of styrene, poly(ethylene glycol) methacrylate and N-[3-(dimethyl-amino) propyl] methacrylamide, conducted in the presence of a cationic initiator, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, using different amounts of ingredients and at different conditions. The structure of the terpolymers was confirmed by (1)H-NMR and FTIR spectroscopy. The nanoparticles, with an average size of 71.3 nm [polydispersity index (PDI), 1.110] and a Zeta potential of 65.6 mV obtained by a zeta sizer, were used in the transfection studies. HeLa cells were transfected in in vitro cell cultures with these non-viral nanoparticle vectors with a green fluorescent protein (GFP)-expressing plasmid DNA. The transfer of the cationic nanoparticles into the cells and GFP expressions with the conjugates of the nanoparticles and the GFP-expressing plasmid were followed by both light and fluorescent microscopy. The GFP expression efficiency was unexpectedly high (up to 90%).Journal of Tissue Engineering and Regenerative Medicine 03/2008; 2(2-3):155-63. DOI:10.1002/term.78 · 4.43 Impact Factor
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ABSTRACT: xiii, 118 leaves : ill. (some col.) ; 30 cm. PolyU Library Call No.: [THS] LG51 .H577M ABCT 2007 Siu Recently, with the patented technology, we have developed a cationic amphiphilic core-shell nanoparticle composed of well defined poly(methyl methacrylate) hydrophobic cores and poly(ethyleneimine) hydrophilic shell. This particle has the combined properties of cationic polymers, nanoparticles and surface functional groups, making it excellent candidate as gene carrier in gene delivery systems. In our previous studies, we have demonstrated that this novel nanoparticle has comparative advantages over the PEI system for in vitro gene delivery. During the gene transfer process, there are a number of barriers that restrict the success of gene delivery. However, cytoplasmic microinjection studies have demonstrated that inefficient gene transfer from the cytosol to the nucleus is the major limiting step. In order to further enhance the transfection efficiency and to provide the nuclear targeting capability, we have tried the inclusion of a nuclear protein HMGBl in our system. It has been reported that the high mobility group protein HMGBl can enhance the transfection efficiency in both naked DNA and liposome-mediated transfections. When DNA is packed with the HMGBl protein, condensed molecules can form and the transfection efficiency is approximately similar to the calcium phosphate method. In the HVJ-liposome system, HMGB1 serves as a DNA binding protein. Within the nuclear envelop, it assists nuclear access and promotes gene stabilization. In our present study, HMGB1 protein was added together with DNA and the PMMA-PEI nanoparticles to form the gene delivery complexes. Formation of complexes was demonstrated using agarose gel retardation assay and the DNA with HMGB1 still bound can be released from the complexes with the use of poly(aspartic acids). Therefore, with the incorporation of HMGB1 in our existing PMMA-PEI core-shell nanoparticle system, the resultant HMGB1-DNA-nanoparticle complexes still maintain their DNA condensing capacity, DNA release ability and DNA protection ability. Furthermore, in in vitro transfection, complexes formed by first condensing the plasmid DNA with nanoparticles and then binding with the HMGB1 protein gave a transfection efficiency significantly higher than that of the PMMA-PEI nanoparticle system without the presence of HMGB1. We believe that this system with the inclusion of HMGB1 has the potential to be developed into a viable and efficient non-viral gene carrier for use in vivo. M.Phil., Dept. of Applied Biology & Chemical Technology, The Hong Kong Polytechnic University, 2007