51
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Cha EJ, Jang ES, Sun IC, Lee IJ, Ko JH, Kim YI, Kwon IC, Kim K, Ahn CH. Development of MRI/NIRF 'activatable' multimodal imaging probe based on iron oxide nanoparticles. J Control Release 2011; 155:152-8. [PMID: 21801769 DOI: 10.1016/j.jconrel.2011.07.019] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 07/04/2011] [Accepted: 07/10/2011] [Indexed: 12/11/2022]
Abstract
A fabrication method of Cy5.5-MMP substrate and PEG conjugated iron oxide nanoparticles with thin silica coating (PCM-CS) and its potential as an 'activatable' dual imaging probe for tumor imaging is described in this report. PCM-CS showed an intensity-averaged diameter of 43.1 ± 6.3 nm by dynamic light scattering without any noticeable aggregation over 7 days. Fluorescence of Cy5.5 on the surface of nanoparticles was fully quenched and the quenching efficiency was 97.2%. PCM-CS showed protease specific fluorescence recovery in vitro caused from the specific peptide cleavage by MMP-2 and the probe displayed the sensitivity on 0.5 nM or less enzyme concentration. Tumor was successfully visualized by NIRF and MRI in vivo by intravenously injected PCM-CS. NIRF signal of tumor was gradually increased up to 12h post injection and the intensity of tumor was about 3-4 times higher than normal tissue. NIRF signal at MMP-2 inhibitor treated tumor was clearly lower than tumor without inhibitor due to the insufficient peptide cleavage. NIRF signal at excised tumor was 5-10 times stronger than other organs. Noticeable darkening in magnetic resonance image was observed at the tumor region and the image was gradually darkened at 12h post injection of PCM-CS. The maximum signal difference between tumor region and healthy muscle was 34%.
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Hoffman J, Hong X, Ahn CH. Device performance of ferroelectric/correlated oxide heterostructures for non-volatile memory applications. NANOTECHNOLOGY 2011; 22:254014. [PMID: 21572192 DOI: 10.1088/0957-4484/22/25/254014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Ferroelectric field effect devices offer the possibility of non-volatile data storage. Attempts to integrate perovskite ferroelectric materials with silicon semiconductors, however, have been largely unsuccessful in creating non-volatile, nondestructive read memory elements because of difficulties in controlling the ferroelectric/semiconductor interface. Correlated oxide systems have been explored as alternative channel materials to form all-perovskite field effect devices. We examine a non-volatile memory using an electric-field-induced metal-insulator transition in PbZr(0.2)Ti(0.8)O(3)/La(1 - x)Sr(x)MnO(3) (PZT/LSMO), PZT/La(1 - x)Ca(x)MnO(3) (PZT/LCMO) and PZT/La(1 - x)Sr(x)CoO(3) (PZT/LSCO) devices. The performance of these devices in the areas of switching time and retention are discussed.
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Percec V, Ahn CH, Cho WD, Johansson G, Schlueter D. Design of new macromolecular architectures by using quasi-equivalent monodendrons as building blocks. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/masy.19971180106] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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54
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Peterca M, Imam MR, Ahn CH, Balagurusamy VSK, Wilson DA, Rosen BM, Percec V. Transfer, amplification, and inversion of helical chirality mediated by concerted interactions of C3-supramolecular dendrimers. J Am Chem Soc 2011; 133:2311-28. [PMID: 21280656 DOI: 10.1021/ja110753s] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The synthesis, structural, and retrostructural analysis of two libraries containing 16 first and second generation C(3)-symmetric self-assembling dendrimers based on dendrons connected at their apex via trisesters and trisamides of 1,3,5-benzenetricarboxylic acid is reported. A combination of X-ray diffraction and CD/UV analysis methods demonstrated that their C(3)-symmetry modulates different degrees of packing on the periphery of supramolecular structures that are responsible for the formation of chiral helical supramolecular columns and spheres self-organizable in a diversity of three-dimensional (3D) columnar, tetragonal, and cubic lattices. Two of these periodic arrays, a 3D columnar hexagonal superlattice and a 3D columnar simple orthorhombic chiral lattice with P222(1) symmetry, are unprecedented for supramolecular dendrimers. A thermal-reversible inversion of chirality was discovered in helical supramolecular columns. This inversion is induced, on heating, by the change in symmetry from a 3D columnar simple orthorhombic chiral lattice to a 3D columnar hexagonal array and, on cooling, by the change in symmetry from a 2D hexagonal to a 2D centered rectangular lattice, both exhibiting intracolumnar order. A first-order transition from coupled columns with long helical pitch, to weakly or uncorrelated columns with short helical pitch that generates a molecular rotator, was also discovered. The torsion angles of the molecular rotator are proportional to the change in temperature, and this effect is amplified in the case of the C(3)-symmetric trisamide supramolecular dendrimers forming H-bonds along their column. The structural changes reported here can be used to design complex functions based on helical supramolecular dendrimers with different degree of packing on their periphery.
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Jang A, Lee KK, Bishop PL, Kim IS, Ahn CH. Development of polymer lab-on-a-chip (LOC) for oxidation-reduction potential (ORP) measurement. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2011; 63:2309-2315. [PMID: 21977654 DOI: 10.2166/wst.2011.645] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Reverse osmosis (RO) desalination has been recognized as a promising method to solve the water shortage problem. Nevertheless, since it is energy intensive and has many problems associated with biofouling/fouling of RO membranes in RO plants, its commercial acceptance is still slow. Especially, as high levels of oxidizing agents negatively affect RO membrane efficiency and life span. So, there is a need to develop sensitive, selective, portable and rapid methods to determine oxidation-reduction potential (ORP) in feed solution. For developing a polymer ORP lab-on-a-chip (LOC), a microchannel patterned on a polymer substrate was successfully filled with 800 nm diameter silica beads using self-assembly bead packing technology. The measured ORPs using the three kinds of redox potential solutions were typically slightly lower than those of the nominal redox potential. But, all of the measurements should be deemed acceptable. The ORP LOC has also a much shorter response time than the conventional potentiometric sensor.
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Kolpak AM, Walker FJ, Reiner JW, Segal Y, Su D, Sawicki MS, Broadbridge CC, Zhang Z, Zhu Y, Ahn CH, Ismail-Beigi S. Interface-induced polarization and inhibition of ferroelectricity in epitaxial SrTiO₃/Si. PHYSICAL REVIEW LETTERS 2010; 105:217601. [PMID: 21231354 DOI: 10.1103/physrevlett.105.217601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2010] [Indexed: 05/30/2023]
Abstract
We use SrTiO₃/Si as a model system to elucidate the effect of the interface on ferroelectric behavior in epitaxial oxide films on silicon. Using both first-principles computations and synchrotron x-ray diffraction measurements, we show that structurally imposed boundary conditions at the interface stabilize a fixed (pinned) polarization in the film but inhibit ferroelectric switching. We demonstrate that the interface chemistry responsible for these phenomena is general to epitaxial silicon-oxide interfaces, impacting on the design of silicon-based functional oxide devices.
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Yi DK, Sun IC, Ryu JH, Koo H, Park CW, Youn IC, Choi K, Kwon IC, Kim K, Ahn CH. Matrix Metalloproteinase Sensitive Gold Nanorod for Simultaneous Bioimaging and Photothermal Therapy of Cancer. Bioconjug Chem 2010; 21:2173-7. [DOI: 10.1021/bc100308p] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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58
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Sun IC, Lee S, Koo H, Kwon IC, Choi K, Ahn CH, Kim K. Caspase sensitive gold nanoparticle for apoptosis imaging in live cells. Bioconjug Chem 2010; 21:1939-42. [PMID: 20936793 DOI: 10.1021/bc1003026] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We developed a new apoptosis imaging probe with gold nanoparticles (AuNPs). A near-infrared fluorescence dye was attached to AuNP surface through the bridge of peptide substrate (DEVD). The fluorescence was quenched in physiological conditions due to the quenching effect of AuNP, and the quenched fluorescence was recovered after the DEVD had been cleaved by caspase-3, the enzyme involved in apoptotic process. The adhesion of DEVD substrates on AuNP surface was accomplished by conjugation of the 3,4-dihydroxy phenylalanine (DOPA) groups which are adhesive to inorganic surface and rich in mussels. This surface modification with DEVD substrates by DOPA groups resulted in increased stability of AuNP in cytosol condition for hours. Moreover, the cleavage of substrate and the dequenching process are very fast, and the cells did not need to be fixed for imaging. Therefore, the real-time monitoring of caspase activity could be achieved in live cells, which enabled early detection of apoptosis compared to a conventional apoptosis kit such as Annexin V-FITC. Therefore, our apoptosis imaging has great potential as a simple, inexpensive, and efficient apoptosis imaging probe for biomedical applications.
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Cha EJ, Kim JE, Ahn CH. pH dependent drug release system using micelles stabilized by cationic drugs. Macromol Res 2010. [DOI: 10.1007/s13233-010-0708-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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60
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Ryu JH, Lee A, Lee S, Ahn CH, Park JW, Leary JF, Park S, Kim K, Kwon IC, Youn IC, Choi K. “One-Step” Detection of Matrix Metalloproteinase Activity Using a Fluorogenic Peptide Probe-Immobilized Diagnostic Kit. Bioconjug Chem 2010; 21:1378-84. [DOI: 10.1021/bc100008b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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61
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Yim MJ, Kim JE, Ahn CH, Kim HA, Lee M, Chae SY. Conjugation of histidine derivatives to PEGylated poly(L-lysine-co-L-phenylalanine) copolymer as a non-viral gene carrier. Macromol Res 2010. [DOI: 10.1007/s13233-010-0604-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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62
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Vaz CAF, Hoffman J, Segal Y, Reiner JW, Grober RD, Zhang Z, Ahn CH, Walker FJ. Origin of the magnetoelectric coupling effect in Pb(Zr0.2Ti0.8)O{3}/La{0.8}Sr{0.2}MnO{3} Multiferroic heterostructures. PHYSICAL REVIEW LETTERS 2010; 104:127202. [PMID: 20366560 DOI: 10.1103/physrevlett.104.127202] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Indexed: 05/29/2023]
Abstract
The electronic valence state of Mn in Pb(Zr0.2Ti0.8)O{3}/La{0.8}Sr{0.2}MnO{3} multiferroic heterostructures is probed by near edge x-ray absorption spectroscopy as a function of the ferroelectric polarization. We observe a temperature independent shift in the absorption edge of Mn associated with a change in valency induced by charge carrier modulation in the La0.8Sr0.2MnO3, demonstrating the electronic origin of the magnetoelectric effect. Spectroscopic, magnetic, and electric characterization shows that the large magnetoelectric response originates from a modified interfacial spin configuration, opening a new pathway to the electronic control of spin in complex oxide materials.
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Lee K, Bae KH, Lee Y, Lee SH, Ahn CH, Park TG. Pluronic/Polyethylenimine Shell Crosslinked Nanocapsules with Embedded Magnetite Nanocrystals for Magnetically Triggered Delivery of siRNA. Macromol Biosci 2010; 10:239-45. [DOI: 10.1002/mabi.200900291] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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64
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Kim JE, Cha EJ, Ahn CH. Reduction-Sensitive Self-Aggregates as a Novel Delivery System. MACROMOL CHEM PHYS 2010. [DOI: 10.1002/macp.200900671] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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65
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Lee SY, Lee Y, Chae SY, Park TG, Ahn CH. Blends of Oppositely Charged PEG-PPG-PEG Copolymers Displaying Improved Physical Thermogelling Properties. MACROMOL CHEM PHYS 2010. [DOI: 10.1002/macp.200900498] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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66
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Lee S, Ryu JH, Park K, Lee A, Lee SY, Youn IC, Ahn CH, Yoon SM, Myung SJ, Moon DH, Chen X, Choi K, Kwon IC, Kim K. Polymeric nanoparticle-based activatable near-infrared nanosensor for protease determination in vivo. NANO LETTERS 2009; 9:4412-6. [PMID: 19842672 PMCID: PMC3618996 DOI: 10.1021/nl902709m] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We report here a new protease activatable strategy based on a polymer nanoparticle platform. This nanosensor delivers chemically labeled matrix metalloproteinase (MMP)-activatable fluorogenic peptides to the specific MMPs of interest in vivo. Intravenous administration of the nanosensor in an MMP-positive SCC-7 xenograft tumor and a colon cancer mouse model verified the enzyme specificity of the nanosensor in vivo. The design platform of the nanosensor is flexible and can be fine-tuned for a wide array of applications such as the detection of biomarkers, early diagnosis of disease, and monitoring therapeutic efficacy.
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Sun IC, Eun DK, Na J, Lee S, Kim IJ, Youn IC, Ko CY, Kim HS, Lim D, Choi K, Messersmith P, Park T, Kim S, Kwon I, Kim K, Ahn CH. Heparin-Coated Gold Nanoparticles for Liver-Specific CT Imaging. Chemistry 2009; 15:13341-7. [DOI: 10.1002/chem.200902344] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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68
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Lim SH, Cha EJ, Huh J, Ahn CH. Micelle Behavior of Copolymers Composed of Linear and Hyperbranched Blocks in Aqueous Solution. MACROMOL CHEM PHYS 2009. [DOI: 10.1002/macp.200900217] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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69
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Lee H, Ahn CH, Park TG. Poly[lactic-co-(glycolic acid)]-Grafted Hyaluronic Acid Copolymer Micelle Nanoparticles for Target-Specific Delivery of Doxorubicin. Macromol Biosci 2009; 9:336-42. [DOI: 10.1002/mabi.200800229] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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70
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Hong X, Posadas A, Zou K, Ahn CH, Zhu J. High-mobility few-layer graphene field effect transistors fabricated on epitaxial ferroelectric gate oxides. PHYSICAL REVIEW LETTERS 2009; 102:136808. [PMID: 19392391 DOI: 10.1103/physrevlett.102.136808] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Indexed: 05/27/2023]
Abstract
The carrier mobility mu of few-layer graphene (FLG) field-effect transistors increases tenfold when the SiO2 substrate is replaced by single-crystal epitaxial Pb(Zr0.2Ti0.8)O3 (PZT). In the electron-only regime of the FLG, mu reaches 7x10(4) cm(2)/V s at 300 K for n=2.4x10(12)/cm(2), 70% of the intrinsic limit set by longitudinal acoustic (LA) phonons; it increases to 1.4x10(5) cm(2)/V s at low temperature. The temperature-dependent resistivity rho(T) reveals a clear signature of LA phonon scattering, yielding a deformation potential D=7.8+/-0.5 eV.
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Segal Y, Reiner JW, Kolpak AM, Zhang Z, Ismail-Beigi S, Ahn CH, Walker FJ. Atomic structure of the epitaxial BaO/Si(001) interface. PHYSICAL REVIEW LETTERS 2009; 102:116101. [PMID: 19392218 DOI: 10.1103/physrevlett.102.116101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Indexed: 05/27/2023]
Abstract
We present the structure of the interface responsible for epitaxy of crystalline oxides on silicon. Using synchrotron x-ray diffraction, we observe a 2 x 1 unit cell reconstruction at the interface of BaO grown on Si(001) terminated with 1/2 ML of Sr. Since this symmetry is not present in bulk BaO or Si, only the interface contributes to diffracted intensity. First principles calculations accurately predict the observed diffraction and identify the structure of the BaO/Si interface, including the elemental composition and a sub-A rumpling due to epitaxial strain of the 7 adjacent BaO and Si layers.
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Mok H, Bae KH, Ahn CH, Park TG. PEGylated and MMP-2 specifically dePEGylated quantum dots: comparative evaluation of cellular uptake. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1645-1650. [PMID: 19117377 DOI: 10.1021/la803542v] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Polyethylene glycol (PEG)-immobilized quantum dot (QD) nanoparticles, which could be specifically dePEGylated in response to the presence of the matrix metalloprotease-2 (MMP-2) enzyme, were prepared. The degree of PEGylation (MW 3400) on the surface of 12 nm streptavidin-coated QDs was stoichiometrically controlled by varying the feed amount of a biotin-substrate-PEG conjugate, where the substrate contained an MMP-2 cleavable peptide sequence. A biotin-cell penetrating peptide (CPP) conjugate was also immobilized onto the surface of the PEGylated QD surface to enhance the cellular uptake after dePEGylation. It was found that more than nine PEG chains per single QD were required to effectively inhibit the cellular uptake of modified QD particles down to around 20%, as compared with that of QD without PEG chains. However, the treatment of MMP-2 enzyme in the medium resulted in a substantial enhancement in the extent of QD cellular uptake by dePEGylation with concomitant resurfacing of sterically hidden CPP moieties. This study analyzed the effects of surface PEGylation density and MMP-2 specific dePEGylation on the cellular uptake of CPP-QD nanoparticles in a quantitative manner.
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Jang A, Zou Z, MacKnight E, Wu PM, Kim IS, Ahn CH, Bishop PL. Development of a portable analyzer with polymer lab-on-a-chip (LOC) for continuous sampling and monitoring of Pb(II). WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2009; 60:2889-2896. [PMID: 19934510 DOI: 10.2166/wst.2009.727] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A new portable analyzer with polymer lab-on-a-chip (LOC) has been designed, fabricated and fully characterized for continuous sampling and monitoring of lead (Pb(II)) in this work. As the working electrodes of the sensor, bismuth (Bi (III)) which allowed the advantage of being more environmentally friendly than traditional mercury drop electrodes was used, while maintaining similar sensitivity and other desirable characteristics. The size of a portable analyzer was 30 cmx23 cmx7 cm, and the weight was around 3 kg. The small size gives the advantage of being portable for field use while not sacrificing portability for accuracy of measurement. Furthermore, the autonomous system developed in coordination with the development of new polymer LOC integrated with electrochemical sensors can provide an innovative way to monitor surface waters in an efficient, cost-effective and sustainable manner.
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Lee SY, Lee Y, Kim JE, Park TG, Ahn CH. A novel pH-sensitive PEG-PPG-PEG copolymer displaying a closed-loop sol–gel–sol transition. ACTA ACUST UNITED AC 2009. [DOI: 10.1039/b912540j] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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75
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Choi YR, Chae SY, Ahn CH, Lee M, Oh S, Byun Y, Rhee BD, Ko KS. Development of polymeric gene delivery carriers: PEGylated copolymers ofl-lysine andl-phenylalanine. J Drug Target 2008; 15:391-8. [PMID: 17613657 DOI: 10.1080/10611860701401561] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Block copolymers consisting of poly(ethylene glycol) (PEG) and poly(amino acid)-based random copolymers were successfully synthesized by the ring opening polymerization of the N-carboxy anhydrides (NCA) of L-lysine and L-phenylalanine. The synthesized copolymers had a molecular weight of around 30,000 and contained L-lysine and L-phenylalanine residues with molar ratios of 10/0, 9/1, 8/2, 7/3 and 6/4. The complex formation of the copolymer and pCMV-luc plasmid DNA was confirmed by the gel retardation assay and zeta potential measurement. Complete neutralization was achieved at an N/P ratio of more than 1.0 and the size of the complex was determined to be around 150 nm by dynamic light scattering. The cytotoxicity and transfection efficiency were tested on the HEK 293T cell line. The synthesized copolymers displayed negligible cytotoxicity, resulting in a cell viability of more than 95%, while those of the poly(L-lysine) (PLL) and poly(ethylenimine) (PEI) homopolymer were around 65 and 55%, respectively, under comparable conditions. The introduction of the hydrophilic PEG is believed to reduce the toxicity of the copolymer, due to its enhanced biocompatibility, and to impart improved stability to the complex under physiological conditions. The transfection efficiency at the optimized charge ratio of 7 was dramatically improved as the molar content of the L-phenylalanine residues in the copolymers increased and reached a maximum value at an L-phenylalanine content of 30 mol%. The transfection efficiency of the PEGK7/plasmid DNA complex was around 80 times higher than that of PLL, despite the presence of neutral PEG as a block segment.
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