Comprehensive NMR Studies of the Structures and Properties of PEI Polymers

Holycross, Daniel R.; Chai, Minghui

doi:10.1021/ma4011796

Cited by 76 publications

(68 citation statements)

References 20 publications

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“…[20] The new signal at d = 42.5 ppm can be assigned to oligomers formed on degradationo fP EI 800 . [21] These signals werem ore significantf or 0.1 mL min À1 than 0.2 mL min À1 flow rates ( Figure S14). An umber of new signals were evident in the region d = 2.5-4 ppm which can be assigned to the protons for NÀCH 2 ÀN, CH 2 OH and CH 2 ÀO-.…”

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confidence: 82%

High‐Shear‐Imparted Tunable Fluorescence in Polyethylenimines

et al. 2018

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In general, fluorescent polyethylenimine (PEI) nanoparticles absorb primarily UV light, with the fluorophores typically having extended conjugated structures. In this work, PEI nanoparticles of circa 10 nm in diameter,d evoid of such structural features and with tunable fluorescence, were generatedi na microfluidic platform. Tunability of the fluorescence was achieved by varying the flow rate of liquid entering the rapidly rotating tube in av ortex fluidic device (VFD), without the need for additional reagents. Chemical incorporation of amide functional groups triggered enhanced fluorescencei ntensity and auto-fluorescence over aw ide range, and the resultingn anoparticles showeds ignificantly reduced cytotoxicity compared to as-received polymers.Fluorescent nanoparticles derived from amino-containing dendritic polymers have been used for biological imaging and biosensors [1][2][3] where the fluorophores are usually extended conjugated chemical structures. [4] Even though simple oxidation, acidification or methylation can further enhancet he intrinsic fluorescence, [5] the mechanism of fluorescencef rom these dendritic polymers is not well understood. Some propose that the origin of fluorescence arises from oxygen-doped interior tertiary amine [6] and interior urea-doped with peripherala mino groups. [7] These fluorescent polymers can contain Schiff base moieties, [5] tertiary amine or carbonyl groups in an dendrimer interior with terminal groups such as monohydroxyl, [8] air [6] or hydrogen peroxide [9] oxidized amines, amine-rich nanoclusters, [5] and carbamato anion. [2] The nature of the dendritic structure and macromolecular backbonec an also significantly influence the fluorescenceproperties. [1,5] Polyethylenimine (PEI) is aw ater-solublec ationic polyelectrolytew hich contains al arge number of amino groups, and has been used to prepare various fluorescent materials. [10] The fluorescenceo fP EI is unexpected given the absence of chromophores. [5] Refluxing 25 kDa PEIi nn itric acid at 120 8Cf or 12 ha ffords photoluminescent nanoparticles (l ex = 360 nm, l em = 450 nm) bearing amide linkages (NHCO). [11] Hyperbranched PEI (hPEI)-based fluorescent particles have been prepared at high temperature (200 8C) [12] or via microwave irradiation. [13] Adding formaldehyde at 90 8Cr esultsi nf luorescent polymericn anoparticles (l ex = 365 nm, l em = 508 nm) or gels (l ex = 350 nm, l em = 476 nm). Similarly,a dding salicylaldehyde impartsf luorescence( l ex = 370 nm, l em = 495 nm) [14] which arises from the formationo fSchiff base moieties. [3,5] Hydrothermal treatmento fh PEI with aldehydes at 95 8Cg enerates fluorescent polymer nanoparticles, [3] depending on the pH which can complicate the processing. The carbamate anion is another moiety responsible for fluorescence( l ex = 364 nm, l em = 470 nm), formed by reacting PEI with CO 2.[2] Based on our knowledge,t unability of fluorescence has never been addressedo nP EI-based nanoparticles with mostly reported optimum excitation in the UV region, as described above...

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confidence: 82%

High‐Shear‐Imparted Tunable Fluorescence in Polyethylenimines

et al. 2018

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“…High resolution NMR spectroscopy has demonstrated its strength in the structural elucidation and characterization of PLA polymers . The stereosequence pattern can be assigned with certainty for non‐overlapping resonances.…”

Section: Resultsmentioning

confidence: 99%

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

Munzeiwa

Nyamori

Omondi

2018

Applied Organom Chemis

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A series of Zn(II) and Cu(II) complexes were synthesized using unsymmetrical N,N′‐ diarylformamidine ligands, i.e. N‐(2‐methoxyphenyl)‐N′‐2,6‐dichorophenyl)‐formamidine (L1), N‐(2‐methoxyphenyl)‐N′‐phenyl)‐formamidine (L2), N‐(2‐methoxyphenyl)‐N′‐(2,6‐dimethylphenyl)‐formamidine (L3) and N‐(2‐methoxyphenyl)‐N′‐(2,6‐diisopropylphenyl)‐formamidine (L4). The complexes, [Zn2(L1)2(OAc)4] (1), [Zn2(L2)2(OAc)4] (2), [Zn2(L3)2(OAc)4] (3), [Zn2(L4)2(OAc)4] (4), [Cu2(L1)2(OAc)4] (5), [Cu2(L2)2(OAc)4] (6), [Cu2(L3)2(OAc)4] (7) and [Cu2(L4)2(OAc)4] (8), were prepared via a mechanochemical method with excellent yields between 95 ‐ 98% by reacting the metal acetates and corresponding ligands. Structural studies showed that both complexes are dimeric with a paddlewheel core structure in which the separation between the two metal centres are 2.9898 (8) and 2.6653 (7) Å in complexes 3 and 7, respectively. Complexes 1 – 8 were used in ring‐opening polymerization of ε‐caprolactone (ε‐CL) and rac‐lactide (rac‐LA). Zn(II) complexes were more active than Cu(II) complexes, with complex 1 bearing electron withdrawing chloro groups being the most active (kapp = 0.0803 h‐1). Low molecular weight poly‐(ε‐CL) and poly‐(rac‐LA) ranging from 1720 to 6042 g mol‐1, with broad molecular weight distribution (PDIs, 1.78 – 1.87) were obtained. Complex 2 gave reaction orders of 0.56 and 1.52 with respect to ε‐CL and rac‐LA, respectively.

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“…As shown in the figure, there are eight types of methylene carbon atoms (a-g) in PEI structure, and the chemical shifts for these carbons were recently assigned by Holycross and Chai. 27) Multiplicity of the 13 C resonances for the same methylene carbons are due to various sizes, oligomers, and impurities of PEI. As indicated by the asterisks on the spectrum of PEI with EDTA, many methylene carbon resonances were shifted to upfield about 0.1-0.25 ppm by EDTA.…”

Section: Resultsmentioning

confidence: 99%

Low Molecular Weight Branched PEI Binding to Linear DNA

Utsuno

Kono

Tanaka

et al. 2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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Polyethylenimine (PEI) is one of the most versatile non-viral vectors used in gene therapy, especially for delivering plasmid DNA to human cells. However, a good understanding of PEI binding to DNA, the fundamental basis for the functioning of PEI as a vector, has been missing in the literature. In this study, PEI (branched, 600 Da) binding to DNA was examined by isothermal titration calorimetry (ITC), quartz crystal microbalance (QCM) and a complementary set of analysis tools. We demonstrated that a separation between the binding heat and the condensation heat is needed and that the excluded site model should be used for PEI binding stage in the ITC analysis. The equilibrium constant for PEI binding to DNA was determined to be 2.5 10 5 M 1 from the ITC analysis, and as 2.3 10 5 M 1 from the QCM analysis. Additionally, we suggested that the 600 Da branched PEI binds to the major groove of DNA and the rearrangement of PEI on DNA may be difficult to occur because of the small dissociation rate. The binding analysis presented here can be employed to improve our understanding of the functioning of PEI and PEI-like non-viral vectors.Key words DNA condensation; polyethylenimine; isothermal titration calorimetry; quartz crystal microbalance; thermodynamics; kinetics The cationic polyelectrolyte polyethylenimine (PEI) is one of the most versatile polymers used for non-viral gene delivery.1-3) PEI binds to DNA via electrostatic interactions between the positively charged PEI amine groups and the negatively charged nucleic acid phosphate groups in the DNA backbone. PEI, by neutralizing the DNA molecule, facilitates its condensation into particles in the 'nano-meter' range.4) It is believed that PEI's strong transfection ability is due to its effective ability to condense the DNA molecule into a nanoparticle, 5-7) which facilitates its cellular uptake and subsequent intracellular trafficking. PEI is available in a broad range of molecular weights. Higher molecular weight PEIs have high transfection efficiency, but lead to excessive cytotoxicity. Low molecular weight PEIs have demonstrated low toxicity on cells, but they also display low transfection efficiency.5) Recently, highly efficient non-viral vectors have been developed by modifying low molecular weight (600 Da) PEI with a variety of functional groups. [8][9][10][11][12] To better understand PEI interactions with the DNA molecule, we previously determined the thermodynamic parameters of PEI binding to DNA using isothermal titration calorimetry (ITC). 13) In that study, two types of binding modes were found to describe the interactions between PEI and DNA. One type of binding involves PEI binding to the DNA groove, another likely binding mode involves external binding of PEI to the DNA phosphate backbone. Recently, Ketola et al. showed that the equilibrium constant of 25 kDa branched PEI to plasmid DNA (7164 bp) using time-resolved fluorescence spectroscopy was 7.3×10 ). 13)The observed difference may be due to the difference in the mass and architecture of the PEI u...

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Comprehensive NMR Studies of the Structures and Properties of PEI Polymers

Cited by 76 publications

References 20 publications

High‐Shear‐Imparted Tunable Fluorescence in Polyethylenimines

High‐Shear‐Imparted Tunable Fluorescence in Polyethylenimines

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

Low Molecular Weight Branched PEI Binding to Linear DNA

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