The oxidation of glucose and related compounds by glucose oxidase from Aspergillus Niger

Pazur J.H., Kleppe K.

Biochemistry. 1964, 3, 578-83.

Synthesis, Characterization, and Long-Term Stability of Hollow Polymer Nanocapsules with Nanometer-Thin Walls

Dergunov, S. A., K. Kesterson, et al. (2010).

Macromolecules (Washington, DC, U. S.) 43(18): 7785-7792.

Hollow polymer nanocapsules are produced by the polymn. within hydrophobic interior of lipid bilayers that act as temporary self-assembled scaffolds. Pore-forming templates are co-dissolved with monomers in the bilayers to create pores with controlled size and chem. environment. Polymn. was monitored with UV spectroscopy and dynamic light scattering. High-resoln. magic angle spinning NMR characterization provided detailed structural information about nanocapsules. Spherical shape was confirmed by electron microscopy. Medium-sized mols. can be entrapped within porous nanocapsules. No release of encapsulated mols. was obsd. within 240 days. 

Ultrasonic gene and drug delivery using eLiposomes

Marjan Javadi, William G. Pitt, Christopher M. Tracy, Jeffery R. Barrow, Barry M. Willardson, Jonathan M. Hartley, Naakaii H. Tsosie

Journal of Controlled Release 167 (2013) 92–100

eLiposomes are liposomes encapsulating emulsions and therapeutics for targeted delivery. By applying ultrasoundto eLiposomes, emulsion droplets can transform from liquid to gas and rupture the lipid bilayer of the eLiposome to release a drug or plasmid. In this study, perfluoropentane (PFC5) emulsions were encapsulated inside folated eLiposomes carrying a model drug (calcein) or a model GFP plasmid to examine the effects of a folate ligand, PFC5 emulsion and various ultrasonic acoustic parameters in drug delivery and gene transfection into HeLa cells.

Confocal microscopy was used to quantify drug delivery and the level of plasmid transfection into HeLa cells. The results showed that drug delivery or transfection was minimal without incorporation of internal PFC5 emulsions and folate ligand on the eLiposome surface. It was also shown that application of ultrasound greatly enhanced the drug delivery and plasmid transfection. Delivery of these therapeutics appears to be to the cytosol, indicating that the expansion of the emulsion droplets disrupted both the eLiposomes and the

endosomes.

Investigating Ligand−Receptor Interactions at Bilayer Surface Using Electronic Absorption Spectroscopy and Fluorescence Resonance Energy Transfer

Navneet Dogra, Xuelian Li, and Punit Kohli

dx.doi.org/10.1021/la300724z | Langmuir 2012, 28, 12989−12998

We investigate interactions between receptors and ligands at bilayer surface of polydiacetylene (PDA) liposomal nanoparticles using changes in electronic absorption spectroscopy and fluorescence resonance energy transfer (FRET). We study the effect of mode of linkage (covalent versus noncovalent) between the receptor and liposome bilayer. We also examine the effect of size-dependent interactions between liposome and analyte through electronic absorption and FRET responses. Glucose (receptor) molecules were either covalently or noncovalently attached at the bilayer of nanoparticles, and they provided selectivity for molecular interactions between glucose and glycoprotein ligands of E. coli. These interactions induced stress on conjugated PDA chain which resulted in changes (blue to red) in the absorption spectrum of PDA. The changes in electronic absorbance also led to changes in FRET efficiency between conjugated PDA chains (acceptor) and fluorophores (Sulphorhodamine-101) (donor) attached to the bilayer surface. Interestingly, we did not find significant differences in UV−vis and FRET responses for covalently and noncovalently bound glucose to liposomes following their interactions with E. coli. We attributed these results to close proximity of glucose receptor molecules to the liposome bilayer surface such that induced stress were similar in both the cases. We also found that PDA emission from direct excitation mechanism was ∼2−10 times larger than that of the FRET-based response. These differences in emission signals were attributed to three major reasons: nonspecific interactions between E. coli and liposomes, size differences between analyte and liposomes, and a much higher PDA concentration with respect to sulforhodamine (SR-101). We have proposed a model to explain our experimental observations. Our fundamental studies reported here will help in enhancing our knowledge regarding interactions involved between soft particles at molecular levels.

Polydiacetylene Liposomes Functionalized with Sialic Acid Bind and Colorimetrically Detect Influenza Virus

JACS:, 1995, 117, 829-830

Anke Reichert, Jon 0. Nagy, Wayne Spevak, and Deborah Charych*

Cell membranes are remarkable structures from a materials science point of view. These highly organized, self-assembled structures provide indispensable functions for cells such as molecular recognition, pumping, gating, energy conversion, and signal transduction.The design of “smart” materials based on membrane structures with specific functional properties is an emerging field of study! We have prepared synthetic, polymerizable liposomes that resemble the organization and functionalization of cell membranes and have employed them as simple colorimetric sensors. The liposomes were designed to specifically bind to influenza virus particles and, in addition, report the binding event by undergoing a visible color change. In effect, these molecular assemblies mimic cell surface molecular recognition as well as signal transduction.

Effect of inorganic positive ions on the adsorption of surfactant Triton X-100 at quartz/solution interface

Science in China Series B: Chemistry

October 2008, Volume 51, Issue 10, pp 918-927

YueHua Shao, 

Ying Li, 

XuLong Cao, 

DaZhong Shen, 

BaoMin Ma, 

HongYan Wang

The electrode-separated piezoelectric sensor (ESPS), an improved setup of quartz crystal microbalance (QCM), has been employed to investigate the adsorption behavior of nonionic surfactant Triton X-100 at the hydrophilic quartz-solution interface in mineralized water medium in situ, which contained CaCl₂ 0.01 mol·L⁻¹, MgCl₂ 0.01 mol·L⁻¹, NaCl 0.35 mol·L⁻¹. In a large scale of surfactant concentration, t effects of Ca²⁺, Mg²⁺ and Na⁺ on the adsorption isotherm and kinetics are obviously different. In aqueous solution containing NaCl only, adsorption of Triton X-100 on quartz-solution interface is promoted, both adsorption rate and adsorption amount increase. While in mineralized water medium, multivalent positive ions Ca²⁺ and Mg²⁺ are firmly adsorbed on quartz-solution interface, result in the increasing of adsorption rate and adsorption amount at low concentration of surfactant and the peculiar desorption of surfactant at high concentration of Triton X-100. The results got by solution depletion method are in good agreement with which obtained by ESPS. The “bridge” and “separate” effect of inorganic positive ions on the adsorption and desorption mechanism of Triton X-100 at the quartz-solution interface is discussed with molecular dynamics simulations (MD), flame atomic absorption spectrometry (FAAS) and atomic force microscopy (AFM) methods.

Synergistic Effect of Electric Field and Ultrasound on Transdermal Transport

Joseph Kost, 

Uwe Pliquett, 

Samir Mitragotri, 

Aye Yamamoto, 

Robert Langer, 

James Weaver

April 1996, Volume 13, Issue 4, pp 633-638

Near-Infrared Luminescence of Lanthanide Calcein and Lanthanide Dipicolinate Complexes Doped into a Silica-PEG Hybrid Material

Kris Driesen, Rik Van Deun, Christiane Go¨rller-Walrand, and Koen Binnemans*

Chem. Mater. 2004, 16, 1531-1535

The near-infrared luminescence of lanthanide complexes of 4′,5′-bis[N,N bis(carboxymethyl)aminomethyl]fluorescein (calcein) and pyridine-2,6-dicarboxylic acid (dipicolinic acid, dpa) doped in a hybrid sol-gel material was investigated. The silica-poly(ethylene glycol) (silica-PEG) inorganic-organic materials were prepared at a neutral pH. The lanthanide ions are well shielded from the environment by the calcein and dpa ligands, and the complexes are stable in the sol-gel matrix after preparation. The dysprosium and neodymium dipicolinate complexes showed near-infrared luminescence (NIR-luminescence) by direct excitation to the 4f-levels. The ytterbium dipicolinate complex doped in the sol-gel showed NIR-luminescence by excitation of the ligand in the UV region. All other tested lanthanide ions (Ln ) Pr, Sm, Er, Ho) did not show luminescence. Neodymium and ytterbium complexes with calcein show intense NIR-luminescence when the ligand is excited by visible light. The corresponding erbium complex doped in the silica-PEG matrix also showed NIR-luminescence at 1525 nm. No NIR-luminescence could be detected for the other lanthanide complexes doped in the matrix (Ln ) Pr, Sm, Dy, Ho).

Porous nanocapsules with "invisible" walls.

Pinkhassik, E. (2010).

Pacifichem 2010, International Chemical Congress of Pacific Basin Societies, Honolulu, HI, United States, December 15-20, 2010

We use lipid bilayers as supramol. self-assembled scaffolds for directed assembly of functional nanomaterials. Recently, we reported a simple method for controlling size, chem. environment, and d. of nanopores spanning nanometer-thin membranes. These membranes are characterized by tunable mol. wt. cut-off, extremely fast mass transfer, and long-term structural stability. Vesicle-templates polymer nanocapsules can retain medium-sized mols. such as pH-sensitive indicator dyes while providing uninhibited access for small mols. to the capsule interior. Nanocapsules showed no cytotoxicity. In one application, we use nanocapsules for targeted delivery of radiog. contrast agents and therapeutic agents to osteoarthritic lesions. In another application, we entrap catalysts within nanocapsules to combine high efficiency of homogeneous catalysts with ease of sepn. from reaction products.

Chemical and enzymic intermediates in the peroxidation of o-dianisidine by horseradish peroxidase. 2. Evidence for a substrate radical-enzyme complex and its reaction with nucleophiles.

Claiborne, A. and I. Fridovich (1979).
Biochemistry 18(11): 2329-2335.

Abstract:
Changes in the optical absorption spectrum of horseradish peroxidase during the oxidn. of o-dianisidine at pH 7.5 reveal an intermediate distinct from the previously described compds. I and II. The rate of decay of this new complex appeared to be rate limiting for the catalytic cycle in this pH range, since imidazole, which augments the catalytic reaction, also enhanced the rate of decay of this complex. Nitrogenous compds. reportedly unable to ligate to hemes, such as 2-methylimidazole and benzimidazole, were nevertheless capable of augmenting the peroxidase-catalyzed rate of oxidn. of o-dianisidine. The activity of nitrogenous compds., in this regard, appeared to be a function of their nucleophilicity and was sensitive to steric factors but relatively free of a deuterium solvent isotope effect. It is suggested that the nucleophile-responsive intermediate is an enzyme-dianisidine radical complex and that abstraction of the 2nd electron from the bound radical is facilitated by binding of nitrogenous nucleophiles. 

Chemical and enzymic intermediates in the peroxidation of o-dianisidine by horseradish peroxidase. 1. Spectral properties of the products of dianisidine oxidation.

Claiborne, A. and I. Fridovich (1979).
Biochemistry 18(11): 2324-2329.

Abstract:
Studies of the optical spectra of the products formed during peroxidn. of o-dianisidine by horseradish peroxidase (HRP) indicate at least 3 distinct species. At pH 3.7 and 4°, peroxidn. of dianisidine at low concns. yields the free dianisidine quinonediimine (the 2-equiv oxidized form) with λmax 452 and 514 nm. At higher concns., the 1st detectable product is not the free quinonediimine but an intermol. complex (meriquinone or charge-transfer complex) consisting of quinonediimine and parental diamine. This complex is freely reversible and is sensitive to simple diln. or acidification, either of which restores the spectrum of the free quinonediimine. Furthermore, at near-neutral pH, the quinonediimine appears to undergo irreversible self-coupling yielding yet a different optical spectrum presumably characteristic of the bisazobiphenyl structure proposed by K. M. Moller and P. Ottolenghi (1966). Butylated hydroxyanisole was shown to react in the presence of peroxidase-H2O2 and dianisidine to yield a spectrum (λmax 575 nm) nearly identical with that obtained when Gibbs' reagent (2,6-dichloroquinone-4-chloroimide) was incubated with butylated hydroxyanisole, thus suggesting that the free quinonediimine itself couples with the phenolic antioxidant. Finally, continuous-flow EPR studies of dianisidine oxidn. both with HRP-H2O2 and with ceric sulfate were unable to detect any free dianisidine semiquinone radical in the steady state; it is concluded that oxidn. of dianisidine occurs in a rapid 2-electron process in both the HRP-H2O2 and Ce(IV) systems

Directed assembly of sub-nanometer thin organic materials with programmed-size nanopores

Delia C. Danila, L. Todd Banner, Evguenia J. Karimova, Lyudmila Tsurkan, Xinyan Wang, and
Eugene Pinkhassik

Angew. Chem. Int. Ed. 2008, 47, 7036 –7039

Abstract:

Nanocolander: Sub-nanometer thin organic materials with uniform imprinted pores are formed by controlled polymerization within temporary self-assembled scaffolds. Pores are measured by a colored size-probe retention assay. A nanocapsule with no pores retains yellow, red, and blue probes and is colored brown; 0.8 nm pores lead to release of yellow probes, while capsules with 1.3 nm pores only retain blue probes.

Liposome−Quantum Dot Complexes Enable Multiplexed Detection of Attomolar DNAs without Target Amplification

Juan Zhou, Qiang-xin Wang, and Chun-yang Zhang

dx.doi.org/10.1021/ja3110329 |J. Am. Chem. Soc. 2013, 135, 2056−2059


Sensitive detection of DNA usually relies on target amplification approaches such as polymerase
chain reaction and rolling circle amplification. Here we describe a new approach for sensitive detection of low abundance DNA using liposome−quantum dot (QD) complexes and single-particle detection techniques. This assay allows for detection of single-stranded DNA at attomolar concentrations without the involvement of target amplification. Importantly, this strategy can be employed for simultaneous detection of multiple DNA targets.

Functionalization of Imprinted Nanopores in Nanometer-Thin Organic Materials

Sergey A. Dergunov and Eugene Pinkhassik

DOI: 10.1002/anie.200803261

Introduction:


Recently, we described a method for creating nanometer-thin organic materials with nanopores of programmed size. Control of pore geometry and mass transfer has been
identified as key to advances in DNA-sequencing devices, microreactors, molecular electronics, and drug-delivery devices. Nanocapsules with selective permeability have gained considerable attention in biomedical applications. Controlling the chemical environment of nanopores is critical for realizing the full potential of nanometer-thin porous materials.[7] Herein, we describe an efficient method for creating uniform nanopores with a programmed chemical environment and demonstrate the successful quatitative conversion of functional groups in the nanopores.

Integrated Nanoreactor Systems: Triggering the Release and Mixing of Compounds Inside Single Vesicles

Pierre-Yves Bolinger, Dimitrios Stamou, and Horst Vogel*
LCPPM, Swiss Federal Institute of Technology Lausanne, CH-1015 Lausanne, Switzerland


Introduction: Lipid vesicles constitute nanocontainer systems ideally suited for the isolation, preservation, transport, and localization of few1 or single2 molecules. Their ultrasmall dimensions (minimal diameters of 20 nm) allow unparalleled reduction of confined volumes to the zeptoliter range (1 zL ) 10-21 L). The availability of lipids
with variations in the hydrocarbon chains and the polar headgroups permits in addition the optimal design of a container that is tight and inert to the reactants and products of many biochemical processes like protein expression,3 enzymatic reactions,4 or mRNA transcription5 to mention a few. The potential of these systems for miniaturization and bionanotechnology was nevertheless realized only after single vesicles were extracted from the ensemble and addressed as individuals, either by means of micromanipulation6 or by directed assembly on patterned surfaces.1,7 Here we present a method that allows the on-demand release and mixing of soluble compounds stored in the interior of individual vesicular nanoreactors.

Synthesis of Bilayer-Coated Nanogels by Selective Cross-Linking of Monomers inside Liposomes

Joris P. Schillemans, Frits M. Flesch, Wim E. Hennink, and Cornelus F. van Nostrum*

Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS),
Utrecht UniVersity, P.O. Box 80.082, 3508 TB Utrecht, The Netherlands


ABSTRACT: In this study, bilayer-coated polyacrylamide hydrogel nanoparticles were prepared by photoinitiated polymerization of acrylamide (AA) and bis(acrylamide) (BA) in the inner compartment of liposomes. The liposomes were formed in AA/BA solutions from lipid/Triton X-100 (TX100) mixed micelles by adsorption of TX100 to Bio-Beads SM2 and were studied by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameters of the liposomes were 100 nm with low polydispersity. Addition of ascorbic acid before photopolymerization prevented macroscopic hydrogel formation by inhibition of free-radical polymerization of nonencapsulated monomers. Bare nanogel particles were finally obtained by removal of the lipid bilayer. As opposed to the commonly used dilution method, this convenient and versatile method of nanogel synthesis will allow incorporation of membrane proteins in the bilayer and the use of monomers that readily pass the lipid membrane.

Determination of Pore Sizes and Relative Porosity in Porous Nanoshell Architectures Using Dextran Retention with Single Monomer Resolution and Proton Permeation

Authors:
Thusitha P. Muhandiramlage, Zhiliang Cheng, David L. Roberts, John P. Keogh, Henry K. Hall, Jr. and Craig A. Aspinwall
Abstract:

Unilamellar phospholipid vesicles prepared using the polymerizable lipid bis-sorbylphosphatidylcholine (bis-SorbPC) yield three-dimensional nanoarchitectures that are highly permeable to small molecules. The resulting porous phospholipid nanoshells (PPNs) are potentially useful for a range of biomedical applications including nanosensors and nanodelivery vehicles for cellular assays and manipulations. The uniformity and size distribution of the pores, key properties for sensor design and utilization, have not previously been reported. Fluorophore-assisted carbohydrate electrophoresis (FACE) was utilized to assess the nominal molecular weight cutoff limit (NMCL) of the PPN via analysis of retained dextran with single monomer resolution. The NMCL of PPNs prepared from pure bis-SorbPC was equivalent to a 1800 Da linear dextran, corresponding to a maximum pore diameter of 2.6 nm. Further investigation of PPNs prepared using binary mixtures of bis-SorbPC and dioleoylphosphatidylcholine (DOPC) revealed a similar NMCL when the bis-SorbPC content exceeded 30 mol %, whereas different size-dependent permeation was observed below this composition. Below 30 mol % bis-SorbPC, dextran retention provided insufficient mass resolution (162 Da) to observe porosity on the experimental time scale; however, proton permeability showed a marked enhancement for bis-SorbPC ≥ 10 mol %. Combined, these data suggest that the NMCL for native pores in bis-SorbPC PPNs results from an inherent property within the lipid assembly that can be partially disrupted by dilution of bis-SorbPC below a critical value for domain formation. Additionally, the analytical method described herein should prove useful for the challenging task of elucidating porosity in a range of three-dimensional nanomaterials