Confer Water Solubility Research Articles

Dramatic Improvement of Homogeneous Carbon Dioxide and Bicarbonate Electroreduction Using a Tetracationic Water-Soluble Cobalt Phthalocyanine.

Electrochemical conversion of carbon dioxide (CO2) offers the opportunity to transform a greenhouse gas into valuable starting materials, chemicals, or fuels. Since many CO2 capture strategies employ aqueous alkaline solutions, there is interest in catalyst systems that can act directly on such capture solutions. Herein, we demonstrate new catalyst designs where the electroactive molecules readily mediate the CO2-to-CO conversion in aqueous solutions between pH 4.5 and 10.5. Likewise, the production of CO directly from 2 M KHCO3 solutions (pH 8.2) is possible. The improved molecular architectures are based on cobalt(II) phthalocyanine and contain four cationic trimethylammonium groups that confer water solubility and contribute to the stabilization of activated intermediates via a concentrated positive charge density around the active core. Turnover frequencies larger than 103 s-1 are possible at catalyst concentrations of down to 250 nM in CO2-saturated solutions. The observed rates are substantially larger than the related cobalt phthalocyanine-containing catalysts. Density functional theory calculations support the idea that the excellent catalytic properties are attributed to the ability of the cationic groups to stabilize CO2-bound reduced intermediates in the catalytic cycle. The homogeneous, aqueous CO2 reduction that these molecules perform opens new frontiers for further development of the CoPc platform and sets a greatly improved baseline for CoPc-mediated CO2 upconversion. Ultimately, this discovery uncovers a strategy for the generation of platforms for practical CO2 reduction catalysts in alkaline solutions.

Internalization of Pegylated Er:Y2O3 Nanoparticles inside HCT-116 Cancer Cells: Implications for Imaging and Drug Delivery.

Lanthanide-doped nanoparticles, featuring sharp emission peaks with narrow bandwidth, exhibit high downconversion luminescence intensity, making them highly valuable in the fields of bioimaging and drug delivery. High-crystallinity Y2O3 nanoparticles (NPs) doped with Er3+ ions were functionalized by using a pegylation procedure to confer water solubility and biocompatibility. The NPs were thoroughly characterized using transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and photoluminescence measurements. The pegylated nanoparticles were studied both from a toxicological perspective and to demonstrate their internalization within HCT-116 cancer cells. Cell viability tests allowed for the identification of the "optimal" concentration, which yields a detectable fluorescence signal without being toxic to the cells. The internalization process was investigated using a combined approach involving confocal microscopy and ICP-MS. The obtained data clearly indicate the efficient internalization of NPs into the cells with emission intensity showing a strong correlation with the concentrations of nanoparticles delivered to the cells. Overall, this research contributes significantly to the fields of nanotechnology and biomedical research, with noteworthy implications for imaging and drug delivery applications.

Vitamin A aldehyde-taurine adducts function in photoreceptor cells

To facilitate the movement of retinoids through the visual cycle and to limit nonspecific chemical reaction, multiple mechanisms are utilized to handle these molecules when not contained within the binding pocket of opsin. Vitamin A aldehyde is sequestered by reversible Schiff base formation with phosphatidylethanolamine (PE) and subsequently undergoes NADPH-dependent reduction. Otherwise inefficient handling of retinaldehyde can lead to the formation of fluorescent di-retinal compounds within the outer segments of photoreceptor cells. These bisretinoid fluorophores initiate photooxidative processes having adverse consequences for retina. Various carrier proteins confer water solubility and maintain the 11-cis-retinoid configuration. Mechanisms for sequestration of retinoid include the formation of a reversible Schiff base between retinaldehyde and taurine (A1-taurine, A1T), the most abundant amino acid in photoreceptor cells. Here we have undertaken to examine the effects of taurine depletion using the transport inhibitors guanidinoethyl sulfonate (GES) and β-alanine. Oral treatment of BALB/cJ mice with β-alanine reduced ocular A1T and the mice exhibited significantly lower scotopic and photopic a-wave amplitudes. As a secondary effect of retinal degeneration, A1T was not detected and taurine was significantly reduced in mice carrying a P23H opsin mutation. The thinning of ONL that is indicative of reduced photoreceptor cell viability in albino Abca4−/− mice was more pronounced in β-alanine treated mice. Treatment of agouti and albino Abca4−/− mice with β-alanine and GES was associated with reduced bisretinoid measured chromatographically. Consistent with a reduction in carbonyl scavenging activity by taurine, methylglyoxal-adducts were also increased in the presence of β-alanine. Taken together these findings support the postulate that A1T serves as a reservoir of vitamin A aldehyde, with diminished A1T explaining reduced photoreceptor light-sensitivity, accentuated ONL thinning in Abca4−/− mice and attenuated bisretinoid formation.

HDL maturation and remodelling

Cholesterol in the circulation is mostly transported in an esterified form as a component of lipoproteins. The majority of these cholesteryl esters are produced in nascent, discoidal high density lipoproteins (HDLs) by the enzyme, lecithin:cholesterol acyltransferase (LCAT). Discoidal HDLs are discrete populations of particles that consist of a phospholipid bilayer, the hydrophobic acyl chains of which are shielded from the aqueous environment by apolipoproteins that also confer water solubility on the particles. The progressive LCAT-mediated accumulation of cholesteryl esters in discoidal HDLs generates the spherical HDLs that predominate in normal human plasma. Spherical HDLs contain a core of water insoluble, neutral lipids (cholesteryl esters and triglycerides) that is surrounded by a surface monolayer of phospholipids with which apolipoproteins associate. Although spherical HDLs all have the same basic structure, they are extremely diverse in size, composition, and function. This review is concerned with how the biogenesis of discoidal and spherical HDLs is regulated and the mechanistic basis of their size and compositional heterogeneity. Current understanding of the impact of this heterogeneity on the therapeutic potential of HDLs of varying size and composition is also addressed in the context of several disease states.

Quantification of reactive oxygen species generation by photoexcitation of PEGylated quantum dots.

Photocatalytic generation of reactive oxygen species (ROS) from quantum dots (QDs) has been widely reported yet quantitative studies of ROS formation and their quantum yields are lacking. This study investigates the generation of ROS by water soluble PEGylated CdSe/ZnS QDs with red emission. PEGylation of QDs is commonly used to confer water solubility and minimise uptake by organs of the reticuloendothelial system; therefore studies of ROS formation are of biomedical relevance. Using non-photolytic visible wavelength excitation, the superoxide anion radical is shown to be the primary ROS species generated with a quantum efficiency of 0.35%. The yield can be significantly enhanced in the presence of the electron donor, nicotinamide adenine dinucleotide (NADH), as demonstrated by oxygen consumption measurements and electron paramagnetic resonance spectroscopy with in situ illumination. Direct production of singlet oxygen is not detectable from the QDs alone. A comparison is made with ROS generation by the same QDs complexed with a sulfonated phthalocyanine which can generate singlet oxygen via Förster resonance energy transfer between the QDs and the phthalocyanine.

Designing antioxidant peptides

BackgroundIonizing radiation causes the generation of damaging reactive oxygen species that lead to cellular damage and death. Organisms such as Deinococcus radiodurans have evolved mechanisms for extreme resistance to ionizing radiation, and resistance has been shown to be a consequence of protection of critical proteins from oxidative inactivation.ObjectivesD. radiodurans accumulates high levels of manganese and of small peptides that together are protective. Our aim was to rationally design antioxidant peptides.MethodsAmino acid analysis was utilized to determine the rates of loss of the 20 amino acids exposed to varying doses of irradiation. The activity of glutamine synthetase and methionine sulfoxide reductase was assayed to follow their inactivation by irradiation.ResultsThe ability of an amino acid to protect enzymes from inactivation by ionizing radiation paralleled its sensitivity to ionizing radiation. Based on this observation and the ability of histidine to confer water solubility, we synthesized the hexapeptide His-Met-His-Met-His-Met and found that it provided markedly increased protection against irradiation.DiscussionSmall peptides containing histidine and methionine were readily soluble and provided enzymes with remarkable protection from inactivation by ionizing radiation.

Luminescent alkynyl-gold(i) coumarin derivatives and their biological activity

The synthesis and characterization of three propynyloxycoumarins are reported in this work together with the formation of three different series of gold(i) organometallic complexes. Neutral complexes are constituted by water soluble phosphines (PTA and DAPTA) which confer water solubility to them. The X-ray crystal structure of 7-(prop-2-in-1-yloxy)-1-benzopyran-2-one and its corresponding dialkynyl complex is also shown and the formation of rectangular dimers for the gold derivative in the solid state can be observed. A detailed analysis of the absorption and emission spectra of both ligands and complexes allows us to attribute the luminescent behaviour to the coumarin organic ligand. Moreover, the presence of the gold(i) metal atom seems to be responsible for an increase of coumarin phosphorescence emission. The biological activity of the complexes showed that the anionic complexes triggered strong cytotoxic effects in two different cell lines whereas the neutral gold alkynyl complexes led to lower effects against tumor cell growth. Thioredoxin reductase (TrxR) inhibition was very strong in the case of the neutral complexes (IC50 values below 0.1 μM) but moderate for the anionic complexes (IC50 values above 0.8 μM).

Endolytic, pH-Responsive HPMA-b-(l-Glu) Copolymers Synthesized via Sequential Aqueous RAFT and Ring-Opening Polymerizations

A facile synthetic pathway for preparing block copolymers with pH-responsive L-glutamic acid segments for membrane disruption is reported. Aqueous reversible addition-fragmentation chain transfer (aRAFT) polymerization was first used to prepare biocompatible, nonimmunogenic poly[N-(2-hydroxypropyl)methacrylamide]. This macro chain transfer agent (CTA) was then converted into a macroinitiator via simultaneous aminolysis and thiol-ene Michael addition using the primary amine substituted N-(3-aminopropyl)methacrylamide. This macroinitiator was subsequently utilized in the ring-opening polymerization of the N-carboxyanhydride monomer of γ-benzyl-L-glutamate. After deprotection, the pH-dependent coil-to-helix transformations of the resulting HPMA-b-(L-Glu) copolymers were monitored via circular dichroism spectroscopy. HPMA segments confer water solubility and biocompatibility while the L-glutamic acid repeats provide reversible coil-to-helix transitions at endosomal pH values (~5-6). The endolytic properties of these novel [HPMA-b-(L-Glu)] copolymers and their potential as modular components in drug carrier constructs was demonstrated utilizing red blood cell hemolysis and fluorescein release from POPC vesicles.

Comparison of two strategies for conferring water solubility to a zinc phthalocyanine substituted with 1,2-diethylamino

Polyamines are naturally occurring compounds that play important roles in multiple cell processes. In most cases, phthalocyanine-polyamine (Pc-polyamine) conjugates have good anticancer activity. However, low solubility in water limits their application in photodynamic therapy (PDT). The common method to solve this problem is quaternizing the nitrogen atoms to obtain cationic derivatives. An alternative strategy by preparing hydrochloride is easily neglected. In this paper, a Pc-polyamine conjugate substituted with 1,2-diethylamino (ZnPc1) was conferred water solubility by two different strategies, which are preparing hydrochloride (ZnPc2) and quaternizing the nitrogen atoms (ZnPc3). The synthetic methods and properties of the two derivatives were compared and discussed. Results indicated that both ZnPc2 and ZnPc3 possessed good solubility in water. However, strategy of preparing hydrochloride is much easier than quaternization process and the singlet oxygen generation ability, the photostability and anticancer activity of ZnPc2 in vitro were also superior to the ZnPc3.

Efficacy and safety of bendamustine for the treatment of patients with recurring Hodgkin lymphoma

The management of patients with Hodgkin lymphoma (HL) recurring after stem cell transplantation (SCT) and multiply relapsed disease remains challenging. We report on 41 such patients who received bendamustine hydrochloride, a bifunctional mechlorethamine derivative mechanistically unrelated to traditional alkylators, after a median of four prior chemotherapy lines, including SCT in 85% of cases. Bendamustine was given at doses of 90-120 mg/m(2) every 21 or 28 d. At first assessment (2-4 cycles), the overall response rate (ORR) was 78% with 12 (29%) complete (CR) and 20 (49%) partial responses (PR). Upon treatment prolongation to 6-8 courses, 40% of PRs progressed, yielding a final ORR of 58% with 31% of CRs. Eight patients (two CRs, six PRs) were subsequently allotransplanted. Median progression-free and overall survival exceeded 11 and 21 months respectively; complete responders displayed a median disease-free survival above 9 months with a relapse rate of only 30%. Outcomes were independent of disease chemosensitivity, previous transplant and bendamustine dose-intensity. No life-threatening or unexpected adverse events occurred. Within the limits of a retrospective analysis and schedule heterogeneity, these results appear very encouraging and prompt prospective trials to confirm bendamustine as a valuable option in the palliative setting and in cytoreductive strategies before allotransplantation.

Metal-coordinated water-soluble cavitands act as C-H oxidation catalysts.

Cavitands can be smoothly derivatized by CuAAC chemistry to incorporate ligand species at the upper rim. These species can coordinate metal species in a number of different conformations, leading to self-assembly. The metal-coordination confers water solubility on the cavitands, and the iron-bound species are capable of catalytic C-H oxidations of fluorene under mild conditions.

Effect of degree of deacetylation on physicochemical and gelation properties of konjac glucomannan

Gelation behaviors of konjac glucomannan (KGM) samples with different degree of deacetylation (DD) obtained using a heterogeneous deacetylation method were studied by dynamic viscoelastic measurements in order to probe the role of acetyl groups in the gelation process of KGM and types of molecular forces responsible for gel formation. Molecular parameters and structure of KGM samples were determined by GPC–MALLS and FT-IR spectroscopy. It was found that water solubility of KGM decreased with increasing DD, providing evidence further that the presence of acetyl groups confers water solubility on KGM. Rheological measurements suggested that hydrogen bonding and hydrophobic interaction are both presented in KGM gels, hydrophobic interaction was strengthened whilst hydrogen bonding was weakened with increasing DD. A faster gelation rate and a more elastic modulus were facilitated by raising temperature or increasing KGM sample concentration. The conditions under which gelation can occur became easier with increasing DD.

Morphology and structure of lipoproteins revealed by an optimized negative-staining protocol of electron microscopy

Plasma lipoprotein levels are predictors of risk for coronary artery disease. Lipoprotein structure-function relationships provide important clues that help identify the role of lipoproteins in cardiovascular disease. The compositional and conformational heterogeneity of lipoproteins are major barriers to the identification of their structures, as discovered using traditional approaches. Although electron microscopy (EM) is an alternative approach, conventional negative staining (NS) produces rouleau artifacts. In a previous study of apolipoprotein (apo)E4-containing reconstituted HDL (rHDL) particles, we optimized the NS method in a way that eliminated rouleaux. Here we report that phosphotungstic acid at high buffer salt concentrations plays a key role in rouleau formation. We also validate our protocol for analyzing the major plasma lipoprotein classes HDL, LDL, IDL, and VLDL, as well as homogeneously prepared apoA-I-containing rHDL. High-contrast EM images revealed morphology and detailed structures of lipoproteins, especially apoA-I-containing rHDL, that are amenable to three-dimensional reconstruction by single-particle analysis and electron tomography.

Highly-sensitive multiplexed in vivo imaging using pegylated upconversion nanoparticles

Lanthanide-based upconversion nanoparticles (UCNPs) have been widely explored in various fields, including optical imaging, in recent years. Although earlier work has shown that UCNPs with different lanthanide (Ln3+) dopants exhibit various colors, multicolor-especially in vivo multiplexed biomedical imaging-using UCNPs has rarely been reported. In this work, we synthesize a series of UCNPs with different emission colors and functionalize them with an amphiphilic polymer to confer water solubility. Multicolor in vivo upconversion luminescence (UCL) imaging is demonstrated by imaging subcutaneously injected UCNPs and applied in multiplexed in vivo lymph node mapping. We also use UCNPs for multicolor cancer cell labeling and realize in vivo cell tracking by UCL imaging. Moreover, for the first time we compare the in vivo imaging sensitivity of quantum dot (QD)-based fluorescence imaging and UCNP-based UCL imaging side by side, and find the in vivo detection limit of UCNPs to be at least one order of magnitude lower than that of QDs in our current non-optimized imaging system. Our data suggest that, by virtue of their unique optical properties, UCNPs have great potential for use in highly-sensitive multiplexed biomedical imaging.

ChemInform Abstract: Carbonic Anhydrase Inhibitors. Part 70. Synthesis and Ocular Pharmacology of a New Class of Water-Soluble, Topically Effective Intraocular Pressure Lowering Agents Derived from Nicotinic Acid and Aromatic/Heterocyclic Sulfonamides

Reaction of twenty aromatic/heterocyclic sulfonamides containing a free amino, imino, hydrazino or hydroxyl group, with nicotinoyl chloride afforded a series of water-soluble (as hydrochloride or triflate salts) compounds. The new derivatives were assayed as inhibitors of three carbonic anhydrase (CA) isozymes, hCA I, hCA II (cytosolic forms) and bCA IV (membrane-bound form); h = human, b = bovine isozyme. Efficient inhibition was observed against all three isozymes, but especially against hCA II and bCA IV (in nanomolar range), two isozymes known to play a critical role in aqueous humour secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were applied as 2% water solutions directly into the eye of normotensive or glaucomatous albino rabbits. Very strong intraocular pressure (IOP) lowering was observed for many of them, and the active drug was detected in eye tissues and fluids. This result prompted us to re-analyse the synthetic work done by other groups for the design of water soluble, topically effective antiglaucoma sulfonamides. According to these researchers, the IOP lowering effect is due to the intrinsic nature of the specific heterocyclic sulfonamide considered, among which the thienothiopyran-2-sulfonamide derivatives represent the best studied case. Indeed, the first agents developed for such applications, such as dorzolamide, are derivatives of this ring system. In order to prove that the tail (in this case the nicotinoyl moiety) conferring water solubility to a sulfonamide CA inhibitor is critically important, similarly to the ring to which the sulfonamido group is grafted, we also prepared a dorzolamide derivative to which the nicotinoyl moiety was attached. This new compound is more water soluble than dorzolamide (as hydrochloride salt), behaves as a strong CA II inhibitor, and acts similarly to the parent derivative in lowering IOP in experimental animals. Thus, it seems that the tail conferring water solubility is more important for topical activity as an antiglaucoma drug than the heterocyclic/aromatic ring to which the sulfonamido moiety is grafted.

ChemInform Abstract: Carbonic Anhydrase Inhibitors. Part 78. Synthesis of Water-Soluble Sulfonamides Incorporating β-Alanyl Moieties, Possessing Long Lasting-Intraocular Pressure Lowering Properties via the Topical Route.

Reaction of 26 aromatic/heterocyclic sulfonamides containing amino, imino, hydrazino or hydroxyl groups with N-tert-butyloxycarbonyl-β-alanine (Boc-β-ala; Boc = t-butoxycarbonyl) in the presence of carbodiimide derivatives afforded, after removal of the protecting group, a series of water-soluble compounds (as salts of strong acids, such as hydrochloric, trifluoroacetic or trifluoromethane sulfonic). The new derivatives were assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more precisely of three of its isozymes, CA I, II (cytosolic forms) and IV (membrane-bound form), involved in important physiological processes. Good inhibition was observed against all three isozymes, but especially against CA II and CA IV (in the nanomolar range), the two isozymes known to play a critical role in aqueous humour secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were applied as 2% aqueous solutions into the eyes of normotensive or glaucomatous albino rabbits, when strong and long-lasting intraocular pressure (IOP) lowering was observed with many of them. Thus, the amino acyl groups conferring water solubility to these sulfonamide CA inhibitors, coupled with their strong enzyme inhibitory properties and balanced lipid solubility seem to be the key factors for obtaining compounds with effective topical antiglaucoma activity.

Deep cavitand receptors with pH-independent water solubility

Pendant oligoethyleneglycol groups confer water solubility to a cavitand over a wide pH range. The kinetic stability of the host-guest complexes reveals an effective stabilization through hydrogen bonding even in the highly competitive aqueous environment.

Nematic and Columnar Ordering of a PEG–Peptide Conjugate in Aqueous Solution

The self-assembly in aqueous solution of a PEG-peptide conjugate is studied by spectroscopy, electron microscopy, rheology and small-angle X-ray and neutron scattering (SAXS and SANS). The peptide fragment, FFKLVFF is based on fragment KLVFF of the amyloid beta-peptide, Abeta(16-20), extended by two hydrophobic phenylalanine units. This is conjugated to PEG which confers water solubility and leads to distinct self-assembled structures. Small-angle scattering reveals the formation of cylindrical fibrils comprising a peptide core and PEG corona. This constrained structure leads to a model parallel beta-sheet self-assembled structure with a radial arrangement of beta sheets. On increasing concentration, successively nematic and hexagonal columnar phases are formed. The flow-induced alignment of both structures was studied in situ by SANS using a Couette cell. Shear-induced alignment is responsible for the shear thinning behaviour observed by dynamic shear rheometry. Incomplete recovery of moduli after cessation of shear is consistent with the observation from SANS of retained orientation in the sample.

Synthesis, characterization and cytotoxicity of phosphoryl choline-grafted water-soluble carbon nanotubes

Carbon nanotubes (CNTs) were rendered water-soluble by grafting on phosphoryl choline (PC). The modified CNTs were characterized utilizing Fourier transform infrared spectra, X-ray photoelectron spectra, thermogravimetric analysis, nuclear magnetic resonance, transmission electron microscopy, ultraviolet/visible absorbance spectra and dynamic laser light-scattering. The results show that the target products are easily dispersed in water and remain dispersed for at least three months. This study showed that both CNTs and CNT-PC induce no cytotoxicity on clonal pheochromocytoma cells (PC12) and human colon carcinoma cell lines (Caco-2). The grafted PC group confers water solubility and keeps the cell-compatibility of CNTs.

Field‐theoretic simulations of polyelectrolyte complexation

Field‐theoretic simulations of polyelectrolyte complexation