Free Aldehyde Groups Research Articles

Preparation and characterization of galactosylated bovine serum albumin nanoparticles for liver-targeted delivery of oridonin

In this study, galactosylated bovine serum albumin (GB), which could be developed for a liver targeting carrier was synthetized and it was identified by Fourier transform infrared (FT-IR) spectrometer. Oridonin loaded bovine serum albumin nanoparticle (ORI-BSA-NP) and oridonin loaded GB nanoparticle (ORI-GB-NP) were prepared and optimized by the desolvation technique. During the preparation of ORI-GB-NP, galactosamine was introduced to end-cap the free aldehyde groups on nanoparticles. The characteristics of ORI-GB-NP such as particle size, zeta potential, particle morphologie, entrapment efficiency and drug loading were evaluated. The nearly spherical nanoparticles, with a narrow size distribution below 200 nm, were negatively charged with zeta potential of about -30 mV. Meanwhile, differential scanning calorimetry (DSC) and X-ray diffraction confirmed the amorphous state of ORI in ORI-GB-NP. The in vitro drug release of ORI from ORI-GB-NP presented a biphasic pattern with an initial burst effect and consequently sustained release. These results implied that the nanoparticles possessed fine physicochemical characteristics and seemed to be a stable delivery system for poorly soluble oridonin.

Methoxy-Poly(ethylene glycol)-block-Poly(ε-caprolactone) Bearing Pendant Aldehyde Groups as pH-Responsive Drug Delivery Carrier

A biodegradable amphiphilic block copolymer of methoxy poly(ethylene glycol)-block-poly(ϵ-caprolactone) bearing pendant aldehyde groups was synthesised by a combination of ring-opening polymerisation and thio-bromo ‘click’ chemistry. The free aldehyde groups on the copolymer were reacted with hydrophobic payloads (p-methoxylaniline as a model drug) by a benzoic–imine linker, which was responsive to pH change. NMR, FTIR, and gel permeation chromatography analysis confirmed the copolymer structures. In vitro release studies revealed that under acid stimulus, hydrolysis of the benzoic–imine bond resulted in a rapid drug release. This new amphiphilic block copolymer is expected to have promising applications in biodegradable controlled drug delivery systems.

Modification and characterization of cellulosic cotton fibers for efficient immobilization of urease

Cotton fibers were first grafted by polyacrylonitril in the presence of KMnO4 and oxalic acid as a combined redox initiator. Moreover, modification of the grafted cotton fibers was done by changing the nitrile group (CN) into hydrazidine group through the reaction with hydrazine hydrate, then the fibers were activated by glutaraldehyde to introduce free aldehyde groups which were able to react with amino groups of urease to form Schiff's base, and result in cotton fibers immobilized urease. The efficiency of the immobilization was evaluated by examining the relative enzymatic activity of enzyme before and after the immobilization of urease. The results showed that the optimum temperature of immobilized urease was 35°C, which was higher than that of the free enzyme (30°C), and the immobilized urease exhibited a higher relative activity than that of free urease over 35°C. The optimal pH for immobilized urease was 6.5, which was lower than that of the free urease (pH 7.0), and the immobilization resulted in stabilization of enzyme over a wider pH range. The kinetic constant value (Km) of immobilized urease was higher than that of the free urease. However, the thermal and operational stabilities of immobilized urease have been improved greatly.

Synthesis and Optoelectronic Properties of Hexahydroxylated 10‐O‐R‐Substituted Anthracenes via a New Modification of the Friedel–Crafts Reaction Using O‐Protected ortho‐Acetal Diarylmethanols

A new modification of the Friedel-Crafts type intramolecular cyclization involving O-protected ortho-acetal diarylmethanols as a new type of reactant, was carried out for the first time in a medium containing a large amount of water at room temperature and enabled synthesis of a series of electron-rich, hexahydroxylated 10-O-R-substituted anthracenes, where R is an alkyl (Me, nBu, n-C(16)H(33)) or arylalkyl group (CH(2)Ph, CH(2)-2-Napht, CH(2)C(6)H(4)CH(2)OAr) and also evaluation of their electronic and optoelectronic properties in solution, crystal, and solid thin film. In this transformation, a central 10-O-R-substituted benzene ring was formed, fused to rings originating from two independent aromatic aldehydes. The reaction proceeded via two identified mechanisms involving acetal and/or free aldehyde groups. The acid sensitive acetal and dibenzyl alkoxy functions have never been used together in the intramolecular Friedel-Crafts type cyclization. The new compounds revealed deep blue fluorescence and quantum yields in solution around 0.3. The electrical properties investigated for thin films obtained by vacuum deposition on glass were 10-O-R-substituent dependent and showed much faster transient current decay in the case of the 10-O-CH(2)Ph derivative than for the material with a 10-O-Me substituent (the lifetime of charge carriers was 25 times shorter in this case). The AFM images of thin films, Stokes shifts, and X-ray analysis of π-stacking interactions in crystals of the new materials have been also obtained.

Making walled‐, highly autofluorescent dinoflagellate algae cells accessible and amenable for immunofluorescence and application of fluorescent probes

Immunofluorescence or fluorescent probe procedures with dinoflagellate algae have been hampered by their intrinsic pigment autofluorescence and rigid cell walls that cannot be digested by cellulolytic or pectinolytic enzymes. Highly autofluorescent, chlorophyll‐containing cells from Symbiodinium were fixed and treated by a freeze‐fracture procedure on microscope slides, intended to preserve their structure, break the cell wall, eliminate endogenous fluorescent pigments, and provide accessibility to antibodies. Formaldehyde fixation was carried out on intact cells in suspension, followed by freeze‐fracture in liquid nitrogen. Finally, they were subjected through a series of tests for pigment extraction to eliminate the cell autofluorescence. Incubation in 70% isopropanol, followed by NaBH4 after freeze‐fracture on glass slides, proved to be the most effective treatment to remove the fluorescence from endogenous pigments and free aldehyde groups remaining after the fixation. The procedure was effective in preserving the cell structures during the lengthy incubations, and the cells were suitable for both, immunolocalization of internal antigens, and visualization of targets of fluorescent probes. The procedure was equally successful when applied to other Symbiodinium species. These results provide a powerful tool for performing immunofluorescence and fluorescent probe detection on these highly autofluorescent, chlorophyll‐containing cells.

Adsorption of mercury(II), methyl mercury(II) and phenyl mercury(II) on chitosan cross-linked with a barbital derivative

The sorption behavior of glutaraldehyde cross-linked chitosan (G-Chitosan) and barbital-glutaraldehyde cross-linked chitosan (BG-Chitosan) was investigated for the sorption of Hg(II), CH3Hg(II) and C6H5Hg(II). The pHZpc values were found to be 7.5 and 7.9 for G-Chitosan and BG-Chitosan respectively. Batch experiments were conducted to study the effect of adsorption under different pH (1–10), temperature (30–70°C) and contact time (20–180min) conditions. The optimum pH was found to be 4.5 and 6–8 for Hg(II), CH3Hg(II) and C6H5Hg(II) respectively in case of G-Chitosan while in case of BG-Chitosan it was >8 for CH3Hg(II) and 7 for Hg(II) and C6H5Hg(II). Adsorption was found to be endothermic in the case of Hg(II) and exothermic for CH3Hg(II) and C6H5Hg(II). FT-IR analysis showed the possibility of metal binding to amino groups and free aldehyde groups of G-Chitosan and amide N and O of BG-Chitosan.

Synthesis, structures, and acute toxicity of gossypol nonsymmetrical aldehyde derivatives

Nonsymmetrical aldehyde derivatives of gossypol, a yellow polyphenolic pigment of cottonseed, were synthesized by reactions with ammonia, aniline, 4-aminoantipyrine, and barbituric acid. Their structures were determined by UV spectrophotometry and IR and (1)H NMR spectroscopy methods. Their acute toxicities in white mice were compared with those of gossypol and the corresponding symmetrical analogues. It was demonstrated that in general, the fewer free aldehyde groups that contained the gossypol derivative, the lower its acute toxicity. Only in the case of a nonsymmetrical gossypol derivative bearing a 4-aminoantipyrine residue did we observe a deviation from the above correlation: its symmetrical counterpart was even more toxic, but still less toxic than gossypol.

TEMPO mediated oxidation of carbohydrates using electrochemical methods

The oxidation of some readily available carbohydrates was investigated in aqueous medium using a catalytic amount of 2,2,6,6-Tetramethyl-1-piperidinyl-oxy (TEMPO) as redox mediator. The regeneration of oxoammonium (active form) was electrochemically performed in alkaline medium at a glassy carbon anode and at controlled potential (0.5 V vs. AgCl/Ag). The primary alcohol groups of the carbohydrates without free aldehyde group, were selectively oxidized to the corresponding sodium uronate with high Faradaic yields. The presence of free aldehyde or hemiacetal groups leads to a decrease in selectivities towards uronic acids and increases the amount of by-products.

Caveolin-1 (P132L), a Common Breast Cancer Mutation, Confers Mammary Cell Invasiveness and Defines a Novel Stem Cell/Metastasis-Associated Gene Signature

Here we used the Met-1 cell line in an orthotopic transplantation model in FVB/N mice to dissect the role of the Cav-1(P132L) mutation in human breast cancer. Identical experiments were performed in parallel with wild-type Cav-1. Cav-1(P132L) up-regulated the expression of estrogen receptor-alpha as predicted, because only estrogen receptor-alpha-positive patients have been shown to harbor Cav-1(P132L) mutations. In the context of primary tumor formation, Cav-1(P132L) behaved as a loss-of-function mutation, lacking any tumor suppressor activity. In contrast, Cav-1(P132L) caused significant increases in cell migration, invasion, and experimental metastasis, consistent with a gain-of-function mutation. To identify possible molecular mechanism(s) underlying this invasive gain-of-function activity, we performed unbiased gene expression profiling. From this analysis, we show that the Cav-1(P132L) expression signature contains numerous genes that have been previously associated with cell migration, invasion, and metastasis. These include i) secreted growth factors and extracellular matrix proteins (Cyr61, Plf, Pthlh, Serpinb5, Tnc, and Wnt10a), ii) proteases that generate EGF and HGF (Adamts1 and St14), and iii) tyrosine kinase substrates and integrin signaling/adapter proteins (Akap13, Cdcp1, Ddef1, Eps15, Foxf1a, Gab2, Hs2st1, and Itgb4). Several of the P132L-specific genes are also highly expressed in stem/progenitor cells or are associated with myoepithelial cells, suggestive of an epithelial-mesenchymal transition. These results directly support clinical data showing that patients harboring Cav-1 mutations are more likely to undergo recurrence and metastasis.

Detoxification and Endothelialization of Glutaraldehyde-Fixed Bovine Pericardium With Titanium Coating

Endothelial cell seeding of glutardialdehyde-fixed biological heart valves is hypothesized to improve biocompatibility and durability; however, the toxicity of glutardialdehyde prevents its use as a biological coating. Therefore, different detoxification strategies are applied, including surface coating with titanium, before in vitro endothelialization of glutaraldehyde-fixed bovine pericardium as the base material for prosthetic heart valves. Bovine pericardium was fixed with 0.25% glutardialdehyde. Detoxification was performed with citric acid, aldehyde dehydrogenase, and plasma deposition with titanium at low temperatures of 30 degrees C to 35 degrees C. Toxic glutaraldehyde ligands were quantified photometrically, and the vitality of seeded cells was tested to validate detoxification methods. Detoxification agents and titanium coating were applied before seeding with human endothelial cells. Endothelial cells were visualized by electron microscopic surface scanning. To evaluate cell adhesion, shear stress was applied by a flow of 5 L/min over 24 hours. Compared with untreated glutaraldehyde-fixed samples, treatment with the different agents reduced free aldehyde groups gradually (citric acid 5% < citric acid 10% < titanium < aldehyde dehydrogenase). A combination of citric acid 10%, aldehyde dehydrogenase, and titanium coating resulted in a reduction of free aldehyde ligands to 17.3+/-4.6% (P < or = 0.05) and demonstrated a vitality of seeded cells of 94+/-6.7% (P < or = 0.05). This procedure yielded a completely confluent layer of regular human endothelial cells (n=5). After application of shear stress for 24 hours on these endothelial layers, cell vitality was 81%. Titanium coating combined with chemical procedures yielded significant detoxification and complete endothelialization of conventional glutaraldehyde-fixed pericardium. This new technique might improve glutardialdehyde-fixed cardiovascular bioimplants for better biocompatibility and longer durability.

Interaction of Safranal and Picrocrocin with ctDNA and Their Preferential Mechanisms of Binding to GC- and AT-Rich Oligonucleotides

Saffron (Crocus sativus L.) shows different biological properties, some of which relate to its special components including safranal (deglycosylated picrocrocin). In our previous study on the mechanism of saffron functions, interaction of saffron carotenoids with DNA and oligonucleotides was reported. The present study aimed to investigate the interaction of safranal with calf thymus DNA (ctDNA), oligo(GC)15, and oligo(AT)15 in comparison with picrocrocin. Circular dichroism (CD) and fluorometric results show the nonintercalative/minor groove binding of the mentioned ligands to ctDNA. The CD plots indicate that picrocrocin interacts with DNA and oligonucleotides at lower concentrations than safranal does, which is accompanied by B- to C-DNA transition. At higher concentrations, it induces more conformational changes, that is, unstacking of DNA and oligonucleotides bases, the same as saffron carotenoids. However, similar results are obtained for safranal interaction with ctDNA (56% AT) and oligo(AT)15, but after adding safranal (with a free aldehyde group) to oligo(GC)15, the CD spectra show some changes (two positive and a displaced negative peaks) that are characteristics of triple-helix DNA. Thus, the mechanism for B- to H-DNA transition, due to the interaction of safranal with GC-rich sequences, is presented here.

Real-time liquid crystal-based glutaraldehyde sensor

Abstract We develop a liquid crystal (LC)-based optical sensor for detecting glutaraldehyde vapor by using real-time orientational responses of 4-cyano-4′-pentylbiphenyl (5CB) to glutaraldehyde. The sensor comprises a thin layer of 5CB (∼20 μm) supported on an amine-decorated surface. When a glutaraldehyde molecule diffuses through the layer of 5CB, it reacts with a surface amine group and forms an imine bond. Subsequently, the resulting free aldehyde group from the glutaraldehyde molecule triggers an orientational transition of 5CB, which manifests as an optical signal visible to the naked eye. Because the performance of the LC-based sensor critically depends on the diffusion of glutaraldehyde in 5CB, we also measured the solubility and diffusivity of glutaraldehyde in 5CB. Based on the diffusivity, an optimal LC sensor with a 20-μm-thick film of 5CB can respond to 207 ppmv glutaraldehyde within 20 s and shows a full response in 4 min. It also shows good specificity. Only a very weak response is observed when this sensor is exposed to acetic acid, and no response is recorded for methanol, ethanol or formaldehyde.

HIgG Detection by Histidine Carrying AFM Tips (Cantilevers)

"Atomic Force Microscope" (AFM) tips (cantilevers) carrying a pseudo-specific ligand, i.e., histidine were prepared and investigated for detection of Human Immunoglobulin-G (HIgG) in aqueous media. The AFM tips (cantilevers) were first treated with HNO(3) and silanized to create amino groups; then glutaraldehyde (GA) was bonded via these surface amino groups; and finally, histidine molecules were immobilized by reaction of the amino groups of histidine with the free aldehyde groups of GA. Optimal immobilization conditions were described. Immobilizations were observed both by optical and confocal laser scanning microscopy. Interactions between the histidine carrying AFM tips (cantilevers) and the aqueous medium containing HIgG with different concentrations were quantified by "the separation distance" measured with the AFM system as the main variable. A quite nice linear correlation between the HIgG concentration and the separation distance was measured with AFM system. Interactions were also followed by an alternative "Modified Lowry" method, in which similar behavior was observed. We were able to measure HIgG concentration in aqueous media down to 0.055 pmol/micro l (8 mg/dl) concentration with this AFM based novel immunosensor.

Poly(ethyleneimine) microcapsules: glutaraldehyde‐mediated assembly and the influence of molecular weight on their properties

AbstractPoly(ethyleneimine) (PEI) microcapsules were prepared via the method of glutaraldehyde (GA)‐mediated covalent layer‐by‐layer (LbL) assembly, which utilized GA to cross‐link the adsorbed PEI layer and to introduce free aldehyde group on the surface for the next PEI adsorption on MnCO3 microparticles, followed by core removal. Evidenced by ellipsometry, the PEI multilayers grew nearly linearly along with the layer number and their thickness was controlled at the nanometer scale. The hollow structure, morphology, and wall thickness were characterized by scanning electron microscopy (SEM), scanning force microscopy (SFM), and confocal laser scanning microscopy (CLSM), revealing that the capsule structure as well as the cut‐off molecular weight of the capsule wall could be tuned by the molecular weight of PEI. This offers a general and novel pathway to fabricate single component capsules with pre‐designed structure (size, shape, and wall thickness) and properties. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Thermal and spectrophotometric studies of new crosslinking method for collagen matrix with glutaraldehyde acetals

Despite the many existing crosslinking procedures, glutaraldehyde (GA) is still the method of choice used in the manufacture of bioprosthesis. The major problems with GA are: (a) uncontrolled reactivity due to the chemical complexity or GA solutions; (b) toxicity due to the release of GA from polymeric crosslinks; and (c) tissue impermeabilization due to polymeric and heterogeneous crosslinks formation, partially responsible for the undesirable calcification of the bioprosthesis. A new method of crosslinking glutaraldehyde acetals has been developed with GA in acid ethanolic solution, and after the distribution inside de matrix, GA is released to crosslinking. Concentrations of hydrochloride acid in ethanolic solutions between 0.1 and 0.001 mol/L with GA concentration between 0.1 and 1.0% were measured in an ultraviolet spectrophotometer to verify the presence of free aldehyde groups and polymeric compounds of GA. After these measurements, the solutions were used to crosslink bovine pericardium. The spectrophotometric results showed that GA was better protected in acetal forms for acid ethanolic solution with HCl at 0.003 mol/L and GA 1.0%(v/v). The shrinkage temperature results of bovine pericardium crosslinked with acetal solutions showed values near 85 degrees C after the exposure to triethylamine vapors.

Selective Enrichment of Tryptophan-Containing Peptides from Protein Digests Employing a Reversible Derivatization with Malondialdehyde and Solid-Phase Capture on Hydrazide Beads

A method for the selective enrichment of tryptophan-containing peptides from complex peptide mixtures such as protein digests is presented. It is based on the reversible reaction of tryptophan with malondialdehyde and trapping of the derivatized Trp-peptides on hydrazide beads via the free aldehyde group of the modified peptides. The peptides are subsequently recovered in their native form by specific cleavage reactions for further (mass spectrometric) analysis. The method was optimized and evaluated using a tryptic digest of a mixture of 10 model proteins, demonstrating a significant reduction in sample complexity while still allowing the identification of all proteins. The applicability of the tryptophan-specific enrichment procedure to complex biological samples is demonstrated for a total yeast cell lysate. Analysis of the processed fraction by 1D-LC-MS/MS confirms the specificity of the enrichment procedure, as more than 85% of the peptides recovered from the enrichment step contained tryptophan. The reduction in sample complexity also resulted in the identification of additional proteins in comparison to the untreated lysate.

Stability of low concentrations of guanine-based antivirals in sucrose or maltitol solutions

Three guanine-based antiviral drugs, entecavir, lobucavir, and acyclovir showed degradation in presence of sucrose in ready-to-use solutions held at 50 °C, with more degradation at pH 4 than at pH 6 or 7. LC/MS analysis of the solutions showed isomeric adducts of the drugs and reducing sugars. Sucrose, a disaccharide and a non-reducing sugar, was the source of monosaccharides, the reducing sugars. Sucrose showed pH-dependent hydrolysis at 50 °C into two monosaccharides, fructose and glucose, with more sucrose hydrolyzing at pH 4 than pH 6 or 7. Additionally, the three drugs showed pH-dependent degradation at 50 °C in fructose and glucose solutions with the following rank order: pH 7 > pH 6 > pH 4. This indicated that the increased degradation of the drugs in sucrose solutions at pH 4 was mainly due to more hydrolysis of sucrose into fructose and glucose compared to pH 6 or 7, and subsequent reactions of the fructose and glucose with the drugs. Based on structures of the major degradants, it is proposed that the main cause of the degradation was nucleophilic addition of the primary amine group of the drugs to the carbonyl group of the fructose and glucose. This reaction was facilitated as the solution pH increased from 4 to 7. All the drugs showed satisfactory stability regardless of the storage temperature or solution pH in maltitol, an alternate sweetener. The free aldehyde or ketone group in maltitol precursors is reduced to a hydroxyl group after the hydrogenation process making maltitol less susceptible to nucleophilic addition.

A Mutant αII-spectrin Designed to Resist Calpain and Caspase Cleavage Questions the Functional Importance of This Process in Vivo

alpha- and beta-spectrins are components of molecular scaffolds located under the lipid bilayer and named membrane skeletons. Disruption of these scaffolds through mutations in spectrins demonstrated that they are involved in the membrane localization or the maintenance of proteins associated with them. The ubiquitous alphaII-spectrin chain bears in its central region a unique domain that is sensitive to several proteases such as calpains or caspases. The conservation of this region in vertebrates suggests that the proteolysis of alphaII-spectrin by these enzymes could be involved in important functions. To assess the role of alphaII-spectrin cleavage in vivo, we generated a murine model in which the exons encoding the region defining this cleavage sensitivity were disrupted by gene targeting. Surprisingly, homozygous mice expressing this mutant alphaII-spectrin appeared healthy, bred normally, and had no histological anomaly. Remarkably, the mutant alphaII-spectrin assembles correctly into the membrane skeleton, thus challenging the notion that this region is required for the stable biogenesis of the membrane skeleton in nonerythroid cells. Our finding also argues against a critical role of this particular alphaII-spectrin cleavage in either major cellular functions or in normal development.

Actin-binding Protein α-Actinin-1 Interacts with the Metabotropic Glutamate Receptor Type 5b and Modulates the Cell Surface Expression and Function of the Receptor

Receptors for neurotransmitters require scaffolding proteins for membrane microdomain targeting and for regulating receptor function. Using a yeast two-hybrid screen, alpha-actinin-1, a major F-actin cross-linking protein, was identified as a binding partner for the C-terminal domain of metabotropic glutamate receptor type 5b (mGlu(5b) receptor). Co-expression, co-immunoprecipitation, and pull-down experiments showed a close and specific interaction between mGlu(5b) receptor and alpha-actinin-1 in both transfected HEK-293 cells and rat striatum. The interaction of alpha-actinin-1 with mGlu(5b) receptor modulated the cell surface expression of the receptor. This was dependent on the binding of alpha-actinin-1 to the actin cytoskeleton. In addition, the alpha-actinin-1/mGlu(5b) receptor interaction regulated receptor-mediated activation of the mitogen-activated protein kinase pathway. Together, these findings indicate that there is an alpha-actinin-1-dependent mGlu(5b) receptor association with the actin cytoskeleton modulating receptor cell surface expression and functioning.

T84-Intestinal Epithelial Exosomes Bear MHC Class II/Peptide Complexes Potentiating Antigen Presentation by Dendritic Cells

Intestinal epithelial cells release antigen-presenting vesicles (exosomes) bearing major histocompatibility complex class II/peptide complexes stimulating specific immune responses in vivo. To characterize further the role of human epithelial exosomes in antigen presentation, their capacity to load antigenic peptides, bind immune target cells, and induce T-cell activation was analyzed in vitro. The capacity of exosomes derived from the HLA-DR4-expressing, intestinal epithelial cell line T84 to load the HLA-DR4-specific peptide (3)H-HSA 64-76 and to activate a HLA-DR4-restricted T-cell hybridoma was tested in the presence or absence of human monocyte-derived dendritic cells (DCs). Interaction of fluorescein isothiocyanate-labeled exosomes with T cells and DCs was analyzed by flow cytometry and confocal microscopy. T84-derived exosomes, enriched in CD9, CD81, CD82, and A33 antigen, were capable of binding specifically human serum albumin (HSA) 64-76 peptide on HLA-DR4 molecules and of interacting preferentially with DCs. HSA-loaded exosomes were unable to activate the T-cell hybridoma directly but induced a productive T-cell activation through DCs. When HSA peptide was bound to exosomal HLA-DR4 molecules instead of in a soluble form, the threshold of peptide presentation by DCs was markedly decreased (x10(-3)). Exosomes released by intestinal epithelial cells bear exogenous peptides complexed to major histocompatibility complex class II molecules and interact preferentially with DCs, strongly potentiating peptide presentation to T cells. Epithelial exosomes constitute a powerful link between luminal antigens and local immune cells by mediating the transfer of tiny amounts of luminal antigenic information and facilitating immune surveillance at mucosal surfaces.