Presence Of Aldehyde Groups Research Articles

Developing and Characterizing a Biocompatible Hydrogel Obtained by Cross-Linking Gelatin with Oxidized Sodium Alginate for Potential Biomedical Applications.

The main goal of this research was to create biocompatible hydrogels using gelatin and a double cross-linking technique involving both covalent and ionic bonds to immobilize propolis. The covalent bonds were formed through Schiff base cross-links between protein-free amino groups (NH2) from the lysine residue and aldehyde groups (CHO) produced by oxidizing sodium alginate with NaIO4, while the ionic bonds were achieved using Mg2+ ions. Hydrogel films were obtained by varying the molar ratios of -CHO/-NH2 under different pH conditions (3.5 and 5.5). The presence of aldehyde groups in the oxidized sodium alginate (OSA) was confirmed using FTIR and NMR spectroscopy. The oxidation degree was monitored over 48 h, and the influence of temperature was examined. Results showed that higher -CHO/-NH2 molar ratios led to increased conversion index values of NH2 groups, and a decrease in swelling degree values was observed in mediums with pH values of 5.5 and 7.4. The encapsulation and release efficiency of propolis decreased with an increase in the hydrogel cross-linking degree. UV irradiation enhanced the antioxidant activity of both free and encapsulated propolis. These findings offer valuable insights for the biomedical and pharmaceutical fields into designing biocompatible hydrogels for propolis immobilization, with potential for controlled release.

Responses of Rat Mesenchymal Stromal Cells to Nanocellulose with Different Functional Groups.

Cellulose nanofibrils (CNFs) are multiscale hydrophilic biocompatible polysaccharide materials derived from wood and plants. TEMPO-mediated oxidation of CNFs (TO-CNF) turns some of the primary hydroxyl groups to carboxylate and aldehyde groups. Unlike carboxylic functional groups, there is little or no information about the biological role of the aldehyde groups on the surface of wood-based CNFs. In this work, we replaced the aldehyde groups in the TO-CNF samples with carboxyl groups by another oxidation treatment (TO-O-CNF) or with primary alcohols with terminal hydroxyl groups by a reduction reaction (TO-R-CNF). Rat mesenchymal stem/stromal cells (MSCs) derived from bone marrow were seeded on polystyrene tissue culture plates (TCP) coated with CNFs with and without aldehyde groups. TCP and TCP coated with bacterial nanocellulose (BNC) were used as control groups. Protein adsorption measurements demonstrated that more proteins were adsorbed from cell culture media on all CNF surfaces compared to BNC. Live/dead and lactate dehydrogenase assays confirmed that all nanocellulose biomaterials supported excellent cell viability. Interestingly, TO-R-CNF samples, which have no aldehyde groups, showed better cell spreading than BNC and comparable results to TCP. Unlike TO-O-CNF surfaces, which have no aldehyde groups either, TO-R-CNF stimulated cells, in osteogenic medium, to have higher alkaline phosphatase activity and to form more biomineralization than TCP and TO-CNF groups. These findings indicate that the presence of aldehyde groups (280 ± 14 μmol/g) on the surface of TEMPO-oxidized CNFs might have little or no effect on attachment, proliferation, and osteogenic differentiation of MSCs.

PHOTOCHEMICAL REDUCTION OF COPPER AND SILVER IONS ON CELLULOSE-CONTAINING FABRICS

The article presents the research results on obtaining thin films of copper (II) chloride or silver nitrate on the surface of cotton fabrics. It has been demonstrated that end links contained in cellulose in the amount of a few percent are exposed to photooxidation. Photooxidation of the end links is associated with the presence of aldehyde groups, therein providing a reducing ability to cellulose. This leads to the reduction of silver nitrate and the formation of elemental silver; thus, copper (II) chloride is reduced to copper monochloride with a partial content of elemental copper. Copper monochloride is a binary semiconductor; this allows producing a surface film containing elemental copper only using additional photochemical treatment with ascorbic acid. The experiments showed that the proportion of final cellulose molecules involved in photochemical reactions was 0.98 % for the production of copper-containing films and 0.47 % for silver-containing films. From SEM images, the films contain uniformly distributed globular particles 100-600 nm in diameter.

Functional group Cinnamomum porrectum wood extractives by Fourier Transform Infrared

Extractive from Cinnamomum porrectum wood was obtained using Soxhlet extraction with five different types of solvent, which are distilled water, ethanol, acetone, chloroform, and benzene. From the result, ethanol extraction shows the highest extractives yield which are 2.692%, following by acetone (1.461%), chloroform (0.940%), benzene (0.109%) and distilled water (0.005%). Extractive make a major contribution to the characteristics of wood or non-wood species. These extractives are low-molecular weight compounds, and the different classes of extractives have different chemical behaviours. In this study, the FT-IR was used to analyse the extractive of the Cinnamomum porrectum wood with ethanol, distilled water, chloroform, benzene and acetone. From the result shows that, the analysis revealed 5 different types of functional group which are O-H stretching in presence of phenolic group, C-H stretching in presence of alkane group, C-F stretching in presence of alkyl halide group; C-O stretching in presence of aldehyde group and C=C stretching in presence of alkene group.

Tuneable catechin functionalisation of carbohydrate polymers

In this contribution, we present a strategy to functionalise three natural carbohydrate polymers (dextran − a neutral polymer, sodium alginate − an anionic polymer and chitosan − a cationic polymer) with catechin with excellent degrees of functionality. In a first step, the carbohydrate polymers were oxidised by sodium periodate to yield aldehyde functionalised carbohydrate polymers. The presence of aldehyde groups was exploited to attach catechin by an acid catalysed nucleophilic reaction. The degree of catechin functionalisation could be easily tuned by varying the acid concentration in the reaction mixture, achieving catechin functionalisation levels of up to 48% for dextran aldehyde catechin, 35% for chitosan-aldehyde-catechin and 22% for sodium alginate aldehyde catechin. 1H, 1H-13C HSQC and DOSY NMR were performed to elucidate the structural differences between the three aldehyde functionalised polysaccharides and how this affects their reactivity and conjugation behaviour. All three carbohydrate polymer-catechin conjugates showed superior free-radical scavenging activity compared with the non-functionalised polymers.

Ocular biocompatibility of gelatin microcarriers functionalized with oxidized hyaluronic acid

Given that the presence of aldehyde groups on the oxidized sugar residues may pose toxicity concerns, it is necessary to examine the safety of gelatin microcarriers (GMC) functionalized with oxidized hyaluronic acid (oHA) for potential ophthalmic applications. In this study, the ocular biocompatibility of biopolymer microcarriers was investigated in vitro using primary rabbit corneal cell cultures and in vivo using the anterior chamber of the rabbit eye model. Our results showed that different types of corneal cells including epithelial, stromal, and endothelial cells remain viable and actively proliferate following 2 and 4days of exposure to test materials. In addition, similar interleukin-6 gene expression levels and comet tail lengths were seen in the presence and absence of biopolymer microcarriers, suggesting no cellular inflammation and genotoxicity. After 7 and 14days of intracameral injection in the rabbit eyes, both the GMC samples and their counterparts functionalized with oHA were well tolerated in the ocular anterior chamber as demonstrated by slit-lamp biomicroscopy. Clinical observations including specular microscopic examinations, corneal topography, and corneal thickness measurements also showed that the rabbits bearing biopolymer microcarriers exhibit no signs of corneal edema and astigmatism as well as endothelial damage, indicating the absence of tissue response. It is concluded that the GMC materials functionalized with oHA (oxidation level: 10.4±0.9%) are compatible toward corneal cells and ocular anterior segment tissues at a concentration of 10mg/ml. The information about the effect of coupling of aldehyde-functionalized HA to gelatin on in vitro and in vivo biocompatibility of biopolymer composites can be used as further development of corneal stromal cell microcarriers for tissue engineering applications.

Characterization Study of a Highly Specific Affinity Membrane for Trypsin Purification

This study aimed to characterize a highly specific affinity membrane for trypsin separation. The basic membrane was fabricated using 15% polysulfone via phase inversion technique. Membrane surface modification was employed by immersing the native membrane into the chitosan solution for 60 minutes dip times. Further modification was performed to activate the PSf/chitosan hybrid membrane using glutaraldehyde before ligand immobilization. The prepared affinity membrane was characterized in term of morphology using scanning electron microscope and the presence of aldehyde group and ovomucoid were confirmed by ATR-FTIR. Performance of affinity membrane was valuted by adsorption study of trypsin enzyme. The observed results show that the developed affinity membrane, with 0.7 mg/ml ligands was able to adsorb trypsin for about 0.219 mg/cm2 membrane

Improved cellular response of chemically crosslinked collagen incorporated hydroxyethyl cellulose/poly(vinyl) alcohol nanofibers scaffold.

The aim of this research is to develop biocompatible nanofibrous mats using hydroxyethyl cellulose with improved cellular adhesion profiles and stability and use these fibrous mats as potential scaffold for skin tissue engineering. Glutaraldehyde was used to treat the scaffolds water insoluble as well as improve their biostability for possible use in biomedical applications. Electrospinning of hydroxyethyl cellulose (5 wt%) with poly(vinyl alcohol) (15 wt%) incorporated with and without collagen was blended at (1:1:1) and (1:1) ratios, respectively, and was evaluated for optimal criteria as tissue engineering scaffolds. The nanofibrous mats were crosslinked and characterized by scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Scanning electron microscope images showed that the mean diameters of blend nanofibers were gradually increased after chemically crosslinking with glutaraldehyde. Fourier transform infrared spectroscopy was carried out to understand chemical interactions in the presence of aldehyde groups. Thermal characterization results showed that the stability of hydroxyethyl cellulose/poly(vinyl alcohol) and hydroxyethyl cellulose/poly(vinyl alcohol)/collagen nanofibers was increased with glutaraldehyde treatment. Studies on cell-scaffolds interaction were carried out by culturing human fibroblast (hFOB) cells on the nanofibers by assessing the growth, proliferation, and morphologies of cells. The scanning electron microscope results show that better cell proliferation and attachment appeared on hydroxyethyl cellulose/poly(vinyl alcohol)/collagen substrates after 7 days of culturing, thus, promoting the potential of electrospun scaffolds as a promising candidate for tissue engineering applications.

An electrochemical immunosensor for the tumor marker α-fetoprotein using a glassy carbon electrode modified with a poly(5-formylindole), single-wall carbon nanotubes, and coated with gold nanoparticles and antibody

We report on a label-free electrochemical immunosensor for α-fetoprotein (α-FP). It is based on the use of a glassy carbon electrode that was first modified with conducting poly(5-formylindole) and single-walled carbon nanotubes (P5FIn/SWNTs), and then coated with gold nanoparticles and the respective antibody. The presence of aldehyde groups warrants direct immobilization of the antibody and results in a convenient method for fabricating of the immunosensor. Gold nanoparticles (GNPs) were deposited on the P5FIn/SWNTs composite material, and the modified electrode was applied to the detection of α-FP. The analytical signal is obtained by measuring the change of amperometric response at a typical working voltage of 100 mV before and after the immunoreaction. The detection limit is 200 fg mL−1. The immunosensor is simple, sensitive, specific and reproducible. It has the potential for reliable point-of-care diagnosis of tumor or other diseases.

Synthesis of Functional Core, Star Polymers via RAFT Polymerization for Drug Delivery Applications

Poly(oligoethylene glycol) methyl ether acrylate was polymerized via reversible addition fragmentation transfer polymerization (RAFT), and then chain extended in the presence of both a cross-linker and vinyl benzaldehyde (VBA), yielding monodisperse star polymers. The presence of aldehyde groups in the core was exploited to attach doxorubicin. The drug loading was controlled by the amount of VBA incorporated (until 28 wt% in drug). The doxorubicin release was studied at pH = 5.5 and 7.4; conditions representative of endosomal and extra cellular environments. In vitro studies revealed that the doxorubicin-conjugated star polymers had a level of cytotoxicity comparable to that found for free doxorubicin. Confocal microscopy and flow cytometry studies confirmed efficient cell uptake of the star polymers.

Fabrication and characterization of cross-linkable hydrogel particles based on hyaluronic acid: potential application in vocal fold regeneration

There is a critical need to engineer hyaluronic acid (HA)-based hydrogels with prolonged in vivo residence time, temporal release of therapeutics and matching viscoelasticity for use in vocal fold tissue engineering. We have previously demonstrated the synthesis and characterization of HA-based soft hydrogel particles (HGP) and particle cross-linked networks as injectable materials to treat vocal fold scarring. In this paper, we report a more versatile technique for preparing cross-linkable HA HGP with reduced sizes. HA HGP were synthesized via chemical cross-linking with divinyl sulfone using a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelle system in the presence of 1-heptanol. These HGP were rendered cross-linkable by introducing aldehyde groups via sodium periodate oxidation (oxHGP). The presence of aldehyde groups was confirmed by multi-photon confocal microscope upon fluorescence staining using cascade blue hydrazide. The aldehyde groups were used as reactive handles for covalent cross-linking with HA that has been previously modified with adipic acid dihydrazide (HADH). The resulting doubly cross-linked networks (DXN) are highly pliable and do not break until approx. 200–300% strain. The measured elastic modulus of the DXN is around 500 Pa, while the dynamic viscosity decreases linearly with frequency in log– log scale. The mechanical characteristics of DXN are similar to that of vocal fold lamina propria. In vitro cell-proliferation assays showed that the cross-linkable HA HGP did not adversely affect the proliferation of the cultured fibroblasts as assessed by MTT assay. A low-molecular-weight model drug, rhodamine 6G (R6G), was loaded into oxHGP, and its release was monitored using UV-Vis spectroscopy. R6G-loaded oxHGP maintained their ability to form DXN when mixed with the HAADH solution. Approximately 84% of entrapped R6G was liberated from oxHGP at a rate of 0.24%/min in the first 6 h. When encapsulated in the DXN, R6G was released at a steady rate of 0.03%/min for over 3 days. These novel hydrogels are promising implant materials for vocal fold tissue regeneration.

Comparative studies on rubber biodegradation through solid-state and submerged fermentation

A comparative study on natural rubber (NR) biodegradation through solid-state fermentation (SSF) and submerged fermentation (SmF) has been carried out for both bacterial as well as fungal species. Changes in the organic carbon content along with the average molecular weight of the treated rubber samples indicated rubber hydrocarbon utilization and its degradation. Proportion of sol and gel content of the treated rubber also varied with the SmF and SSF treatment. Further, presence of aldehyde groups in the treated rubber indicated rubber biodegradation. The comparative results showed SSF to be a better treatment method for rubber biodegradation.

Protective vaccination against murine visceral leishmaniasis using aldehyde-containing Quillaja saponaria sapogenins

The presence of aldehyde groups at C-23 and C-24 of the triterpen aglycon moiety was disclosed in 1 H NMR spectra of both the Riedel de Haen saponin (R) ( δ 9.336) and Quillaja saponaria QuilA saponin ( δ 9.348). The sign of the C-28 acylated linked moiety ( δ 176) was present in both saponins, while the δ 171 at C-28 (carboxy group) corresponding to the deacylated saponin, was only detected in the QuilA preparation, indicating 50% of hydrolysis of the ester moiety, probably due to the storage in aqueous solution. The normoterpen moiety was present in both saponins (signals at δ 14–18).The chemical removal of saponin glicidic moieties gave rise to their sapogenin fractions. Their 1 H NMR spectra showed the presence of two signals ( δ 9.226 and 9.236) for sapogenin R and two signals ( δ 9.338 and 9.352) for the QuilA sapogenin. The intensity of the signals suggested two conformational isomers of sapogenin R in the ratio 53% of equatorial aldehyde group to 47% of axial aldehyde group, and two conformational isomers of QuilA sapogenin in the ratio 76% of equatorial aldehyde group to 24% of axial aldehyde group. The chemical treatment abolished the saponin slight in vivo toxicity, reduced their hemolytic potential, did not affect their aldehyde contents, but gave rise to an enriched axial aldehyde-containing sapogenin R with enhanced potential on antibody humoral response (anti-IgM, IgG, IgG1, IgG2a, IgG2b and IgG3) and to an enriched equatorial aldehyde-containing QuilA-sapogenin that induced a mainly cellular specific immune response (increased intradermal response to leishmanial antigen and IFNγ sera levels) and effective protection against murine infection by L. donovani (77% reduction in liver parasitic load). Our results suggest that the Riedel de Haen saponin is probably a Quillaja saponaria saponin.

Surface and electrokinetic characterization of functional aldehyde polymer colloids

Polymer colloids of aldehyde functionality were prepared by the emulsifier-free emulsion copolymerization of styrene and acrolein with potasium persulfate as initiator. Two aldehyde latexes were prepared, one of them with methanol (10% (w/w) of the monomers) charged into the reactor. By carrying out conductimetric and potentiometric titration experiments, together with 1H nuclear magnetic resonance and Fourier transform infrared analysis, the presence of aldehyde groups was detected with a surface concentration of approximately 1.2 × 10 −4 μeq cm −2 for the two latexes synthesized. Also, sulfate groups were detected which gave rise to a surface charge density of around 2.9 μC cm −2 for both latexes. The electrophoretic mobilities (μ e) of these functionalized latexes were studied versus the solution pH and in the presence of several electrolytes with different counterion valences. The μ e values were constant in the pH range 5–10, while exhibiting a maximum when plotted versus the electrolyte concentration. This maximum disappeared when the electrolyte was LaCl 3. The stability factors of the aldehyde latexes were measured at pH 6 and 9. The critical coagulation concentrations (CCCs) were very similar for both latexes at these pH values. The average CCC was 367 mM which is too high when considering the low surface charge density provided by the sulfate groups. The surface aldehyde groups seem to improve the colloidal stability of these latexes.

Defensive relationships between Caulerpa prolifera and its shelled sacoglossan predators

The prey-predator relationship between the green alga Caulerpa prolifera and three shelled sacoglossans, Oxynoe olivaceca, Lobiger serradifalci and Cylindrobulla fragilis, have been investigated in order to clarify the role of the chemical molecules in the defense of both alga and molluscs. Caulerpa prolifera contains as main component, among the secondary metabolites, caulerpenyne (1), a small molecule displaying a sesquiterpenoid skeleton. A defensive role, due to the presence of a protected 1,4-dialdehyde, was previously suggested for caulerpenyne (1). In spite of this protection, three sacoglossans, the infaunal C. fragilis and the epifaunal L. serradifalci and O. olivacea, live closely associated with Caulerpa prolifera. The Thyrrhenian O. olivacea is able to modify the algal metabolite into a couple of more toxic compounds, oxytoxin-1 (2) and -2 (3), characterized by the presence of aldehyde groups. The same defensive strategy is adopted by populations of O. olivacea from Spanish coasts and by populations of C. Fragilis and L. serradifalci from S W Italy. The biotransformation of caulerpenyne (1) leads first to oxytoxin-1 (2), a monoaldehyde, which is compartmentalized into the parapodia of L. serradifalci and into the tail of O. olivacea and then, in O. olivacea and C. fragilis, to oxytoxin-2 (3) which displays the 1,4-conjugated dialdehyde partial moiety, present also in the structure of the potent antifeedant polygodial (4). The presence of the organic molecules has been detected by chemical methods, in particular by NMR (Nuclear Magnetic Resonance) of the extracts of the fresh tissues of the molluscs with deuterated solvents, avoiding any Chromatographie step and chemical treatment.

Chemical modification of pullulan: 1. Periodate oxidation

The present paper describes the periodate oxidation of pullulan. Special attention is paid to the structures and characteristics of the activated products. Pullulan contains three different anhydroglucoside moieties in the repeating unit. Therefore, periodate oxidation of pullulan results in different types of dialdehyde structures. From titrimetric analysis of the formic acid generated during the oxidation of pullulan, the numbers of singly and doubly oxidized anhydroglucoside units can be calculated. The aldehyde content in completely periodate-oxidized pullulan as determined by reaction with hydroxylamine hydrochloride is only 67%. A plausible explanation is the presence of a stable, six-membered hemiacetal. The presence of aldehyde groups with different reactivities is also evidenced by the data collected from reduction experiments and by 13C n.m.r. Finally, the hydrolytic stability of the polysaccharide backbone was studied.

Biochemistry of terminal deoxynucleotidyltransferase (TdT): characterization and mechanism of inhibition of TdT by P1,P5-bis(5'-adenosyl) pentaphosphate

The catalysis of DNA synthesis by calf thymus terminal deoxynucleotidyltransferase (TdT) is strongly inhibited in the presence of Ap5A, while replicative DNA polymerases from mammalian, bacterial, and oncornaviral sources are totally insensitive to Ap5A addition. The Ap5A-mediated inhibition of TdT seems to occur via its interaction at both the substrate binding and primer binding domains as judged by classical competitive inhibition plots with respect to both substrate deoxynucleoside triphosphate (dNTP) and DNA primer and inhibition of ultraviolet light mediated cross-linking of substrate dNTP and oligomeric DNA primer to their respective binding sites. Further kinetic analyses of Ap5A inhibition revealed that the dissociation constant of the Ap5A-enzyme complex, with either substrate binding or primer binding domain participating in the complex formation, is approximately 6 times higher (Ki = 1.5 microM) compared to the dissociation constant (Ki = 0.25 microM) of the Ap5A-TdT complex when both domains are available for binding. In order to study the binding stoichiometry of Ap5A to TdT, an oxidized derivative of Ap5A, which exhibited identical inhibitory properties as its parent compound, was employed. The oxidation product of Ap5A, presumably a tetraaldehyde derivative, binds irreversibly to TdT when the inhibitor-enzyme complex is subjected to borohydride reduction. The presence of aldehyde groups in the oxidized Ap5A appeared essential for inhibitory activity since its reduction to alcohol via borohydride reduction or its linkage to free amino acids prior to use as an inhibitor rendered it completely ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)