Number Of Primary Amine Groups Research Articles

Poly(vinyl amine) microparticles derived from N-Vinylformamide and their versatile use

Cationic polymers with primary amine groups that can easily be functionalized or coupled with substrates by complexation or hydrogen bonding are especially advantageous in preparing particles for biomedical applications. Poly(vinyl amine) (PVAm) is a cationic polyelectrolyte containing the highest number of primary amine groups among any other polymers. Here, we introduce a general method in synthesizing PVAm microparticles via a surfactant-free water-in-oil emulsion technique using cyclohexane as the oil phase and aqueous PVAm solution as the dispersed phase. PVAm particles were prepared to employ two different bifunctional chemical crosslinkers, divinyl sulfone (DVS) and poly(ethylene glycol) diglycidyl ether (PEGGE). The prepared particles were further treated with HCl to protonate the amine groups of PVAm within particles. The effect of crosslinker types and pH on the hydrolytic degradation of PVAm particles were also investigated at three different solution pHs, 5.4, 7.4, and 9, to simulate the skin, blood, and intestinal pH environments, respectively. The blood compatibility of the PVAm particles was evaluated by in vitro hemolysis and blood clotting assays. Furthermore, antifungal and antibacterial efficacy of PVAm-based particles and their protonated forms were tested against C. albicans yeast and E. coli, S. aureus, B. subtilis, and P. aeruginosa bacterial strains.

Fabrication of hollow fiber loose nanofiltration separation layers based on nucleophilic addition and Schiff base reactions and the investigation on separation performance of low molecular weight dye/salt systems

Efficiently achieving selective separation of low molecular weight dye/salt systems is significant to promote the development of membrane technology in the field of wastewater treatment. In this work, polyvinyl amine (PVAM), a linear polymer with a large number of primary amine groups (-NH2) and a part of formamide groups (–NH–CHO), was chosen as the primary cross-linker. The primary cross-linked membrane with a thin and compactness separation layer was prepared via nucleophilic addition and Schiff base reactions on the surface of hollow fiber ultrafiltration membrane. Then, the unreacted –NH2 on the membrane surface were used for secondary cross-linking with glutaraldehyde (GA) and terephthalaldehyde (TPA) to obtain two cross-linked membranes with different separation layer structures, respectively. The influences of the cross-linker's rigidity and flexibility on the compactness of the separation layer are expounded detail and the evolution process in the microstructure of the separation layer is revealed. Neutral Red (MW = 288.8 g mol−1) can be completely removed while maintaining high flux (42.6 L m−2 h−1 bar−1). Moreover, the rejection to dyes was almost uninfluenced by salt. This study provides a reference for preparing LNFs with stable microstructures and high efficiency for the selective separation of low molecular weight dye/salt systems.

Synthesis and mechanism research of a new low molecular weight shale inhibitor on swelling of sodium montmorillonite

AbstractShale gas as green and clean energy is attracting more interest. However, shale hydration and swelling have become the major challenges using water‐based drilling fluids, replacing oil‐based drilling fluids, for developing shale gas. In this work, a low molecular weight branched polyamine (NETS) as clay swelling inhibitor was synthesized. The NETS performed excellent inhibition property by linear expansion experiments and cuttings hot‐rolling recovery. The inhibition mechanism of NETS was investigated using X‐ray diffraction, fourier transform infrared spectroscopy, cation exchange capacity, X‐ray photoelectron spectroscopy, scanning electron microscopy, and zeta potential. The results show that the NETS can adsorb on Na‐Mt, decrease the basal spacing of wet Na‐Mt from 1.91 to 1.43 nm, and replace majority sodium ions from interlayer of Na‐Mt. However, replaceability of sodium ions and inhibition of water molecules of ethylenediamine are worse than NETS. These indicate that the primary amines of NETS had strong interaction with Na‐Mt, tensed clay layers and decrease the basal spacing. The combination of long hydrophobic chain and primary amines makes NETS to adsorb on surface of Na‐Mt, intercalate into interlayer of Na‐Mt with tilted monolayer arrangement, and replace sodium ions. The more the number of primary amine groups, the better the inhibition performance. Therefore, NETS has a great potential to be an outstanding shale inhibitor of water‐based drilling fluids in the future.

Polyamine chitosan adsorbent for the enhanced adsorption of anionic dyes from water

ABSTRACTA simple synthesis route for amine protected-introduced-released chitosan (APIR-CS) was investigated to improve the adsorption of anionic dyes. The C2 amine groups of the chitosan (CS) were initially protected via a Schiff-base reaction by benzaldehyde. They were then synthesized by the introduction of ethylenediamine into C6 hydroxyl groups on CS via epichlorohydrin. The final product was obtained after removal of the Schiff base with dilute hydrochloride solution. Amine-introduced chitosan (AI-CS) was directly synthesized at the C2 amine groups. The adsorbents were characterized by FTIR, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). For Congo red (CR) and methyl orange (MO), most of the amine groups in CS were converted to–N˭CH2 groups after the benzaldehyde treatment. Hydrochloric acid treatment after the cross-linking reaction released protected nitrogen atoms into the form of the primary amine again. APIR-CS had significantly greater adsorption capacities than AI-CS. The increased adsorption performance was attributed to the large number of primary amine groups on the surfaces. The adsorption mechanism was based on electrostatic interaction, while the adsorption process was mainly physisorption.

Polyamidoamine dendrimers with different surface charge as carriers in anticancer drug delivery

Second-generation (G2) polyamidoamine (PAMAM) dendrimers are branched polymers containing 16 surface primary amine groups. Due to their structural properties, these polymers can be used as universal carriers in various drug delivery systems. Amine-terminated PAMAM dendrimers are characterized by a high positive surface charge, leading to effective but nonspecific interactions with negatively charged cell plasmatic membranes. To reduce the nonspecific internalization of PAMAM dendrimers, their primary amine groups are often modified by acetic or succinic anhydrides, polyethylene glycol derivatives and other compounds. In this work, the role of primary amine groups, which are localized on the surface of doxorubicin-conjugated (Dox) dendrimers, was studied with regard to their intracellular distribution and internalization rates using SKOV3 human ovarian adenocarcinoma cells. It was demonstrated that all Dox-labeled G2-derivatives containing different numbers of acetamide groups synthesized in this work show high rates of cellular uptake at 37°С. As expected, the conjugate carrying the maximum number of primary amine groups demonstrated the highest rates of binding and endocytosis. At the same time, the G2-Dox conjugate containing the maximum number of acetamide groups showed colocalization with LAMP2, a marker of lysosomes and late endosomes, as well as the highest level of cytotoxic activity against SKOV3 cells. We conclude that second-generation PAMAM dendrimers are characterized by varied pathways of internalization and intracellular distribution due to the number of primary amine groups on their surface and, as a consequence, a different surface charge.

Intercalation behavior of branched polyethyleneimine into sodium bentonite and its effect on rheological properties

The inhibitive mechanism of low-molecular-weight branched polyethyleneimine (BPEI) with multiple primary amines and 1,6-hexamethylenediamine (HMDA) with two primary amines adsorbed on sodium bentonite (Na+Bent) has been investigated using isothermal adsorption, adsorption kinetics, scanning electron microscopy (SEM), X-ray diffraction (XRD) and elemental analysis (EA) techniques. The results indicate that as the number of primary amine groups in the inhibitor increases, the saturated adsorption amount decreases, and the adsorption rate increases. Low-molecular-weight BPEI molecules enter the interlayer space of Na+Bent and significantly reduce this space compared to that in hydrated Na+Bent. Moreover, there is no change in the clay interlayer space of Na+Bent with increasing BPEI concentration. A monolayer of BPEI intercalates into the clay interlayer and replaces the sodium ions in the interlayer. The BPEI molecules become firmly embedded in the Na+Bent interlayer between the primary amine groups and Si-O groups, resulting in the removal of water molecules. The inhibitive performance shows that BPEI inhibits clay hydration more effectively than HMDA and other inhibitors, and also indicates that as the number of primary amines increases, the inhibitive performance increases. When <1wt% BPEI was added, the rheological properties improved significantly, and the American Petroleum Institute standard (API) fluid loss could be controlled well, indicating that BPEI can effectively create a balance between swelling inhibition and the rheological properties of water-based drilling fluids. Overall, the results indicate that BPEI is promising as a commercial shale inhibitor.

Investigation of the inhibition mechanism of the number of primary amine groups of alkylamines on the swelling of bentonite

The inhibition mechanism of alkylamines that have different numbers of primary amine groups adsorbed on sodium bentonite has been investigated using isothermal adsorption, adsorption kinetics, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis (EA), cation exchange capacity (CEC), thermogravimetric analysis (TGA), linear expansion experiments and rolling recovery. The saturated adsorption capacity of alkylamines on sodium bentonite decreased with the increase in the number of primary amine groups. The adsorption rate constant increases rapidly with the increase in the number of primary amine groups on the premise that they are both water-soluble and hydrophobic. A flat-lying monolayer of each alkylamine was intercalated, replacing sodium ions in the interlayer and becoming firmly embedded in the interlayer space of sodium bentonite between the primary amine groups and silicon-oxygen tetrahedra. As a result, the water molecules present in the clay interlayer space were expelled, and the interlayer space of the clay decreased to the maximum extent. The inhibition performance of alkylamines on bentonite clearly increases with the increasing of number of primary amine groups. Therefore, a mixture of alkylamines with multiple primary amine groups is a promising intercalating inhibitor that can be used along with water-based drilling fluids has broad application prospects.

On the efficiency of NHS ester cross-linkers for stabilizing integral membrane protein complexes.

We have previously presented a straightforward approach based on high-mass matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) to study membrane proteins. In addition, the stoichiometry of integral membrane protein complexes could be determined by MALDI-MS, following chemical cross-linking via glutaraldehyde. However, glutaraldehyde polymerizes in solution and reacts nonspecifically with various functional groups of proteins, limiting its usefulness for structural studies of protein complexes. Here, we investigated the capability of N-hydroxysuccinimide (NHS) esters, which react much more specifically, to cross-link membrane protein complexes such as PglK and BtuC(2)D(2). We present clear evidence that NHS esters are capable of stabilizing membrane protein complexes in situ, in the presence of detergents such as DDM, C12E8, and LDAO. The stabilization efficiency strongly depends on the membrane protein structure (i.e, the number of primary amine groups and the distances between primary amines). A minimum number of primary amine groups is required, and the distances between primary amines govern whether a cross-linker with a specific spacer arm length is able to bridge two amine groups.

Carbon dioxide capture on primary amine groups entrapped in activated carbon at low temperatures

For purposes of selective CO2 uptake under ambient conditions, a few number of primary amine groups are selected, including aminoclay (H2N-CL), 3-aminopropyltriethoxysilane (APTES), and dopamine hydrochloride (DA). Coatings of both H2N-CL into activated carbon (AC) show enhanced CO2 adsorption capacity at 273 and 298K and 1atm, resulting in 3.069/1.950mmol/g, compared to 2.872/1.824mmol/g of pristine AC. However, APTES and DA coated AC at 273 and 298K and 1atm are reduced to 2.433/1.762 and 0.429/0.389mmol/g. Particularly, the coating of H2N-CL nanoparticles into AC exhibits enhanced selectivity of 8.8/18.7, compared to 7.6/15.9 in pristine AC for CO2/N2 at 273 and 298K at 1atm.

PH-dependent nano-capturing of tartaric acid using dendrimers

The ability of dendrimers to bind to various target molecules through non-covalent interactions was used to capture water soluble organic reagents, such as tartaric acid (TA), from different matrices, i.e. aqueous solutions and wine samples. The influence of the pH, dendrimer type, generation and feeding concentration on the host-guest complexation of TA was investigated. The maximum binding capacity of TA in aqueous solutions was achieved by amine end-capped dendrimers at pH 5. At extreme pH values of 2 and 11, the binding of TA dropped strikingly, demonstrating the pH-dependency underlying the host-guest interactions. The linear correlation between the maximum binding capacity of TA at pH 5 and the number of primary amine groups on the surface of PAMAM and PPI dendrimers strongly indicated that host-guest complex formation between TA and dendrimers is largely dependent on electrostatic interactions. Molecular simulations confirmed the predominant electrostatic nature of the interactions between TA and the amine end-capped dendrimers and also provided important information on the spatial distribution of TA within the PAMAM G5 dendrimer. All these results designate dendrimers as potential nano-capturing systems for the removal/recovery of TA from complex matrices such as wine, industrial waste or fruit juices.

Hydrophobic modification of low molecular weight polyethylenimine for improved gene transfection

Hydrophobic modification of low molecular weight (LMW) polyethylenimine (PEI) is known to increase gene transfection efficiency of LMW PEI. However, few studies have explored how the conjugated hydrophobic groups influence the properties of the modified LMW PEI mainly due to difficulties in obtaining well defined final product compositions and limitations in current chemical synthesis routes. The aim of this study was to modify LMW PEI (Mn 1.8 kDa, PEI-1.8) judiciously with different hydrophobic functional groups and to investigate how hydrophobicity, molecular structure and inclusion of hydrogen bonding properties in the conjugated side groups as well as the conjugation degree (number of primary amine groups of PEI-1.8 modified with hydrophobic groups) influence PEI-1.8 gene transfection efficiency. The modified polymers were characterized for DNA binding ability, particle size, zeta potential, in vitro gene transfection efficiency and cytotoxicity in SKOV-3 human ovarian cancer and HepG2 human liver carcinoma cell lines. The study shows that modified PEI-1.8 polymers are able to condense plasmid DNA into cationic nanoparticles, of sizes ∼100 nm, whereas unmodified polymer/DNA complexes display larger particle sizes of 2 μm. Hydrophobic modification also increases the zeta potential of polymer/DNA complexes. Importantly, modified PEI-1.8 shows enhanced transfection efficiency over the unmodified counterpart. Higher transfection efficiency is obtained when PEI-1.8 is modified with shorter hydrophobic groups (MTC–ethyl) as opposed to longer ones (MTC–octyl and MTC–deodecyl). An aromatic structured functional group (MTC–benzyl) also enhances transfection efficiency more than an alkyl functional group (MTC–octyl). An added hydrogen-bonding urea group in the conjugated functional group (MTC–urea) does not enhance transfection efficiency over one without urea (MTC–benzyl). The study also demonstrates that modification degree greatly influences gene transfection, and ∼100% substitution of primary amine groups leads to significantly lower gene transfection efficiency. These findings provide insights to modification of PEI for development of effective and non-cytotoxic non-viral vectors.

PAMAM Dendrimer-Based Multifunctional Conjugate for Cancer Therapy: Synthesis, Characterization, and Functionality

Poly(amidoamine) (PAMAM) dendrimer-based multifunctional cancer therapeutic conjugates have been designed and synthesized. The primary amino groups on the surface of the generation 5 (G5) PAMAM dendrimer were neutralized through partial acetylation, providing enhanced solubility of the dendrimer (in conjugation of FITC (fluorescein isothiocyanate)) and preventing nonspecific targeting interactions (in vitro and in vivo) during delivery. The functional molecules fluorescein isothiocyanate (FITC, an imaging agent), folic acid (FA, targets overexpressed folate receptors on specific cancer cells), and paclitaxel (taxol, a chemotherapeutic drug) were conjugated to the remaining nonacetylated primary amino groups. The appropriate control dendrimer conjugates have been synthesized as well. Characterization of the G5 PAMAM dendrimer and its nanosize conjugates, including the molecular weight and number of primary amine groups, has been determined by multiple analytical methods such as gel permeation chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), potentiometric titration, high-performance liquid chromatography (HPLC), and UV spectroscopy. These multifunctional dendrimer conjugates have been tested in vitro for targeted delivery of chemotherapeutic and imaging agents to specific cancer cells. We present here the synthesis, characterization, and functionality of these dendrimer conjugates.

Measurement of primary amine groups on surface-modified silica and their role in metal binding

The characterization of a chelating silica, modified by coupling ethylenediamine to a surface-linked epoxide, was carried out using an improved ninhydrin-based procedure for the measurement of primary amines, and elemental analysis. Whilst the primary amine content of model monoamines was accurately assessed, for diamines in which the amine groups were separated by 2, 3 or 4 carbon atoms, the number of primary amine groups was underestimated. Chemically modified silicas were prepared by activation of the surface with different loadings of an epoxide modifier, which was in turn coupled to ethylendiamine. Elemental analysis and the ninhydrin reaction were used to assess the involvement of primary amine groups in copper complexation by these modified silicas and the degree of bridging resulting from the modification. Increasing the quantity of epoxide modifier resulted in an increased coverage of epoxide groups on the silica surface, but whilst this increased the quantity of diamine that could be coupled onto the surface, increased diamine bridging occurred. The copper capacity of the silica was linked to the primary amine content of the silica and not to its total nitrogen content. Copper complexation or chelation by the resin is therefore more favoured by the linear modification than by the bridged form.

Neomycin is an agonist at a polyamine site on the N-methyl-D-aspartate receptor.

Neomycin appears as a full agonist and spermidine as a partial agonist at the site where polyamines enhance 1-[1-(2-thienyl)cyclohexyl][3H]piperidine ([3H]TCP) binding on the N-methyl-D-aspartate (NMDA) receptor. Other aminoglycosides also enhance [3H]TCP binding with efficacies roughly proportional to the number of primary amine groups. The polyamine antagonists ifenprodil and arcaine inhibit enhancement of [3H]TCP binding by spermidine or neomycin. The inhibition of [3H]TCP binding by arcaine is apparently competitively reduced by neomycin and spermidine, supporting a common site. Diethylenetriamine (previously described as a polyamine antagonist) may be a partial agonist. Enhancement by neomycin or spermidine is not additive to that of Mg2+, consistent with competition of Mg2+ and spermidine or neomycin at the site where these compounds enhance [3H]TCP binding. Polyamines also enhance the binding of the competitive antagonist 2-(2-carboxypiperazin-4-yl)[3H]propyl-1-phosphonic acid ([3H]CPP). Neomycin, which does not enhance [3H]CPP binding, inhibits the enhancement by spermidine. That this site is distinct from the site where spermidine and neomycin increase [3H]TCP binding is supported by different pharmacology. Arcaine and diethylenetriamine do not inhibit spermidine enhancement of [3H]CPP binding. Mg2+ also does not compete with the spermidine enhancement of [3H]CPP binding. Ifenprodil inhibits the spermidine enhancement of [3H]CPP binding. The data suggest two or more polyamine sites, with arcaine selective for the site that enhances [3H]TCP binding. Neomycin is an agonist at one polyamine site and antagonist to the second.