Charged Amino Research Articles

Plasma-Activated Electrospun Polylactide Fiber Meshes as Matrices for Tissue Engineering

Poly (L-lactide-co-D/L-lactide)-based fiber meshes resembling structural features of the native extracellular matrix have been prepared by electrospinning. Subsequent coating of the electrospun fibers with an ultrathin plasma polymerized allylamine (PPAAm) layer changed the hydrophobic nature of the polylactide surface into a hydrophilic polymer network and provided positively charged amino groups on the fiber surface able to interact with negatively charged pericellular matrix components. Cell experiments in vitro using different types of human epithelial cells (gingiva, uroepithel) revealed that the PPAAm-activated surfaces promoted the occupancy of the meshes by cells accompanied by improved initial cell spreading. An in vivo study in a rat intramuscular implantation model demonstrated that the local inflammatory tissue response did not differ between PPAAm-coated and untreated polylactide meshes.

Chemical design of pH-sensitive nanovalves on the outer surface of mesoporous silicas for controlled storage and release of aromatic amino acid

Mesoporous silicas with hexagonally arranged pore channels were synthesized in water–ethanol-ammonia solution using cetyltrimethylammonium bromide as template. Directed modification of silica surface with N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups was realized by postsynthetic activation of halogenoalkylsilicas, which have surface uniformly or selectively distributed 3-chloropropyl groups, with 2-aminodiphenylamine in the liquid phase. Chemical composition of silica materials was estimated by IR spectroscopy and chemical analysis of the surface products of reactions. Characteristics of porous structure of MCM-41-type silicas were determined from X-ray and low-temperature nitrogen ad-desorption measurements. Release ability of synthesized silica carriers was established on encapsulation of 4-aminobenzoic acid in pore channels and subsequent delivery at pH=6.86 and pH=1.00. It was found that N-[N′-(N′-phenyl)-2-aminophenyl]-3-aminopropyl groups block pore entrances at neutral pH preventing 4-aminobenzoic acid release. At pH=1.00 repulsion of positively charged surface aromatic amino groups localized near pore orifices provides unhindered liberation of aromatic amino acid from mesoporous channels.

A molecular model to explain the controlled release from SBA-15 functionalized with APTES

A molecular model with the approximate pore diameter of SBA-15 was constructed for the first time to investigate the effect of functionalize the matrix with 3-aminopropyl-triethoxy-silane (APTES) in the release of Chicago Sky Blue 6B (CSB). It was expected that the positively charged amino groups of APTES could interact with the negatively charged sulphonic groups of CSB allowing controlling the release process. Indeed the experimental study showed that the release kinetics of CSB from SBA-15-APTES is two orders of magnitude smaller than from native SBA-15. However molecular modelling calculations investigating the possible interactions of APTES and SBA-15 yield unexpected results. In the model including only the condensation between the silanol groups of SBA-15 and APTES, the calculated interaction energy of CSB was quite similar than with the model of native SBA-15. However when additional electrostatic interactions of the –NH2 groups of APTES with the mesoporous matrix were modelled the mesoporous channels underwent a considerable deformation. These results point to the structure deformation as the cause of the greater retention of CSB in SBA-15-APTES and warn about the special features of APTES when used to functionalize mesoporous silica materials. The model built in this paper could be used to construct predictive models in analogous drug delivery systems.

Novel Functionalization of Boron-Doped Diamond by Microwave Pulsed-Plasma Polymerized Allylamine Film

We report the novel modification of a hydrogen-terminated polycrystalline boron-doped electrode with a microwave pulsed-plasma polymerized allylamine. Boron-doped diamond (BDD) was coated with a very thin layer of adherent cross-linked, pinhole- and additive-free allylamine plasma polymer (PPAAm) resistant to hydrolysis and delamination and characterized by a high density of positively charged amino groups. The pulsed microwave plasma was applied to improve the cross-linking degree and bonding of the plasma polymeric films to boron-doped diamond. The amine-treated BDD films were assessed by advanced surface analytical techniques, such as X-ray photoelectron spectroscopy (XPS), FT-IR, scanning electron microscopy (SEM), laser-induced fluorescence, and water contact angle measurements. The amine-modified Si/BDD surface was functionalized with selected organic molecules containing a carboxylic group in the presence of coupling agents such as diisopropylcarbodiimide (DIC). The anthraquinone derivatives Boc-Ly...

Drug-dendrimer supramolecular complexation studied from molecular dynamics simulations and NMR spectroscopy

Fully atomistic molecular dynamics (MD) simulations and NMR spectroscopy were employed to get insights about the molecular details of drug-dendrimer supramolecular association phenomena, using piroxicam (PRX) and the third generation poly(amido amine) (PA- MAM-G3) dendrimer as model systems. Theoretical results concerning the complex stoichiometry suggest that PRX forms drug-dendrimer complexes of the type 24:1 at pH 7.0. This result was validated with the experimental quantities obtained from aqueous solubility profiles, which led to an empiric stoichiometry of 23:1 for the PRX:PA- MAM-G3 system. The predicted binding mode between PRX and PAMAM-G3 accounts for the preferred encap- sulation of the drug inside dendrimer cavities, which is mainly driven by van der Waals and hydrogen bonding interactions, and to a lesser extent, for the external asso- ciation of the guest through electrostatic contacts with the positively charged amino groups of PAMAM periphery. The binding mode obtained from MD simulations was confirmed with 2D-NOESY experiments, which evidence the preferred internal complexation of PRX with PAMAM- G3. The predominance of internal encapsulation over external contacts in the PRX:PAMAM-G3 system differs from the general behaviour expected for acidic anionic guests, for which external electrostatic interactions with the positively charged PAMAM surface have been postulated as the most relevant factor for drug association.

Peptide formation mechanism on montmorillonite under thermal conditions.

The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150°C for 336h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9% of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.

Interactions between Trehalose and Amino Acids by Molecular Dynamics Simulations

Although trehalose is used as a protein stabilizer, the mechanism by which this stability is induced is not fully understood at present. In this study, we investigated the interactions between trehalose and all 20 common amino acids using all- atom molecular dynamics simulations. It is found that all the amino acids exhibit a preference for contact with water, especially the polar and charged amino acids.Conversely, only the hydrophobic amino acids were found to have a slight preference for contact with trehalose molecules. This tendency is most pronounced in the case of contact between trehalose and aromatic or hydrophobic side chains, whereas the backbones of each amino acids all show similar propensities for contact with water. Furthermore, hydrogen bonds between amino acids and trehalose were found to be significantly weaker than those between amino acids and water, although both trehalose and water can interact with the amino acids via hydrogen bonds. These findings are important with regard to the exploration of the molecular mechanism of protein stability induced by trehalose and the rational design of highly efficient protein stabilizers.

In <i>Silico</i> investigation for hemoglobin characterizations leads to new aspects in susceptibility to glycosylation

In silico analysis were performed between some species for hemoglobin characterizations specially resistivity to glycosylation. Multiple alignments of both hemoglobin subunits were revealed L-K-V-K-E-G-E-A-L-R-P-T-F-F-D-L-S-A-V- K-H-G-K-V-H-D-L-S-L-H-K-L-V-D-P-N-F-L-L-L-A-F-T-P-A-K-V-L-Y conserved in camel, human, cow and horse entirely. Hemoglobin sequences are well conserved in evolution and between species. Camelus families HBA were in same cluster (91% bootstrapping). However for HBB they were in same cluster (95% bootstrapping). Camel hemoglobin appeared to be more basic than either that of other species. Based on isoelectric points, camel HBB has high mobility than HBA in electrophoresis. The charged and hydrophilic amino acids of hemoglobin in camel were more than human. The non-enzymatic binding of glucose to the protein or HbA1c is revealed both subunits hemoglobin in human is resistance to N-glycosylation but camel HBB is only resistant to O-glycosylation. HBB is less susceptible to glycosylation than HBA. Also HBB has critical roles in camel for instance resistivity to glycosylation and diabetes subsequently. Abbreviations: HB, Hemoglobin; HBA, α-chain of hemoglobin; HBB, β-chain of hemoglobin; GHB, glycosylated hemoglobin; AA, Amino Acid; NA, nucleic acid; Vs., versus; p I , Isoelectric Point.

Surface-Coated Polylactide Fiber Meshes as Tissue Engineering Matrices with Enhanced Cell Integration Properties

Poly(L-lactide-co-D/L-lactide)-based fiber meshes resembling structural features of the native extracellular matrix have been prepared by electrospinning. Subsequent coating of the electrospun fibers with an ultrathin plasma-polymerized allylamine (PPAAm) layer after appropriate preactivation with continuous O2/Ar plasma changed the hydrophobic nature of the polylactide surface into a hydrophilic polymer network and provided positively charged amino groups on the fiber surface able to interact with negatively charged pericellular matrix components. In vitro cell experiments using different human cell types (epithelial origin: gingiva and uroepithelium; bone cells: osteoblasts) revealed that the PPAAm-activated surfaces promoted the occupancy of the meshes by cells accompanied by improved initial cell spreading. This nanolayer is stable in its cell adhesive characteristics also afterγ-sterilization. An in vivo study in a rat intramuscular implantation model demonstrated that the local inflammatory tissue response did not differ between PPAAm-coated and untreated polylactide meshes.

Effect of Amino Group Charge on the Photooxidation Kinetics of Aromatic Amino Acids

The kinetics of the photooxidation of aromatic amino acids histidine (His), tyrosine (Tyr), and tryptophan (Trp) by 3,3',4,4'-benzophenonetetracarboxylic acid (TCBP) has been investigated in aqueous solutions using time-resolved laser flash photolysis and time-resolved chemically induced dynamic nuclear polarization. The pH dependence of quenching rate constants is measured within a large pH range. The chemical reactivities of free His, Trp, and Tyr and of their acetylated derivatives, N-AcHis, N-AcTyr, and N-AcTrp, toward TCBP triplets are compared to reveal the influence of amino group charge on the oxidation of aromatic amino acids. The bimolecular rate constants of quenching reactions between the triplet-excited TCBP in the fully deprotonated state and tryptophan, histidine, and tyrosine with a positively charged amino group are kq = 2.2 × 10(9) M(-1) s(-1) (4.9 < pH < 9.4), kq = 1.6 × 10(9) M(-1) s(-1) (6.0 < pH < 9.2), and kq = 1.5 × 10(9) M(-1) s(-1) (4.9 < pH < 9.0), respectively. Tryptophan, histidine, and tyrosine with a neutral amino group quench the TCBP triplets with the corresponding rate constants kq = 8.0 × 10(8) M(-1) s(-1) (pH > 9.4), kq = 3.0 × 10(8) M(-1) s(-1) (pH > 9.2), and kq = (4.0-10.0) × 10(8) M(-1) s(-1) (9.0 < pH < 10.1) that are close to those for the N-acetylated derivatives. Thus, it has been established that the presence of charged amino group changes oxidation rates by a significant factor; i.e., His with a positively charged amino group quenches the TCBP triplets 5 times more effectively than N-AcHis and His with a neutral amino group. The efficiency of quenching reaction between the TCBP triplets and Tyr and Trp with a positively charged amino group is about 3 times as high as that of both Tyr and Trp with a neutral amino group, N-AcTyr and N-AcTrp.

Swelling behavior of chemically cross-linked poly(N-IPAAm-allylglycine) hydrogels: Effects of NaCl and pH

The influence of NaCl and pH on the swelling behavior of a series of chemically cross-linked ionic poly(N-IPAAm-allylglycine) hydrogels in aqueous solutions was investigated at 298K. The hydrogels were synthesized by free radical polymerization using methylenebisacrylamide as crosslinker. For all investigated hydrogels, the mass fraction of polymerizable substances was constant (0.1). The hydrogels differ in the amount of crosslinker (mole fraction: 0.02 and 0.05, respectively) and in the amount of the comonomer allylglycine (mole fraction: from 0.05 to 0.2). The experimental results for the degree of swelling in aqueous salt solutions of NaCl exhibit two transitions: the first (second) transition occurs at salt mass fractions between about 10−6 and 10−4 (≈10−2). The first transition reduces the degree of swelling by about 20%. That transition is caused by the screening of the charged amino and carboxylic groups of allylglycine by the salt ions. After that transition the gel still contains much water. In the second transition the gel collapses like non-ionic N-IPAAm – hydrogels. The swelling of the ionic hydrogels is also influenced by the pH of the aqueous solution. The degree of swelling reveals a minimum at 4<pH<8. In that region most allylglycine comonomers are present as zwitterions, i.e., the otherwise ionic hydrogel behaves like a non-ionic gel and the degree of swelling is low. A previously developed thermodynamic model was applied to describe the swelling behavior. The model is able to reproduce the experimental data quantitatively when some model parameters are adjusted to selected experimental results for the degree of swelling.

Investigating the hydrogen-bond acceptor site of the nicotinic pharmacophore model: a computational and experimental study using epibatidine-related molecular probes

The binding mode of nicotinic agonists has been thoroughly investigated in the last decades. It is now accepted that the charged amino group is bound by a cation-π interaction to a conserved tryptophan residue, and that the aromatic moiety is projected into a hydrophobic pocket deeply located inside the binding cleft. A hydrogen bond donor/acceptor, maybe a water molecule solvating this receptor subsite, contributes to further stabilize the nicotinic ligands. The position of this water molecule has been established by several X-ray structures of the acetylcholine-binding protein. In this study, we computationally analyzed the role of this water molecule as a putative hydrogen bond donor/acceptor moiety in the agonist binding site of the three most relevant heteromeric (α4β2, α3β4) and homomeric (α7) neuronal nicotinic acetylcholine receptor (nAChR) subtypes. Our theoretical investigation made use of epibatidine 1 and deschloroepibatidine 2 as molecular probes, and was then extended to their analogues 3 and 4, which were subsequently synthesized and tested at the three target receptor subtypes. Although the pharmacological data for the new ligands 3 and 4 indicated a reduction of the affinity at the studied nAChRs with respect to reference agonists, a variation of the selectivity profile was clearly evidenced.

Prediction of the interaction between spermidine and the G-G mismatch containing acceptor stem in tRNAIle: Molecular modeling, density functional theory, and molecular dynamics study

Polyamines, putrescine, spermidine (SPD), and spermine are closely linked to cell growth, and highly regulate the levels of transcription, translation and protein turnover. We propose that SPD stimulates the formation of Ile-tRNAIle by inducing a selective structural change of the G-G mismatch containing acceptor stem in tRNAIle. Here, we provide insight into how SPD recognizes and stabilizes the G-G mismatch containing acceptor stem in tRNAIle with molecular modeling (MM), density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. The results of the MM and DFT calculations indicate that the negatively charged region of the G-G mismatch containing acceptor stem in tRNAIle is preferentially recognized by positively charged SPD. In addition, MD simulations indicate that all of the positively charged amino groups of SPD under physiological conditions (N1(NH3+), N5(NH2+), and N10(NH3+) could form hydrogen bonds with tRNAIle and trigger the SPD-induced stabilization and structural change of the G-G mismatch containing acceptor stem in tRNAIle. Thus, this approach should be useful for determining the preferential binding site and appropriate binding mode of polyamines on tRNAIle.

Integrated Hollow Mesoporous Silica Nanoparticles for Target Drug/siRNA Co‐Delivery

A hollow mesoporous silica nanoparticle (HMSNP) based drug/siRNA co-delivery system was designed and fabricated, aiming at overcoming multidrug resistance (MDR) in cancer cells for targeted cancer therapy. The as-prepared HMSNPs have perpendicular nanochannels connecting to the internal hollow cores, thereby facilitating drug loading and release. The extra volume of the hollow core enhances the drug loading capacity by two folds as compared with conventional mesoporous silica nanoparticles (MSNPs). Folic acid conjugated polyethyleneimine (PEI-FA) was coated on the HMSNP surfaces under neutral conditions through electrostatic interactions between the partially charged amino groups of PEI-FA and the phosphate groups on the HMSNP surfaces, blocking the mesopores and preventing the loaded drugs from leakage. Folic acid acts as the targeting ligand that enables the co-delivery system to selectively bind with and enter into the target cancer cells. PEI-FA-coated HMSNPs show enhanced siRNA binding capability on account of electrostatic interactions between the amino groups of PEI-FA and siRNA, as compared with that of MSNPs. The electrostatic interactions provide the feasibility of pH-controlled release. In vitro pH-responsive drug/siRNA co-delivery experiments were conducted on HeLa cell lines with high folic acid receptor expression and MCF-7 cell lines with low folic acid receptor expression for comparison, showing effective target delivery to the HeLa cells through folic acid receptor meditated cellular endocytosis. The pH-responsive intracellular drug/siRNA release greatly minimizes the prerelease and possible side effects of the delivery system. By simultaneously delivering both doxorubicin (Dox) and siRNA against the Bcl-2 protein into the HeLa cells, the expression of the anti-apoptotic protein Bcl-2 was successfully suppressed, leading to an enhanced therapeutic efficacy. Thus, the present multifunctional nanoparticles show promising potentials for controlled and targeted drug and gene co-delivery in cancer treatment.

Preparation of a Novel Amino-Phosphate Zwitterionic Stationary Phase for Hydrophilic Interaction Chromatography

A new stationary phase which contains both negatively charged phosphate groups and positively charged amino groups was successfully synthesized by modification of amino-functionalized silica particles with trichlorophosphine oxide (POCl3) for hydrophilic interaction chromatography (HILIC). The composition of the surface grafts was determined by Fourier transform infrared spectroscopy and elemental analysis. Various parameters, such as column temperature, water content, pH values and ionic strength of the mobile phase were investigated to study the retention mechanism. The results demonstrated that the stationary phase involved a complex retention process including surface adsorption, partitioning and electrostatic interactions. Under optimized conditions, the separation of nucleobases and nucleosides, water-soluble vitamins, organic acids on the novel stationary phase could be achieved in the HILIC mode.

Interfacial Self-assembly of NixCd1–xS/ODA Hybrids with Photoluminescent and Superhydrophobic Performance

We report herein a simple strategy for fabricating two-dimensional (2D) petal-like NixCd1–xS/octadecylamine (ODA) hybrids exhibiting both photoluminescent and superhydrophobic properties via a facile liquid–liquid interfacial self-assembly technique. First, thioglycolic acid stabilized CdS quantum dots (QDs) doped with nickel were synthesized in aqueous solution. Then, relying on the facile H2O/CHCl3 interfacial platform, through the electrostatic interactions between positively charged amino groups of ODA and negatively charged carboxyl groups of a QD surface, we have successfully fabricated petal-like NixCd1–xS/ODA hybrids. These NixCd1–xS/ODA hybrids present enhanced photoluminescence compared with NixCd1–xS QDs, especially in high quantum yield, which is enhanced from 3% to 50%. Moreover, the NixCd1–xS/ODA hybrid film has a water contact angle of 152.7°, leading to its excellent hydrophobic property. Finally, by virtue of their excellent polymer compatibility and optical properties, we extended the ro...

Chitosan–glycerol-phosphate (GP) gels release freely diffusible GP and possess titratable fixed charge

Chitosan–glycerol-phosphate (GP) solutions undergo a sol–gel transition upon heating. A model of heat-induced transfer of protons from chitosan to GP in solution has been proposed to explain this sol–gel transition. This model suggests that reduced inter-chain electrostatic repulsion by a decreased protonation of positively charged amino groups – via proton transfer to GP2− thereby reduced to GP− – would allow chitosan polymer chains to precipitate together and form a solid hydrogel structure. The hypothesis that GP has the single role of acting as a proton acceptor and not as a divalent electrostatic cross-linker of chitosan amine groups suggests that it should freely diffuse out of the gel after the gel formation. We found indeed that GP is free to diffuse and the experimental diffusion profile corresponds to a free diffusion model indicating that it plays no role in electrostatic cross-linking.Finally since chitosan amine groups in the gel are not bound to GP, we examined whether they are titratable in the gel. We show that chitosan in the hydrogel indeed possesses titratable amine groups with significant fixed charge up to +80mM and follows the same ionization behavior as chitosan in solution. The results of these studies are significant in light of the current and future biomedical applications of this system, including its recent clinical approval as a biomaterial for cartilage repair.

PH-Responsive Delivery of Doxorubicin from Citrate–Apatite Nanocrystals with Tailored Carbonate Content

In this work, the efficiency of bioinspired citrate-functionalized nanocrystalline apatites as nanocarriers for delivery of doxorubicin (DOXO) has been assessed. The nanoparticles were synthesized by thermal decomplexing of metastable calcium/citrate/phosphate solutions both in the absence (Ap) and in the presence (cAp) of carbonate ions. The presence of citrate and carbonate ions in the solution allowed us to tailor the size, shape, carbonate content, and surface chemistry of the nanoparticles. The drug-loading efficiency of the two types of apatite was evaluated by means of the adsorption isotherms, which were found to fit a Langmuir-Freundlich behavior. A model describing the interaction between apatite surface and DOXO is proposed from adsorption isotherms and ζ-potential measurements. DOXO is adsorbed as a dimer by means of a positively charged amino group that electrostatically interacts with negatively charged surface groups of nanoparticles. The drug-release profiles were explored at pHs 7.4 and 5.0, mimicking the physiological pH in the blood circulation and the more acidic pH in the endosome-lysosome intracellular compartment, respectively. After 7 days at pH 7.4, cAp-DOXO released around 42% less drug than Ap-DOXO. However, at acidic pH, both nanoassemblies released similar amounts of DOXO. In vitro assays analyzed by confocal microscopy showed that both drug-loaded apatites were internalized within GTL-16 human carcinoma cells and could release DOXO, which accumulated in the nucleus in short times and exerted cytotoxic activity with the same efficiency. cAp are thus expected to be a more promising nanocarrier for experiments in vivo, in situations where intravenous injection of nanoparticles are required to reach the targeted tumor, after circulating in the bloodstream.

Ion exchange voltammetry at branched polyethylenimine cross-linked with ethylene glycol diglycidyl ether and sensitive determination of ascorbic acid

The construction and characterization of an electrochemical sensing platform based on a cationic polymer modified electrode are described in this work. The cationic polymer is prepared as a thin film on a glassy carbon electrode (GC) surface by in situ cross-linking of branched polyethylenimine (BPEI) with ethylene glycol diglycidyl ether (EGDE). Positively charged amino groups of this polymer (BPEI-EGDE) act as effective anion exchange groups. The ion exchange properties of BPEI-EGDE are investigated by determining the permeability of electroactive anions through the polymer film using cyclic voltammetry. Furthermore, the modified electrodes are used for the electrochemical detection of ascorbic acid (AA), which is feasible with the films alone or when hexacyanoferrate ([Fe(CN)6]4−), is electrostatically confined (by ion exchange) in the cationic BPEI-EGDE film. When compared with bare GC electrodes, a large decrease in AA oxidation overpotential is observed at the [Fe(CN)6]4−-modified electrode surface. Kinetic parameters of electrocatalytic oxidation of AA by electrogenerated [Fe(CN)6]3− are evaluated by cyclic voltammetry and chronoamperometry. Finally, this method is employed for the determination of AA in a pharmaceutical tablet.

Highly efficient adsorption of Cr(VI) from aqueous solutions by amino-functionalized titanate nanotubes

For highly efficient removal of Cr(VI) from aqueous solutions, amino-functionalized titanate nanotubes (NH2-TNTs) with excellent adsorption performance have been synthesized by covalently grafting [1-(2-amino-ethyl)-3-aminopropyl]trimethoxysilane (AAPTS) onto protonated titanate nanotubes (HTNTs) with great amounts of surface hydroxyl groups. TEM and XRD results confirmed that the nanotubular morphology and crystal structure of HTNTs and NH2-TNTs were preserved. FTIR spectra demonstrated that AAPTS was covalently bonded on the surface of HTNTs. Batch adsorption experiments showed that pseudo-second-order kinetics model and Langmuir isotherm model fitted the adsorption data very well for both materials, and the Cr(VI) adsorption capacity on NH2-TNTs calculated by Langmuir model was up to 153.85mgg−1 at initial pH 5.4 and 30°C, much larger than that on HTNTs (26.60mgg−1). Moreover, uptake of Cr(VI) ions onto NH2-TNTs could be completed within only 5min for 95% adsorption of the maximum. Influence of different species of Cr(VI) under varying pH was also considered. FTIR and XPS analysis indicated that Cr(VI) ions were first exchanged with NO3- linked on the positively charged amino groups and then partially reduced to Cr(III). Afterwards, Cr(III) were then totally chelated with amino groups and no Cr(III) was detected in the solution after Cr(VI) adsorption at pH range of 1–12.