Amino-functionalized Mesoporous Silica Research Articles

Surface-functionalization of mesoporous SBA-15 silica materials for controlled release of methylprednisolone sodium hemisuccinate: Influence of functionality type and strategies of incorporation

Mesoporous SBA-15 silica materials functionalized with several organic moieties, that include different polarities and hydrophobicities, were investigated as matrices for controlled drug delivery. The functionalities were incorporated into SBA-15 using two methods: direct synthesis or co-condensation route and post-synthesis grafting. Methylprednisolone sodium hemisuccinate, a synthetic pharmaceutical compound used as anti-inflammatory and immunosuppressant, was loaded onto the pristine and functionalized mesoporous SBA-15 silica materials. The influence of the type of organic moieties as well as their incorporation method onto the inorganic silica framework has been evaluated. The results show that SBA-15 functionalized with aminopropyl trimethoxysilane groups has the largest capacity of drug adsorption, clearly higher than the provided by materials functionalized with other groups, independently of the synthesis route. Additionally, materials synthesized by the co-condensation approach show a lower degree of drug retention than the same material synthesized by grafting technique. This fact is attributed to the distinct localization of the functionality, more accessible in the case of the grafting procedure, and hence suggesting that stronger interactions among the SBA-15 functionalized surfaces and the model drug are established. To ascertain whether other organosilanes containing amino groups can provide more effective loading and controlled drug delivery, at neutral and acidic conditions (pH of 7.4 and 4.6, respectively), it was also investigated the incorporation by grafting of several amino organic moieties onto the SBA-15 silica materials. It was concluded that as the number of amino groups incorporated into SBA-15 material increased, not only the drug loading capacity was higher, but the functionalized silica material vehicles slowed down the drug delivery. Finally, it was confirmed that cell viability was largely unaffected by amino-functionalized mesoporous SBA-15 silica materials after 72 h of incubation time.

Amino-Functionalized Urea–Formaldehyde Framework Mesoporous Silica for U(VI) Adsorption in Wastewater Treatment

A mesoporous silica prototype (MSP) was produced by attaching SiO2 colloid to urea formaldehyde resin. Treatment of the MSP using different grafting methods yielded three different amino-functionalized mesoporous silica samples. The materials were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, 13C nuclear magnetic resonance, zeta potential measurements, and isothermal N2 sorption/desorption. For a 1:2000 solid-to-liquid ratio, all adsorbents could almost completely remove uranyl from sulfate and carbonate solutions of 3.6 mg L–1 U(VI) at pH 3.5 to 5.5 and pH 6.5 to 9.5, respectively. The adsorption equilibrium time was less than 30 min. The adsorption equilibrium curve showed that the maximum sorption capacity was 117 mg L–1 at pH 4.0. Through the experimental adsorption, it was found that the most effective sample could reduce the U(VI) concentration from 3.6 mg L–1 to 0.79 μg L–1 with 99.98% removed. In d...

Optimal synthesis of amino-functionalized mesoporous silicas for the adsorption of heavy metal ions

Amino-functionalized mesoporous silicas (AFMS) were synthesized by a neutralization route using the anionic surfactant dodecanoic acid (DAA) as structure-directing agent (SDA), aminopropyltrimethoxysilane (APTMS) as co-structure-directing agent (CSDA), and tetraethoxysilane (TEOS) as silicon source. The synthesis parameters, which affect the structural properties and the amino loadings of the resultant AFMS, were optimized. Various techniques, such as FT-IR, XRD, N2 adsorption-desorption, and TEM, were used to characterize the synthesized AFMS. The selective removal of Cu2+, Pb2+, Cd2+, and Zn2+ from aqueous solutions in single-, binary-, ternary-, and quaternary-component systems by the synthesized AFMS was thoroughly investigated. The measured single-component adsorption isotherms of Cu2+, Pb2+, Cd2+, and Zn2+ on the AFMS optimally synthesized can be well described by the Sips model, in which the extracted adsorption capacities are 2.34, 2.86, 1.71, and 1.36 mmol/g (0.149, 0.593, 0.192, and 0.089 g/g) for Cu2+, Pb2+, Cd2+, and Zn2+, respectively, higher than those on other adsorbents reported in the literature. Furthermore, Pb2+ and Cu2+ can be more selectively removed by the synthesized adsorbent, compared to Cd2+ and Zn2+, confirmed by the results on the multi-component adsorption.

Amino-Functionalized Mesoporous Silica Based Polyethersuflone-Polyvinylpyrrolidone Composite Membrane for Elevated Temperature Fuel Cells

Inorganic-organic nanostructured hybrid membranes of polyethersuflone (PES)-polyvinylpyrrolidone (PVP) were prepared with mesoporous silica materials. Hollow mesoporous silica is synthesized via cationic surface-assistant etching method, while amino-functionalized hollow mesoporous silica and amino-functionalized mesoporous silica spheres were synthesized via post-grafting strategy. After the addition of mesoporous silica and amino-functionalized mesoporous silica into the matrix of PA doped PES-PVP composite membranes, all composite membranes show similar PA uptake. However, the proton conductivity of the composite membranes increases significantly with the substantial decrease in the activation energy for proton diffusion, especially for the amino-functionalized hollow mesoporous silica material. That reason is most likely due to the facilitated proton transportation in the ordered mesoporous channels via the hydrogen bond between the –NH2 groups and H3PO4. Cell performance also confirms the superiority of the addition of inorganic fillers in PES-PVP membrane, and the highest peak power density at 180 oC was 480 mW cm-2 for NH2-HMS based composite membrane, which is 92.7 % higher than that of PA doped PES-PVP composite membrane at the identical condition. The results show promising application of NH2-HMS based PES-PVP composite membrane for elevated temperature proton exchange membrane fuel cells. Figure 1

PH-Responsive Core-Shell Structured Nanoparticles for Triple-Stage Targeted Delivery of Doxorubicin to Tumors.

The application of cytotoxic chemotherapeutics in cancer therapy has been largely restricted by their lack of selectivity. Despite the existence of numerous targeted delivery systems, it is practically challenging to develop one single system to simultaneously cover tumor-targeted delivery of chemotherapeutics at the tissue, cellular, and subcellular levels. To solve this problem, pH-responsive core-shell structured nanoparticles (CSNPs) were self-assembled in this study to provide triple-stage targeted delivery of doxorubicin (DOX) from the injection site to the nuclei of cancer cells. Amino-functionalized mesoporous silica nanoparticles (MSN) were doubly modified with TAT peptide and acid-cleavable polyethylene glycol (PEG) as the DOX-loaded cationic core. The anionic shell was constituted by galactose-modified poly(allylamine hydrochloride)-citraconic anhydride, a hepato-carcinoma-targeting polymer with charge-reversible property. In vitro results showed that PEG effectively reduced protein adsorption and phagocytic capture of CSNPs in the circulating blood (pH 7.4), thus facilitating passive accumulation in tumors (tissue level). Following PEG detachment via acidic hydrolysis in tumor microenvironment (pH 6.5), the exposed galactose ligands endowed CSNPs with active internalization into hepato-carcinoma cells (cellular level). Afterward, the acidity in endosomes and lysosomes (pH 5.0) triggered the conversion of anionic shell into positive charges, leading to core-shell disassembly and subsequent TAT-mediated delivery of DOX to the nuclei (subcellular level). Importantly, the efficiencies of each targeting moiety were nicely preserved when combining together in CSNPs. As a result, improved tumorous distribution and potent therapeutic efficacy of CSNPs were noted in tumor-bearing mice at a relatively low dose. CSNPs therefore provide an efficient and nontoxic platform for the targeted delivery of antitumor drugs.

Co-delivery of erlotinib and doxorubicin by pH-sensitive charge conversion nanocarrier for synergistic therapy

Pretreatment of lung cancer cells with epidermal growth factor receptor (EGFR) inhibitor erlotinib has been recently reported that could dramatically synergize their apoptotic response to DNA damage agent doxorubicin (DOX). To translate this synergistic therapy into in vivo anticancer therapy and clinical practice, we designed a novel pH-sensitive charge conversion nanocarrier (M-HHG2C18-L) that contained erlotinib/DOX combination and produced a sequential staggered drug release for synergistic lung cancer therapy. In this study, a synthetic zwitterionic oligopeptide lipid (1,5-dioctadecyl-l-glutamyl2-histidyl-hexahydrobenzoic acid, HHG2C18) was used to construct a pH-sensitive lipid bilayer (HHG2C18-L), which was subsequently applied to coat amino-functionalized mesoporous silica nanoparticles (MSN-NH2). Erlotinib and DOX were separately incorporated into HHG2C18-L and MSN-NH2 respectively to obtain pH-sensitive charge conversion erlotinib/DOX co-delivery nanoparticles (M-HHG2C18-L(E+D)). We confirmed that M-HHG2C18-L(E+D) were able to reverse surface zeta potential from negative to positive at tumor extracellular pH, thus facilitating the targeted cancer cell internalization. Furthermore, as erlotinib was sequestered in the exterior lipid bilayer and the controlled release ability of MSN-NH2, erlotinib released faster than DOX during the cellular transport. Additionally, HHG2C18-L became more positive at tumor intracellular pH and enhanced Coulombic repulsion with MSN-NH2, leading to increased sequential staggered release of erlotinib and DOX. Due to the pretreatment and time-staggered inhibition of EGFR with erlotinib and the enhanced intracellular release of DOX to the nucleus, the maximized synergistic cell killing effect was achieved. Compared to non-sensitive erlotinib/DOX co-delivery nanoparticles (M-SPC-L(E+D)) and simultaneous DRUG coadministration. M-HHG2C18-L(E+D) with sequential staggered drug release and pH-sensitive charge conversional properties showed great synergistic effects in antiproliferation and apoptosis of A549 human cancer cells in vitro. The in vivo study demonstrated that M-HHG2C18-L(E+D) exhibited considerable tumor accumulation and potent suppression of tumor growth in Lewis lung carcinoma tumor bearing mice. It was also demonstrated that M-HHG2C18-L(E+D) showed no systemic toxicity and possessed distinguished effect on extending survival period. These results suggested that M-HHG2C18-L(E+D) had great potential application in cancer treatment.

Thermally Stable Amine-Grafted Adsorbent Prepared by Impregnating 3-Aminopropyltriethoxysilane on Mesoporous Silica for CO2 Capture

In this paper, an amino-functionalized adsorbent for CO2 capture was synthesized by impregnating 3-aminopropyltriethoxysilane (APTES) on mesoporous silica. Amino functional groups were chemically bonded to silica support. Because of chemical bonds, the thermal stability of this adsorbent (205 °C) was greater than that of an adsorbent prepared by impregnating polyethylenimine on the same mesoporous silica (160 °C). The cyclic CO2 loading capacity was improved by increasing adsorption temperature, reaching a maximum of 89.3 mg CO2/g at 100 °C and then reduced at temperatures above 100 °C. Optimum regeneration temperature was determined at 120 °C. The adsorbent was stable for multiple adsorption–regeneration cycles operating at adsorption temperature of 100 °C in pure CO2 and regeneration temperature of 120 °C in atmosphere, respectively. The amino-functionalized mesoporous silica is a thermally stable adsorbent with relatively high CO2 loading capacity and high optimum adsorption and regeneration temperatur...

Adsorption and desorption characteristics of DNA onto the surface of amino functional mesoporous silica with various particle morphologies

Recently, deoxyribonucleic acid (DNA) adsorption on solid materials has been reported for applications such as genetic diagnosis of diseases, gene delivery, and biosensors. Mesoporous silica (MPS) is an excellent carrier because of its high surface area and large pore volume. Functionalization of the MPS surface can be controlled by silane coupling reagents, and the MPS particle morphology can be easily changed by the synthetic conditions. In this study, to evaluate the ability of DNA adsorption on MPS, the MPS surface was functionalized using four reagents, 3-aminopropyltriethoxysilane (−NH2), N-(2-aminoethyl)-3-aminopropyltriethoxysilane (−2ENH2), N-(6-aminohexyl)aminopropyltrimethoxysilane (−2HNH2), and (3-trimethoxysilylpropyl)diethylenetriamine (−3NH2), each having a different number of amino groups and alkyl chain lengths. Moreover, we prepared three types of MPSs with different particle morphologies: sheet-type structure (MPS sheet), spherical MPS (MCM-41s), and nonporous spherical silica. A high adsorption capacity was observed in MPS sheets with −2HNH2 (sheet-2HNH2) and −3NH2 (sheet-3NH2), as well as MCM-41s with −3NH2 (41s-3NH2). The adsorption and desorption rates of DNA on these three MPSs were then examined and the best results were obtained with 41s-3NH2. These results demonstrate that the amino functionalized MPS materials are useful DNA adsorbents.

Encapsulating quantum dots with amino functionalized mesoporous hollow silica microspheres for the sensitive analysis of formaldehyde in seafood

We developed a hybrid fluorescent material using amino functional mesoporous hollow silica microspheres (MHSM) encapsulated with CdTe quantum dots (QDs).

Control of particle uptake kinetics from particulate mesoporous silica films by cells through covalent linking of particles to the substrate - towards sequential drug delivery for tissue engineering applications.

A sequential release of biological cues is of high interest in tissue engineering applications, as both the proliferation and the differentiation of stem cells can be drugged. In previous studies we have shown that particulate films of mesoporous silica particles can be successfully applied for influencing stem cell fates through intracellular drug delivery after particle internalisation by the cells. In this study, we develop this concept towards an enhanced control of the particle uptake kinetics through either adsorption or covalent linking of the mesoporous silica particles to the substrate. Microscopy glass slides were initially functionalized by an aminosilane to which a thin layer of hyaluronic acid was covalently attached through an amide bond. A sub-monolayer of amino-functionalized mesoporous silica nanoparticles with a diameter of 400 nm were then adsorbed to the hyaluronic acid-functionalized surface by adsorption under high-shear conditions. Subsequently, the adsorbed particles were covalently linked to the hyaluronic acid through an amide bond. Corresponding films without the covalent coupling step were used as the control. Muscle stem cells attach and proliferate nicely on all films, and do internalize particles in all cases. However, the kinetics of particle internalization was clearly delayed for the covalently attached particles in comparison to physisorbed particles. Thus, the results imply that tuning of the particle-substrate interactions through linking chemistries is a promising means of achieving sequential particle-mediated drug release from films and that corresponding chemistries should also be applicable for 3D scaffold systems.

Amino-functionalized mesoporous silica based polyethersulfone–polyvinylpyrrolidone composite membranes for elevated temperature proton exchange membrane fuel cells

It is important to find alternative membranes to the state-of-the-art polybenzimidazole based high temperature proton exchange membranes with high proton conductivity at elevated temperature but with simple synthesis procedures.

Correction: Tethering silver ions on amino-functionalized mesoporous silica for enhanced and sustained antibacterial properties

Correction for ‘Tethering silver ions on amino-functionalized mesoporous silica for enhanced and sustained antibacterial properties’ by Chengwei Wang et al., RSC Adv., 2015, 5, 104289–104298.

Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption–desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

Amino-functionalized mesoporous silica as solid base catalyst for regioselective aza-Michael reaction of aryl tetrazoles

The modified MCM-41 with aminopropyl groups was synthesized, characterized and its catalytic activity was evaluated in aza-Michael addition of various aryl tetrazoles to activated olefin esters under reflux condition. The synthesized new compounds were characterized using spectroscopic and physical methods. The catalyst was reused in five consecutive experiments without obvious loss of activity. The results showed with application of aminopropylated MCM-41 only N2 alkylation occurs on tetrazole rings. However, when triethylamine was used as the base, a mixture of N1 and N2 alkylation was observed. In addition, antimicrobial studies investigated and results indicated that the products did not show considerable antimicrobial activity.

Investigation of Carbon Dioxide Adsorption on Amino-Functionalized Mesoporous Silica

Carbon dioxide (CO2) adsorption on unfunctionalized and amino-functionalized SBA-3 materials are investigated and compared in this study. The synthesized materials are characterized by various techniques such as X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) method, Fourier transform infrared (FT-IR) and Scanning electron microscopy (SEM).The isotherms of these materials have been measured using volumetric method at 298 K up to 5 bar. The adsorption capacity of CO2 by mesoporous silica was enhanced through functionalization with amine groups. It is observed that the pentaethylene hexamine functionalized SBA-3 (SBA-3/PEHA) shows a higher adsorption capacity towards CO2 compared to other adsorbents.

A comparative study on different functionalized mesoporous silica nanomagnetic sorbents for efficient extraction of parabens

Different silica-based magnetic sorbents including mesoporous silica–Fe3O4 nanocomposite (Fe3O4@MCM-41), amino-functionalized mesoporous silica–Fe3O4 nanocomposite (Fe3O4@MCM-41–NH2) and graphene oxide/amino-functionalized mesoporous silica–Fe3O4 nanocomposite (Fe3O4@MCM-41–NH2–GO) were synthesized and their extraction efficiencies were compared in solid-phase extraction procedure of important parabens prior to gas chromatography–flame ionization detection. The sorbents extraction efficiencies followed the order of Fe3O4@MCM-41–NH2 > Fe3O4@MCM-41–NH2-GO > Fe3O4@MCM-41. Parameters affecting SPE procedure including amount of sorbent, eluting solvent type, adsorption and desorption times, and ionic strength were studied and optimized. The method’s performance was studied in terms of accuracy, linearity, precision and limits of detection. Detection limits of the method were <0.9 µg L−1 and linearity was in the range of 10–1000 µg L−1. Finally, the applicability of the proposed method was demonstrated for extraction of selected parabens in some cosmetic products. Good quantitative recoveries for spiked samples (85–107 %) and satisfactory precision (RSD ≤ 5.6 %) were also obtained.

Synthesis of amino-functionalized mesoporous silica sheets and their application for metal ion capture

Novel mesoporous silica sheets with surface amino-functional groups (sheet-NH2) were prepared for the efficient adsorption of aqueous metal ions. The sheet-NH2 were synthesized by a dual-templating process using Pluronic P123 and N-palmitoyl-l-alanine as templates. Two silicone regents were used to form the silica framework: tetraethoxysilane and 3-aminopropyltriethoxysilane. In the synthetic process, the as-prepared silicate was refluxed in ethanol to remove the organic templates remaining from the surface amino groups derived from APTES. The prepared sheet-NH2 showed widths of several micrometres and small thicknesses of approximately 50 nm. The pore diameter, pore volume and BET surface area of sheet-NH2 were determined by nitrogen adsorption–desorption isotherms to be 3.1 nm, 0.73 cm3 g−1 and 189.9 m2 g−1, respectively. TEM, XRD, FT-IR and TG–DTA analysis demonstrated that the sheet material had a disordered mesoporous structure and contained organic chains. The adsorptions of aqueous zinc(II) and copper(II) metal ions were examined and compared with amino-functionalized conventional mesoporous silica (MCM-NH2), calcined mesoporous silica sheets and silica beads with no porous structures. Notably, the sheet-NH2 exhibited the highest adsorption of both zinc and copper ions among the examined materials. In addition, the metal ion sorption equilibrium data of sheet-NH2 were fitted to the Langmuir isotherm model.

Synthesis of P(NIPAM-co-Am)/Mesoporous Silica Composites and Their Temperature- Responsive Anion Exchange

The purpose of this study is to examine the structure and the temperature-responsive anion exchange property of amino-functionalized mesoporous silica coated with temperature-responsive copolymer, poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)). For this purpose, the composites which contained 0, 10, or 20 wt% of Am were synthesized. From the TG results, it was found that the amounts of copolymer immobilized on the mesoporous silica were 1.6 - 2.6 wt%. XRD patterns revealed that the structures of composites were hexagonal and almost the same as that of original mesoporous silica without polymer. At low temperature the methyl orange (MO) anions adsorbed and desorbed reversibly with changing pH of the solution, while at high temperature the MO anions did not. This temperature, at which the amount of adsorbed MO anions changed considerably, shifted to the higher temperature side with increasing the amount of added Am.

Tethering silver ions on amino-functionalized mesoporous silica for enhanced and sustained antibacterial properties

Amino group-based tethering method is an effective strategy to load Ag ions for long-term and highly efficient antibacterial activity. The developed Ag–CaMSS is a promising surgical implantation material with excellent antibacterial activity.

ChemInform Abstract: Amino Functionalized Mesoporous Silica Decorated with Iron Oxide Nanoparticles as a Magnetically Recoverable Nanoreactor for the Synthesis of a New Series of 2,4‐Diphenylpyrido[4,3‐d]pyrimidines.

AbstractThe advantages of the present method are high yields, simplicity, and easy work‐up.