Amine functionalization of cholecyst-derived extracellular matrix with generation 1 PAMAM dendrimer

This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Biomacromolecules, copyright © American Chemical Society after peer review. To access the final edited and published work, see http://pubs.acs.org/doi/pdf/10.1021/bm701055k.A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype

Tailoring hierarchical meso- macroporous 3D scaffolds: from nano to macro

Bone tissue regeneration requires the use of 3D scaffolds which mimic the architecture of the natural extracellular matrix, creating an adequate microenvironment for bone cell growth. Such 3D scaffolds need surface properties suitable for biological recognition in the early stage of cell adhesion, necessary to ensure complete cell colonization, retained cell functionality, and subsequently bone regeneration. Herein, hierarchical 3D scaffolds based on new hydroxyapatite/mesoporous glass nanocomposite bioceramic (MGHA) exhibiting different scales of porosity have been synthesized. These 3D scaffolds possess: (i) highly ordered mesopores with diameters of 10 nm; (ii) macropores with diameters in the 30-80 mu m range with interconnections of 1-10 mu m; and (iii) large macropores of ca. 500 mu m. To improve their surface properties, 3D scaffolds were modified through direct functionalization with amine propyl groups, which notably improve preosteoblast adhesion, proliferation (2.3 fold), differentiation (4.8 fold) and further cell colonization of these scaffolds. The observed enhancement can be related to these amine groups which favour early adhesion, e. g., based on nonspecific protein adsorption as was demonstrated by ellipsometry. These results suggest that the combination of hierarchical structure design and amine surface modification of hydroxyapatite/mesoporous nanocomposite scaffolds yields a double increase in cell proliferation, as well as a quadruple increase in cell differentiation, demonstrating the potential of these nanocomposite materials for bone tissue regeneration purposes

Properties of Polyacrylamide and Functional Multi-walled Carbon Nanotube Composite

In this study we have investigated the structural and electrical properties of multi-walled carbon nanotube (MWCNT) reinforced polyacrylamide (PAM)-based composites. Two types of nanotubes were prepared and used i.e. acid functionalized MWCNT-COOH and amine-functionalized MWCNT-A. The nanocomposite was prepared using the solution cast technique. The samples were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), mechanical testing and electrical conductivity measurement. A comparative study has been made on the physical property of PAM/MWCNT-COOH and PAM/MWCNT-A nanocomposites. It was observed that the amine-functionalization of nanotube improved the filler dispersion into the polymer matrix. SEM photographs ascertain that the MWCNT-A nanoparticles were evenly dispersed in PAM matrix. The electrical conductivity of PAM/MWCNT-COOH was in the range of 0.03-0.5 Scm-1, while PAM/MWCNT-A had higher electrical conductivity of 0.4 to 1.2 Scm-1. The ultimate tensile strength of PAM/MWCNT-A nanocomposites was found to increase from 21-26 MPa, relative to PAM/MWCNT-COOH series (19-23 MPa)

Adsorptive removal of Fe(III) using gallic acid anchored iron magnetic nano-adsorbents synthesized via two different routes under microwave irradiation

9-20Under microwave solvent free conditions, bare iron magnetic nanoparticles (Fe3O4-MNPs) have been silica coated, amine functionalized and gallic acid grafted, in presence and absence of tetraethylorthosilicate (TEOS). The synthesized adsorbents in both cases have been followed up by Fourier transform infrared, scan electron microscopy and transmission electron microscopy analyses to verify and compare the progress of surface modification. The effects of various parameters on the adsorption efficiency of Fe(III) such as pH of solution, amount of adsorbent and contact time have been studied and optimized. The adsorbents Fe3O4-MNPs-SiO2-CPTMS-1,2-EDA-GA and MNPs-CPTMS-1,2-EDA-GA exhibit higher Fe(III) capacities (4.980 and 4.700 mmol/g) than their analogous Fe3O4-MNPs-SiO2-APTMS-GA and Fe3O4-MNPs-APTMS-GA (4.324 and 4.230 mmol/g). The studies of sorption kinetics showed rapid sorption dynamics by a second-order kinetic model, suggesting chemisorption mechanism. Fe(III) adsorption equilibrium data have been fitted well to the Langmuir isotherm. The results of medium stability as criteria for potential coating and values of metal uptake capacity support the possibility of the direct use of alkoxysilanes as an alternative to TEOS not only for coating but also for amine functionalization. This is strengthened by almost equal capability of gallic acid anchored adsorbents for extraction of trace concentrations of Fe(III) spiked natural water samples

Epithelialization of hydrogels achieved by amine functionalization and co-culture with stromal cells

The aim of this study was to develop a hydrogel which would be suitable for corneal cell re-epithelialization when used as a corneal implant. To achieve this, a series of hydrogels were functionalized with primary amines by post-polymerization reactions between amine compounds and glycidyl ether groups attached to the hydrogels. We report a strong correlation between the structure of the amine and the viability of stromal cells and epithelial cells cultured on these hydrogels. Subsequent co-culture of epithelial and stromal cells on the amine modified hydrogels allowed successful expansion of epithelial cells on surfaces functionalized with alkyl α–ω diamines with carbon chain lengths of between 3 and 6. Analysis of variance showed that corneal epithelial cells had a strong preference for surfaces functionalized by the reaction of excess 1,3 diaminopropane with units of glycidyl methacrylate compared to the reaction products of other amines (ammonia; 1,2-diaminoethane; 1,4-diaminobutane or 1,6-diaminohexane). We suggest this approach of amine functionalization combined with stromal/epithelial co-culture offers a promising new approach to achieving a secure corneal epithelium. Keywords: Epithelial cell

A Facile Method for the Non-Covalent Amine Functionalization of Carbon-Based Surfaces for Use in Biosensor Development

Affinity biosensors based on graphene field-effect transistor (GFET) or resistor designs require the utilization of graphene’s exceptional electrical properties. Therefore, it is critical when designing these sensors, that the electrical properties of graphene are maintained throughout the functionalization process. To that end, non-covalent functionalization may be preferred over covalent modification. Drop-cast 1,5-diaminonaphthalene (DAN) was investigated as a quick and simple method for the non-covalent amine functionalization of carbon-based surfaces such as graphene, for use in biosensor development. In this work, multiple graphene surfaces were functionalized with DAN via a drop-cast method, leading to amine moieties, available for subsequent attachment to receptor molecules. Successful modification of graphene with DAN via a drop-cast method was confirmed using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and real-time resistance measurements. Successful attachment of receptor molecules also confirmed using the aforementioned techniques. Furthermore, an investigation into the effect of sequential wash steps which are required in biosensor manufacture, on the presence of the DAN layer, confirmed that the functional layer was not removed, even after multiple solvent exposures. Drop-cast DAN is thus, a viable fast and robust method for the amine functionalization of graphene surfaces for use in biosensor development

Characterization of Epoxy/Amine Networks with Glycidal Polyhedral Oligomeric Silsesquioxane Surface Modified Silica Nanoparticles

Silica nanoparticles were surface modified with octa-functional glycidal polyhedral oligomeric silsesquioxane (G-POSS) and incorporated into an epoxy/amine system in an effort to increase the mechanical performance of the inorganic/organic hybrid material. The silica nanoparticles were first functionalized with 3-aminoprpyltrimethoxysilane (APTMOS) at 5 and 10 weight percent, and then modified with G-POSS at ratios of 1:10 and 1:5 (APTMOS: G-POSS). The modified particles were then incorporated into an epoxy/amine network consisting of diglycidyl ether of bisphenol A (DGEBA) and aromatic amine, diamine diphenyl sulfone (4,4’ DDS) at 1 and 5 weight percent, resulting in 8 different formulations. The incorporation of the modified silica nanoparticles caused changes in crosslink density depending on the amount functionalization density, G-POSS modification, and loading. Samples with nanoparticles of higher functionalization density and lower G-POSS modification exhibited higher crosslink density due to high functionalization and lower free volume. It was determined that incorporation of inorganic POSS cage disrupted network formation and chain packing. Similar trends follow suite with the strength of the material in compressive analysis. The incorporation of the nanoparticles slightly decreased the gel point of the material as compared to that of the control. Furthermore, it was determined that there is an optimum degree of modification and loading that would influence the mechanical properties and performance of the material to its optimal values

Amine Functionalization of Bacterial Cellulose for Targeted Delivery Applications

Bacterial cellulose (BC), produced by acetic acid bacteria Gluconacetobacter xylinus, is ideal for delivery and related biomedical functions. It is FDA approved for wound dressings and internal applications, non-toxic to endothelial cells and has little effect on blood profiles. Conjugation of therapeutics to BC can be accomplished through the available alcohol groups of the anhydroglucose units (AGU), making targeted delivery possible. Amine was introduced to BC through a reaction involving epichlorohydrin and ammonium hydroxide. The chemical structure was analyzed using infrared spectroscopy and quantified through pH titration. Conjugation of amine to BC was demonstrated through fluorescein-5’-isothiocyanate (FITC) and bromocresol green (BCG) attachment. Due the its large molecular size, the protein horseradish peroxidise (HRP) was conjugated to aminated-BC through a bis(sulfosuccinimidyl)suberate (BS3) linker to reduce steric congestion on the BC surface. Hydrogen peroxide was used to hydrolyze BC to create nanocrystalline cellulose (NCC-BC) with dimensions capable of intracellular delivery. Amine was introduced to NCC-BC and the chemical structure was analyzed using infrared spectroscopy and quantified through pH titration. HRP was optimized to demonstrate protein attachment, while avidin-HRP was used to demonstrate the ability of maximizing protein loading. An avidin-biotin glucose oxidase and avidin-biotin β-galactosidase complex was conjugated to aminated NCC-BC to demonstrate the application of a drug carrier of therapeutic proteins

Carbonaceous Nanomaterials as Flame Retardant Coating on Fabric

abstract: Flame retardants (FRs) are applied to variety of consumer products such as textiles and polymers for fire prevention and fire safety. Substantial research is ongoing to replace traditional FRs with alternative materials that are less toxic, present higher flame retardancy and result in lower overall exposure as there are potential health concerns in case of exposure to popular FRs. Carbonaceous nanomaterials (CNMs) such as carbon nanotubes (CNTs) and graphene oxide (GO) have been studied and applied to polymer composites and electronics extensively due to their remarkable properties. Hence CNMs are considered as potential alternative materials that present high flame retardancy. In this research, different kinds of CNMs coatings on polyester fabric are produced and evaluated for their use as flame retardants. To monitor the mass loading of CNMs coated on the fabric, a two-step analytical method for quantifying CNMs embedded in polymer composites was developed. This method consisted of polymer dissolution process using organic solvents followed by subsequent programmed thermal analysis (PTA). This quantification technique was applicable to CNTs with and without high metal impurities in a broad range of polymers. Various types of CNMs were coated on polyester fabric and the efficacy of coatings as flame retardant was evaluated. The oxygen content of CNMs emerged as a critical parameter impacting flame retardancy with higher oxygen content resulting in less FR efficacy. The most performant nanomaterials, multi-walled carbon nanotubes (MWCNTs) and amine functionalized multi-walled carbon nantoubes (NH2-MWCNT) showed similar FR properties to current flame retardants with low mass loading (0.18 g/m2) and hence are promising alternatives that warrant further investigation. Chemical/physical modification of MWCNTs was conducted to produce well-dispersed MWCNT solutions without involving oxygen for uniform FR coating. The MWCNTs coating was studied to evaluate the durability of the coating and the impact on the efficacy during use phase by conducting mechanical abrasion and washing test. Approximately 50% and 40% of MWCNTs were released from 1 set of mechanical abrasion and washing test respectively. The losses during simulated usage impacted the flame retardancy negatively.Dissertation/ThesisDoctoral Dissertation Materials Science and Engineering 201

Incorporation Of Acoustic And Chemical Modifications To Biochar For Pollution Abatement

A series of my researches aim to develop an advanced suitable carbon activation techniques using ultrasound waves, and chemical functionalization for the application of environmental remediation. Ultrasound irradiation exfoliates the graphitic layers of biochar, and creates new/opens the blocked pores, thus creating active sites for chemical activation using amine. CO2 is one of the major air pollutants and a leading cause of the global warming. Thus, it is imperative to establish a proper CCS technology. Reductive photocarboxylation could be an effective way to attach CO2 on carbonaceous structure such as biochar. Biochars have highly porous structure, high surface area and graphitic oxide clusters that consist of the reactive oxygen functional groups such as ̶ COOH, C=O, ̶ OH that are susceptible to amine functionalization. Amine, a nucleophile, can react with CO2, which is an electrophie, to boost adsorption efficiency of the biochar. Furthermore, to identify the impact of amination, the work was carried out in the presence of two different activating agents carbodiimide-benzotriazole and potassium hydroxide and five different amines - tetraethylenepentamine, diethanolamine, monoethanolamine, polyethylenimine, piperazine and their binary and ternary mixtures. The work was further extended to investigate the role of different biomass origin on CO2 capture. Biochars were synthesized from herbaceous, agro-industrial and crop based biomasses and were subjected to three different treatment conditions that involved- I. physical activation, II. chemical activation and III. integrated ultrasonic-amine activation. The last step of this series of works involved investigating the synergistic and antagonistic impact of pyrolysis temperature (in the range of 500-800 ºC) on ultrasound activation and the subsequent CO2 adsorption. It is worth to mention that the conventional carbon activation requires elevated temperature (\u3e700 ºC) and prolonged activation time (\u3e3 hrs). While the method discussed in this dissertation was conducted at near ambient temperature for a very short duration (~30-60sec) and consumes a significantly lower level of energy than conventional carbon activation processes. In addition, this advanced carbon modification method can be adopted for other environmental applications, in addition to CO2 capture and pollutant removal from water and air