Colorimetric determination of reactive solid-supported primary and secondary amino groups

CO2 Adsorption Capacity of Organic Alkali Sorbent CPEI from Polyethyleneimine

Support-free cross-linked polyethyleneimine sorbent (CPEI) for CO2 capture was evaluated as the regenerable sorbent. The total amines available for the CO2 capture on CPEI were determined by the polyethyleneimine/glutaraldehyde ratio for the synthesis of CPEI. The CO2 capacity of CPEI in the slurry bubble column reactor reached 4.92 mmol/g, which is 1.97 times higher than that obtained under anhydrous conditions. The adsorption kinetics of CPEI in the reactor were investigated in terms of the CPEI amount, the CO2 fraction, the gas flow rate, temperature, and the total amines available. The experimental breakthrough curves for the sorbent were well-fitted with a fractional-order kinetic model. The modeling analysis found the influence of diffusion resistance on the adsorption is more significant than that of the driving force. The CO2 capacity of CPEI remained almost constant during the temperature swing adsorption/desorption cycles.

A microparticulate based formulation to protect therapeutic enzymes from proteolytic digestion: phenylalanine ammonia lyase as case study

Phenylketonuria is a genetic disorder affecting the metabolism of phenylalanine (phe) due to a deficiency in the enzyme phenylalanine hydroxylase. This disorder is characterized by an elevated phe blood level, which can lead to severe intellectual disabilities in newborns. The current strategy to prevent these devastating consequences is limited to a life-long phe-free diet, which implies major lifestyle changes and restrictions. Recently, an injectable enzyme replacement therapy, Pegvaliase, has been approved for treating phenylketonuria, but is associated with significant side-effects. In this study a phe-metabolizing system suitable for oral delivery is designed to overcome the need for daily injections. Active phenylalanine ammonia-lyase (PAL), an enzyme that catalyses phe metabolism, is loaded into mesoporous silica microparticles (MSP) with pore sizes ranging from 10 to 35 nm. The surface of the MSP is lined with a semipermeable barrier to allow permeation of phe while blocking digestive enzymes that degrade PAL. The enzymatic activity can be partially preserved in vitro by coating the MSP with poly(allylamine) and poly(acrylic acid)-bowman birk (protease inhibitor) conjugate. The carrier system presented herein may provide a general approach to overcome gastro-intestinal proteolytic digestion and to deliver active enzymes to the intestinal lumen for prolonged local action.

Biofunctional Nanofibrous Substrate for Local TNF-Capturing as a Strategy to Control Inflammation in Arthritic Joints

Rheumatoid arthritis (RA) is an autoimmune disease that affects the synovial cavity of joints, and its pathogenesis is associated with an increased expression of pro-inflammatory cytokines, namely tumour necrosis factor-alpha (TNF-α). It has been clinically shown to have an adequate response to systemic administration of TNF-α inhibitors, although with many shortcomings. To overcome such limitations, the immobilization of a TNF-α antibody on a nanofibrous substrate to promote a localized action is herein proposed. By using this approach, the antibody has its maximum therapeutic efficacy and a prolonged therapeutic benefit, avoiding the systemic side-effects associated with conventional biological agents' therapies. To technically achieve such a purpose, the surface of electrospun nanofibers is initially activated and functionalized, allowing TNF-α antibody immobilization at a maximum concentration of 6 µg/mL. Experimental results evidence that the biofunctionalized nanofibrous substrate is effective in achieving a sustained capture of soluble TNF-α over time. Moreover, cell biology assays demonstrate that this system has no deleterious effect over human articular chondrocytes metabolism and activity. Therefore, the developed TNF-capturing system may represent a potential therapeutic approach for the local management of severely affected joints.

Spermidine-mediated poly(lactic-co-glycolic acid) nanoparticles containing fluorofenidone for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a progressive, fatal lung disease with poor survival. The advances made in deciphering this disease have led to the approval of different antifibrotic molecules, such as pirfenidone and nintedanib. An increasing number of studies with particles (liposomes, nanoparticles [NPs], microspheres, nanopolymersomes, and nanoliposomes) modified with different functional groups have demonstrated improvement in lung-targeted drug delivery. In the present study, we prepared, characterized, and evaluated spermidine (Spd)-modified poly(lactic-co-glycolic acid) (PLGA) NPs as carriers for fluorofenidone (AKF) to improve the antifibrotic efficacy of this drug in the lung. Spd-AKF-PLGA NPs were prepared and functionalized by modified solvent evaporation with Spd and polyethylene glycol (PEG)-PLGA groups. The size of Spd-AKF-PLGA NPs was 172.5±4.3 nm. AKF release from NPs was shown to fit the Higuchi model. A549 cellular uptake of an Spd-coumarin (Cou)-6-PLGA NP group was found to be almost twice as high as that of the Cou-6-PLGA NP group. Free Spd and difluoromethylornithine (DFMO) were preincubated in A549 cells to prove uptake of Spd-Cou-6-PLGA NPs via a polyamine-transport system. As a result, the uptake of Spd-Cou-6-PLGA NPs significantly decreased with increased Spd concentrations in incubation. At higher Spd concentrations of 50 and 500 µM, uptake of Spd-Cou-6-PLGA NPs reduced 0.34- and 0.49-fold from that without Spd pretreatment. After pretreatment with DFMO for 36 hours, cellular uptake of Spd-Cou-6-PLGA NPs reached 1.26-fold compared to the untreated DFMO group. In a biodistribution study, the drug-targeting index of Spd-AKF-PLGA NPs in the lung was 3.62- and 4.66-fold that of AKF-PLGA NPs and AKF solution, respectively. This suggested that Spd-AKF-PLGA NPs accumulated effectively in the lung. Lung-histopathology changes and collagen deposition were observed by H&E staining and Masson staining in an efficacy study. In the Spd-AKF-PLGA NP group, damage was further improved compared to the AKF-PLGA NP group and AKF-solution group. The results indicated that Spd-AKF-PLGA NPs are able to be effective nanocarriers for anti-pulmonary fibrosis therapy.

Retention of stemness and vasculogenic potential of human umbilical cord blood stem cells after repeated expansions on PES-nanofiber matrices

Despite recent advances in cardiovascular medicine, ischemic diseases remain a major cause of morbidity and mortality. Although stem cell-based therapies for the treatment of ischemic diseases show great promise, limited availability of biologically functional stem cells mired the application of stem cell-based therapies. Previously, we reported a PES-nanofiber based ex vivo stem cell expansion technology, which supports expansion of human umbilical cord blood (UCB)-derived CD133(+)/CD34(+) progenitor cells ∼225 fold. Herein, we show that using similar technology and subsequent re-expansion methods, we can achieve ∼5 million-fold yields within 24 days of the initial seeding. Interestingly, stem cell phenotype was preserved during the course of the multiple expansions. The high level of the stem cell homing receptor, CXCR4 was expressed in the primary expansion cells, and was maintained throughout the course of re-expansions. In addition, re-expanded cells preserved their multi-potential differential capabilities in vitro, such as, endothelial and smooth muscle lineages. Moreover, biological functionality of the re-expanded cells was preserved and was confirmed by a murine hind limb ischemia model for revascularization. These cells could also be genetically modified for enhanced vasculogenesis. Immunohistochemical evidences support enhanced expression of angiogenic factors responsible for this enhanced neovascularization. These data further confirms that nanofiber-based ex-vivo expansion technology can generate sufficient numbers of biologically functional stem cells for potential clinical applications.

The effect of nanofibre surface amine density and conjugate structure on the adhesion and proliferation of human haematopoietic progenitor cells

Previous studies have shown that substrate surface chemistry and topography exhibit significant impact on haematopoietic progenitor cell adhesion, proliferation and differentiation. In the present study, the effect of surface amine density and structure of grafted polymer chains on the adhesion and expansion of haematopoietic progenitor cells was investigated. Cryopreserved human umbilical cord blood CD133(+) cells were expanded in cytokine-supplemented medium on ethylenediamine (EDA)- or 2-aminoethyl methacrylate hydrochloride (AEMA)-grafted polyethersulphone (PES) nanofibre scaffolds for 10 days. Although the percentage of CD34(+) cells among the expanded cells increased with the surface amine density, the maximum fold expansion of CD34(+) cells was obtained at a moderate amine density of 20-80 nmol cm(-2). When comparing nanofibre matrices with similar amine densities, but prepared with two different methods, cells cultured on the AEMA-grafted PES nanofibre matrix showed lower fold expansion in terms of total cell number (300 ± 84 fold) and CD34(+) cell number (68 ± 19-fold) in comparison with those cultured on EDA-grafted nanofibres (787 ± 84-fold and 185 ± 84-fold, respectively). These results indicate that the surface amine density and the conjugate structure are important determinants for the preservation of CD34 surface marker and expansion efficiency of CD34(+) cells.

Quantification of primary amine groups available for subsequent biofunctionalization of polymer surfaces

Biocompatible polymers are commonly functionalized with specific moieties such as amino groups to modify their surface properties and/or to attach bioactive compounds. A reliable method is usually required to characterize amino group surface densities. In this study, aminated polyethylene terephthalate (PET) films were generated via an aminolysis reaction involving either ethylenediamine molecules (EtDA), in order to vary easily the amino group density on PET surfaces, or 25 kDa polyvinylamine (PVAm) as an alternative reagent preventing bulk damages resulting from the aminolysis reaction. Among commonly used dyes for amino group quantification, Orange II and Coomassie Brillant Blue (CBB) were selected to quantify the extent of amine grafting resulting from these derivatization procedures. Rapid and convenient colorimetric assays were compared to surface atomic compositions obtained from X-ray photoelectron spectroscopy (XPS) measurements. Orange II was found to be the most appropriate dye for quantifying primary amine groups in a reliable and specific way. Due to its unique negative charge and low steric hindrance compared to CBB, the Orange II dye was very sensitive and provided reliable quantification over a wide range of amino group surface densities (ca. 5 to at least 200 pmol/mm(2)). In order to further validate the use of the Orange II dye for amino group quantification, a heterobifunctional linker reacting with amino groups was then grafted on modified PET surfaces. Interestingly, the good correlation between the densities of adsorbed Orange II and covalently grafted linkers suggests that the Orange II method is a relevant, reliable, easy, and inexpensive method to predict the amount of amino groups available for subsequent functionalization of polymer surfaces.

Designing a binding interface for control of cancer cell adhesion via 3D topography and metabolic oligosaccharide engineering

This study combines metabolic oligosaccharide engineering (MOE), a technology where the glycocalyx of living cells is endowed with chemical features not normally found in sugars, with custom-designed three-dimensional biomaterial substrates to enhance the adhesion of cancer cells and control their morphology and gene expression. Specifically, Ac(5)ManNTGc, a thiol-bearing analog of N-acetyl-d-mannosamine (ManNAc) was used to introduce thiolated sialic acids into the glycocalyx of human Jurkat T-lymphoma derived cells. In parallel 2D films and 3D electrospun nanofibrous scaffolds were prepared from polyethersulfone (PES) and (as controls) left unmodified or aminated. Alternately, the materials were malemided or gold-coated to provide bio-orthogonal binding partners for the thiol groups newly expressed on the cell surface. Cell attachment was modulated by both the topography of the substrate surface and by the chemical compatibility of the binding interface between the cell and the substrate; a substantial increase in binding for normally non-adhesive Jurkat line for 3D scaffold compared to 2D surfaces with an added degree of adhesion resulting from chemoselective binding to malemidede-derivatived or gold-coated surfaces. In addition, the morphology of the cells attached to the 3D scaffolds via MOE-mediated adhesion was dramatically altered and the expression of genes involved in cell adhesion changed in a time-dependent manner. This study showed that cell adhesion could be enhanced, gene expression modulated, and cell fate controlled by introducing the 3D topograhical cues into the growth substrate and by creating a glycoengineered binding interface where the chemistry of both the cell surface and biomaterials scaffold was controlled to facilitate a new mode of carbohydrate-mediated adhesion.

Determination of amine and aldehyde surface densities: application to the study of aged plasma treated polyethylene films

The aim of this work was to test and to compare different methods reported in the literature to quantify amine and aldehyde functions on the surface of polyethylene (PE) films treated by ammonia plasma and to specify their stability against time. A low pressure ammonia plasma reactor was used to functionalize PE films with amine groups, which could be subsequently used for further immobilization of biomolecules. In order to determine the density of amine groups on the surface of treated films, various molecule probes and spectrophotometric analytical methods have been investigated. Two methods using (i) sulfosuccinimidyl 6-[3'-(2-pyridyldithio)-propionamido] hexanoate (sulfo-LC-SPDP) and (ii) 2-iminothiolane (ITL) associated with bicinchoninic acid (BCA) have been proved to be reliable and sensitive enough to estimate the surface concentration of primary amine functions. The amount of primary amino groups on the functionalized polyethylene films was found to be between 1.2 and 1.4 molecules/nm2. In a second step, the surface concentration of glutaraldehyde (GA), which is currently used as a spacer arm before immobilization of biomolecules, has been assessed: two methods were used to determine the surface density of available aldehyde functions, after the reaction of GA with the aminated polyethylene film. The concentration of GA was found to be in the same range as primary amine concentration. The influence of aging time on the density of available amino and aldehyde groups on the surfaces were evaluated under different storage conditions. The results showed that 50% of the initial density of primary amine functions remained available after storage during 6 days of the PE samples in PBS (pH 7.6) at 4 degrees C. In the case of aldehyde groups, the same percentage of the initial density (50%) remained active after storage in air at RT over a longer period, i.e., 15 days.

Surface-aminated electrospun nanofibers enhance adhesion and expansion of human umbilical cord blood hematopoietic stem/progenitor cells

Interaction between hematopoietic stem/progenitor cells (HSPCs) and their extra cellular matrix components is an integral part of the signaling control for HSPC survival, proliferation and differentiation. We hypothesized that both substrate topographical cues and biochemical cues could act synergistically with cytokine supplementation to improve ex vivo expansion of HSPCs. In this study, we compared the ex vivo expansion of human umbilical cord blood CD34(+) cells on unmodified, hydroxylated, carboxylated and aminated nanofibers and films. Results from 10-day expansion cultures showed that aminated nanofiber mesh and film were most efficient in supporting the expansion of the CD34(+)CD45(+) cells (195-fold and 178-fold, respectively), as compared to tissue culture polystyrene (50-fold, p<0.05). In particular, aminated nanofiber meshes supported a higher degree of cell adhesion and percentage of HSPCs, as compared to aminated films. SEM imaging revealed the discrete colonies of cells proliferating and interacting with the aminated nanofibers. This study highlights the potential of a biomaterials approach to influence the proliferation and differentiation of HSPCs ex vivo.

Surface-immobilization of adhesion peptides on substrate for ex vivo expansion of cryopreserved umbilical cord blood CD34+ cells

The interaction between integrins and extracellular matrix proteins play an important role in the regulation of hematopoiesis. Human hematopoietic progenitor cells express very late antigen-4 (VLA-4) and VLA-5, which mediate their interaction with fibronectin by recognizing the connecting segment-1 (CS-1 and RGD motifs, respectively. In this study, we investigated the ex vivo expansion of human umbilical cord blood (UCB) CD34+ cells on synthetic substrates surface-immobilized with peptides containing the CS-1 binding motif (EILDVPST) and the RGD motif (GRGDSPC). These peptides were covalently conjugated to poly(ethylene terephthalate) (PET) film at a surface density of 2.0-2.3 nmol/cm2. UCB CD34+ cells were cultured for 10 days in serum-free medium supplemented with recombinant human thrombopoietin, stem cell factor, flt3-ligand and interleukin 3. The highest cell expansion fold was observed on the CS-1 peptide-modified surface, where total nucleated cells, total colony forming unit, and long-term culture initiating cells were expanded by 589.6+/-58.6 (mean+/-s.d.), 76.5+/-8.8, and 3.2+/-0.9-fold, respectively, compared to unexpanded cells. All substrates surface-immobilized with peptides, including the control peptides, were more efficient in supporting the expansion of CD34+, CFU-GEMM and LTC-ICs than tissue culture polystyrene surface. Nevertheless, after 10-days of ex vivo expansion from 600 CD34+ cells, only cells cultured on CS-1-immobilized surface yielded positive engraftment, even though the frequency was low. PET surface immobilized with RGD peptide was less efficient than that with CS-1 peptide. Our results suggest that covalently immobilized adhesion peptides can significantly influence the proliferation characteristics of cultured UCB CD34+ cells.

Chromatographic performance of a thin microporous bed of nitrocellulose

Chromatography along thin (125 microm) porous beds of nitrocellulose, layered on top of an polyester backing, shows good separation efficiency with plate heights of 10-20 microm. Flow is controlled by capillary forces and shows low rate variations between the individual disposable devices. Positively charged groups were introduced into the nitrocellulose and efficient separation of transferrin isoforms, differing by only 0.1 pI units, was found after a short migration distance (1 cm). The upper surface is not covered, which allows sample and reagents to be added, and the clear backing permits detection. The chromatography can easily be combined on-line with sensitive immunoassay detection down to the microM (10(-12) M) range. This microscaled combination device should have a wide range of applications in analytical biochemistry.