Search

Novel non-toxic Eu3+-induced polyelectrolyte nano-aggregates (EIPAs) are used as a light-emitting nanomaterial to sense bacteria on the surface of cotton fabric. EIPAs are formed through coordination interaction between Eu3+(tta) 3 phen complexes with positive charges and polyanionic hyaluronic acid (HA) with negative charges, and EIPAs were chemically bonded onto cotton fabrics through pentaerythritol (PER) crosslinking. Based on this innovation, the obtained fluorescence cotton fabrics (FCF) have a wide excitation spectrum, intense emission spectrum, and long fluorescence lifetime, which makes the fabric fluorescence stable and bright. These EIPAs and their photophysical properties impart FCF with the ability to report both Staphylococcus aureus and Escherichia coli. Furthermore, FCF has antibacterial activity against Staphylococcus aureus. Therefore, this new FCF integrates the advantages of superior lanthanide fluorescence, non-cytotoxicity, antibacterial activity, wearable and smart sensing. • The feasibility of bacterial contamination sensing just with the fluorescence of EIPAs on FCF. • EIPAs with high quantum yield, long lifetime and biocompatible polyelectrolytes were chemically bonded onto cotton fabrics. • As the key advantages, fluorescent cotton fabrics is a non-toxic, biocompatible, wearable and smart sensing fabric. [ABSTRACT FROM AUTHOR]

In this work, titania nanotube arrays (TiO 2 -NTs) were prepared by anodization, and the Eu(III) complexes (Eu (TTA) 3 phen with 2-thenoyltrifluoroacetone (TTA) and 1, 10-phenanthroline (phen)) were successfully coated onto the walls of the nanotubes. When a solution of glucose, cholesterol or triglycerides was dropped onto Eu(III) complex-modified TiO 2 -NTs, the fluorescence intensity of this material changes (glucose enhances fluorescence, cholesterol and triglycerides quench fluorescence). These phenomena are explained via an energy transfer process. The sensitivity of the fluorescence intensity to glucose, cholesterol or triglycerides concentration enables design of a multifunctional solid sheet-like detector. Under optimized experimental conditions, the change in fluorescence intensity ratio (ΔF/F 0) is linear with the concentration of glucose, cholesterol or triglycerides. To test the utility of the detector, glucose in orange juice, cholesterol in milk powder, and triglycerides in coconut oil were measured using this method and the results were in good agreement analytical data provided by a food testing company. The new method proposed here is simple, sensitive, reliable and suitable for practical applications. Unlabelled Image • Europium modified TiO 2 nanotube arrays were prepared by one-step anodization and in-situ Eu complex coating. • Fluorescence intensity of Europium modified TiO 2 nanotube arrays show good selectivity to glucose/cholesterol/triglycerides. • Europium modified TiO 2 nanotube arrays can accurately detect glucose, cholesterol or triglycerides content in food. • This method proposed is simple, sensitive, reliable and suitable for practical applications. [ABSTRACT FROM AUTHOR]

In this work, two type of europium (Eu) modified Titania nanotube arrays (TiO 2 -NTs) are demonstrated. Highly ordered TiO 2 -NTs were prepared by anodizing the surface of titanium surface at different voltages (30V, 45V, 55V). Eu-doping of TiO 2 -NTs was carried out by adding Eu3+ to the electrolyte during anodization, and Eu-coated TiO 2 -NTs were obtained by incubating nanotubes in EuCl 3 solution. The surface were characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Raman spectroscopy, UV/VIS-NIR spectroscopy and by measuring photoluminescence (PL) spectra. The nanotube diameter decreases as the anodization voltage is decreased, while the wall thickness increases. More importantly, the morphology of the TiO 2 -NTs is not influenced by Eu-doping and Eu-coating, except that the nanotube diameter become about 8 nm smaller after Eu-doping. Eu-doped TiO 2 -NTs obtained at 55V have the maximum diameter, the highest Eu-doping content, the best stability, the widest band gap and relatively strong photoluminescence. Thus, there is a potential to use these nanotube surfaces for photocatalytic and biosensor applications. • Europium modified TiO 2 nanotube arrays (Europium doped and coated) can be synthesized to have different diameters. • Europium doped TiO 2 nanotube arrays show a good stability in air and water. • Europium doped TiO 2 nanotube arrays obtained at 55V shows the best photoluminescence property. [ABSTRACT FROM AUTHOR]

To develop hemocompatible surfaces, a cationic tannin derivate (TN) was used to prepare polyelectrolyte multilayers (PEMs) with the glycosaminoglycans heparin (HEP) and chondroitin sulfate (CS). The surface chemistry of the PEMs was characterized using X-ray photoelectron spectroscopy and water contact angle measurements. PEMs assembled with chitosan (CHI) and HEP or CS were used as controls. We investigate the hemocompatibility of PEMs by analyzing the adsorption of key blood serum proteins, adhesion and activation of platelets, and blood clotting kinetics. TN- and CHI-based PEMs adsorb similar amounts of albumin, whereas fibrinogen adsorption was more pronounced on TN-based PEMs, due to strong association with catechol groups. However, TN-based PEMs significantly reduce both platelet adhesion and platelet activation, while CHI-based PEMs promote platelet adhesion and activation. The whole-blood clotting kinetics assay also shows lower blood coagulation on TN-based PEMs. TN is an amphoteric, cationic, condensed tannin derivative with resonance structures. It also contains catechol groups, which are similar to those in mussel adhesive protein. These chemical features enable strong association with fibrinogen, which promotes the platelet-repelling effect. This study provides a new perspective for understanding platelet adhesion and activation on biomaterial surfaces, toward the development of new blood-compatible surfaces using a tannin derivative-based polymer. • Novel GAGs-Tanfloc polyelectrolyte multilayers reduce platelet adhesion on surfaces. • New surfaces also reduce whole blood clotting. • Blood compatibility properties can be related to the chemical structure of Tanfloc. • Heparin-Tanfloc polyelectrolyte multilayer is a promising candidate for developing blood-compatible surface coatings. [ABSTRACT FROM AUTHOR]

• Polyelectrolyte multilayers based on a cationic condensed tannin are produced. • The cationic tannin derivative is blended with pectin and iota-carrageenan. • The polyelectrolyte multilayers prevent bacterial adhesion and biofilm formation. Bacterial adhesion and biofilm formation are significant issues associated with microbial infections in biomedical applications. It has been a challenge to prepare durable coatings with antiadhesive and antimicrobial activities. We show that a condensed tannin derivative (amino-functionalized) can be assembled with polysaccharides (pectin and iota -carrageenan) to create polyelectrolyte multilayers (PEMs). PEMs were prepared from the layer-by-layer approach by assembling polycationic-polyanionic pairs in an acetic acid-acetate buffer (pH 5.0). The tannin-based material (polycationic polymer) was characterized by X-ray photoelectron spectroscopy (XPS), while PEMs were characterized through XPS, in-situ Fourier transform surface plasmon resonance, atomic force microscopy, and water contact angle measurements. Compared to the native glass substrate, all PEMs present nanoscale surface roughness, and hydrophilic surfaces. A stability test performed in PBS for 7 days confirms that 15-layer PEMs are durable in aqueous environments. Initial adhesion and antimicrobial tests against Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) show that the PEMs exhibit antiadhesive and bactericidal activities after 6 h. The antibacterial test in-vitro indicates that PEMs can kill and prevent the attachment and proliferation of bacteria significantly, especially during initial exposure. These PEMs can be applied as coatings to avoid infections imparted by microbial adhesion in biomedical applications. [ABSTRACT FROM AUTHOR]

In plant spores and pollen, sporopollenin occurs as a structural polymer with remarkable resistance to chemical degradation. This recalcitrant polymer is well-suited to analysis by non-destructive infrared spectroscopy. However, existing infrared characterization of sporopollenin has been limited in scope and occasionally contradictory. This study provides a comprehensive structural analysis of sporopollenin in the Pinus ponderosa pollen exine using infrared spectroscopy, including detailed band assignments, descriptions of chemical reactivity, and comparison to multiple reference substances. We observe that the infrared spectral characteristics of sporopollenin prepared by enzymatic digestion of the polysaccharide-based intine are largely consistent with a copolymer of aliphatic lipids and trans -4-hydroxycinnamic acid, without distinct contributions from α-pyrone or carotenoid substructures. Image 1 • Sporopollenin consists primarily of trans- 4-hydroxycinnamic and fatty acids. • Terpenoids and α-pyrones are not detected in the structure of sporopollenin. • Common methods for sporopollenin isolation result in chemical derivatization. • IR spectroscopy reveals sporopollenin chemistry as it exists in planta. [ABSTRACT FROM AUTHOR]

This study reports the synthesis, characterization and biological properties of films based on poly(vinyl alcohol) (PVA) and a cationic tannin polymer derivative (TN). Films are obtained from polymeric blends by tuning the PVA/TN weight ratios. The materials are characterized through infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle measurements, mechanical analyses, and scanning electron microscopy. More hydrophilic surfaces are created by modulating the PVA and TN concentrations in the blends. Disintegration tests showed that the films present durability in phosphate buffer (pH 7.4) and low stability in simulated gastric fluid (pH 1.2). The film created at 90/10 PVA/TN weight ratio and crosslinked at 109 PVA/glutaraldehyde molar ratio (sample PVA10/TN10) supports the attachment and proliferation of bone marrow mesenchymal stem cells after 7 days of culture. The scaffolding capacity of the PVA10/TN10 surface is compared with titanium, one of the most important biomedical materials used in bone replacements. Also, the PVA/TN films exhibited cytocompatibility, antioxidant and antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. These properties make PVA/TN films are candidates for biomedical applications in the tissue engineering field. Image 1 • New poly(vinyl alcohol)/cationic tannin films are produced. • The more hydrophilic film surface has antimicrobial and antioxidant activities. • The hydrophilic film supports the attachment and proliferation of cells. [ABSTRACT FROM AUTHOR]

Here, we have demonstrated the production and characterization of hydrogel scaffolds based on chitosan/gellan gum (CS/GG) assemblies, without any covalent and metallic crosslinking agents, conventionally used to yield non-soluble polysaccharide-based materials. The polyelectrolyte complexes (physical hydrogels called as PECs) are characterized by Fourier-transform infrared spectroscopy, wide-angle X-ray scattering, and scanning electron microscopy. Hydrogels containing chitosan (CS) excesses (ranging from 60 to 80 wt%) were created. Durable polysaccharide-based scaffolds with structural homogeneity and interconnecting pore networks are developed by modulating the CS/GG weight ratio. The CS/GG hydrogel prepared at 80/20 CS/GG weight ratio (sample CS/GG80-20) is cytocompatible, supporting the attachment, growth, and spreading of bone marrow mesenchymal stem cells (BMSCs) after nine days of cell culture. The cytocompatibility is correlated to the swelling capacity of the PEC in PBS buffer (pH 7.4). By controlling the CS content, we can tune the water uptake of the material, enhancing the capacity to serve as a three-dimensional cell scaffold for BMSCs. This work presents for the first time that CS/GG hydrogels can be applied as scaffolds for tissue engineering purposes. Image 1 • Durable chitosan/gellan gum scaffold assemblies are developed. • Chitosan/gellan gum hydrogels are cytocompatible. • The hydrogel promotes growth and spreading of bone mesenchymal stem cells. • Scaffolding behavior is achieved by increasing the chitosan content into the hydrogel. [ABSTRACT FROM AUTHOR]

Curcumin (CUR) is a hydrophobic drug which has been loaded into polymeric carrier matrices by using experimental strategies with many steps, as well as by using conventional and volatile organic solvents. For the first time, this study reports the use of an ionic liquid ([Hmim][HSO 4 −]) to solubilize polycation-polyanion polymer pairs and hydrophobic CUR in the same system. By using the [Hmim][HSO 4 −] as an appropriated solvent, CUR (ca. 10% wt) is loaded into a polyelectrolyte complex (PEC) based on chitosan and commercial iota -carrageenan, following a straightforward method (in-situ approach). A solution containing chitosan, iota -carrageenan, and CUR is produced in [Hmim][HSO 4 −] and subsequently precipitated in an ice-water bath to form the CUR-loaded PEC. The ionic liquid is synthesized following a straightforward experimental route, and after PEC production, it is recovered and reused. X-ray photoelectron spectroscopy analysis shows that chitosan and iota -carrageenan are principally interacting by coulombic forces. Also, X-ray photoelectron spectroscopy and infrared spectroscopy analyses confirm that CUR is loaded into the PEC structure. Wide-angle X-ray scattering, scanning electron microscopy, and differential scanning calorimetry also confirm that CUR loaded PEC (ca. 105 mg g−1) comprise a more disorganized structure when compared to the pristine drug. The CUR is released in simulated gastric fluid (SGF, pH 1.2) because the PEC material increases 3.3-fold its solubility in SGF when compared to the raw curcumin. The ionic liquid can remain in the PEC structure, potentially imparting cytotoxicity. A simple aqueous washing step is sufficient to remove the residual [Hmim][HSO 4 −] and promote cytocompatibility. Cell viability assay performed on bone marrow-derived stem cells demonstrates that CUR significantly increases the cell viability promoted by the PEC. • Chitosan/carrageenan polyelectrolyte complexes are prepared. • A polyelectrolyte complex/curcumin-based material is created by precipitation of a miscible mixture. • A strategy in-situ is developed to load curcumin into the polyelectrolyte complex. • An aqueous washing step removes the residual ionic liquid into the material structure. • The loaded curcumin improves the cytocompatibility and cell viability on mesenchymal stem cells. [ABSTRACT FROM AUTHOR]

Eu 3+ -induced polystyrene- co -poly(acrylic acid) aggregates (EIPAs) were synthesized using a self-assembly approach, and their structures and photophysical characteristics were examined to achieve effective monochromatic red emission in polymer light-emitting diodes (PLEDs). By adjusting the monomer ratio in RAFT polymerization, the size of Eu 3+ -induced block copolymer nanoaggregates can be regulated, thereby modulating the luminescence intensity. High-performance bilayer polymer light-emitting devices were fabricated using poly(9,9-dioctylfluorene) (PFO) and 2-( tert -butylphenyl)-5-biphenylyl-1,3,4-oxadiazole (PBD) as the host matrix, with EIPAs as the guest dopant. The devices exhibited narrow red emission at 615 nm with a full width at half-maximum (fwhm) of 15 nm across doping concentrations of 1, 3, 5, and 10 wt %. At a doping concentration of 3 wt %, the device achieved a maximum brightness of 1864.48 cd/m 2 at 193.82 mA/cm 2 and an external quantum efficiency of 3.20% at a current density of 3.5 mA/cm 2 . These results indicate that incorporating polystyrene- co -poly(acrylic acid) with Eu 3+ complexes enhances the excitation and emission intensity, as well as the structural stability of the emitting layer in PLEDs, thereby improving the device performance.

Protein crystals with sufficiently large solvent pores can non-covalently adsorb polymers in the pores. In principle, if these polymers contain cell adhesion ligands, the polymer-laden crystals could present ligands to cells with tunable adhesion strength. Moreover, porous protein crystals can store an internal ligand reservoir, so that the surface can be replenished. In this study, we demonstrate that poly(ethylene glycol) terminated with a cyclic cell adhesion ligand peptide (PEG-RGD) can be loaded into porous protein crystals by diffusion. Through atomic force microscopy (AFM), force-distance correlations of the mechanical interactions between activated AFM tips and protein crystals were precisely measured. The activation of AFM tips allows the tips to interact with PEG-RGD that was pre-loaded in the protein crystal nanopores, mimicking how a cell might attach to and pull on the ligand through integrin receptors. The AFM experiments also simultaneously reveal the detailed morphology of the buffer-immersed nanoporous protein crystal surface. We also show that porous protein crystals (without and with loaded PEG-RGD) serve as suitable substrates for attachment and spreading of adipose-derived stem cells. This strategy can be used to design surfaces that non-covalently present multiple different ligands to cells with tunable adhesive strength for each ligand, and with an internal reservoir to replenish the precisely defined crystalline surface.

Bacterial infections are a common mode of failure for medical implants. This study aims to develop antibacterial polyelectrolyte multilayer (PEM) coatings that contain a plant-derived condensed tannin polymer (Tanfloc, TAN) with inherent antimicrobial activity. Tanfloc is amphoteric, and herein we show that it can be used as either a polyanion or a polycation in PEMs, thereby expanding the possibility of its use in PEM coatings. PEMs are ordinarily formed using a polycation and a polyanion, in which the functional (ionic) groups of the two polymers are complexed to each other. However, using the amphoteric polymer Tanfloc with weakly basic amine and weakly acidic catechol and pyrogallol groups enables PEM formation using only one or the other of its functional groups, leaving the other functional group available to impart antibacterial activity. This work demonstrates Tanfloc-containing PEMs using multiple counter-polyelectrolytes including three polyanionic glycosaminoglycans of varying charge density, and the polycations N , N , N -trimethyl chitosan and polyethyleneimine. The layer-by-layer (LbL) assembly of PEMs was monitored using in situ Fourier-transform surface plasmon resonance (FT-SPR), confirming a stable LbL assembly. X-ray photoelectron spectroscopy (XPS) was used to evaluate surface chemistry, and atomic force microscopy (AFM) was used to determine the surface roughness. The LDH release levels from cells cultured on the Tanfloc-containing PEMs were not statistically different from those on the negative control (p > 0.05), confirming their non-cytotoxicity, while exhibiting remarkable antiadhesive and bactericidal properties against Pseudomonas aeruginosa ( P. aeruginosa ) and Staphylococcus aureus ( S. aureus ), respectively. The antibacterial effects were attributed to electrostatic interactions and Tanfloc's polyphenolic nature. This work underscores the potential of Tanfloc as a versatile biomaterial for combating infections on surfaces.

Owing to significant differences across species in liver functions, in vitro human liver models are used for screening the metabolism and toxicity of compounds, modeling diseases, and cell-based therapies. However, the extracellular matrix (ECM) scaffold used for such models often does not mimic either the complex composition or the nanofibrous topography of native liver ECM. Thus, here novel methods are developed to electrospin decellularized porcine liver ECM (PLECM) and collagen I into nano- and microfibers (≈200-1000 nm) without synthetic polymer blends. Primary human hepatocytes (PHHs) on nanofibers in monoculture or in coculture with nonparenchymal cells (3T3-J2 embryonic fibroblasts or primary human liver endothelial cells) display higher albumin secretion, urea synthesis, and cytochrome-P450 1A2, 2A6, 2C9, and 3A4 enzyme activities than on conventionally adsorbed ECM controls. PHH functions are highest on the collagen/PLECM blended nanofibers (up to 34-fold higher CYP3A4 activity relative to adsorbed ECM) for nearly 7 weeks in the presence of the fibroblasts. In conclusion, it is shown for the first time that ECM composition and topography synergize to enhance and stabilize PHH functions for several weeks in vitro. The nanofiber platform can prove useful for the above applications and to elucidate cell-ECM interactions in the human liver., (© 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.)

Heart failure is the leading cause of death in the US and worldwide. Despite modern therapy, challenges remain to rescue the damaged organ that contains cells with a very low proliferation rate after birth. Developments in tissue engineering and regeneration offer new tools to investigate the pathology of cardiac diseases and develop therapeutic strategies for heart failure patients. Tissue -engineered cardiac scaffolds should be designed to provide structural, biochemical, mechanical, and/or electrical properties similar to native myocardium tissues. This review primarily focuses on the mechanical behaviors of cardiac scaffolds and their significance in cardiac research. Specifically, we summarize the recent development of synthetic (including hydrogel) scaffolds that have achieved various types of mechanical behavior-nonlinear elasticity, anisotropy, and viscoelasticity-all of which are characteristic of the myocardium and heart valves. For each type of mechanical behavior, we review the current fabrication methods to enable the biomimetic mechanical behavior, the advantages and limitations of the existing scaffolds, and how the mechanical environment affects biological responses and/or treatment outcomes for cardiac diseases. Lastly, we discuss the remaining challenges in this field and suggestions for future directions to improve our understanding of mechanical control over cardiac function and inspire better regenerative therapies for myocardial restoration.

Slippery surfaces are sought after due to their wide range of applications in self-cleaning, drag reduction, fouling-resistance, enhanced condensation, biomedical implants etc. Recently, non-textured, all-solid, slippery surfaces have gained significant attention because of their advantages over super-repellent surfaces and lubricant-infused surfaces. Currently, almost all non-textured, all-solid, slippery surfaces are hydrophobic. In this work, we elucidate the systematic design of non-textured, all-solid, slippery hydrophilic (SLIC) surfaces by covalently grafting polyethylene glycol (PEG) brushes to smooth substrates. Furthermore, we postulate a plateau in slipperiness above a critical grafting density, which occurs when the tethered brush size is equal to the inter-tether distance. Our SLIC surfaces demonstrate exceptional performance in condensation and fouling-resistance compared to non-slippery hydrophilic surfaces and slippery hydrophobic surfaces. Based on these results, SLIC surfaces constitute an emerging class of surfaces with the potential to benefit multiple technological landscapes ranging from thermofluidics to biofluidics., Competing Interests: DECLARATION OF INTERESTS A.K.K. and H.V. are inventors on a patent filed by Colorado State University.

Ultralow protein fouling behavior is a common target for new high-performance materials. Ultralow fouling is often defined based on the amount of irreversibly adsorbed protein (< 5 ng cm -2 ) measured by a surface ensemble averaging method. However, protein adsorption at solid interfaces is a dynamic process involving multiple steps, which may include adsorption, desorption, and irreversible protein denaturation. In order to better optimize the performance of antifouling surfaces, it is imperative to fully understand how proteins interact with surfaces, including kinetics of adsorption and desorption, conformation, stability, and amount of adsorbed proteins. Defining ultralow fouling surfaces based on a measurement at or near the limit of detection of a surface-averaged measurement may not capture all of this behavior. Single-molecule microscopy techniques can resolve individual protein-surface interactions with high temporal and spatial resolution. This information can be used to tune the properties of surfaces to better resist protein adsorption. In this work, we demonstrate how combining surface plasmon resonance, X-ray photoelectron spectroscopy, atomic force microscopy, and single-molecule localization microscopy provides a more complete picture of protein adsorption on low fouling and ultralow fouling polyelectrolyte multilayer and polymer brush surfaces, over different regimes of protein concentration. In this case, comparing the surfaces using surface plasmon resonance alone is insufficient to rank their resistance to protein adsorption. Our results suggest a revision of the accepted definition of ultralow fouling surfaces is timely: with the advent of time-resolved studies of protein adsorption kinetics at the single-molecule level, it is neither necessary nor sufficient to rely on a surface averaging techniques to qualify ultralow fouling surfaces. Since protein adsorption is a dynamic process, understanding how surface properties affect the kinetics of protein adsorption will enable the design of future generations of advanced antifouling materials. STATEMENT OF SIGNIFICANCE: The design of ultralow fouling surfaces is often optimized based on a single surface-averaging technique measuring the amount of irreversibly adsorbed protein. This work provides a critical comparison of alternative techniques for evaluating protein adsorption on low fouling and ultralow fouling surfaces, and demonstrates how additional information about the dynamics of protein-surface interactions at the interface can be obtained by application of single-molecule microscopy. This approach could be used to better elucidate mechanisms of protein resistance and design principles for advanced ultralow fouling materials., (Copyright © 2019. Published by Elsevier Ltd.)

Blood vessels present a dense, non-uniform, polysaccharide-rich layer, called the endothelial glycocalyx. The polysaccharides in the glycocalyx include polyanionic glycosaminoglycans (GAGs). This polysaccharide-rich surface has excellent and unique blood compatibility. We report new methods for preparing and characterizing dense GAG surfaces that can serve as models of the vascular endothelial glycocalyx. The GAG-rich surfaces are prepared by adsorbing heparin or chondroitin sulfate-containing polyelectrolyte complex nanoparticles (PCNs) to chitosan-hyaluronan polyelectrolyte multilayers (PEMs). The surfaces are characterized by PeakForce tapping atomic force microscopy, both in air and in aqueous pH 7.4 buffer, and by PeakForce quantitative nanomechanics (PF-QNM) mode with high spatial resolution. These new surfaces provide access to heparin-rich or chondroitin sulfate-rich coatings that mimic both composition and nanoscale structural features of the vascular endothelial glycocalyx., (Copyright © 2018. Published by Elsevier Ltd.)

Here we present a novel matrix-mimetic nanoassembly based on polysaccharides. Chitosan electrospun fiber networks are decorated with heparin-containing polyelectrolyte complex nanoparticles (PCNs) that present basic fibroblast growth factor (FGF-2), both stably adsorbed to the surfaces and released into solution. These FGF-2/PCN complexes can be released from the fibers with zero-order kinetics over a period of 30 days. Further modification of fibers with a single bilayer of polyelectrolyte multilayer (PEM) composed of N,N,N-trimethyl chitosan and heparin completely prevent release, and the FGF-2/PCN complexes are retained on the fibers for the duration of the release experiment (30 days). We also compare the mitogenic activity of these FGF-2/PCN complexes delivered in two different states: adsorbed to a surface and dissolved in solution. FGF-2/PCN complexes exhibit mitogenic activity with respect to ovine bone marrow-derived mesenchymal stem cells, even after being preconditioned by incubating for 27 days at 37°C in solution. However, when the FGF-2/PCN complexes are adsorbed to chitosan and coated with PEMs, the mitogenic activity of the FGF-2 steadily decreases with increasing preconditioning time. This work demonstrates a new system for stabilizing and controlling the delivery of heparin-binding growth factors, using polysaccharide-based matrix-mimetic nanomaterials. This work also contributes to our understanding of the preferred mode of growth factor delivery from porous scaffolds., (Copyright © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

A new method is presented for functionalizing electrospun nanofibers with GAGs and growth factors by PEM deposition. Electrospun chitosan nanofibers, spun from trifluoroacetic acid and dichloromethane, were coated with PEMs, using the polysaccharides heparin and N,N,N-trimethyl chitosan. FGF-2 was adsorbed on the PEM-coated nanofibers. Nanofiber neutralization, PEM construction, and FGF-2 adsorption were monitored using FT-IR spectroscopy and X-ray photoelectron spectroscopy. Alcian blue staining was used to confirm the presence of heparin. SEM was used to study nanofiber morphology., (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study focuses on the development of single dose vaccines based on biodegradable polyanhydride microspheres that have the unique capability to modulate the immune response mechanism. The polymer system employed consists of copolymers of 1,6-bis(p-carboxyphenoxy)hexane and sebacic acid. Two copolymer formulations that have been shown to provide extended release kinetics and protein stability were investigated. Using tetanus toxoid (TT) as a model antigen, in vivo studies in C3H/HeOuJ mice demonstrated that the encapsulation procedure preserves the immunogenicity of the TT. The polymer itself exhibited an adjuvant effect, enhancing the immune response to a small dose of TT. The microspheres provided a prolonged exposure to TT sufficient to induce both a primary and a secondary immune response (i.e., high antibody titers) with high-avidity antibody production, without requiring an additional administration. Antigen-specific proliferation 28 weeks after a single immunization indicated that immunization with the polyanhydride microspheres generated long-lived memory cells and plasma cells (antibody-secreting B cells) that generally do not occur without maturation signals from T helper cells. Furthermore, by altering the vaccine formulation, the overall strength of the T helper type 2 immune response was selectively diminished, resulting in a balanced immune response, without reducing the overall titer. This result is striking, considering free TT induces a T helper type 2 immune response, and has important implications for developing vaccines to intracellular pathogens. The ability to selectively tune the immune response without the administration of additional cytokines or noxious adjuvants is a unique feature of this delivery vehicle that may make it an excellent candidate for vaccine development.