Biological and mechanical interplay at the Macro- and Microscales Modulates the Cell-Niche Fate.

Tissue development, regeneration, or de-novo tissue engineering in-vitro, are based on reciprocal cell-niche interactions. Early tissue formation mechanisms, however, remain largely unknown given complex in-vivo multifactoriality, and limited tools to effectively characterize and correlate specific micro-scaled bio-mechanical interplay. We developed a unique model system, based on decellularized porcine cardiac extracellular matrices (pcECMs)-as representative natural soft-tissue biomaterial-to study a spectrum of common cell-niche interactions.

Quantification of aldehyde terminated heparin by SEC-MALLS-UV for the surface functionalization of polycaprolactone biomaterials.

A straight forward strategy of heparin surface grafting employs a terminal reactive-aldehyde group introduced through nitrous acid depolymerization. An advanced method that allows simultaneously monitoring of both heparin molar mass and monomer/aldehyde ratio by size exclusion chromatography, multi-angle laser light scattering and UV-absorbance (SEC-MALLS-UV) has been developed to improve upon heparin surface grafting. Advancements over older methods allow quantitative characterization by direct (aldehyde absorbance) and indirect (Schiff-based absorbance) evaluation of terminal functional aldehydes.

Characterization of a bioactive fiber scaffold with entrapped HUVECs in coaxial electrospun core-shell fiber.

Human umbilical vein endothelial cells (HUVECs) were successfully entrapped in polyethylene oxide (PEO) core /polycaprolactone (PCL) shell electrospun fibers thus creating a "bioactive fiber." The viability and release of biomolecules from the entrapped cells in the bioactive fibers were characterized. A key modification to the core solution was the inclusion of 50% fetal bovine serum (FBS), which improved cell viability substantially.

Induction of myogenic differentiation of human mesenchymal stem cells cultured on Notch agonist (Jagged-1) modified biodegradable scaffold surface.

Engineered scaffold surface provides stem cells with vital cues that could determine the eventual fate of stem cells. In this work, biodegradable poly(L-lactide-co-ε-caprolactone) (PLCL) scaffold conjugated with Notch agonist-Jagged-1(JAG) peptide (2.1 kDa) was prepared to initiate myogenic differentiation of human mesenchymal stem cells (hMSCs).

A mathematical model for analyzing the elasticity, viscosity, and failure of soft tissue: comparison of native and decellularized porcine cardiac extracellular matrix for tissue engineering.

The clinical success of tissue-engineered constructs commonly requires mechanical properties that closely mimic those of the human tissue. Determining the viscoelastic properties of such biomaterials and the factors governing their failure profiles, however, has proven challenging, although collecting extensive data regarding their tensile behavior is straightforward. The easily calculated Young's modulus remains the most reported mechanical measure, regardless of its limitations, even though single-relaxation-time (SRT) models can provide much more information, which remain scarce due to a lack of manageable tools for implementing these models.

Human mesenchymal stem-cell behaviour on direct laser micropatterned electrospun scaffolds with hierarchical structures.

Direct laser machining and electrospinning are utilized to obtain a bi-layered hybrid scaffold with hierarchical topographical features to mimic extracellular matrix-like microenvironment of cells. Adult bone marrow derived human mesenchymal stem cells (hMSCs) are cultured in vitro in these hybrid scaffolds, and cell orientation, proliferation, viability, and differentiation are evaluated. The results show that this novel hybrid scaffold not only supports cell growth like traditional scaffolds, but also elicits positive responses from the cells, like lineage commitment and alignment, which are essential features of future scaffolds.

A mathematical model predicting the coculture dynamics of endothelial and mesenchymal stem cells for tissue regeneration.

In most tissue engineering applications, understanding the factors affecting the growth dynamics of coculture systems is crucial for directing the population toward a desirable regenerative process. Yet, no comprehensive analysis method exists to quantify coculture population dynamics, let alone, a unifying model addressing the "environmental" factors influencing cell growth, all together. Here we suggest a modification of the Lotka-Volterra model to analyze the population dynamics of cocultured cells and predict their growth profiles for tissue engineering applications.

Understanding the nano-topography changes and cellular influences resulting from the surface adsorption of human hair keratins.

Recent interest in the use of human hair keratins as a biomaterial has grown, fuelled by improvements in keratin extraction methods and better understanding of keratin bioactivity. The use of keratins as a bioactive coating for in vitro cell culture studies is an attractive proposition. In this light, the surface adsorption of human hair keratins onto tissue culture polystyrene surfaces has been investigated.

Novel gradient casting method provides high-throughput assessment of blended polyester poly(lactic-co-glycolic acid) thin films for parameter optimization.

Pure polymer films cannot meet the diverse range of controlled release and material properties demanded for the fabrication of medical implants or other devices. Additives are added to modulate and optimize thin films for the desired qualities. To characterize the property trends that depend on additive concentration, an assay was designed which involved casting a single polyester poly(lactic-co-glycolic acid) (PLGA) film that blends a linear gradient of any PLGA-soluble additive desired.

A new insight for an old system: protein-PEG colocalization in relation to protein release from PCL/PEG blends.

Quantification of protein-polymer colocalization in a phase-separated polymer blend gives important insights into the protein release mechanism. Here, we report on the first visualization of protein-poly(ethylene glycol) (protein-PEG) colocalization in poly(ε-caprolactone)/poly(ethylene glycol) (PCL/PEG) blend films using a combined application of confocal Raman mapping and confocal laser scanning microscopy (CLSM) imaging. The degree of protein-PEG colocalization was further quantified via a novel image processing technique.

Direct laser machining-induced topographic pattern promotes up-regulation of myogenic markers in human mesenchymal stem cells.

The engineering of tissue is preferably done with stem cells, which can be differentiated into the tissue of interest using biochemical or physical cues. While much effort has been focused on using biological factors to regulate stem cell differentiation, recently interest in the contribution of physical factors has increased. In this work, three-dimensional (3-D) microchannels with topographic micropatterns were fabricated by femtosecond laser machining on a biodegradable polymer (poly(L-lactide-co-ε-caprolactone)) substrate.

In vitro assessment of cellular responses to rod-shaped hydroxyapatite nanoparticles of varying lengths and surface areas.

Rod-shaped hydroxyapatite nanoparticles of varying dimensions (≈ 60 ± 10, 120 ± 15, 240 ± 30 nm in length, labeled respectively as nHA60, nHA120 and nHA240) with specific surface areas (47.02, 23.33, 46.

High-throughput screening of PLGA thin films utilizing hydrophobic fluorescent dyes for hydrophobic drug compounds.

Hydrophobic, antirestenotic drugs such as paclitaxel (PCTX) and rapamycin are often incorporated into thin film coatings for local delivery using implantable medical devices and polymers such as drug-eluting stents and balloons. Selecting the optimum coating formulation through screening the release profile of these drugs in thin films is time consuming and labor intensive. We describe here a high-throughput assay utilizing three model hydrophobic fluorescent compounds: fluorescein diacetate (FDAc), coumarin-6, and rhodamine 6G that were incorporated into poly(d,l-lactide-co-glycolide) (PLGA) and PLGA-polyethylene glycol films.

SnO2 nanosheets grown on graphene sheets with enhanced lithium storage properties.

We demonstrate a new hydrothermal method to directly grow SnO(2) nanosheets on a graphene oxide support that is subsequently reduced to graphene. This unique SnO(2)/graphene hybrid structure exhibits enhanced lithium storage properties with high reversible capacities and good cycling performance.

Assembly of graphene sheets into hierarchical structures for high-performance energy storage.

The electrodes with the hierarchical nanoarchitectures could offer a huge increase in energy storage capacity. However, the ability to achieve such hierarchical architectures on a multiple scale still has remained a great challenge. In this paper, we report a scalable self-assembly strategy to create bioinspired hierarchical structures composed of functionalized graphene sheets to work as anodes of lithium-ion batteries.

Graphene-supported anatase TiO2 nanosheets for fast lithium storage.

We have designed a unique hybrid structure by directly growing ultrathin anatase TiO(2) nanosheets onto graphene support for fast lithium storage. With exposed (001) high-energy facets, these TiO(2) nanosheets serve as ideal hosts for fast and efficient lithium storage. On the other hand, the graphene support serves as a highly conductive substrate that is beneficial to the high-rate performance.

Fast formation of SnO2 nanoboxes with enhanced lithium storage capability.

SnO(2) nanoboxes with uniform morphology, good structural stability, and tunable interior volume can be facilely synthesized by template-engaged coordinating etching of pregrown Cu(2)O nanocubes at room temperature. When evaluated for their lithium storage properties, these SnO(2) nanoboxes manifest improved capacity retention.

Modeling of drug release from bulk-degrading polymers.

This paper aims to provide a comprehensive review of the various models or simulations for predicting drug release from bulk-degrading systems. A brief description of bulk degradation processes and factors affecting the degradation rate, and consequently the release kinetics, is presented first. Next, several important classical models, often used as the basis for subsequent model development, are discussed.

Adhesion, proliferation, and gene expression profile of human umbilical vein endothelial cells cultured on bilayered polyelectrolyte coatings composed of glycosaminoglycans.

This study characterized human umbilical vein endothelial cell (HUVEC) adhesion, proliferation, and gene expression on bilayered polyelectrolyte coatings composed of an outermost layer of glycosaminoglycans (hyaluronan, heparin, or chondroitin sulfate), with an underlying layer of poly-L-lysine or chitosan. The proportion of cells that adhered to the various polyelectrolyte coatings after 1 and 2 h incubations was quantified by the WST-8 assay. Interchanging poly-L-lysine with chitosan resulted in significant differences in cellular adhesion to the outermost glycosaminoglycan layer after 1 h, but these differences became insignificant after 2 h.

Effect of intermolecular dipole-dipole interactions on interfacial supramolecular structures of C3-symmetric hexa-peri-hexabenzocoronene derivatives.

Two-dimensional (2D) supramolecular assemblies of a series of novel C(3)-symmetric hexa-peri-hexabenzocoronene (HBC) derivatives bearing different substituents adsorbed on highly oriented pyrolytic graphite were studied by using scanning tunneling microscopy at a solid-liquid interface. It was found that the intermolecular dipole-dipole interactions play a critical role in controlling the interfacial supramolecular assembly of these C(3)-symmetric HBC derivatives at the solid-liquid interface. The HBC molecule bearing three -CF(3) groups could form 2D honeycomb structures because of antiparallel dipole-dipole interactions, whereas HBC molecules bearing three -CN or -NO(2) groups could form hexagonal superstructures because of a special trimeric arrangement induced by dipole-dipole interactions and weak hydrogen bonding interactions ([C-H···NC-] or [C-H···O(2)N-]).

Engineering nonspherical hollow structures with complex interiors by template-engaged redox etching.

Despite the significant advancement in making hollow structures, one unsolved challenge in the field is how to engineer hollow structures with specific shapes, tunable compositions, and desirable interior structures. In particular, top-down engineering the interiors inside preformed hollow structures is still a daunting task. In this work, we demonstrate a facile approach for the preparation of a variety of uniform hollow structures, including Cu(2)O@Fe(OH)(x) nanorattles and Fe(OH)(x) cages with various shapes and dimensions by template-engaged redox etching of shape-controlled Cu(2)O crystals.

Cytotoxicity of zinc oxide (ZnO) nanoparticles is influenced by cell density and culture format.

A parameter that has often been overlooked in cytotoxicity assays is the density and confluency of mammalian cell monolayers utilized for toxicology screening. Hence, this study investigated how different cell seeding densities influenced their response to cytotoxic challenge with ZnO nanoparticles. Utilizing the same volume (1 ml per well) and concentration range (5-40 μg/ml) of ZnO nanoparticles, contradictory results were observed with higher-density cell monolayers (BEAS-2B cells) obtained either by increasing the number of seeded cells per well (50,000 vs.