Customizable Composite Fibers for Engineering Skeletal Muscle Models.

Engineering tissue-like scaffolds that can mimic the microstructure, architecture, topology, and mechanical properties of native tissues while offering an excellent environment for cellular growth has remained an unmet need. To address these challenges, multicompartment composite fibers are fabricated. These fibers can be assembled through textile processes to tailor tissue-level mechanical and electrical properties independent of cellular level components. Textile technologies also allow control of the distribution of different cell types and the microstructure of fabricated constructs and the direction of cellular growth within the 3D microenvironment. Here, we engineered composite fibers from biocompatible cores and biologically relevant hydrogel sheaths. The fibers are mechanically robust to being assembled using textile processes and could support adhesion, proliferation, and maturation of cell populations important for the engineering of skeletal muscles. We also demonstrated that the changes in the coating of the multicompartment fibers could potentially enhance myogenesis in vitro.

Flexible and Stretchable PEDOT-Embedded Hybrid Substrates for Bioengineering and Sensory Applications.

Herein, we introduce a flexible, biocompatible, robust and conductive electrospun fiber mat as a substrate for flexible and stretchable electronic devices for various biomedical applications. To impart the electrospun fiber mats with electrical conductivity, poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, was interpenetrated into nitrile butadiene rubber (NBR) and poly(ethylene glycol) dimethacrylate (PEGDM) crosslinked electrospun fiber mats. The mats were fabricated with tunable fiber orientation, random and aligned, and displayed elastomeric mechanical properties and high conductivity. In addition, bending the mats caused a reversible change in their resistance. The cytotoxicity studies confirmed that the elastomeric and conductive electrospun fiber mats support cardiac cell growth, and thus are adaptable to a wide range of applications, including tissue engineering, implantable sensors and wearable bioelectronics.

Mechanical and Biochemical Stimulation of 3D Multilayered Scaffolds for Tendon Tissue Engineering.

Tendon injuries are frequent and occur in the elderly, young, and athletic populations. The inadequate number of donors combined with many challenges associated with autografts, allografts, xenografts, and prosthetic devices have added to the value of engineering biological substitutes, which can be implanted to repair the damaged tendons. Electrospun scaffolds have the potential to mimic the native tissue structure along with desired mechanical properties and, thus, have attracted noticeable attention. In order to improve the biological responses of these fibrous structures, we designed and fabricated 3D multilayered composite scaffolds, where an electrospun nanofibrous substrate was coated with a thin layer of cell-laden hydrogel. The whole construct composition was optimized to achieve adequate mechanical and physical properties as well as cell viability and proliferation. Mesenchymal stem cells (MSCs) were differentiated by the addition of bone morphogenetic protein 12 (BMP-12). To mimic the natural function of tendons, the cell-laden scaffolds were mechanically stimulated using a custom-built bioreactor. The synergistic effect of mechanical and biochemical stimulation was observed in terms of enhanced cell viability, proliferation, alignment, and tenogenic differentiation. The results suggested that the proposed constructs can be used for engineering functional tendons.

Stimuli-responsive hydrogels for manipulation of cell microenvironment: From chemistry to biofabrication technology.

Native tissues orchestrate their functions by complex interdependent cascades of biochemical and biophysical cues that vary spatially and temporally during cellular processes. Scaffolds with well-tuned structural, mechanical, and biochemical properties have been developed to guide cell behavior and provide insight on cell-matrix interaction. However, static scaffolds very often fail to mimic the dynamicity of native extracellular matrices. Stimuli-responsive scaffolds have emerged as powerful platforms that capture vital features of native tissues owing to their ability to change chemical and physical properties in response to cytocompatible stimuli, thus enabling on-demand manipulation of cell microenvironment. The vast expansion in biorthogonal chemistries and stimuli-responsive functionalities has fuelled further the development of new smart scaffolds that can permit multiple irreversible or reversible spatiotemporal modulation of cell-directing cues, thereby prompting in-depth studies to interpret the decisive elements that regulate cell behavior. Integration of stimuli-responsive hydrogels with current biofabrication technologies has allowed the development of dynamic scaffolds with organizational features and hierarchical architectures similar to native tissues. This review highlights the progress achieved using stimuli-responsive hydrogels in fundamental cell biology studies, with particular emphasis on the interplay between chemistry, biomaterials design, and biofabrication technologies for manipulation of cell microenvironment.

The Effect of Poly (Glycerol Sebacate) Incorporation within Hybrid Chitin-Lignin Sol-Gel Nanofibrous Scaffolds.

Chitin and lignin primarily accumulate as bio-waste resulting from byproducts of crustacean crusts and plant biomass. Recently, their use has been proposed for diverse and unique bioengineering applications, amongst others. However, their weak mechanical properties need to be improved in order to facilitate their industrial utilization. In this paper, we fabricated hybrid fibers composed of a chitin-lignin (CL)-based sol-gel mixture and elastomeric poly (glycerol sebacate) (PGS) using a standard electrospinning approach. Obtained results showed that PGS could be coherently blended with the sol-gel mixture to form a nanofibrous scaffold exhibiting remarkable mechanical performance and improved antibacterial and antifungal activity. The developed hybrid fibers showed promising potential in advanced biomedical applications such as wound care products. Ultimately, recycling these sustainable biopolymers and other bio-wastes alike could propel a "greener" economy.

Characterization, mechanistic analysis and improving the properties of denture adhesives.

OBJECTIVE: Denture adhesives are widely used to avoid the detachment and sliding of dentures. However, the adhesion properties can be affected by variation in mouth conditions such as the level of salivation. The objective of this study was to understand the effect of environmental conditions on the adhesion properties of a commercially available denture adhesive named as Poligrip® Free manufactured by GlaxoSmithKline Ltd., UK and to identify the reasons for the observed variation in its adhesion strength. METHODS: The failure mechanisms of denture adhesive have been assessed through using different physical, mechanical and thermal characterization experiments. All methods were used in different pH, temperatures, and salivation conditions and at the end, a strategy was proposed to overcome the failure of the paste in hyposalivation as well. RESULTS: In vitro models mimicking the denture gingival interface were designed to evaluate the adhesion properties of the investigated adhesive. Changes in the adhesion strength in response to three major factors related to the oral conditions including level of salivation, pH, and temperature were measured. The results of lap shear, tensile test, and internal interactions suggested a cohesion failure, where the lowest adhesion strength was due to hyposalivation. Fourier transform infrared spectroscopy (FTIR) and rheological analysis confirmed the importance of hydrogen bonds and hydration in the adhesion strength of the paste. SIGNIFICANCE: The investigated scenarios are widely observed in patient using denture adhesives and the clinical reports have indicated the inconsistency in adhesion strength of the commercial products. After identifying the potential reasons for such behavior, methods such as the addition of tripropylene glycol methyl ether (TPME) to enhance internal hydrogen bonds between the polymers are proposed to improve adhesion in the hyposalivation scenario.

Cell-laden composite suture threads for repairing damaged tendons.

Tendons have limited regenerative capacity due to their low cellularity and hypovascular nature, which results in poor clinical outcomes of presently used therapies. As tendon injuries are often observed in active adults, it poses an increasing socio-economic burden on healthcare systems. Currently, suture threads are used during surgical repair to anchor the tissue graft or to connect injured ends. Here, we created composite suture threads coated with a layer of cell-laden hydrogel that can be used for bridging the injured tissue aiming at tendon regeneration. In addition, the fibres can be used to engineer 3-dimensional constructs through textile processes mimicking the architecture and mechanical properties of soft tissues, including tendons and ligaments. Encapsulated human tendon-derived cells migrated within the hydrogel and aligned at the surface of the core thread. An up-regulation of tendon-related genes (scleraxis and tenascin C) and genes involved in matrix remodelling (matrix metalloproteinases 1, matrix metalloproteinases 2) was observed. Cells were able to produce a collagen-rich matrix, remodelling their micro-environment, which is structurally comparable to native tendon tissue.

Glucose-Sensitive Hydrogel Optical Fibers Functionalized with Phenylboronic Acid.

Hydrogel optical fibers are utilized for continuous glucose sensing in real time. The hydrogel fibers consist of poly(acrylamide-co-poly(ethylene glycol) diacrylate) cores functionalized with phenylboronic acid. The complexation of the phenylboronic acid and cis-diol groups of glucose enables reversible changes of the hydrogel fiber diameter. The analyses of light propagation loss allow for quantitative glucose measurements within the physiological range.

Textile Processes for Engineering Tissues with Biomimetic Architectures and Properties.

Textile technologies in which fibers containing biological factors and cells are formed and assembled into constructs with biomimetic properties have attracted significant attention in the field of tissue engineering. This Forum article highlights the most prominent advances of the field in the areas of fiber fabrication and construct engineering.