Deciphering the combinatorial roles of geometric, mechanical, and adhesion cues in regulation of cell spreading

Advanced injectable hydrogels for bone tissue regeneration

Diseases or defects of the skeleton are hazardous because of their specificity and intricacy. Bone tissue engineering has become an important area of research that offers promising new tools for making biomimetic hydrogels that can be used to treat bone diseases. New hydrogels with a distinctive 3D network structure, high water content, and functional capabilities are ranked among the most promising candidates for bone tissue engineering. This makes them helpful in treating cartilage injury, skull deformity, and arthritis. This review will briefly introduce the variety of biocompatible functional hydrogels used in cell culture and bone tissue regeneration. Many gel design concepts, such as crosslinking procedures, controlled release properties, and alternative bionic methodology, were stressed regarding injectable hydrogels to form bone tissue. Hydrogels manufactured from biocompatible materials are a promising option for minimally invasive surgery because of their adaptable physicochemical qualities, ability to fill irregularly shaped defect sites, and ability to grow hormones or release drugs in response to external stimuli. Also included in this overview is a quick rundown of the more practical designs employed in treating bone disorders. Essential details on injectable hydrogel scaffolds for bone tissue regeneration are described in this article.

Development of a Piezoelectric PVDF-TrFE Fibrous Scaffold to Guide Cell Adhesion, Proliferation, and Alignment

Severe peripheral nervous system injuries currently hold limited therapeutic solutions. Existing clinical techniques such as autografts, allografts, and newer nerve guidance conduits have shown variable outcomes in functional recovery, adverse immune responses, and in some cases low or minimal availability. This can be attributed in part to the lack of chemical, physical, and electrical cues directing both nerve guidance and regeneration. To address this pressing clinical issue, electrospun nanofibers and microfibers composed of piezoelectric polyvinylidene flouride-triflouroethylene (PVDF-TrFE) have been introduced as an alternative template for tissue engineered biomaterials, specifically as it pertains to their relevance in soft tissue and nerve repair. Here, biocompatible scaffolds of PVDF-TrFE are fabricated and their ability to generate an electrical response to mechanical deformations and produce a suitable regenerative microenvironment is examined. It is determined that 20% (w/v) PVDF-TrFE in (6:4) dimethyl formamide (DMF):acetone solvent maintains a desirable piezoelectric coefficient and the proper physical and electrical characteristics for tissue regeneration. Further, it is concluded that scaffolds of varying thickness promoted the adhesion and alignment of Schwann cells and fibroblasts. This work offers a prelude to further advancements in nanofibrous technology and a promising outlook for alternative, autologous remedies to peripheral nerve damage.

Cellulose Biomaterials for Tissue Engineering

In this review, we highlight the importance of nanostructure of cellulose-based biomaterials to allow cellular adhesion, the contribution of nanostructure to macroscale mechanical properties, and several key applications of these materials for fundamental scientific research and biomedical engineering. Different features on the nanoscale can have macroscale impacts on tissue function. Cellulose is a diverse material with tunable properties and is a promising platform for biomaterial development and tissue engineering. Cellulose-based biomaterials offer some important advantages over conventional synthetic materials. Here we provide an up-to-date summary of the status of the field of cellulose-based biomaterials in the context of bottom-up approaches for tissue engineering. We anticipate that cellulose-based material research will continue to expand because of the diversity and versatility of biochemical and biophysical characteristics highlighted in this review.

Multiplexed Biomolecular Arrays Generated via Parallel Dip-Pen Nanolithography

The capability of transferring target materials especially functionality-reliable biomolecules, into specific locations and with arbitrarily designed patterns are of critical importance for high-throughput disease diagnosis, multiplexing, and drug screening. Herein, we report the simultaneous patterning of two types of biomolecules using the parallel dip-pen nanolithography technology where an array of the atomic force microscope (AFM) tips can be selectively and alternately coated with target biomolecules via a specially designed inkwell array. Moreover, mixing target biomolecules at a proper volumetric ratio with polyethylene glycol dissolved in PBS buffer solution that works as an ink carrier can not only facilitate the smooth transfer of ink materials from the AFM tip to the substrate, it can also help to adjust the ink diffusion constant of different biomolecules to be highly similar so that the multiplexed biofunctional dot and/or line arrays at similar sizes can be reliably generated.

Matrix Stiffness Modulates Mesenchymal Stem Cell Sensitivity to Geometric Asymmetry Signals

Human stem cells hold significant potential for the treatment of various diseases. However, their use as a therapy is hampered because of limited understanding of the mechanisms by which they respond to environmental stimuli. Efforts to understand extracellular biophysical cues have demonstrated the critical roles of geometrical and mechanical signals in determining the fate of stem cells. The goal of this study was to explore the interplay between cell polarity and matrix stiffness in stem cell lineage specification. We hypothesize that confining cells to asymmetric extracellular matrix islands will impart polarity at a single-cell level and will interact with mechanical signals to define the lineage of stem cells. To test these hypotheses, we employed microcontact printing to create patterned symmetric and asymmetric hydrogel islands of soft and hard surface stiffness. Human mesenchymal stem cells (hMSCs) were confined to these islands at the single-cell level and given the ability to differentiate along adipogenic or osteogenic routes. Our results demonstrated that cell polarity defines the lineage specification of hMSCs only on islands with low stiffness. Insight gained from this study provides a rational basis for designing stem cell cultures to enhance tissue engineering and regenerative medicine strategies.

The Horizon of Materiobiology: A Perspective on Material-Guided Cell Behaviors and Tissue Engineering

Although the biological functions of cell and tissue can be regulated by biochemical factors (e.g., growth factors, hormones), the biophysical effects of materials on the regulation of biological activity are receiving more attention. In this Review, we systematically summarize the recent progress on how biomaterials with controllable properties (e.g., compositional/degradable dynamics, mechanical properties, 2D topography, and 3D geometry) can regulate cell behaviors (e.g., cell adhesion, spreading, proliferation, cell alignment, and the differentiation or self-maintenance of stem cells) and tissue/organ functions. How the biophysical features of materials influence tissue/organ regeneration have been elucidated. Current challenges and a perspective on the development of novel materials that can modulate specific biological functions are discussed. The interdependent relationship between biomaterials and biology leads us to propose the concept of "materiobiology", which is a scientific discipline that studies the biological effects of the properties of biomaterials on biological functions at cell, tissue, organ, and the whole organism levels. This Review highlights that it is more important to develop ECM-mimicking biomaterials having a self-regenerative capacity to stimulate tissue regeneration, instead of attempting to recreate the complexity of living tissues or tissue constructs ex vivo. The principles of materiobiology may benefit the development of novel biomaterials providing combinative bioactive cues to activate the migration of stem cells from endogenous reservoirs (i.e., cell niches), stimulate robust and scalable self-healing mechanisms, and unlock the body's innate powers of regeneration.

Nanostructured scaffold as a determinant of stem cell fate

The functionality of stem cells is tightly regulated by cues from the niche, comprising both intrinsic and extrinsic cell signals. Besides chemical and growth factors, biophysical signals are important components of extrinsic signals that dictate the stem cell properties. The materials used in the fabrication of scaffolds provide the chemical cues whereas the shape of the scaffolds provides the biophysical cues. The effect of the chemical composition of the scaffolds on stem cell fate is well researched. Biophysical signals such as nanotopography, mechanical forces, stiffness of the matrix, and roughness of the biomaterial influence the fate of stem cells. However, not much is known about their role in signaling crosstalk, stem cell maintenance, and directed differentiation. Among the various techniques for scaffold design, nanotechnology has special significance. The role of nanoscale topography in scaffold design for the regulation of stem cell behavior has gained importance in regenerative medicine. Nanotechnology allows manipulation of highly advanced surfaces/scaffolds for optimal regulation of cellular behavior. Techniques such as electrospinning, soft lithography, microfluidics, carbon nanotubes, and nanostructured hydrogel are described in this review, along with their potential usage in regenerative medicine. We have also provided a brief insight into the potential signaling crosstalk that is triggered by nanomaterials that dictate a specific outcome of stem cells. This concise review compiles recent developments in nanoscale architecture and its importance in directing stem cell differentiation for prospective therapeutic applications.

Nanoengineered Platforms to Guide Pluripotent Stem Cell Fate

Tissue engineering utilizes cells, signaling molecules, and scaffolds towards creating functional tissue to repair damaged organs. Pluripotent stem cells (PSCs) are a promising cell source due to their ability to self-renewal indefinitely and their potential to differentiate into almost any cell type. Great strides have been taken to parse the physiological mechanisms by which PSCs respond to their microenvironment and commit to a specific lineage. The combination of physical cues and chemical factors is thought to have the most profound influence on stem cell behavior, therefore a major focus of tissue engineering strategies is scaffold design to incorporate these signals. One overlooked component of the in vivo microenvironment researchers attempt to recapitulate with three dimensional (3D) substrates is the nanoarchitecture formed by the fibrillar network of extracellular matrix (ECM) proteins. These nanoscale features have the ability to impact cell adhesion, migration, proliferation, and lineage commitment. Significant advances have been made in deciphering how these nanoscale cues interact with stem cells to determine phenotype, but much is still unknown as to how the interplay between physical and chemical signals regulate in vitro and in vivo cellular fate. This review dives deeper to investigate nanoscale platforms for engineering tissue, as well use the use of these nanotechnologies to drive pluripotent stem cell lineage determination.