Elastin-Collagen Based Hydrogels as Model Scaffolds to Induce Three-Dimensional Adipocyte Culture from Adipose Derived Stem Cells

Contribution of the ELRs to the development of advanced in vitro models

Developing in vitro models that accurately mimic the microenvironment of biological structures or processes holds substantial promise for gaining insights into specific biological functions. In the field of tissue engineering and regenerative medicine, in vitro models able to capture the precise structural, topographical, and functional complexity of living tissues, prove to be valuable tools for comprehending disease mechanisms, assessing drug responses, and serving as alternatives or complements to animal testing. The choice of the right biomaterial and fabrication technique for the development of these in vitro models plays an important role in their functionality. In this sense, elastin-like recombinamers (ELRs) have emerged as an important tool for the fabrication of in vitro models overcoming the challenges encountered in natural and synthetic materials due to their intrinsic properties, such as phase transition behavior, tunable biological properties, viscoelasticity, and easy processability. In this review article, we will delve into the use of ELRs for molecular models of intrinsically disordered proteins (IDPs), as well as for the development of in vitro 3D models for regenerative medicine. The easy processability of the ELRs and their rational design has allowed their use for the development of spheroids and organoids, or bioinks for 3D bioprinting. Thus, incorporating ELRs into the toolkit of biomaterials used for the fabrication of in vitro models, represents a transformative step forward in improving the accuracy, efficiency, and functionality of these models, and opening up a wide range of possibilities in combination with advanced biofabrication techniques that remains to be explored.

Protein-Based Hydrogels and Their Biomedical Applications

Hydrogels made from proteins are attractive materials for diverse medical applications, as they are biocompatible, biodegradable, and amenable to chemical and biological modifications. Recent advances in protein engineering, synthetic biology, and material science have enabled the fine-tuning of protein sequences, hydrogel structures, and hydrogel mechanical properties, allowing for a broad range of biomedical applications using protein hydrogels. This article reviews recent progresses on protein hydrogels with special focus on those made of microbially produced proteins. We discuss different hydrogel formation strategies and their associated hydrogel properties. We also review various biomedical applications, categorized by the origin of protein sequences. Lastly, current challenges and future opportunities in engineering protein-based hydrogels are discussed. We hope this review will inspire new ideas in material innovation, leading to advanced protein hydrogels with desirable properties for a wide range of biomedical applications.

Recent Progress in Biomedical Sensors Based on Conducting Polymer Hydrogels

Biosensors are increasingly taking a more active role in health science. The current needs for the constant monitoring of biomedical signals, as well as the growing spending on public health, make it necessary to search for materials with a combination of properties such as biocompatibility, electroactivity, resorption, and high selectivity to certain bioanalytes. Conducting polymer hydrogels seem to be a very promising materials, since they present many of the necessary properties to be used as biosensors. Furthermore, their properties can be shaped and enhanced by designing conductive polymer hydrogel-based composites with more specific functionalities depending on the end application. This work will review the recent state of the art of different biological hydrogels for biosensor applications, discuss the properties of the different components alone and in combination, and reveal their high potential as candidate materials in the fabrication of all-organic diagnostic, wearable, and implantable sensor devices.

Unsung versatility of elastin-like polypeptide inspired spheroid fabrication: A review

Lately, 3D cell culture technique has gained a lot of appreciation as a research model. Augmented with technological advancements, the area of 3D cell culture is growing rapidly with a diverse array of scaffolds being tested. This is especially the case for spheroid cultures. The culture of cells as spheroids provides opportunities for unanticipated vision into biological phenomena with its application to drug discovery, metabolic profiling, stem cell research as well as tumor, and disease biology. Spheroid fabrication techniques are broadly categorised into matrix-dependent and matrix-independent techniques. While there is a profusion of spheroid fabrication substrates with substantial biological relevance, an economical, modular, and bio-compatible substrate for high throughput production of spheroids is lacking. In this review, we posit the prospects of elastin-like polypeptides (ELPs) as a broad-spectrum spheroid fabrication platform. Elastin-like polypeptides are nature inspired, size-tunable genetically engineered polymers with wide applicability in various arena of biological considerations, has been employed for spheroid culture with profound utility. The technology offers a cheap, high-throughput, reproducible alternative for spheroid culture with exquisite adaptability. Here, we will brief the applicability of 3D cultures as compared to 2D cultures with spheroids being the focal point of the review. Common approaches to spheroid fabrication are discussed with existential limitations. Finally, the versatility of elastin-like polypeptide inspired substrates for spheroid culture has been discussed.

Cell-Biomaterial Interactions

In animals, the extracellular matrix (ECM) forms a three-dimensional network occupying the intercellular spaces (interstitial matrix) or serving as physical and biochemical support for cells and tissues (basement membrane) [...].

How Mechanical and Physicochemical Material Characteristics Influence Adipose-Derived Stem Cell Fate

Adipose-derived stem cells (ASCs) are a subpopulation of mesenchymal stem cells. Compared to bone marrow-derived stem cells, they can be harvested with minimal invasiveness. ASCs can be easily expanded and were shown to be able to differentiate into several clinically relevant cell types. Therefore, this cell type represents a promising component in various tissue engineering and medical approaches (e.g., cell therapy). In vivo cells are surrounded by the extracellular matrix (ECM) that provides a wide range of tissue-specific physical and chemical cues, such as stiffness, topography, and chemical composition. Cells can sense the characteristics of their ECM and respond to them in a specific cellular behavior (e.g., proliferation or differentiation). Thus, in vitro biomaterial properties represent an important tool to control ASCs behavior. In this review, we give an overview of the current research in the mechanosensing of ASCs and current studies investigating the impact of material stiffens, topography, and chemical modification on ASC behavior. Additionally, we outline the use of natural ECM as a biomaterial and its interaction with ASCs regarding cellular behavior.

Biomedical Applications of Collagen

Extracellular matrix proteins (ECMs) provide structural support and dynamic signaling cues that regulate cell behavior and tissue morphogenesis [...].

Systematic review on spheroids from adipose‐derived stem cells: Spontaneous or artefact state?

Three-dimensional (3D) cell cultures represent the spontaneous state of stem cells with specific gene and protein molecular expression that are more alike the in vivo condition. In vitro two-dimensional (2D) cell adhesion cultures are still commonly employed for various cellular studies such as movement, proliferation and differentiation phenomena; this procedure is standardized and amply used in laboratories, however their representing the original tissue has recently been subject to questioning. Cell cultures in 2D require a support/substrate (flasks, multiwells, etc.) and use of fetal bovine serum as an adjuvant that stimulates adhesion that most likely leads to cellular aging. A 3D environment stimulates cells to grow in suspended aggregates that are defined as "spheroids." In particular, adipose stem cells (ASCs) are traditionally observed in adhesion conditions, but a recent and vast literature offers many strategies that obtain 3D cell spheroids. These cells seem to possess a greater ability in maintaining their stemness and differentiate towards all mesenchymal lineages, as demonstrated in in vitro and in vivo studies compared to adhesion cultures. To date, standardized procedures that form ASC spheroids have not yet been established. This systematic review carries out an in-depth analysis of the 76 articles produced over the past 10 years and discusses the similarities and differences in materials, techniques, and purposes to standardize the methods aimed at obtaining ASC spheroids as already described for 2D cultures.

Naturally prefabricated 3D chitinous skeletal scaffold of marine demosponge origin, biomineralized ex vivo as a functional biomaterial

Solutions developed by nature for structural and functional optimization of three-dimensional (3D) skeletal structures provide unique windows not only into the evolutionary pathways of organisms, but also into bioinspired materials science and biomimetics. Great examples are naturally formed 3D chitinous scaffolds of marine sponge remain a focus of modern biomedicine and tissue engineering. Due to its properties like renewability, bioactivity, and biodegradability such constructs became very interesting players as components of organic-inorganic biocomposites. Herein, we developed chitin-based biocomposites by biomimetic ex vivo deposition of calcium carbonate particles using hemolymph from the cultivated mollusk Cornu aspersum and chitinous matrix from the marine demosponge Aplysina fistularis. The biological potential of the developed biofunctionalized scaffolds for bone tissue engineering was evaluated by investigating the spreading and viability of a human fetal osteoblast cell line has been determined for the first time. Performed analyses like dynamic mechanical analysis and atomic force microscopy shown that biofunctionalized scaffold possess about 4 times higher mechanical resistance. Moreover, several topographical changes have been observed, as e.g., surface roughness (Rq) increased from 31.75 ± 2.7 nm to 120.7 ± 0.3 nm. The results are indicating its potential for use in the modification of cell delivery systems in future biomedical applications.

De Novo Synthesis of Elastin-like Polypeptides (ELPs): An Applied Overview on the Current Experimental Techniques

Elastin-like polypeptides (ELPs) are protein-based biopolymers genetically produced from polypeptides composed of a repeating pentapeptide sequence V-P-G-X-G. The inherent properties of recombinant ELPs, such as smart nature, controlled sequence complexity, physicochemical properties, and biocompatibility, make these polymers suitable for use in nanobiotechnological applications, as biofunctionalized scaffolds for tissue-engineering purposes and drug delivery. In this work, we report the design and synthesis of two elastomeric self-assembling polypeptides (ELPs) that mimic the endogenous human tropoelastin. Using molecular biology techniques, two artificial genes that encode two ELP concatemers of approximate molecular mass 60 kDa, one of them carrying biotin-binding peptide motifs, were constructed. These motifs could facilitate biofunctionalization of the ELPs through tethering biotinylated factors, such as growth factors. The ELPs were heterologously overexpressed in E. coli and subsequently purified in two steps: a nonchromatographic technique by organic solvent extraction, followed by nickel-nitrilotriacetic acid (Ni-NTA) affinity chromatography. The characterization of the biochemical properties and biocompatibility of ELPs was also performed in this study. The ELP carrying the biotin-binding motifs was tested for its capability to bind biotin, and indeed, it was observed that it can bind biotinylated proteins specifically. Additionally, results concerning the cytotoxicity of the ELPs exhibited excellent compatibility of the ELPs with mammalian cells in vitro. We anticipate that these ELPs can be used as components of a scaffold that mimics the extracellular matrix (ECM) for the regeneration of endogenously highly elastic tissues.

Human Adipose-Derived Stromal/Stem Cell Culture and Analysis Methods for Adipose Tissue Modeling In Vitro: A Systematic Review

Human adipose-derived stromal/stem cells (hASC) are widely used for in vitro modeling of physiologically relevant human adipose tissue. These models are useful for the development of tissue constructs for soft tissue regeneration and 3-dimensional (3D) microphysiological systems (MPS) for drug discovery. In this systematic review, we report on the current state of hASC culture and assessment methods for adipose tissue engineering using 3D MPS. Our search efforts resulted in the identification of 184 independent records, of which 27 were determined to be most relevant to the goals of the present review. Our results demonstrate a lack of consensus on methods for hASC culture and assessment for the production of physiologically relevant in vitro models of human adipose tissue. Few studies have assessed the impact of different 3D culture conditions on hASC adipogenesis. Additionally, there has been a limited use of assays for characterizing the functionality of adipose tissue in vitro. Results from this study suggest the need for more standardized culture methods and further analysis on in vitro tissue functionality. These will be necessary to validate the utility of 3D MPS as an in vitro model to reduce, refine, and replace in vivo experiments in the drug discovery regulatory process.

Overcoming functional challenges in autologous and engineered fat grafting trends

Autologous fat grafting offers significant promise for the repair of soft tissue deformities; however, high resorption rates indicate that engineered solutions are required to improve adipose tissue (AT) survival. Advances in material development and biofabrication have laid the foundation for the generation of functional AT constructs; however, a balance needs to be struck between clinically feasible delivery and improved structural integrity of the grafts. A new approach combining the objectives from both the clinical and research communities will assist in developing morphologically and genetically mature AT constructs, with controlled spatial arrangement and increased potential for neovascularization. In a rapidly progressing field, this review addresses research in both the preclinical and bioengineering domains and assesses their ability to resolve functional challenges.