Synthetic Scaffolds Research Articles

Electrospun Biomimetic Nanofibrous Scaffolds: A Promising Prospect for Bone Tissue Engineering and Regenerative Medicine.

Skeletal-related disorders such as arthritis, bone cancer, osteosarcoma, and osteoarthritis are among the most common reasons for mortality in humans at present. Nanostructured scaffolds have been discovered to be more efficient for bone regeneration than macro/micro-sized scaffolds because they sufficiently permit cell adhesion, proliferation, and chemical transformation. Nanofibrous scaffolds mimicking artificial extracellular matrices provide a natural environment for tissue regeneration owing to their large surface area, high porosity, and appreciable drug loading capacity. Here, we review recent progress and possible future prospective electrospun nanofibrous scaffolds for bone tissue engineering. Electrospun nanofibrous scaffolds have demonstrated promising potential in bone tissue regeneration using a variety of nanomaterials. This review focused on the crucial role of electrospun nanofibrous scaffolds in biological applications, including drug/growth factor delivery to bone tissue regeneration. Natural and synthetic polymeric nanofibrous scaffolds are extensively inspected to regenerate bone tissue. We focused mainly on the significant impact of nanofibrous composite scaffolds on cell adhesion and function, and different composites of organic/inorganic nanoparticles with nanofiber scaffolds. This analysis provides an overview of nanofibrous scaffold-based bone regeneration strategies; however, the same concepts can be applied to other organ and tissue regeneration tactics.

The Use of 3D Polylactic Acid Scaffolds with Hydroxyapatite/Alginate Composite Injection and Mesenchymal Stem Cells as Laminoplasty Spacers in Rabbits.

Several types of laminoplasty spacer have been used to fill bone gaps and maintain a widened canal. A 3D scaffold can be used as an alternative spacer to minimize the risk observed in allografts or autografts. This study aims to evaluate the in vivo biocompatibility and tissue–scaffold integration of a polylactic acid (PLA) scaffold with the addition of alginate/hydroxyapatite (HA) and mesenchymal stem cell (MSc) injections. This is an experimental study with a pretest and post-test control group design. A total of 15 laminoplasty rabbit models were divided into five groups with variations in the autograft, PLA, HA/alginate, and MSc scaffold. In general, there were no signs of inflammation in most samples (47%), and there were no samples with areas of necrosis. There were no significant differences in the histopathological results and microstructural assessment between the five groups. This demonstrates that the synthetic scaffolds that we used had a similar tissue reaction and tissue integration profile as the autograft (p > 0.05). We recommend further translational studies in humans so that this biocompatible fabricated scaffold can be used to fill bone defects.

ECM roles and biomechanics in cardiac tissue decellularization.

Natural biomaterials hold enormous potential for tissue regeneration. The rapid advance of several tissue-engineered biomaterials, such as natural and synthetic polymer-based scaffolds, has led to widespread application of these materials in the clinic and in research. However, biomaterials can have limited repair capacity; obstacles result from immunogenicity, difficulties in mimicking native microenvironments, and maintaining the mechanical and biochemical (i.e., biomechanical) properties of native organs/tissues. The emergence of decellularized extracellular matrix (ECM)-derived biomaterials provides an attractive solution to overcome these hurdles since decellularized ECM provides a nonimmune environment with native three-dimensional structures and bioactive components. More importantly, decellularized ECM can be generated from the tissue of interest, such as the heart, and keep its native macro- and microstructure and tissue-specific composition. These decellularized cardiac matrices/scaffolds can then be reseeded using cardiac cells, and the resulting recellularized construct is considered an ideal choice for regenerating functional organs/tissues. Nonetheless, the decellularization process must be optimized and depends on tissue type, age, and functional goal. Although most decellularization protocols significantly reduce immunogenicity and deliver a matrix that maintains the tissue macrostructure, suboptimal decellularization can change ECM composition and microstructure, which affects the biomechanical properties of the tissue and consequently changes cell-matrix interactions and organ function. Herein, we review methods of decellularization, with particular emphasis on cardiac tissue, and how they can affect the biomechanics of the tissue, which in turn determines success of reseeding and in vivo viability. Moreover, we review recent developments in decellularized ECM-derived cardiac biomaterials and discuss future perspectives.

Synergistic Improvement of 5-Aminolevulinic Acid Production with Synthetic Scaffolds and System Pathway Engineering.

Engineered synthetic scaffolds to organize metabolic pathway enzymes and system pathway engineering to fine-tune metabolic fluxes play essential roles in microbial production. Here, we first obtained the most favorable combination of key enzymes for 5-aminolevulinic acid (5-ALA) synthesis through the C5 pathway by screening enzymes from different sources and optimizing their combination in different pathways. Second, we successfully constructed a multienzyme complex assembly system with PduA*, which spatially recruits the above three key enzymes for 5-ALA synthesis in a designable manner. By further optimizing the ratio of these key enzymes in synthetic scaffolds, the efficiency of 5-ALA synthesis through the C5 pathway was significantly improved. Then, the competitive metabolism pathway was fine-tuned by rationally designing different antisense RNAs, further significantly increasing 5-ALA titers. Furthermore, for efficient 5-ALA synthesis, obstacles of NADH and NADPH imbalances and feedback inhibition of the synthesis pathway were also overcome through engineering the NADPH regeneration pathway and transport pathway, respectively. Finally, combining these strategies with further fermentation optimization, we achieved a final 5-ALA titer of 11.4 g/L. These results highlight the importance of synthetic scaffolds and system pathway engineering to improve the microbial cell factory production performance.

Advancement of Organoid Technology in Regenerative Medicine.

PurposeOrganoids are three-dimensional cultures of stem cells in an environment similar to the body’s extracellular matrix. This is also a novel development in the realm of regenerative medicine. Stem cells can begin to develop into 3D structures by modifying signaling pathways. To form organoids, stem cells are transplanted into the extracellular matrix. Organoids have provided the required technologies to reproduce human tissues. As a result, it might be used in place of animal models in scientific study. The key goals of these investigations are research into viral and genetic illnesses, malignancies, and extracellular vesicles, pharmaceutical discovery, and organ transplantation. Organoids can help pave the road for precision medicine through genetic editing, pharmaceutical development, and cell therapy.MethodsPubMed, Google Scholar, and Scopus were used to search for all relevant papers written in English (1907–2021). The study abstracts were scrutinized. Studies on the use of stem-cell-derived organoids in regenerative medicine, organoids as 3D culture models for EVs analysis, and organoids for precision medicine were included. Articles with other irrelevant aims, meetings, letters, commentaries, congress and conference abstracts, and articles with no available full texts were excluded.ResultsAccording to the included studies, organoids have various origins, types, and applications in regenerative and precision medicine, as well as an important role in studying extracellular vesicles.ConclusionOrganoids are considered a bridge that connects preclinical studies to clinical ones. However, the lack of a standardized protocol and other barriers addressed in this review, hinder the vast use of this technology.Lay SummaryOrganoids are 3D stem cell propagations in biological or synthetic scaffolds that mimic ECM to allow intercellular or matrix-cellular crosstalk. Because these structures are similar to organs in the body, they can be used as research models. Organoids are medicine’s future hope for organ transplantation, tumor biobank formation, and the development of precision medicine. Organoid models can be used to study cell-to-cell interactions as well as effective factors like inflammation and aging. Bioengineering technologies are also used to define the size, shape, and composition of organoids before transforming them into precise structures. Finally, the importance of organoid applications in regenerative medicine has opened a new window for a better understanding of biological research, as discussed in this study.

Immunostimulatory Polymers as Adjuvants, Immunotherapies, and Delivery Systems

Activating innate immunity in a controlled manner is necessary for the development of next-generation therapeutics. Adjuvants, or molecules that modulate the immune response, are critical components of vaccines and immunotherapies. While small molecules and biologics dominate the adjuvant market, emerging evidence supports the use of immunostimulatory polymers in therapeutics. Such polymers can stabilize and deliver cargo while stimulating the immune system by functioning as pattern recognition receptor (PRR) agonists. At the same time, in designing polymers that engage the immune system, it is important to consider any unintended initiation of an immune response that results in adverse immune-related events. Here, we highlight biologically derived and synthetic polymer scaffolds, as well as polymer–adjuvant systems and stimuli-responsive polymers loaded with adjuvants, that can invoke an immune response. We present synthetic considerations for the design of such immunostimulatory polymers, outline methods to target their delivery, and discuss their application in therapeutics. Finally, we conclude with our opinions on the design of next-generation immunostimulatory polymers, new applications of immunostimulatory polymers, and the development of improved preclinical immunocompatibility tests for new polymers.

Guided Bone Regeneration with a Nitric‐Oxide Releasing Polymer Inducing Angiogenesis and Osteogenesis in Critical‐Sized Bone Defects

Synthetic scaffolds, as bone grafts, provide a favorable environment for the repair and growth of new bone tissue at defect sites. However, the lack of angio- and osteo-induction limits the usefulness of artificial scaffolds for bone regeneration. Nitric oxide (NO) performs essential roles in healing processes, such as regulating inflammation and addressing incomplete revascularization. In this study, a polymer capable of controlled NO release is developed to promote the osteogenic capacity in artificial scaffolds. The biological efficiency of the NO compound is assessed by its effect on pre-osteoblasts and macrophages in vitro and the extent of vascularization and bone formation in the calvaria defect model in vivo. The compound does not inhibit cell adhesion or proliferation. NO treatment significantly increases both alkaline phosphatase activity and mineralization in pre-osteoblasts. Macrophages treated with NO secrete high levels of anti-inflammatory factors and adopt the pro-regenerative phenotype. In the critical-sized defect model, the collagen scaffold containing the NO compound enhances neovascularization and bone formation. The developed NO-releasing system promotes osteogenesis and regeneration of damaged bone tissue. As the multiple functions of NO involve macrophage modulation and angiogenesis, such release systems may be valuable for guiding bone regeneration in critical-sized defects.

Recent Applications on Dual-Catalysis for C–C and C–X Cross-Coupling Reactions

AbstractCoupling reactions stand amid the most significant reactions in synthetic organic chemistry. Of late, these coupling strategies are being viewed as a versatile synthetic tool for a wide range of organic transformations in many sectors of chemistry, ranging from indispensable synthetic scaffolds and natural products of biological significance to novel organic materials. Further, the use of dual-catalysis in accomplishing various interesting cross-coupling transformations is an emerging field in synthetic organic chemistry, owing to their high catalytic performance rather than the use of a single catalyst. In recent years, synthetic organic chemists have given considerable attention to hetero-dual catalysis; wherein these catalytic systems have been employed for the construction of versatile carbon–carbon [C(sp 3)–C(sp 3), C(sp 3)–C(sp 2), C(sp 2)–C(sp 2)] and carbon–heteroatom (C–N, C–O, C–P, C–S) bonds. Therefore, in this mini-review, we are emphasizing recently developed various cross-coupling reactions catalysed by transition-metal dual-catalysis (i.e., using palladium and copper catalysts, but omitting the reports on photoredox/metal catalysis).1 Introduction2 Cu/Pd-Catalysed Bond Formation2.1 Pd/Cu-Catalysed C(sp 3)–C(sp 2) Bond Formation2.2 Pd/Cu-Catalysed C(sp 2)–C(sp 2) Bond Formation2.3 Pd/Cu-Catalysed C(sp)–C(sp 2) Bond Formation2.4 Pd/Cu-Catalysed C(sp 3)–C(sp 3) Bond Formation2.5 Pd/Cu-Catalysed C–X (X = B, N, P, S, Si) Bond Formation3 Conclusion

A General and Efficient Solution to Monofluoroalkylation: Divergent Synthesis of Aliphatic Monofluorides with Modular Synthetic Scaffolds

Monofluoroalkanes are important in many pharmaceuticals, agrochemicals and functional materials. However, the lack of easily available and transformable monofluoroalkylating reagents that facilitate a broad array of transformations has hampered the application of monofluoroalkylation. Herein, we report a general and efficient method of preparing diverse aliphatic monofluorides with monofluoroalkyl triflate as the synthetic scaffold. Using both nickel-catalyzed hydromonofluoroalkylation of unactivated alkenes and copper-catalyzed C-C bond formation, the general diversification of the monofluoroalkylating scaffold has been exhibited. The broad utility of this monofluoroalkylating reagent is shown by concise conversion into various conventional fluoroalkylating reagents and construction of monofluoro-alkoxy, -alkylamino motifs with commercially available heteroatom-based coupling partners.

A General and Efficient Solution to Monofluoroalkylation: Divergent Synthesis of Aliphatic Monofluorides with Modular Synthetic Scaffolds

Monofluoroalkane has seen its prevalence in many pharmaceuticals, agrochemicals and functional materials. However, the lack of easily available and transformable monofluoroalkylating reagents that facilitate broad array of transformations has hampered the application of monofluoroalkylation. Herein, we report a general and efficient method of preparing diverse aliphatic monofluorides with modular synthetic scaffold-monofluoroalkyl triflate. Leveraged by both nickel-catalyzed hydromonofluoroalkylation of unactivated alkenes and copper-catalyzed C-C bond formation, the general diversification of the monofluoroalkylating scaffold has been exhibited. Aside from new methodologies, we have further demonstrated broad utilities of this monofluoroalkylating reagent by concise conversion to various conventional fluoroalkylating reagents and construction of monofluoro-alkoxy, -alkylamino motifs with commercially available heteroatom-based coupling partners.

Compatibility and function of human induced pluripotent stem cell derived cardiomyocytes on an electrospun nanofibrous scaffold, generated from an ionomeric polyurethane composite.

Synthetic scaffolds are needed for generating organized neo-myocardium constructs to promote functional tissue repair. This study investigated the biocompatibility of an elastomeric electrospun degradable polar/hydrophobic/ionic polyurethane (D-PHI) composite scaffold with human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The composite material was electrospun to generate scaffolds, with nanofibres oriented in aligned or random directions. These features enabled the authors to evaluate the effect of characteristic elements which mimic that of the native extracellular matrix (alignment, chemical heterogeneity, and fiber topography) on hiPSC-CMs activity. The functional nature of the hiPSC-CM cultured on gelatin and Matrigel-coated scaffolds were assessed, investigating the influence of protein interactions with the synthetic substrate on subsequent cell phenotype. After 7 days of culture, high hiPSC-CM viability was observed on the scaffolds. The cells on the aligned scaffold were elongated and demonstrated aligned sarcomeres that oriented parallel to the direction of the fibers, while the cells on random scaffolds and a tissue culture polystyrene (TCPS) control did not exhibit such an organized morphology. The hiPSC-CMs cultured on the scaffolds and TCPS expressed similar levels of cardiac troponin-T, but there was a higher expression of ventricular myosin light chain-2 on the D-PHI composite scaffolds versus TCPS, indicating a higher proportion of hiPSC-CM exhibiting a ventricular cardiomyocyte like phenotype. Within 7 days, the hiPSC-CMs on aligned scaffolds and TCPS beat synchronously and had similar conductive velocities. These preliminary results show that aligned D-PHI elastomeric scaffolds allow hiPSC-CMs to demonstrate important cardiomyocytes characteristics, critical to enabling their future potential use for cardiac tissue regeneration.

Bone regeneration of mouse critical-sized calvarial defects with human mesenchymal stem cell sheets co-expressing BMP2 and VEGF

Over-dependence on existing synthetic scaffolds and insufficient osteoinductive and vasculogenic growth factors have limited the development of bone regeneration. The study aimed to assess the feasibility of using marrow-derived mesenchymal stem cells (BMSCs) cell sheets co-expressing bone morphogenetic proteins 2 (BMP2) and vascular endothelial growth factor (VEGF) for repairing critical-sized calvarial defects. BMSCs cell sheets were genetically engineered to express BMP2/VEGF alone or together. Alterations in osteogenic markers were examined by quantitative real-time PCR (qRT-PCR) and western blotting. A critical-sized calvarial bone defect model was used to investigate the osteogenesis effects of BMP2/VEGF cell sheets alone or in combination. The efficacy was assessed with micro-computed tomography (micro-CT) and histology. Invitro, the expression of BMP2 and VEGF through lentiviral transduction was confirmed by qRT-PCR and western blotting against BMP2 and VEGF. Lentiviral delivery of BMP2 and VEGF resulted in the upregulation of osteogenic markers. Invivo, in a critical-sized calvarial bone defect model, 3D-reconstructed micro-CT images revealed that treatment of the calvarial defects with the BMP2/VEGF cell sheet resulted in significantly greater amounts of newly formed bone at 8 weeks after surgery than treatment with cell sheets with single gene transduction or vehicle controls. The results were confirmed by histological assessment by H&E staining and Masson staining. This study demonstrates that BMP2/VEGF co-expressing BMSCs sheets promote bone regeneration in critical-sized calvarial bone defects. The BMP2/VEGF cell sheets provide a functional bioactive scaffold for critical-size bone reconstruction.

Delivery of Cells to the Cornea Using Synthetic Biomaterials.

The cornea is subject to a myriad of ocular conditions often attributed to cell loss or cell dysfunction. Owing to the superficial positioning of tissues composing the anterior segment of the eye, particularly the cornea, regenerative medicine in this region is aided by accessibility as compared with the invasive delivery methods required to reach deep ocular tissues. As such, cell therapies employing the use of carrier substrates have been widely explored. This review covers recent advances made in the delivery of stem cells, corneal epithelial cells, and corneal endothelial cells. Particular focus is placed on the most popular forms of synthetic scaffolds currently being examined: contact lenses, electrospun substrates, polymeric films, and hydrogels.

Development of a borosilicate bioactive glass scaffold incorporating calcitonin gene-related peptide for tissue engineering.

Protein delivery and release from synthetic scaffold materials are major challenges within the field of bone tissue engineering. In this study, 13-93B1.5 borosilicate bioactive glass (BSG) base paste was 3D printed to produce BSG-based scaffolds with high porosity (59.85±6.04%) and large pore sizes (350-400μm) for functionalization with a sodium alginate (SA)/calcitonin gene-related peptide (CGRP) hydrogel mixture. SA/CGRP hydrogel was uniformly filled into the interconnected pores of 3D printed BSG constructs to produce BSG-SA/CGRP scaffolds which were subject to bioactivity and biocompatibility analysis. BSG scaffolds filled with SA hydrogel underwent dissolution in simulated body fluid (SBF), resulting in the precipitation of hydroxyapatite (HA) on the borosilicate glass evidenced by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Around 90% of CGRP was released from scaffolds after 7days of immersion in SBF, reaching a final released concentration of 893.00±63.30ng/mL. Cellular adhesion, proliferation, and differentiation of human bone marrow mesenchymal stem cells (HBMSCs) cultured with BSG-SA/CGRP scaffolds revealed improved biocompatibility and osteogenic capabilities compared with BSG-SA scaffolds in the absence of CGRP. When subcutaneously implanted in rat models, BSG-SA/CGRP scaffolds induced low localized inflammation without causing bodily harm in vivo. Findings revealed that bioactive glass scaffolds incorporating CGRP met the scaffold requirements for bone regeneration and that the addition of CGRP promoted osteogenic differentiation where it may potentially be utilized for future regenerative applications.

The Emerging Use of ASC/Scaffold Composites for the Regeneration of Osteochondral Defects.

Articular cartilage is composed of chondrocytes surrounded by a porous permeable extracellular matrix. It has a limited spontaneous healing capability post-injury which, if left untreated, can result in severe osteochondral disease. Currently, osteochondral (OC) defects are treated by bone marrow stimulation, artificial joint replacement, or transplantation of bone, cartilage, and periosteum, while autologous osteochondral transplantation is also an option; it carries the risk of donor site damage and is limited only to the treatment of small defects. Allografts may be used for larger defects; however, they have the potential to elicit an immune response. A possible alternative solution to treat osteochondral diseases involves the use of stromal/stem cells. Human adipose-derived stromal/stem cells (ASCs) can differentiate into cartilage and bone cells. The ASC can be combined with both natural and synthetic scaffolds to support cell delivery, growth, proliferation, migration, and differentiation. Combinations of both types of scaffolds along with ASCs and/or growth factors have shown promising results for the treatment of OC defects based on in vitro and in vivo experiments. Indeed, these findings have translated to several active clinical trials testing the use of ASC-scaffold composites on human subjects. The current review critically examines the literature describing ASC-scaffold composites as a potential alternative to conventional therapies for OC tissue regeneration.

Switchable Control of Scaffold Protein Activity via Engineered Phosphoregulated Autoinhibition.

Scaffold proteins operate as organizing hubs to enable high-fidelity signaling, fulfilling crucial roles in the regulation of cellular processes. Bottom-up construction of controllable scaffolding platforms is attractive for the implementation of regulatory processes in synthetic biology. Here, we present a modular and switchable synthetic scaffolding system, integrating scaffold-mediated signaling with switchable kinase/phosphatase input control. Phosphorylation-responsive inhibitory peptide motifs were fused to 14-3-3 proteins to generate dimeric protein scaffolds with appended regulatory peptide motifs. The availability of the scaffold for intermolecular partner protein binding could be lowered up to 35-fold upon phosphorylation of the autoinhibition motifs, as demonstrated using three different kinases. In addition, a hetero-bivalent autoinhibitory platform design allowed for dual-kinase input regulation of scaffold activity. Reversibility of the regulatory platform was illustrated through phosphatase-controlled abrogation of autoinhibition, resulting in full recovery of 14-3-3 scaffold activity.

Osteoblasts in a Perfusion Flow Bioreactor-Tissue Engineered Constructs of TiO2 Scaffolds and Cells for Improved Clinical Performance.

Combining biomaterial scaffolds with cells serves as a promising strategy for engineering critical size defects; however, homogenous cellular growth within large scaffolds is challenging. Mechanical stimuli can enhance bone regeneration by modulating cellular growth and differentiation. Here, we compare dynamic seeding in a perfusion flow bioreactor with static seeding for a synthetic bone scaffold for up to 21 days using the cell line MC3T3-E1 and primary human osteoblast, confocal laser scanning microscopy, and real-time reverse transcriptase-polymerase chain reaction. The secretion of bone-related proteins was quantified using multiplex immunoassays. Dynamic culture improved cellular distribution through the TiO2 scaffold and induced a five-fold increase in cell number after 21 days. The relative mRNA expression of osteopontin of MC3T3-E1 was 40-fold enhanced after 7 and 21 days at a flow rate of 0.08 mL/min, and that of collagen type I alpha I expression was 18-fold after 21 days. A flow rate of 0.16 mL/min was 10-fold less effective. Dynamic culture increased the levels of dickkopf-related protein 1 (60-fold), osteoprotegrin (29-fold), interleukin-6 (23-fold), interleukin-8 (36-fold), monocyte chemoattractant protein 1 (28-fold) and vascular endothelial growth factor (6-fold) in the medium of primary human osteoblasts after 21 days compared to static seeding. The proposed method may have clinical potential for bone tissue engineering.

Snake Venom Hydrogels as a Rapid Hemostatic Agent for Uncontrolled Bleeding.

Uncontrolled bleeding from traumatic injury remains the leading cause of preventable death with loss of balance between blood clotting (coagulation) and blood clot breakdown (fibrinolysis). A major limitation of existing hemostatic agents is that they require a functioning clotting system to control the bleeding and are largely based on gauze delivery scaffolds. Herein, a novel rapid wound sealant, composed of two recombinant snake venom proteins, the procoagulant ecarin, to rapidly initiate blood clotting and the antifibrinolytic textilinin, to prevent blood clot breakdown within a synthetic thermoresponsive hydrogel scaffold is developed. In vitro, it is demonstrated that clotting is rapidly initiated with only nanomolar concentrations of venom protein and clot breakdown is effectively inhibited by textilinin. A stable clot is formed within 60 s compared to normal clot formation in 8 min. In vivo studies reveal that the snake venom hydrogel rapidly controls warfarin-induced bleeding, reducing the bleed volume from 48% to 12% and has demonstrated immune compatibility. A new class of hemostatic agents that achieve formation of rapid and stable blood clots even in the presence of blood thinners is demonstrated here.

Rapid fabrication of tendon-like collagen gel via simultaneous fibre alignment and intermolecular cross-linking under mechanical loading

Artificial tissue replacement is a promising strategy for better healing outcomes for tendon and ligament injuries, due to the very limited self-regeneration capacity of these tissues in mammals, including humans. Because clinically available synthetic and biological scaffolds for tendon repair have performed more poorly than autografts, both biological and mechanical compatibility need to be improved. Here we propose a rapid fabrication method for tendon-like structure from collagen hydrogel, simultaneously achieving collagen fibre alignment and intermolecular cross-linking. Collagen gel, 24 h after polymerization, was subjected to mechanical loading in the presence of the chemical cross-linker, genipin, for 24 or 48 h. Mechanical loading during gel incubation oriented collagen fibres in the loading direction and made chemical cross-linking highly effective in a loading magnitude-dependent manner. Gel incubated with 4 g loading in the presence of genipin for 48 h possessed tensile strength of 4 MPa and tangent modulus of 60 MPa, respectively, which could fulfill the minimum biomechanical requirement for artificial tendon. Although mechanical properties of gels fabricated using the present method can be improved by using a larger amount of collagen in the starting material and through optimisation of mechanical loading and cross-linking, the method is a simple and effective for producing highly aligned collagen fibrils with excellent mechanical properties.

A Tunable Tumor Microenvironment through Recombinant Bacterial Collagen-Hyaluronic Acid Hydrogels.

Laboratory models of the tumor microenvironment require control of mechanical and biochemical properties to ensure accurate mimicry of patient disease. In contrast to pure natural or synthetic materials, hybrid approaches that pair recombinant protein fragments with synthetic scaffolding show many advantages. Here we demonstrate production of a recombinant bacterial collagen-like protein (CLP) for thiol-ene pairing to norbornene functionalized hyaluronic acid (NorHA). The resultant hydrogel material shows an adjustable modulus with evidence for strain-stiffening behavior that resembles natural tumor matrices. Cysteine terminated peptide binding motifs are incorporated to adjust the cell-adhesion points. The modular hybrid gel shows good biocompatibility and was demonstrated to control cell adhesion, proliferation, and the invasive properties of MCF7 and MD-MBA-231 breast adenocarcinoma cells. The ease in which multiple structural and bioactive components can be integrated provides a robust framework to form models of the tumor microenvironment for fundamental studies and drug development.