Porous matrix of calcium alginate/gelatin with enhanced properties as scaffold for cell culture

Synthesis of agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads: Characterization and application as controlled-release microencapsulated fertilizers

Synthesis of novel agro-industrial wastes/sodium alginate/bovine gelatin-based polysaccharide hydrogel beads, micromeritic/morphometric characteristics of the prepared formulations, greenhouse trials using controlled-release microencapsulated fertilizers, and acute fish toxicity testing were conducted simultaneously for the first time within the scope of an integrated research. In the present analysis, for the first time, 16 different morphometric features, and 32 disinct plant growth traits of the prepared composite beads were explored in detail within the framework of a comprehensive digital image analysis. The hydrogel beads composed of 19 different agro-industrial wastes/materials were successfully synthesized using the ionotropic external gelation technique and CaCl2 as cross-linker. According to micromeritic characteristics, the ionotropically cross-linked beads exhibited 77.86 ± 3.55 % yield percentage and 2.679 ± 0.397 mm average particle size. The dried microbeads showed a good swelling ratio (270.02 ± 80.53 %) and had acceptable flow properties according to Hausner's ratio (1.136 ± 0.028), Carr's index (11.94 ± 2.17 %), and angle of repose (25.03° ± 5.33°) values. The settling process of the prepared microbeads was observed in the intermediate flow regime, as indicated by the average particle Reynolds numbers (169.17 ± 82.81). Experimental findings and non-parametric statistical tests reveal that dried fertilizer matrices demonstrated noteworthy performance on the cultivation of red hot chili pepper plant (Capsicum annuum var. fasciculatum) according to the results of greenhouse trials. Surface morphologies of the best-performing fertilizer matrices were also characterized by Scanning Electron Microscopy. Moreover, the static fish bioassay experiment confirmed that no abnormalities and acute toxic reactions occurred in shortfin molly fish (Poecilia sphenops) fed with dried leaves of red hot chili pepper plants grown with formulated fertilizers. This study showcased a pioneering investigation into the synthesis of microcapsules using synthesized hydrogel beads along with digital image processing for bio-waste management and sustainable agro-application.

Fabrication of Porous Collagen Scaffolds Containing Embedded Channels with Collagen Membrane Linings

Tissues and organs contain an extracellular matrix (ECM). In the case of blood vessels, endothelium cells are anchored to a specialized basement membrane (BM) embedded inside the interstitial matrix (IM). We introduce a multi-structural collagen-based scaffold with embedded microchannels that mimics in vivo structures within vessels. Our scaffold consists of two parts, each containing two collagen layers, i.e., a 3D porous collagen layer analogous to IM lined with a thin 2D collagen film resembling the BM. Enclosed microchannels were fabricated using contact microprinting. Microchannel test structures with different sizes ranging from 300 to 800 µm were examined for their fabrication reproducibility. The heights and perimeters of the fabricated microchannels were ~20% less than their corresponding values in the replication PDMS mold; however, microchannel widths were significantly closer to their replica dimensions. The stiffness, permeability, and pore size properties of the 2D and 3D collagen layers were measured. The permeability of the 2D collagen film was negligible, making it suitable for mimicking the BM of large blood vessels. A leakage test at various volumetric flow rates applied to the microchannels showed no discharge, thereby verifying the reliability of the proposed integrated 2D/3D collagen parts and the contact printing method used for bonding them in the scaffold. In the future, multi-cell culturing will be performed within the 3D porous collagen and against the 2D membrane inside the microchannel, hence preparing this scaffold for studying a variety of blood vessel-tissue interfaces. Also, thicker collagen scaffold tissues will be fabricated by stacking several layers of the proposed scaffold.

The promising prospect of human hair follicle regeneration in the shadow of new tissue engineering strategies

Hair loss disorder (alopecia) affects numerous people around the world. The low effectiveness and numerous side effects of common treatments have prompted researchers to investigate alternative and effective solutions. Hair follicle (HF) bioengineering is the knowledge of using hair-inductive (trichogenic) cells. Most bioengineering-based approaches focus on regenerating folliculogenesis through manipulation of regulators of physical/molecular properties in the HF niche. Despite the high potential of cell therapy, no cell product has been produced for effective treatment in the field of hair regeneration. This problem shows the challenges in the functionality of cultured human hair cells. To achieve this goal, research and development of new and practical approaches, technologies and biomaterials are needed. Based on recent advances in the field, this review evaluates emerging HF bioengineering strategies and the future prospects for the field of tissue engineering and successful HF regeneration.

Fabrication of triple-crosslinked gelatin/alginate hydrogels for controlled release applications

Hydrogels have been demonstrated as smart drug carriers to recognize the tumor microenvironment for cancer treatment, where the dynamic crosslinks in the hydrogel network contribute to the stimuli-responsive features but also result in poor stability and weak mechanical property of the hydrogels. Here, phenylboronic acid-grafted polyethyleneimine (PBA-PEI)-modified gelatin (PPG) was synthesized to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds, and then calcium ions (Ca2+) were added to introduce the third calcium-carboxylate crosslinking in the network to form the triple-crosslinked PPG/ADA-Ca2+ hydrogels. Given the three types of dynamic bonds in the network, PPG/ADA-Ca2+ hydrogels possessed a self-healing manner, stimuli-responsiveness, and better mechanical properties compared to single- or double-crosslinked hydrogels. The controlled release capability of PPG/ADA-Ca2+ hydrogels was also demonstrated, showing the encapsulated molecules can be rapidly released from the hydrogel network in the presence of hydrogen peroxide while the release rate can be slowed down at acidic pH. Furthermore, PPG/ADA-Ca2+ hydrogels presented selected cytotoxicity and drug delivery to cancer cells due to the regulated degradation by the cellular microenvironment. Taken together, PPG/ADA-Ca2+ hydrogels have been demonstrated as promising biomaterials with multiple desirable properties and dynamic features to perform controlled molecule release for biomedical applications.

Influence of Cross-Linking Conditions on Drying Kinetics of Alginate Hydrogel

Hydrogels are three-dimensional cross-linked polymeric networks capable of a large amount of fluid retention in their structure. Hydrogel outputs manufactured using additive manufacturing technologies are exposed to water loss, which may change their original shape and dimensions. Therefore, the possibility of retaining water is important in such a structure. In this manuscript, kinetic analysis of water evaporation from sodium alginate-based hydrogels exposed to different environmental conditions such as different temperatures (7 and 23 °C) and ambient humidity (45, 50 and 95%) has been carried out. The influence of the cross-linking method (different calcium chloride concentration-0.05, 0.1 and 0.5 M) of sodium alginate and cross-linking time on the water loss was also considered. Studies have shown that a decrease in the temperature and increase in the storage humidity can have a positive effect on the water retention in the structure. The storage conditions that led to the least weight and volume loss were T 7 °C and 95% humidity. These experiments may help in selecting the appropriate hydrogel preparation method for future applications, as well as their storage conditions for minimum water loss and, consequently, the least change in dimensions and shape.

A Bioengineered Quercetin-Loaded 3D Bio-Polymeric Graft for Tissue Regeneration and Repair

Phytochemicals extracted from plant sources have potential remedial effects to cure a broad range of acute to severe illnesses and ailments. Quercetin is a flavonoid isolated from different dietary sources such as vegetables and fruits, exhibiting strong anti-inflammatory, anti-oxidative and non-toxic effects on the biological system. However, the direct uptake or administration of quercetin results in loss of functionality, poor activity, and reduced shelf-life of the bioactive component. In this regard, to improve the uptake, potential, and efficiency of natural components with prolonged storage in the host's body after administration, numerous polymer drug delivery systems have been created. In the current study, three-dimensional (3D) porous (porosity: 92%; pore size: 81 µm) bio-polymeric foaming gelatin-alginate (GA) beads were fabricated for the entrapment of quercetin as therapeutic drug molecules-gelatin-alginate-quercetin (GAQ). The GAQ beads showed a significant uptake of quercetin molecules resulting in a reduction of reduced porosity up to 64% and pore size 63 µm with a controlled release profile in the PBS medium, showing ~80% release within 24 h. Subsequently, the GAQ beads showed remarkable antioxidant effects, and 95% anti-inflammatory activities along with remarkable in vitro cell culture growth and the observed proliferation of seeded fibroblast cells. Thus, we can conclude that the consistent release of quercetin showed non-toxic effects on normal cell lines and the bioactive surface of the GAQ beads enhances cell adhesion, proliferation, and differentiation more effectively than control GA polymeric beads and tissue culture plates (TCP). In summary, these findings show that these GAQ beads act as a biocompatible 3D construct with enormous potential in medicinal administration and tissue regeneration for accelerated healing.

A Three-Dimensional Bioprinted Copolymer Scaffold with Biocompatibility and Structural Integrity for Potential Tissue Regeneration Applications

The present study was to investigate the rheological property, printability, and cell viability of alginate−gelatin composed hydrogels as a potential cell-laden bioink for three-dimensional (3D) bioprinting applications. The 2 g of sodium alginate dissolved in 50 mL of phosphate buffered saline solution was mixed with different concentrations (1% (0.5 g), 2% (1 g), 3% (1.5 g), and 4% (2 g)) of gelatin, denoted as GBH-1, GBH-2, GBH-3, and GBH-4, respectively. The properties of the investigated hydrogels were characterized by contact angle goniometer, rheometer, and bioprinter. In addition, the hydrogel with a proper concentration was adopted as a cell-laden bioink to conduct cell viability testing (before and after bioprinting) using Live/Dead assay and immunofluorescence staining with a human corneal fibroblast cell line. The analytical results indicated that the GBH-2 hydrogel exhibited the lowest loss rate of contact angle (28%) and similar rheological performance as compared with other investigated hydrogels and the control group. Printability results also showed that the average wire diameter of the GBH-2 bioink (0.84 ± 0.02 mm (*** p < 0.001)) post-printing was similar to that of the control group (0.79 ± 0.05 mm). Moreover, a cell scaffold could be fabricated from the GBH-2 bioink and retained its shape integrity for 24 h post-printing. For bioprinting evaluation, it demonstrated that the GBH-2 bioink possessed well viability (>70%) of the human corneal fibroblast cell after seven days of printing under an ideal printing parameter combination (0.4 mm of inner diameter needle, 0.8 bar of printing pressure, and 25 °C of printing temperature). Therefore, the present study suggests that the GBH-2 hydrogel could be developed as a potential cell-laden bioink to print a cell scaffold with biocompatibility and structural integrity for soft tissues such as skin, cornea, nerve, and blood vessel regeneration applications.

Wet Electrospun Nanofibers-Fortified Gelatin/Alginate-Based Nanocomposite as a Single-Dose Biomimicking Skin Substitute

We report the development and evaluation of a series of well-designed single-dose extracellular matrix (ECM)-mimicking nanofibers (NFs)-reinforced hydrogel (HG)-based skin substitute for wound healing. The HG matrix of the proposed skin substitute is composed of gelatin (GE) and sodium alginate (SA), and incorporates hyaluronic acid (HA) as a key component of the natural ECM, as well as the antimicrobial Punica granatum extract (PE). This HG nanocomposite was cross-linked by the biocompatible N-(3-(dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride (EDC) cross-linker, and was reinforced with fragmented trans-ferulic acid (FA)-loaded cellulose acetate/polycaprolactone (PCL/CA) NFs. The NFs were obtained via wet electrospinning into a poly(vinyl alcohol) (PVA) coagulating solution to closely resemble the porous structure of the ECM fibers, which facilitates cell migration, attachment, and proliferation. The proposed design of the skin substitute allows adjustable mechanical characteristics and outstanding physical properties (swelling and biodegradability), as well as an excellent porous microstructure. The developed skin substitutes were characterized using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and electron microscopy. In addition, the biodegradability, biocompatibility, bioactivity, mechanical, and in vitro drug release characteristics were investigated. Moreover, an in vivo excisional full-thickness defect model was conducted to assess skin regeneration and healing effectiveness. The average diameters of the plain and FA-loaded NFs are 210 ± 12 nm and 452 ± 25 nm, respectively. The developed ECM-mimicking skin substitutes demonstrated good antibacterial activity, free-radical scavenging activity, cytocompatibility, porosity, water absorption ability, and good biodegradability. In vivo application of the ECM-mimicking skin substitutes revealed their excellent wound-healing activity and their suitability for single-dose treatment of deep wounds with reducing the wound diameter to 0.95 mm after 15 days of treatment. Moreover, the histological investigation of the wound area demonstrated that the applied skin substitutes have not only enhanced the wound healing progress, but also can participate in improving the quality of the regenerated skin in the treated area via facilitating collagen fibers regeneration and deposition.

Microencapsulated basil oil (Ocimum basilicum Linn.) enhances growth performance, intestinal morphology, and antioxidant capacity of broiler chickens in the tropics

OBJECTIVE

Microencapsulation is a technique to improve stability, bioavailability, and controlled release of active ingredients at a target site. This experiment aimed to investigate the effects of microencapsulated basil oil (MBO) on growth performance, apparent ileal digestibility (AID), jejunal histomorphology, bacterial population as well as antioxidant capacity of broiler chickens in a tropical climate.

METHODS

A total of 288 one-day-old female broilers (Ross 308) were randomly allocated into 4 groups (6 replicates of 12 birds), based on a completely randomized design. Dietary treatments were as follows: i) basal diet (NC), ii) basal diet with avilamycin at 10 ppm (PC), iii) basal diet with free basil oil (FBO) at 500 ppm, and iv) basal diet with MBO at 500 ppm, respectively.

RESULTS

Dietary supplementation of MBO improved average daily gain, and feed conversion ratio of broilers throughout the 42-d trial period (p<0.05), whereas MBO did not affect average daily feed intake compared with NC group. The broilers fed MBO diet exhibited a greater AID of crude protein and gross energy compared with those in other groups (p<0.05). Lactobacillus spp. and Escherichia coli populations were not affected by feeding dietary treatments. Both FBO and MBO had positive effects on jejunal villus height (VH), villus height to crypt depth ratio (VH:CD) and villus surface area of broilers compared to NC and PC groups (p<0.05). Superoxide dismutase level in the duodenal mucosa of MBO group was significantly increased (p<0.01), whereas malondialdehyde level was significantly decreased (p<0.01).

CONCLUSION

Microencapsulation could be considered as a promising driver of the basil oil efficiency, consequently MBO at 500 ppm could be potentially used as a feed additive for improvement of intestinal integrity and nutrient utilization, leading to better performance of broiler chickens.

Alginate: Enhancement Strategies for Advanced Applications

Alginate is an excellent biodegradable and renewable material that is already used for a broad range of industrial applications, including advanced fields, such as biomedicine and bioengineering, due to its excellent biodegradable and biocompatible properties. This biopolymer can be produced from brown algae or a microorganism culture. This review presents the principles, chemical structures, gelation properties, chemical interactions, production, sterilization, purification, types, and alginate-based hydrogels developed so far. We present all of the advanced strategies used to remarkably enhance this biopolymer's physicochemical and biological characteristics in various forms, such as injectable gels, fibers, films, hydrogels, and scaffolds. Thus, we present here all of the material engineering enhancement approaches achieved so far in this biopolymer in terms of mechanical reinforcement, thermal and electrical performance, wettability, water sorption and diffusion, antimicrobial activity, in vivo and in vitro biological behavior, including toxicity, cell adhesion, proliferation, and differentiation, immunological response, biodegradation, porosity, and its use as scaffolds for tissue engineering applications. These improvements to overcome the drawbacks of the alginate biopolymer could exponentially increase the significant number of alginate applications that go from the paper industry to the bioprinting of organs.

Thermoresponsive semi-interpenetrating gelatin-alginate networks for encapsulation and controlled release of scent molecules

Plant-based meats, which are nutritious foods from non-animal sources, provide clues for addressing the negative externalities associated with conventional meat production. Interest in plant-based meat has increased and is driving the rapid growth of its market. Plant-based meat should be equipped with a temperature-dependent scent release system similar to the scent release mechanism of conventional meat, to deliver a desirable meat-like flavor to consumers and obtain higher market acceptance. In this study, we prepared thermoresponsive gelatin-alginate hybrid hydrogels to control the release of scent molecules. The polymer network of gelatin-alginate hydrogels was reinforced by a semi-interpenetrating network (sIPN). sIPN formation conferred resistance to external stimuli, such as shear force, swelling, and temperature, resulting in a sustained release of the meat scent. In addition, controlled size microcapsules fabricated from the same composition via an electrostatic extrusion process showed a sustained release pattern of the loaded scent at 70 °C, and the scent release rate was precisely controlled within an approximately 2-fold range by adjusting the alginate concentration. These observations suggest the potential use of edible biological macromolecules as food additives that can control the release of scent molecules from the plant-based meat during cooking.

Equilibrium, Thermodynamic, Reuse, and Selectivity Studies for the Bioadsorption of Lanthanum onto Sericin/Alginate/Poly(vinyl alcohol) Particles

In a scenario of high demand, low availability, and high economic value, the recovery of rare-earth metals from wastewater is economically and environmentally attractive. Bioadsorption is a promising method as it offers simple design and operation. The aim of this study was to investigate lanthanum bioadsorption using a polymeric bioadsorbent of sericin/alginate/poly(vinyl alcohol)-based biocomposite. Batch system assays were performed to evaluate the equilibrium, thermodynamics, regeneration, and selectivity of bioadsorption. The maximum capture amount of lanthanum at equilibrium was 0.644 mmol/g at 328 K. The experimental equilibrium data were better fitted by Langmuir and Dubinin-Radushkevich isotherms. Ion exchange mechanism between calcium and lanthanum (2:3 ratio) was confirmed by bioadsorption isotherms. Thermodynamic quantities showed that the process of lanthanum bioadsorption was spontaneous (-17.586, -19.244, and -20.902 kJ/mol), endothermic (+15.372 kJ/mol), and governed by entropic changes (+110.543 J/mol·K). The reusability of particles was achieved using 0.1 mol/L HNO₃/Ca(NO₃)₂ solution for up to five regeneration cycles. The bioadsorbent selectivity followed the order of lanthanum > cadmium > zinc > nickel. Additionally, characterization of the biocomposite prior to and post lanthanum bioadsorption showed low porosity (9.95 and 12.35%), low specific surface area (0.054 and 0.019 m²/g), amorphous character, and thermal stability at temperatures up to 473 K. This study shows that sericin/ alginate/poly(vinyl alcohol)-based biocomposites are effective in the removal and recovery of lanthanum from water.

Lyophilized Emulsions in the Form of 3D Porous Matrices as a Novel Material for Topical Application

Researchers are constantly searching for innovations that can be applied to the cosmetic industry. Production of porous materials stored in a lyophilized form and swollen directly before use may be beneficial considering their facilitated packaging, transport and storage. In this study, we propose porous materials based on sodium alginate, gelatin, glycerol and lipids (cottonseed oil and beeswax) obtained by freeze-drying and cross-linking. Material composition with the most promising properties was modified by the addition of PLA microparticles with Calendula officinalis flower extract. The structure and properties of obtained porous materials were analyzed. ATR-FTIR, mechanical properties, residual moisture content, porosity and density were assessed, as well as swelling properties and degradation after their cross-linking. The loading capacity and in vitro release of Calendula officinalis flower extract were performed for samples with incorporated PLA microparticles containing plant extract. The modification of the composition and fabrication method of materials significantly influenced their physicochemical properties. The selected plant extract was successfully incorporated into polymeric microparticles that were subsequently added into developed materials. Prepared materials may be considered during designing new cosmetic formulations.

A Review on the Adaption of Alginate-Gelatin Hydrogels for 3D Cultures and Bioprinting

Sustaining the vital functions of cells outside the organism requires strictly defined parameters. In order to ensure their optimal growth and development, it is necessary to provide a range of nutrients and regulators. Hydrogels are excellent materials for 3D in vitro cell cultures. Their ability to retain large amounts of liquid, as well as their biocompatibility, soft structures, and mechanical properties similar to these of living tissues, provide appropriate microenvironments that mimic extracellular matrix functions. The wide range of natural and synthetic polymeric materials, as well as the simplicity of their physico-chemical modification, allow the mechanical properties to be adjusted for different requirements. Sodium alginate-based hydrogel is a frequently used material for cell culture. The lack of cell-interactive properties makes this polysaccharide the most often applied in combination with other materials, including gelatin. The combination of both materials increases their biological activity and improves their material properties, making this combination a frequently used material in 3D printing technology. The use of hydrogels as inks in 3D printing allows the accurate manufacturing of scaffolds with complex shapes and geometries. The aim of this paper is to provide an overview of the materials used for 3D cell cultures, which are mainly alginate-gelatin hydrogels, including their properties and potential applications.

A bioprinted composite hydrogel with controlled shear stress on cells

In recent decades, three dimensional (3D) bio-printing technology has found widespread use in tissue engineering applications. The aim of this study is to scrutinize different parameters of the bioprinter - with the help of simulation software - to print a hydrogel so much so that avoid high amounts of shear stress which is detrimental for cell viability and cell proliferation. Rheology analysis was done on several hydrogels composed of different percentages of components: alginate, collagen, and gelatin. The results have led to the combination of percentages collagen:alginate:gelatin (1:4:8)% as the best condition which makes sol-gel transition at room temperature possible. The results have shown the highest diffusion rate and cell viability for the cross-linked sample with 1.5% CaCl₂ for the duration of 1 h. Finally, we have succeeded in printing the hydrogel that is mechanically strong with suitable degradation rate and cell viability.

Nanoscale microenvironment engineering based on layer-by-layer self-assembly to regulate hair follicle stem cell fate for regenerative medicine

Hair regenerative medicine, a promising strategy for the treatment of hair loss, will likely involve the transplantation of autologous hair follicular stem cells (HFSCs) and dermal papilla cells (DPCs) into regions of hair loss. Cyclic hair regeneration results from the periodic partial activation of HFSCs. However, previous studies have not successfully achieved large-scale HFSC expansion in vitro without the use of feeder cells, with a lack of research focused on regulating HFSC fate for hair follicular (HF) regeneration. Hence, an emerging focus in regenerative medicine is the reconstruction of natural extracellular matrix (ECM) regulatory characteristics using biomaterials to generate cellular microenvironments for expanding stem cells and directing their fate for tissue regeneration.

Methods: HFSCs were coated with gelatin and alginate using layer-by-layer (LbL) self-assembly technology to construct biomimetic ECM for HFSCs; after which transforming growth factor (TGF)-β2 was loaded into the coating layer, which served as a sustained-release signal molecule to regulate the fate of HFSCs both in vitro and in vivo. In vitro experiments (cell culture and siRNA) were employed to investigate the molecular mechanisms involved and in vivo implantation was carried out to evaluate hair induction efficiency.

Results: Nanoscale biomimetic ECM was constructed for individual HFSCs, which allowed for the stable amplification of HFSCs and maintenance of their stem cell properties. TGF-β2 loading into the coating layer induced transformation of CD34⁺ stem cells into highly proliferating Lgr5⁺ stem cells, similar to the partial activation of HFSCs in HF regeneration. Thus, LbL coating and TGF-β2 loading partially reconstructed the quiescent and activated states, respectively, of stem cells during HF regeneration, thereby mimicking the microenvironment that regulates stem cell fate for tissue regeneration during HF cycling. Improved HF regeneration was achieved when the two HFSC states were co-transplanted with neonatal mouse dermal cells into nude mice.

Conclusion: This study provides novel methods for the construction of stem cell microenvironments and experimental models of HF regeneration for the treatment of hair loss.

Stiffness-mediated mesenchymal stem cell fate decision in 3D-bioprinted hydrogels

Background

Hydrogels with tuneable mechanical properties are an attractive material platform for 3D bioprinting. Thus far, numerous studies have confirmed that the biophysical cues of hydrogels, such as stiffness, are known to have a profound impact on mesenchymal stem cell (MSC) differentiation; however, their differentiation potential within 3D-bioprinted hydrogels is not completely understood. Here, we propose a protocol for the exploration of how the stiffness of alginate-gelatin (Alg-Gel) composite hydrogels (the widely used bioink) affects the differentiation of MSCs in the presence or absence of differentiation inducing factors.

Methods

Two types of Alg-Gel composite hydrogels (Young's modulus: 50 kPa vs. 225 kPa) were bioprinted independently of porosity. Then, stiffness-induced biases towards adipogenic and osteogenic differentiation of the embedded MSCs were analysed by co-staining with alkaline phosphatase (ALP) and oil red O. The expression of specific markers at the gene level was detected after a 3-day culture.

Results

Confocal microscopy indicated that all tested hydrogels supported MSC growth and viability during the culture period. Higher expression of adipogenic and osteogenic markers (ALP and lipoprotein lipase (LPL)) in stiffer 3D-bioprinted matrices demonstrated a more significant response of MSCs to stiffer hydrogels with respect to differentiation, which was more robust in differentiation-inducing medium. However, the LPL expression in stiffer 3D-bioprinted constructs was reduced at day 3 regardless of the presence of differentiation-inducing factors. Although MSCs embedded in softer hydrogels to some extent proceeded toward adipogenic and osteogenic lineages within a few days, their differentiation seemed to be slower and more limited. Interestingly, the hydrogel itself (without differentiation-inducing factors) exhibited a slight effect on whether MSCs differentiated towards an adipogenic or an osteogenic fate. Considering that the mechano-regulated protein Yes-associated protein (YAP) is involved in MSC fate decisions, we further found that inhibition of YAP significantly downregulated the expression of ALP and LPL in MSCs in stiffer constructs regardless of the induced growth factors present.

Conclusions

These results demonstrate that the differentiation of MSCs in 3D-bioprinted matrices is dependent on hydrogel stiffness, which emphasizes the importance of biophysical cues as a determinant of cellular behaviour.

Freeze-gelled alginate/gelatin scaffolds for wound healing applications: An in vitro, in vivo study

In this study, fabrication of a three-dimensional porous scaffold was performed using freeze gelation method. Recently, fabrication of scaffolds using polymer blends has become common for many tissue engineering applications due to their unique tunable properties. In this work, we fabricated alginate-gelatin porous hydrogels for wound healing application using a new method based on some modifications to the freeze-gelation method. Alginate and gelatin were mixed in three different ratios and the resulting solutions underwent freeze gelation to obtain 3D porous matrices. We analyzed the samples using different characterization tests. The scanning electron microscopy (SEM) results indicated that the freeze gelation method was successful in obtaining porous morphologies for all the fabricated alginate-gelatin samples as previously was seen in single-polymer fabrication using this method. The alginate to gelatin ratio affected swelling, biodegradation, cell culture and mechanical properties of the matrices. The scaffold with the lowest content of gelatin had the highest swelling ratio while biodegradation and cell proliferation and viability were increased with the gelatin content. Regarding the mechanical properties, as the gelatin content increased, the scaffold became more ductile and showed higher tensile strength. The in-vivo results also showed the biocompatibility of the blend scaffold and its positive role in wound healing process in rats. The low-cost procedure used in this study to fabricate the porous alginate-gelatin scaffolds can be adapted and modified to suit different tissue engineering applications.

Bioplatform Fabrication Approaches Affecting Chitosan-Based Interpolymer Complex Properties and Performance as Wound Dressings

Chitosan can form interpolymer complexes (IPCs) with anionic polymers to form biomedical platforms (BMPs) for wound dressing/healing applications. This has resulted in its application in various BMPs such as gauze, nano/microparticles, hydrogels, scaffolds, and films. Notably, wound healing has been highlighted as a noteworthy application due to the remarkable physical, chemical, and mechanical properties enabled though the interaction of these polyelectrolytes. The interaction of chitosan and anionic polymers can improve the properties and performance of BMPs. To this end, the approaches employed in fabricating wound dressings was evaluated for their effect on the property-performance factors contributing to BMP suitability in wound dressing. The use of chitosan in wound dressing applications has had much attention due to its compatible biological properties. Recent advancement includes the control of the degree of crosslinking and incorporation of bioactives in an attempt to enhance the physicochemical and physicomechanical properties of wound dressing BMPs. A critical issue with polyelectrolyte-based BMPs is that their effective translation to wound dressing platforms has yet to be realised due to the unmet challenges faced when mimicking the complex and dynamic wound environment. Novel BMPs stemming from the IPCs of chitosan are discussed in this review to offer new insight into the tailoring of physical, chemical, and mechanical properties via fabrication approaches to develop effective wound dressing candidates. These BMPs may pave the way to new therapeutic developments for improved patient outcomes.

Bioactive, degradable and multi-functional three-dimensional membranous scaffolds of bioglass and alginate composites for tissue regenerative applications

Multifunctional bioactive hydrogel ECM like membrane for 3D dynamic tissue/disease modelling.

Cell Bioprinting: The 3D-Bioplotter™ Case

The classic cell culture involves the use of support in two dimensions, such as a well plate or a Petri dish, that allows the culture of different types of cells. However, this technique does not mimic the natural microenvironment where the cells are exposed to. To solve that, three-dimensional bioprinting techniques were implemented, which involves the use of biopolymers and/or synthetic materials and cells. Because of a lack of information between data sources, the objective of this review paper is, to sum up, all the available information on the topic of bioprinting and to help researchers with the problematics with 3D bioprinters, such as the 3D-Bioplotter™. The 3D-Bioplotter™ has been used in the pre-clinical field since 2000 and could allow the printing of more than one material at the same time, and therefore to increase the complexity of the 3D structure manufactured. It is also very precise with maximum flexibility and a user-friendly and stable software that allows the optimization of the bioprinting process on the technological point of view. Different applications have resulted from the research on this field, mainly focused on regenerative medicine, but the lack of information and/or the possible misunderstandings between papers makes the reproducibility of the tests difficult. Nowadays, the 3D Bioprinting is evolving into another technology called 4D Bioprinting, which promises to be the next step in the bioprinting field and might promote great applications in the future.

Biomimetic Materials and Fabrication Approaches for Bone Tissue Engineering

Various strategies have been explored to overcome critically sized bone defects via bone tissue engineering approaches that incorporate biomimetic scaffolds. Biomimetic scaffolds may provide a novel platform for phenotypically stable tissue formation and stem cell differentiation. In recent years, osteoinductive and inorganic biomimetic scaffold materials have been optimized to offer an osteo-friendly microenvironment for the osteogenic commitment of stem cells. Furthermore, scaffold structures with a microarchitecture design similar to native bone tissue are necessary for successful bone tissue regeneration. For this reason, various methods for fabricating 3D porous structures have been developed. Innovative techniques, such as 3D printing methods, are currently being utilized for optimal host stem cell infiltration, vascularization, nutrient transfer, and stem cell differentiation. In this progress report, biomimetic materials and fabrication approaches that are currently being utilized for biomimetic scaffold design are reviewed.

Research on the printability of hydrogels in 3D bioprinting

As the biocompatible materials, hydrogels have been widely used in three- dimensional (3D) bioprinting/organ printing to load cell for tissue engineering. It is important to precisely control hydrogels deposition during printing the mimic organ structures. However, the printability of hydrogels about printing parameters is seldom addressed. In this paper, we systemically investigated the printability of hydrogels from printing lines (one dimensional, 1D structures) to printing lattices/films (two dimensional, 2D structures) and printing 3D structures with a special attention to the accurate printing. After a series of experiments, we discovered the relationships between the important factors such as air pressure, feedrate, or even printing distance and the printing quality of the expected structures. Dumbbell shape was observed in the lattice structures printing due to the hydrogel diffuses at the intersection. Collapses and fusion of adjacent layer would result in the error accumulation at Z direction which was an important fact that could cause printing failure. Finally, we successfully demonstrated a 3D printing hydrogel scaffold through harmonize with all the parameters. The cell viability after printing was compared with the casting and the results showed that our bioprinting method almost had no extra damage to the cells.

Protein adsorption through Chitosan-Alginate membranes for potential applications

Background

Chitosan and Alginate were used as biopolymers to prepare membranes for protein adsorption. The network requires a cross-linker able to form bridges between polymeric chains. Viscopearl-mini^® (VM) was used as a support to synthesize them. Six different types of membranes were prepared using the main compounds of the matrix: VM, Chitosan of low and medium molecular weight, and Alginate.

Results

Experiments were carried out to analyze the interactions within the matrix and improvements were found against porous cellulose beads. SEM characterization showed dispersion in the compounds. According to TGA, thermal behaviour remains similar for all compounds. Mechanical tests demonstrate the modulus of the composites increases for all samples, with major impact on materials containing VM. The adsorption capacity results showed that with the removal of globular protein, as the adsorbed amount increased, the adsorption percentage of Myoglobin from Horse Heart (MHH) decreased. Molecular electrostatic potential studies of Chitosan–Alginate have been performed by density functional theory (DFT) and ONIOM calculations (Our own N-layered integrated molecular orbital and molecular mechanics) which model large molecules by defining two or three layers within the structure that are treated at different levels of accuracy, at B3LYP/6-31G(d) and PM6/6-31G(d) level of theory, using PCM (polarizable continuum model) solvation model.

Conclusions

Finally, Viscopearl-mini^® acts as a suitable support on the matrix for the synthesis of Chitosan–Alginate membranes instead of cross-linkers usage. Therefore, it suggests that it is a promise material for potential applications, such as: biomedical, wastewater treatment, among others.Graphical abstract

Bio-based nickel alginate and copper alginate films with excellent flame retardancy: preparation, flammability and thermal degradation behavior

A bio-based nickel alginate film and copper alginate film were prepared via a facile ion exchange and casting approach. The addition of nickel ions obviously improved the flame retardancy of alginate.