3D bioprinting of self-strengthening living materials using cellulose nanofiber-producing bacteria in sodium alginate hydrogel

A rapid prototyping technology, formed by three-dimensional (3-D) printing and then crosslinked by spraying Ca2+ solution, is developed to fabricate a sodium alginate (SA) hydrogel scaffold. The porosity, swelling ratio, and compression modulus of the scaffold are investigated. A friction mechanism is developed by studying the reproducible friction behavior. Our results show that the scaffold can have 3-D structure with a porosity of 52%. The degree of swelling of the SA hydrogel scaffold is 8.5, which is nearly the same as bulk SA hydrogel. SA hydrogel exhibits better compressive resilience than bulk hydrogel despite its lower compressive modulus compared to bulk hydrogel. The SA hydrogel scaffold exhibits a higher frictional force at low sliding velocity (10−6 to 10−3 m/s) compared to bulk SA hydrogel, and they are equal at high sliding velocity (10−2 to 1 m/s). For a small pressure (0.3 kPa), the SA hydrogel scaffold shows good friction reproducibility. In contrast, bulk SA hydrogel shows poor reproducibility with respect to friction behavior. The differences in friction behaviors between the SA hydrogel scaffold and bulk SA hydrogel are related to the structure of the scaffold, which can keep a stable hydrated lubrication layer.

Optimization of 3D bioprinting of human neuroblastoma cells using sodium alginate hydrogel

A controlled-release inerting inhibitor (CRII) was prepared by embedding the little inhibiting balls (LIB) into the sodium alginate (SA) hydrogel. The water retention and flowability of the SA hydrogel were studied, and the controlled-release effect of the CRII was analyzed by CO2 production rate and scanning electron microscopy. At last, the inhibiting performance and the long-lasting effect of the CRII were investigated. The experimental results show that the 1.5 wt% SA hydrogel has the best water retention and good flowability. Meanwhile, the SA hydrogel also has a great effect on CO2 retention. During the heating process, 88.86% of CO2 produced by the LIB escaped into the air, while only 42.57% of the CRII did. As the temperature gradually increases, a large number of micropores are formed on the surface of LIB, which achieves the controlled-release of inhibitory components. In comparison to the raw coal, the temperature at which CO enters the exponential growth is delayed by 18.8°C for the CRII-treated coal sample, and the release of CO is reduced by 86.3% at 127.8°C. Comparing the CRII-treated coal samples placed for 1 and 8 days, the average inhibition rate of the latter decreased by 0%, −1.81%, 0.56% and 2.59% in four stages (45 ~ 75°C, 75 ~ 100°C, 100 ~ 160°C and 160 ~ 180°C), respectively. The average inhibition rate of the coal samples treated by CRII did not decrease basically before 160°C, while the coal samples treated by NaCl aqueous solution under the same conditions showed a significant decrease in the early stage. In future studies, it is a worthwhile focus that how to optimize the ratio of each component in the LIB and further study the controlled-release performance.

Preoperative marking or tattooing is a clinical procedure conducted during laparoscopic surgeries in which gastrointestinal lesions are identified by injecting India ink. However, diffusion of the carbon particles from the ink leads to its spreading in the surrounding tissues, resulting in unnecessarily extensive tissue resectioning. In this study, we determined whether this diffusion could be prevented using a sodium alginate (Alg-Na) hydrogel. We observed that the use of a 1.75% Alg-Na solution could significantly prevent the diffusion of carbon particles into the tissues of mice after subcutaneously injecting them with India ink. Similar results were observed in resected porcine large intestines. A good correlation between the concentration of Alg-Na and tattooed area was observed, in which an increase in its concentration led to an increase in its viscosity and injection pressure. To examine the effect of the molecular weight of Alg-Na on the tattooing area, a solution of 2% Alg-Na was irradiated with an electron beam at varying electron doses. Since irradiation could reduce the molecular weight, viscosity, and injection pressure of Alg-Na, a good correlation between these parameters and the tattooed area was observed. We concluded that an adequately viscous Alg-Na hydrogel could be used for clear preoperative marking. Preoperative marking or tattooing is performed in clinical situations using an India ink to identify gastrointestinal lesions. However, diffusion of the carbon particles from the ink results in unclear marking. We observed that subcutaneously injected sodium alginate solutions formed a gel and prevented the diffusion of carbon particles into the tissues of mice. Similar results were observed in resected porcine large intestines. The tattooed area was well correlated with the molecular weight and viscosity of sodium alginate, indicating that an adequately viscous sodium alginate hydrogel is useful for clear marking.

In order to obtain biocompatible carriers with mechanical properties close to living tissues, 3D-printing was carried out on a modified 3D-printer created on the basis of the Wanhao Duplicator 4S (China) by installing a special extrusion head - a syringe extruder for the possibility of printing sodium alginate and chitosan hydrogels. The optimal compositions of hydrogels for 3D-printing using “supporting” hydrogels based on agar or gelatin, which allow forming print objects, have been determined. Stable structures were obtained in the form of a Menger cube with a satisfactory shape and size. Optimal speeds of movement of the extruder-syringe for 3D-printing with sodium alginate hydrogel into agar “supporting” gel – 9–11 mm/s, for sodium alginate into gelatinous “supporting” gel – 2 mm/s, for chitosan into “supporting” gel with the addition of (NH4)2HPO4 – 6–8 mm/s.Keywords3D-printingHydrogelChitosanSodium alginate

A uniform-unsaturated crosslinking strategy to construct injectable alginate hydrogel

Nitric oxide releasing polyvinyl alcohol and sodium alginate hydrogels as antibacterial and conductive strain sensors

Sodium alginate fasten cellulose nanocrystal Ag@AgCl ternary nanocomposites for the synthesis of antibacterial hydrogels

Postoperative wound repair of solid tumors resection, which is afflicted by the complex tumor microenvironment (TME) and associated with the bacterial infection, is worsening and demands prompt solutions. Meanwhile, the tumor recurrence is frequently seen during the subsequent treatment due to intraoperative bleeding. For effective postoperative cancer therapy, nanoscale carriers occur as innovative and sensitive tools for monitoring the wound state, avoiding bacterial infection, and restraining tumor recurrence. Herein, a multifunctional sodium alginate (SA) hydrogel immobilizing hemoglobin (Hb) and pH-sensitive fluorescent changing carbon quantum dots (CQDs) is rationally designed. The multifunctionalization of obtained alginate@hemoglobin@CQDs hydrogel (SA@Hb@CQDs) simultaneously consists of detection, hemostasis, and chemodynamic therapy (CDT) with monitoring of wound pH based on CQDs, stanching triggered from SA hydrogel, and Fenton reaction induced by Hb. We demonstrated that SA@Hb@CQDs can stop bleeding quickly, collect wound status information in real-time, and avert bacterial infection as well as inhibit local tumor recurrence effectively. Therefore, our work provides a promising combination approach for postoperative tumor therapy.

The fabrication of scaffolds for bone tissue engineering (BTE) applications often involves the utilization of two distinct categories of biomaterials, namely calcium phosphates and calcium silicates. The selection of these materials is based on their biocompatibility, bioactivity, and mechanical characteristics that closely resemble those of natural bone. The present research examined the utilization of hydroxyapatite (HAP) and tri-calcium silicate (TCS), which are among the most commonly utilized materials in calcium phosphates and calcium silicates, in the context of bone scaffolding applications. A molecular dynamics simulation was conducted to investigate the impact of different concentrations of ceramic nanoparticles, when combined with sodium alginate (SA) hydrogel, on the fabrication of bone scaffolds.The stability and self-assembly were assessed through several parameters, such as the solvent-accessible surface area (SASA), radius of gyration (Rg), radial distribution function (g(r)), root-mean-square deviation (RMSD), root-mean-square fluctuation (RMSF), hydrogen bonding, van der Waals, electrostatic, and total energies. The findings indicate that the addition of 10 wt% HAP and TCS to the SA hydrogel matrix results in a more compact, stable, and potentially less hydrated structure. Accordingly, the experimental validation of these simulation approved our in silico findings. Experimental rheology and mechanical properties evaluation validate our simulation results, indicating a superior characteristic of TCS10 and HAP10 inks and 3D-printed scaffolds among other composition ratios. This could potentially benefit the in vitro and in vivo performance of the scaffold and its interaction with cells. The aforementioned traits are considered fundamental for the successful execution of the scaffold in the field of BTE. The findings indicate that TCS samples exhibit superior properties when compared to HAP samples, specifically in terms of composition with SA hydrogel.

BackgroundMyocardial fibrosis is a pathological hallmark of heart failure post infarction, emphasizing the need for innovative treatment strategies. This research assesses the antifibrotic potential of a sodium alginate (SA) hydrogel loaded with extracellular vesicles (EVs) from bone marrow mesenchymal stem cells and PAP (p38α antagonistic peptides), aiming to interfere with fibrosis‐inducing pathways in myocardial tissue after infarction.MethodsWe induced fibrosis in mouse cardiac fibroblasts through hypoxia and disrupted the Mapk14 gene to study its contribution to fibrosis. Mesenchymal stem cell‐derived EVs, loaded with PAP, were encapsulated in the SA hydrogel (EVs‐PAP@SA). The formulation was tested in vitro for its effect on fibrotic marker expression and cell behavior, and in vivo in a murine model of myocardial infarction for its therapeutic efficacy.ResultsMap k14 silencing showed a decrease in the fibrotic response of cardiac fibroblasts. Treatment with the EVs‐PAP@SA hydrogel notably reduced profibrotic signaling, increased cell proliferation and migration, and lowered apoptosis rates. The in vivo treatment with the hydrogel post myocardial infarction significantly diminished myocardial fibrosis and improved cardiac performance.ConclusionsThe study endorses the SA hydrogel as an effective vehicle for delivering mesenchymal stem cell‐derived EVs and PAP to the heart post myocardial infarction, providing a novel approach for modulating myocardial fibrosis and promoting cardiac healing.

Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges in wastewater treatment. For traditional photocatalytic materials, there are always some limitations. For example, their photocatalytic performance is limited due to their high band gap (UV range) and recombination time of photogenerated electron-hole pairs [1]. Additionally, photocatalytic materials face the challenges of secondary pollution to the environment and poor recycling performance. Hydrogel photocatalysts has been of high removal efficiency of water pollutants due to its adsorption capacities and good environmental compatibility. Hydrogels are macromolecular hydrophilic polymetric gels with cross-linked 3D structures that can easily entrap water molecules in their pores or interstitial spaces to swell up while remaining insoluble. Hydrogels exhibit high structural flexibility, chemical stability, elasticity and permeability, enhancing their water absorption capability. In this review, we will mainly focus on the photocatalytic degradation properties of sodium alginate (SA) hydrogel and explore its further application in wastewater treatment (dye degradation). Also, we compare the metal-ion-doped graphene hydrogel (MGH) with SA hydrogel in efficiency, conditions control and further prospects etc.

Introduction: Polymethyl methacrylate (PMMA) is a polymer known for properties such as aesthetic quality, ease of processing and a wide range of applications in dentistry. PMMA has drawbacks, including its odour and taste, poor thermal conductivity and potential allergenic properties. Sodium alginate (SA) hydrogels are also polymers, recognised for their gel-forming ability, biodegradability, controlled release, adjustable mechanical properties and antimicrobial characteristics. Both PMMA and hydrogels are polymers, and when combined, they can create a composite dental material that can significantly enhance the development of dental practice materials. The aim of the study is to analyse whether hydrogel can be incorporated into a PMMA matrix. Materials and Methods: An in vitro study was conducted using 36 samples made by combining conventionally used PMMA with food-graded SA at different concentrations. Sample discs were prepared and checked for their chemical composition and surface morphology using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), and the results were evaluated. Results: PMMA with SA hydrogel showed distinct stretches of organic chemical bonding in FTIR graphs. SEM-EDS showed magnified images of samples, showing their physical morphology. Conclusion: PMMA and SA hydrogel can be combined in a ratio of 1:2 (polymer: SA hydrogel). The SA hydrogel particles are dispersed in the PMMA matrix.

The grafting of chitosan (CH) and sodium alginate (SA) biopolymers with glycidyl methacrylate (GMA) and acrylamide (AAm) monomers, combined with graphene oxide (GO), led to the formation of bio-based hydrogels. These hydrogels, named CH -GO -hydrogel (GO/CH-g-poly (AAm-co-GMA)), CH -GO -hydrogel (CH-g-poly (AAm-co-GMA)), SA -GO -hydrogel (GO/SA-g-poly(AAm-co-GMA)), and SA -hydrogel (SA-g-poly(AAm-co-GMA)), were tested as selective dye adsorbents. While the chitosan-based hydrogels exhibited positive zeta potential values ranging from +27.5 to +0.1 mV, alginate-based samples had negative values between −10.4 to −41.7 mV in pH conditions from 3.0 to 9.0. Adding GO nano-fillers reduced the swelling capacity of both hydrogels, with water absorption (WA) values for SA -GO -hydrogel and SA -hydrogel recorded at 10.1 and 22.2 g/g, respectively. The ability of these materials to adsorb dyes, specifically crystal violet (cationic) and Congo red (anionic), was confirmed. Factors such as adsorbent dosage, initial pH, dye concentration, shaking time, and temperature were analyzed to determine dye adsorption capacity. Interestingly, the pristine hydrogels, free of GO, performed better than their nanocomposite counterparts. Adsorption capacities (qm) for crystal violet and Congo red with SA -hydrogel, SA -GO -hydrogel, CH -hydrogel, and CH -GO -hydrogel was 909.1, 714.3, 454.5, and 400.0 mg/g, respectively.

Background: Poor tendon-to-bone healing in chronic rotator cuff tears (RCTs) is related to unsatisfactory outcomes. Exosomes derived from mesenchymal stem cells reportedly enhance rotator cuff healing. However, the difficulty in producing exosomes with a stronger effect on enthesis regeneration must be resolved. Purpose: To study the effect of exosomes derived from kartogenin (KGN)-preconditioned human bone marrow mesenchymal stem cells (KGN-Exos) on tendon-to-bone healing in a rat model of chronic RCT. Study Design: Controlled laboratory study. Methods: Exosome-loaded sodium alginate hydrogel (SAH) was prepared. Moreover, exosomes were labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide (DiR) or 1,1′-dioctadecyl-3,3,3′3′-tetramethylindocarbocyanine perchlorate (Dil) for in vivo tracking. Bilateral rotator cuff repair (RCR) was conducted in an established chronic RCT rat model. A total of 66 rats were randomized to control, untreated exosome (un-Exos), and KGN-Exos groups to receive local injections of pure SAH, un-Exos, or KGN-Exos SAH at the repaired site. The presence of DiR/Dil-labeled exosomes was assessed at 1 day and 1 week, and tendon-to-bone healing was evaluated histologically, immunohistochemically, and biomechanically at 4 and 8 weeks. Results: Both un-Exos and KGN-Exos exhibited sustained release from SAH for up to 96 hours. In vivo study revealed that un-Exos and KGN-Exos were localized to the repaired site at 1 week. Moreover, the KGN-Exos group showed a higher histological score and increased glycosaminoglycan and collagen II expression at 4 and 8 weeks. In addition, more mature and better-organized collagen fibers with higher ratios of collagen I to collagen III were observed at 8 weeks in the tendon-to-bone interface compared with those in the control and un-Exos groups. Biomechanically, the KGN-Exos group had the highest failure load (28.12 ± 2.40 N) and stiffness (28.57 ± 2.49 N/mm) among the 3 groups at 8 weeks. Conclusion: Local injection of SAH with sustained KGN-Exos release could effectively promote cartilage formation as well as collagen maturation and organization for enthesis regeneration, contributing to enhanced biomechanical properties after RCR. Clinical Relevance: KGN-Exos injection may be used as a cell-free therapeutic option to accelerate tendon-to-bone healing in chronic RCT.