Shear-thinning Properties Research Articles

Rheology and printability of biopolymeric oil-in-water high internal phase Pickering emulsions: a review.

Biopolymeric oil-in-water (O/W) high internal phase Pickering emulsions (HIPPEs) due to their unique rheological behaviors of HIPPEs such as shear-thinning property, viscoelasticity, and thixotropic recovery have emerged as highly promising printing inks in the 3D printing process. O/W biopolymer-based HIPPEs are categorized as complex fluids, where rheological parameters are crucial for optimizing printability. However, existing reviews have not fully elucidated the interrelationship between rheology and printability for HIPPEs in enhancing the quality and performance of printed parts. This review delved into the influence factors of the continuous phase (e.g., biopolymer type, concentration, pH, and ionic strength) and the oil phase (e.g., oil type, volume fraction, and encapsulated components) on their rheology, to adjust their rheological behaviors in order to prepare more eligible HIPPEs as printing inks. Moreover, a spectrum of rheology-printability relationships, derived from empirical trends and rigorous analytical models, is examined to provide generalized rheological guidelines for achieving successful printability in O/W biopolymer-based HIPPEs. Furthermore, unique challenges and future perspectives on preparing their complex rheological behaviors suitable for additive manufacturing in O/W biopolymer-based HIPPEs were presented. Leveraging these insights significantly reduces reliance on trial-and-error methods in printing, thereby fostering the robust development of novel O/W biopolymer-based HIPPEs and enhancing the overall quality of printed products.

Development and Characterization of Niaprazine-Loaded Xanthan Gum-Based Gel for Oral Administration

Niaprazine is a sedative-hypnotic drug initially developed as an antihistamine and used for its notable sedative effects, particularly in children. Following its withdrawal from the market by the producer, the drug has been administered as magistral formulations available in syrup form, but there are several important disadvantages to this, including instability, taste issues, lack of controlled release, and the potential for unreliable dosing due to incomplete swallowing. There is also an increased risk of dental caries, as well as the fact that these formulations are not suitable for children who suffer from diabetes. The purpose of the current investigation is to prepare and characterize xanthan gum-based gels for the oral administration of niaprazine. Niaprazine gels appear as transparent-whiteish, non-sticky substances, with the drug uniformly dispersed throughout the systems. They are also stable over time. Dynamic rheology revealed their advantageous shear-thinning properties, which enable the formulation to be flexibly dosed orally through administration via syringe. During experimentation, the evaluation of the mucoadhesion features and the in vitro drug release profile were also performed. The results demonstrate that the formulation may represent an alternative to niaprazine syrup, allowing easy preparation, administration, and increased compliance in various categories of patients, including pediatric.

Development and optimization of raloxifene hydrochloride loaded lipid nanocapsule based hydrogel for transdermal delivery.

Development and optimization of raloxifene hydrochloride loaded lipid nanocapsule hydrogel for transdermal delivery. A 33 Box-Behnken Design and numerical optimization was performed to obtain the optimized formulation. Subsequently, the optimized raloxifene hydrochloride loaded lipid nanocapsule was developed using phase inversion temperature and characterized for physicochemical properties. Furthermore, the optimized lipid nanocapsule was loaded into a hydrogel and evaluated for rheology, spreadability, ex-vivo skin permeation, deposition and irritation. The numerical optimization suggested an optimal formula with desirability value of 0.852 and low prediction errors. The optimized formulation showed good % drug entrapment efficiency (79.56 ± 2.34%), nanometer size (56.68 ± 1.2 nm), monodisperse nature (PDI = 0.176 ± 0.2), spherical morphology and good drug-excipient compatibility. The raloxifene hydrochloride loaded lipid nanocapsule hydrogel showed shear thinning properties, sustained drug delivery, dermal compatibility and significantly higher permeability (2-fold), retention (3.37) for raloxifene hydrochloride compared to the control. The present study showed a successful development of raloxifene hydrochloride loaded lipid nanocapsule hydrogel with improved skin permeation, retention, and good topical compatibility. This formulation may overcome the challenges associated with raloxifene hydrochloride oral delivery including low bioavailability.

12-Hydroxy-Lauric Acid Tethered Self-Assembled Heterochiral Diphenylalanine-Based Mechanoresponsive and Proteolytically Stable Hydrogel: A Dual Player for Handling Cancer and Bacterial Challenges.

Deciphering the most promising strategy for the evolution of cancer patient management remains a multifaceted, challenging affair to date. Additionally, such approaches often lead to microbial infections as side effects, probably due to the compromised immunity of the patients undergoing such treatment. Distinctly, this work delineates a rational combinatorial strategy harnessing stereogenic harmony in the diphenylalanine fragment, tethering it to an amphiphile 12-hydroxy-lauric acid at the N-terminus (compounds I-III) such that a potential therapeutic could be extracted out from the series. Aligned to the goal, the cytotoxic properties and cell viability of the compounds were investigated using two distinct cell lines: MCF-7 (human breast cancer cell) and HEK 293 (human embryonic kidney). Our rigorous investigations revealed that compounds I-III exhibited substantial cytotoxic impact on the MCF7 cell line. But from a pool of three constructs, compound III (12-hydroxy-lauric acid -d-Phe-l-Phe-OH) showed better selectivity toward cancerous MCF7 over normal HEK 293 in comparison to others, backed by computational calculations. Henceforth, it was fished out from the series and used for its elaborate anticancer activities using cell reactive oxygen species generation, DNA fragmentation, and caspase-dependent gene expression employing extrinsic and intrinsic apoptotic factors as well as inflammatory biomarkers, namely, TNF-α and IL1-β. We anticipated that compound III, possessing mechanoresponsiveness and a nanofibrillar network, could be administered in patients with injections because of its shear-thinning properties. Moreover, the optimum partition coefficient of compound III might have allowed the scaffold to penetrate the cellular membranes and form a dilactate complex (compound VI) when exposed to the accumulated lactates/lactic acids, a common phenomenon observed within the hypoxic cancerous tumor cores, in accordance with the Warburg mechanism, thereby evading the cytotoxicity within normal cells. Besides, the supramolecular β-sheets of compound III manifest substantial antimicrobial efficacy against the common pathogens, two Gram-positive bacteria, S. aureus and B. subtilis, two Gram-negative bacteria, E. coli and P. aeruginosa, and a fungus, C. albicans, along with proteolytic stability and high mechanical strength at physiological pH. Overall, we speculate that the discovery of these multifunctional bioinspired materials holds future promise as preferential therapeutics for the remediation of immune-susceptible cancer patients, afflicted by microbial infections arising alone or as side effects of chemotherapeutic medications.

Rheological Characterization and Printability of Sodium Alginate-Gelatin Hydrogel for 3D Cultures and Bioprinting.

The development of biocompatible hydrogels for 3D bioprinting is essential for creating functional tissue models and advancing preclinical drug testing. This study investigates the formulation, printability, mechanical properties, and biocompatibility of a novel Alg-Gel hydrogel blend (alginate and gelatin) for use in extrusion-based 3D bioprinting. A range of hydrogel compositions were evaluated for their rheological behavior, including shear-thinning properties, storage modulus, and compressive modulus, which are crucial for maintaining structural integrity during printing and supporting cell viability. The printability assessment of the 7% alginate-8% gelatin hydrogel demonstrated that the 27T tapered needle achieved the highest normalized Printability Index (POInormalized = 1), offering the narrowest strand width (0.56 ± 0.02 mm) and the highest printing accuracy (97.2%) at the lowest printing pressure (30 psi). In contrast, the 30R needle, with the smallest inner diameter (0.152 mm) and highest printing pressure (80 psi), resulted in the widest strand width (0.70 ± 0.01 mm) and the lowest accuracy (88.8%), resulting in a POInormalized of 0.274. The 30T and 27R needles demonstrated moderate performance, with POInormalized values of 0.758 and 0.558, respectively. The optimized 7% alginate and 8% gelatin blend demonstrated favorable printability, mechanical strength, and cell compatibility with MDA-MB-213 breast cancer cells, exhibiting high cell proliferation rates and minimal cytotoxicity over a 2-week culture period. This formulation offers a balanced approach, providing sufficient viscosity for precision printing while minimizing shear stress to preserve cell health. This work lays the groundwork for future advancements in bioprinted cancer models, contributing to the development of more effective tools for drug screening and personalized medicine.

Improving the bioactivity and mechanical properties of poly(ethylene glycol)-based hydrogels through a supramolecular support network.

Most synthetic hydrogels are formed through radical polymerization to yield a homogenous covalent meshwork. In contrast, natural hydrogels form through mechanisms involving both covalent assembly and supramolecular interactions. In this communication, we expand the capabilities of covalent poly(ethylene glycol) (PEG) networks through co-assembly of supramolecular peptide nanofibers. Using a peptide hydrogelator derived from the tryptophan zipper (Trpzip) motif, we demonstrate how in situ formation of nanofiber networks can tune the stiffness of PEG-based hydrogels, while also imparting shear thinning, stress relaxation, and self-healing properties. The hybrid networks show enhanced toughness and durability under tension, providing scope for use in load bearing applications. A small quantity of Trpzip peptide renders the non-adhesive PEG network adhesive, supporting adipose derived stromal cell adhesion, elongation, and growth. The integration of supramolecular networks into covalent meshworks expands the versatility of these materials, opening up new avenues for applications in biotechnology and medicine.

Personalized Medicine Through Semisolid-Extrusion Based 3D Printing: Dual-Drug Loaded Gummies for Enhanced Patient Compliance

PurposeThe purpose of this research was to develop and characterize dual-drug Isoniazid-Pyridoxine gummies using Semisolid Extrusion (SSE) 3D printing technology, aimed at personalized dosing for a broad patient demographic, from pediatric to geriatric. This study leverages SSE 3D printing, an innovative approach in personalized medicine, to enable precise dose customization and improve patient adherence. By formulating dual drug-loaded gummies, the research addresses the challenges of pill burden and poor palatability associated with traditional tuberculosis regimens, ultimately enhancing the therapeutic experience and effectiveness for patients across various age groups.MethodsGummies were formulated using varying ratios of gelatin, carrageenan, and xylitol, and printed using the BIO X 3D printer. Rheological properties were evaluated to confirm printability, shear-thinning behavior, and viscosity recovery. In vitro drug release and stability were assessed under refrigerated (5 ± 3°C) and ambient (25 ± 2°C) storage conditions. FT-IR spectroscopy was used to examine drug-excipient interactions.ResultsThe optimized F3 formulation, containing 900 mg Isoniazid and 30 mg Pyridoxine, demonstrated successful printability and structural integrity. Over 80% of both drugs were released within 30 min. Rheological testing confirmed ideal shear-thinning and viscoelastic properties for extrusion-based printing. Suitable textural properties for pediatric patient compliance were observed. Stability studies showed that both drug content and release profiles remained consistent for 30 days under refrigerated storage.ConclusionsThis study determines the potential of SSE 3D printing in fabricating personalized Isoniazid-Pyridoxine-loaded gummies, offering a novel, patient-friendly dosage form for tuberculosis treatment. The optimized formulation exhibited excellent printability, stability, and rapid drug release, positioning 3D-printed gummies as a promising alternative to conventional oral dosage forms in enhancing patient adherence.Graphical abstract

Rapidly Forming Recombinant Miniature Spidroins Hydrogels Composed of Nanofibrils with Tunable Mechanical Properties for Bio 3D Printing and Biomimetic Cellular Scaffolds

AbstractRecombinant spidroins offer numerous possibilities for creating new biomaterials. However, their polymorphic and prone to aggregation characteristics present challenges in both their production and practical application. Here, mutant recombinant spidroins are reported forming hydrogels rapidly and controllably at 37 °C and with visible light irradiation. In the mutant spidroins phenylalanine residues (F) are systematically substituted by tyrosine residues (Y) in repeat motifs of (GGX), which contributes to the self‐assembly of β‐sheet and further formation of amyloid‐like nanofibrils. As expected, micellar/globular spidroins solution converts to spidroins hydrogel composed of nanofibrils network and subsequently further crosslinked by di‐tyrosine. The conformation transformation process is verified by spectroscopy, transmission electron microscopy (TEM), and molecular dynamics simulation. Furthermore, the spidroin hydrogels are used as bioink and biomimetic cellular scaffolds according to their good biocompatibility, shear thinning properties, and nanofibril network structure. The findings reveal the structural transformation mechanism of spidroins and expand their applications in biomedical engineering.

Research on shear-thinning and surface properties of CaO–SiO2–CaF2–Al2O3-based mould flux

The main feature of high-efficiency continuous casting production is the increase in casting speed. This leads to an increased risk of slag entrapment in the liquid surface area of the mould and steel leakage due to the bonding of the casting billet. Both traditional mould flux and non-Newtonian fluid mould flux with only shear-thinning properties cannot effectively solve these problems. This study selected a practical high-casting speed thin slab mould flux from a steel plant as the original mould flux. Add 4.6–12.1% Al2O3 and 3.6–4.9% MnO and other additives to prepare a new type of mould flux with both shear thinning characteristics and high surface tension. The shear-thinning properties, interface properties and microstructure of the mould flux were detected and studied using methods such as the rotating cylinder method. The results showed that with the increase of Al2O3 content, the shear-thinning properties of the mould flux first enhanced and then weakened. The strongest effect was observed when the Al2O3 content was 8.7%. The contact angle, surface tension and interface tension of the mould flux were significantly improved and the degree of molecular polymerisation gradually increased. The shear-thinning properties of mould flux are mainly related to the Si–O–Al structure. The interaction force between Al3+ in the slag and the surface O2− of the mould flux increases, and the surface tension of the mould flux increases. When the Al2O3 content is more than 10.5%, a large amount of AlO2− will be repelled to the surface of the mould flux, and the change in surface tension is no longer significant.

Tuning Star Polymer Architecture to Tailor Secondary Structures and Mechanical Properties of Diblock Polypeptide Hydrogels for Direct Ink Writing.

Hydrogel three-dimensional (3D) printing has emerged as a highly valuable fabrication tool for applications ranging from electronics and biomedicine. While conventional hydrogels such as gelatin, alginate, and hyaluronic acid satisfy biocompatibility requirements, they distinctly lack reproducibility in terms of mechanical properties and 3D printability. Aiming to offer a high-performance alternative, here we present a range of amphiphilic star-shaped diblock copolypeptides of l-glutamate and l-leucine residues with different topologies. Hydrophobic side chains of the l-leucine polymer block drive conformational self-assembly in water, spontaneously forming hydrogels with tunable mechanical properties, through variation of star topology. Their amenable shear-thinning and self-recovery properties render them suitable as hydrogel inks for direct ink writing. Well-defined 3D-printed structures can be readily generated and rapidly photo-cross-linked using visible light (405 nm) after methacrylamide functionalization, while hydrogel inks demonstrate good biocompatibility with top-seeded and encapsulated MC3T3 cells.

Functional characteristics of whole-food arabinoxylans from sweet maize varieties

A comparative study was conducted to elucidate differences in the functional properties of arabinoxylans (AXs) derived from different sweet maize fibers (AX2, AX6, and AX39). AX39 had the highest A/X value of 0.68 and the largest Mw, while AX6 contained more disubstituted xylose. The difference in Mw led to the changes in viscosity of AXs. When the concentration was 9%, the difference in viscosity of AXs was obvious: AX39 > AX6 > AX2, and AX39 showed distinct shear thinning property. Moreover, ferulic acid and p-coumaric acid were the dominant phenolic acids in AXs. The content of ferulic acid was proportional to antioxidant activity, and AX2 with the highest content of ferulic acid (96.13 μg/g) had the highest antioxidant activity. The contents of short-chain fatty acids (SCFAs) produced during the in vitro fermentation of AXs were influenced by their structural properties. The total SCFAs of AX39 and AX2 were higher than that in AX6 due to their higher A/X and ferulic acid content. These results indicate that AX from different sources has different structural and functional characteristics, appropriate AXs can be selected according to actual needs to enhance the texture or nutritional value of the food.

Numerical study of paste-bridge transfer process for laser induced high-viscosity silver paste

Laser-induced forward transfer (LIFT) is promising for solar-cell metallization and electronic printing due to its low dependence on paste viscosity and nozzle-free process. In this paper, the transfer process and morphological characteristics for LIFT of high-viscosity silver paste were studied through simulations and experiments. The shear-thinning rheological properties were considered using the fitted Carreau model. Variations of paste protrusion with single pulse energy and time were obtained from the high-speed imaging. The evolution of initial pressure that induces the paste protrusion was solved inversely and quantitatively expressed by a polynomial function. The internal pressure should be sufficiently larger than 40 MPa to induce the effective transfer. In the simulation, the induced bubble undergoes a non-spherical transition from mushroom to pea-pod and capsule shapes due to constraints from surrounding paste and substrate. The deposition morphology formed by the induced mushroom-shaped bubble shows high printing precision with thin width (<30 μm) and large height (∼10 μm). The simulated diameter and height of transferred single voxel agree with those from experimental measurement. It can gain insight into the transfer dynamics of high-viscosity pastes and provide process optimization for precision printing of voxels by LIFT.

α-D Nucleoside Based Self-Healing Supramolecular Hydrogels Derived from the α-D Anomers of 2'-Deoxyguanosine and Fluorescent 8-Azapurine 2'-Deoxyribofuranosides.

Self-assembly of α-D nucleosides to supramolecular hydrogels is described in detail. Hydrogel formation is studied on α-D 2'-deoxyguanosine (α-dG), and the fluorescent 8-azapurine α-D nucleosides 2-amino-8-aza-2'-deoxyadenosine (α-2-NH2-z8Ad) and 8-aza-2'-deoxyisoguanosine (α-z8iGd). These compounds were prepared from α-D 8-aza-2'-deoxyguanosine by an activation/amination protocol followed by deamination. Protonation and deprotonation pKa values of monomeric nucleosides were determined. Fluorescence measurements displayed the pH-dependent fluorescence intensity of α-D 8-azapurine nucleosides. α-dG and α-z8iGd self-assemble to gels that are selective for K+-ions. The α-dG gel is transparent and the α-z8iGd gel shows fluorescence. α-2-NH2-z8Ad forms fluorescent gels in the presence of alkali metal ions of different size. SEM images expose a large condensed and flat structure for the α-dG gel, whereas the α-2-NH2-z8Ad gel consists of flakes that are connected to bundles. A porous structure generated by helical cylindric fibers was found for the α-z8iGd gel. All α-D hydrogels show long-term lifetime stability. The α-z8iGd hydrogel in KCl solution has the highest Tgel value. The minimum gelation concentration of the hydrogels is 0.3-0.5 mg nucleoside/100 μL alkali ion solution. In periodical step-strain experiments, the hydrogels of α-dG, α-2-NH2-z8Ad and α-z8iGd displayed thixotropy. Based on their self-healing and shear-thinning properties the hydrogels are injectable.

Optimized battery electrodes with primer layers by simultaneous two-layer slot-die coating

AbstractMulti-layer coating is a promising method for optimizing the properties of battery electrodes. This study examines the simultaneous coating of anodes with a primer layer without the necessity of a second coating and drying step, as it is the case for sequential coating processes. The primer layer is used to concentrate the binder in proximity to the substrate, thereby enhancing the adhesion strength of the electrode. Two systems comprising anode and primer, differing in rheological properties, are selected for coating investigation. It is demonstrated that the viscosity ratio of the multi-layer coating has a pronounced effect on coating suitability. In a two-layer system, the viscosity ratio also changes with shear rate due to the possibly different shear thinning properties. This results in the observation that combinations with strong viscosity ratios might only be stable in specific coating speed ranges. In contrast, combinations with moderate viscosity ratios exhibit a reduction in stable process windows as the viscosity ratio between the top and bottom layer increases. A mechanical characterization of the adhesion strength of dried and calendered electrodes demonstrated a notable enhancement in adhesion strength when a primer was utilized. In addition, capacity retention tests revealed that the electrochemical properties were not adversely affected by the primer.

The Impact of Nanocarbon Powder on the Characteristics of a Gel Propellant System with a High Concentration of Aluminum.

The addition of aluminum particles to a gel propellant has garnered attention through its potential for enhancing fuel properties. In order to enhance the energy performance of gel propellants, it is imperative to prepare gel propellants with high concentrations of aluminum. However, high-concentration aluminum-containing gels encounter two challenges. First, the combustion process leads to the agglomeration of aluminum particles, resulting in incomplete combustion. Additionally, elevated concentrations of aluminum particles increase the viscosity of the gel, impeding its atomization process and, subsequently, affecting combustion efficiency. These aforementioned issues pose practical obstacles for the application of high-concentration aluminum-containing gel propellants. In this research, a high-concentration aluminum-containing gel formulation was supplemented with nanocarbon powder. By investigating the impact of nanocarbon on various properties of the gel, its potential for addressing the above issues was analyzed. The investigation into the combustion performance of aluminum-containing gel blended with carbon powder revealed that the addition of 10 wt % nanocarbon powder to the gel system leads to a significant increase in the volumetric calorific value of the gel propellant by 21.21%. This enhancement not only improves the energy performance but also addresses the issue of incomplete combustion associated with aluminum. The rheology experiments conducted on gels demonstrate that the addition of nanocarbon powder results in an increased viscosity of the gel at lower shear rates, thereby enhancing its ability to withstand external disturbances during storage. Furthermore, this incorporation also enhances the gel's shear thinning properties, leading to a significant reduction in viscosity at higher shear rates and facilitating easier atomization of the gel system. In summary, the incorporation of nanocarbon powder can optimize the storage, atomization, and combustion processes of the gel, offering a straightforward and efficient approach to enhance the practical performance of metallized gel propellants.

Jammed Pickering Emulsion Gels.

Emulsion gels with specific rheological properties have widespread applications in foods, cosmetics, and biomedicines. However, the constructions of water-in-oil emulsion gels are still challenging, due to the limited interactions available in the continuous oil phase. Here, a versatile strategy is developed to prepare a new type of emulsion gels, called Jammed Pickering emulsion gels (JPEGs). In the JPEG system, SiO2 NPs in the oil phase serve as colloidal surfactants to stabilize water-in-oil Pickering emulsions, while positively-charged NH2-PEG-NH2 molecules in the water phase cross-link negatively-charged SiO2 NPs at the water/oil interface, making NP-stabilized water droplets hard to deform and thus jamming the emulsion system to form emulsion gels. The strategy to prepare JPEGs is versatile and applicable to diverse oil phases. The designed JPEGs possess many advantages, including good biocompatibility for widespread applications, shear-thinning rheological properties for easy processing, good stability Over a wide temperature range and Against centrifugation, good adhesion to wet tissues for tissue engineering, and well-controlled sustained release Under intestinal conditions. The developed JPEGs are demonstrated to be a promising delivery platform and the strategy to achieve JPEGs will trigger more innovations of material design.

Flagellum Pumping Efficiency in Shear-Thinning Viscoelastic Fluids.

Microorganism motility often takes place within complex, viscoelastic fluid environments, e.g., sperm in cervicovaginal mucus and bacteria in biofilms. In such complex fluids, strains and stresses generated by the microorganism are stored and relax across a spectrum of length and time scales and the complex fluid can be driven out of its linear response regime. Phenomena not possible in viscous media thereby arise from feedback between the swimmer and the complex fluid, making swimming efficiency co-dependent on the propulsion mechanism and fluid properties. Here we parameterize a flagellar motor and filament properties together with elastic relaxation and nonlinear shear-thinning properties of the fluid in a computational immersed boundary model. We then explore swimming efficiency, defined as a particular flow rate divided by the torque required to spin the motor, over this parameter space. Our findings indicate that motor efficiency (measured by the volumetric flow rate) can be boosted or degraded by relatively moderate or strong shear-thinning of the viscoelastic environment.

Heat transfer enhancement for electro-thermo-convection of FENE-P viscoelastic fluid in a square cavity

This study numerically investigates the heat transfer enhancement for viscoelastic electro-thermo-convection in a two-dimensional differentially heated cavity with injection from below. The flow motion is assumed to be incompressible, which is driven by the Coulomb force and the thermal buoyant force. The polymers are described by the FENE-P model which exhibits typical shear-thinning and elastic properties. Based on the extensibility parameter (L), the cases are divided into several scenarios, corresponding to weak elasticity with strong shear-thinning, moderate elasticity with moderate shear-thinning, and strong elasticity with weak shear-thinning, respectively. We find that the competition between the shear-thinning and elasticity dominates the flow state and heat transport. The shear-thinning effect tends to facilitate heat transfer, while its elastic properties tend to decrease it. In the scenario of weak elasticity with strong shear-thinning (L2=10), the polymer additives significantly improve the heat transfer enhancement (HTE) of the electric field as the polymer viscosity ratio (β) decreases or Weissenberg number (Wi) increases, where the maximum HTE reaches around 92.1%. The amount of HTE first increases rapidly with Wi but then remains almost constant once a critical Wi is exceeded. However, the HTE significantly decreases in the scenario of strong elasticity with weak shear-thinning (300≤L≤1000) since the elasticity dominates over the shear-thinning. These heat transfer performances are then corroborated with the boundary layer and kinetic energy budget analysis.

Synthesis, Characterization and Osteogenic Properties of Chitin-Polydioxanone Composite Gel.

In this study, we have developed a Chitin(Ch)-Poly(dioxanone)(PDO) gel system, which can be potentially used for tissue engineering. Hydrogel has been widely used in biomedical applications for its tuneable properties and biocompatibility. Chitin (Ch) is a natural biopolymer used for its ability to mimic the natural extracellular matrix due to its N-acetyl glucosamine structural units. Poly (dioxanone) (PDO) is a FDA-approved synthetic biopolymer known for its mechanical properties, good biocompatibility, and poor inflammatory response. Based on this, we have developed Ch-PDO composite gel using simple regeneration chemistry and characterized it using FT-IR and SEM. The developed composite gel showed improved gel strength, good swelling ability, and controlled degradation behaviour. It also showed good inject ability with shear thinning properties and hemocompatibility. Further, the biocompatibility and cell adhesion studies of the prepared gels were studied using dental follicle stem cells (DFSCs). The prepared Ch-PDO gel was biocompatible and showed DFSCs cell attachment. Osteogenic mineralization, RUNX2 and OPN expression of the prepared Ch and Ch-PDO gel was studied and Ch-PDO gel showed an enhanced mineralization and RUNX2 and OPN expression showed enhanced osteogenic activity in Ch-PDO. Therefore, the developed chitin-PDO gel could be potentially used for bone tissue engineering.

Injectable hyaluronate-based hydrogel with a dynamic/covalent dual-crosslinked architecture for bone tissue engineering: Enhancing osteogenesis and immune regulation

In orthopedic practice, accommodating irregular defects caused by trauma or surgery with traditional preformed bone graft substitutes is often challenging. As a result, injectable hydrogels with seed cells have garnered significant interest in bone repair due to their adaptability and minimally invasive properties. However, they cannot simultaneously achieve injectability and mechanical properties, providing a biophysical and biochemical environment for cell support. In this study, a novel injectable hydrogel system (OA hydrogel) loaded with aspirin and bone mesenchymal stem cells (BMSCs) was developed to enhance osteogenesis and immune regulation in small irregular bone defects. OA hydrogels possessed self-healing and shear-thinning properties due to dynamic/covalent hydrazone bonds between aldehyde-modified hyaluronic acid methacrylate (ADH-HAMA) and oxidized hyaluronic acid (OHA). By photopolymerization of the enclosed HAMA, the OADC hydrogel was further reinforced, making it more suitable for cell proliferation. In vitro, composite hydrogels improved the osteogenic differentiation of BMSCs. Additionally, it promoted the M2 polarization of human monocytic leukemia (THP-1) cells. In vivo, the synergistic effect of acetylsalicylic acid (ASA) and BMSCs encapsulated within the OADC hydrogel promoted new bone formation in rat calvaria through increased recruitment and polarization of M2 macrophages. These findings underscore the significant promise of hydrogels for bone tissue engineering applications.