Rheological properties of gelatine hydrogels affected by flow- and horizontally-induced cooling rates during 3D cryo-printing

Construction of bupivacaine-loaded gelatin-based hydrogel delivery system for sciatic nerve block in mice

Peripheral nerve blockade (PNB) is a common treatment to relieve postoperative pain. However, local anesthetics alone have a short duration of action and severe side effects during postoperative analgesia. In order to overcome these limitations, the present study reported an injectable hydrogel with a drug slow-release profile for regional nerve blockade. The injectable hydrogel was prepared by crosslinking with gelatin and NHS-PEG-NHS, which was degradable in the physiological environment and displayed sustainable release of anesthetics locally, thus improving the disadvantage of the high toxicity of local anesthetics. In this regard, we conducted a series of in vitro characterizations and proved that the hydrogel has a porous three-dimensional mesh structure with high drug loading capability, and sustainable drug release profile. And cytotoxicity experiments confirmed the good biocompatibility of the hydrogel. It was shown that using the animal sciatic nerve block model, the analgesic effect was greatly improved in vivo, and there was no obvious evidence of permanent inflammation or nerve damage in the block site's sections. This locally slow-release platform, combined with local anesthetics, is therefore a promising contender for long-acting analgesia.

Poroviscoelastic relaxations and rate-dependent adhesion in gelatin

Hydrogels, polymeric networks swollen with water, exhibit time/rate-dependent adhesion due to their poroviscoleastic constitution. In this study, we conducted probe-tack experiments on gelatin and investigated the influence of dwelling times and unloading rates on pull-off forces and work of adhesion. We utilized in situ contact imaging to monitor separation kinematics and interfacial crack velocities. We found that the crack velocities scaled nonlinearly with the unloading rate, in a power law with an exponent of 0.8 and were independent of dwelling time. At maximum unloading rates corresponding to subsonic interfacial crack speeds, we observed an order of magnitude enhancement in the apparent work of adhesion. The enhancement of adhesion and the crack velocities were related by a power law with an exponent of 0.39. The maximum vertical extension during unloading, a measure of crack opening, exhibited linear correlation with the enhancement of adhesion. Both correlations were in line with the rate-dependent work of fracture modeled for viscoelastic solids (e.g., Persson and Brener model). We explored the links between dwelling times corresponding to varying degrees of poroelastic diffusion and the adhesion. We found 40% additional enhancement in adhesion at the highest unloading rate. This enhancement is due to the unbalanced osmotic pressure, also known as the suction effect. The influence of dwelling times on adhesion was negligible for the interfacial cracks propagating slower than the diffusive time scales. These results identify viscoelastic relaxations as the dominant mechanism governing the rate-dependent enhancement of adhesion, and hence pave the way for tuning rate-dependent adhesion in soft multiphasic materials.

Current significance and future perspective of 3D-printed bio-based polymers for applications in energy conversion and storage system

The increasing global population has led to a surge in energy demand and the production of environmentally harmful products, highlighting the urgent need for renewable and clean energy sources. In this context, sustainable and eco-friendly energy production strategies have been explored to mitigate the adverse effects of fossil fuel consumption to the environment. Additionally, efficient energy storage devices with a long lifespan are also crucial. Tailoring the components of energy conversion and storage devices can improve overall performance. Three-dimensional (3D) printing provides the flexibility to create and optimize geometrical structure in order to obtain preferable features to elevate energy conversion yield and storage capacitance. It also serves the potential for rapid and cost-efficient manufacturing. Besides that, bio-based polymers with potential mechanical and rheological properties have been exploited as material feedstocks for 3D printing. The use of these polymers promoted carbon neutrality and environmentally benign processes. In this perspective, this review provides an overview of various 3D printing techniques and processing parameters for bio-based polymers applicable for energy-relevant applications. It also explores the advances and current significance on the integration of 3D-printed bio-based polymers in several energy conversion and storage components from the recently published studies. Finally, the future perspective is elaborated for the development of bio-based polymers via 3D printing techniques as powerful tools for clean energy supplies towards the sustainable development goals (SDGs) with respect to environmental protection and green energy conversion.

Application of xanthan and locust bean gum mix or sorbitol in the jelly formulation to improved jelly 3D printing using a fused deposition modeling printer

This study examined the impacts of applying a xanthan and locust bean gum mix or sorbitol to a jelly formulation on the rheological parameters necessary for 3D printing a jelly applying the fused deposition modeling method. A jelly formulation was fortified with a gum mix (xanthan gum:locust bean gum = 0.625:0.375) at 1% (w/w), or added with sorbitol instead of sugar. Both treatments increased the values of storage modulus and yield stress, related to fidelity and shape retention, and adding the gum mix, in particular, increased the gel strength. Applying these treatments to the formulation that lacks the rheological parameters and gel strength required for 3D printing changed those values in a direction fulfilling the material requirements. This research confirmed that the application of xanthan and locust bean gum mix or sorbitol could adjust the properties of materials used in 3D printing for improved printability.

Rheological insights on Carboxymethyl cellulose hydrogels

Hydrogels are copiously studied for tissue engineering, drug delivery, and bone regeneration owing to their water content, mechanical strength, and elastic behaviour. The preparation of stable and mechanically strengthened hydrogels without using toxic crosslinkers and expensive approaches is immensely challenging. In this study, we prepared Carboxymethyl cellulose based hydrogels with different polymer concentration via a less expensive physical crosslinking approach without using any toxic crosslinkers and evaluated their mechanical strength. In this hydrogel system, the carbopol concentration was fixed at 1 wt/v% and the Carboxymethyl cellulose concentration was varied between 1 and 5 wt/v%. In this hydrogel system, Carbopol serves as the crosslinker to bridge Carboxymethyl cellulose polymer through hydrogen bonds. Rheological analysis was employed in assessing the mechanical properties of the prepared hydrogel, in particular, the viscoelastic behaviour of the hydrogels. The viscoelastic nature and mechanical strength of the hydrogels increased with an increase in the Carboxymethyl cellulose polymer concentration. Further, our results suggested that gels with Carboxymethyl cellulose concentration between 3 wt/v % and 4 wt/v % with yield stresses of 58.83 Pa and 81.47 Pa, respectively, are potential candidates for use in transdermal drug delivery. The prepared hydrogels possessed high thermal stability and retained their gel network structure even at 50 °C. These findings are beneficial for biomedical applications in transdermal drug delivery and tissue engineering owing to the biocompatibility, stability, and mechanical strength of the prepared hydrogels.

3D-Printed Hydrogel for Diverse Applications: A Review

Hydrogels have emerged as a versatile and promising class of materials in the field of 3D printing, offering unique properties suitable for various applications. This review delves into the intersection of hydrogels and 3D printing, exploring current research, technological advancements, and future directions. It starts with an overview of hydrogel basics, including composition and properties, and details various hydrogel materials used in 3D printing. The review explores diverse 3D printing methods for hydrogels, discussing their advantages and limitations. It emphasizes the integration of 3D-printed hydrogels in biomedical engineering, showcasing its role in tissue engineering, regenerative medicine, and drug delivery. Beyond healthcare, it also examines their applications in the food, cosmetics, and electronics industries. Challenges like resolution limitations and scalability are addressed. The review predicts future trends in material development, printing techniques, and novel applications.

Evaluation of heat transfer in porous scaffolds under cryogenic treatment: a numerical study

The present work had evaluated the effect of cryogenic treatment (233 K) on the degradation of polymeric biomaterial using a numerical model. The study on effect of cryogenic temperature on mechanical properties of cell-seeded biomaterials is very limited. However, no study had reported material degradation evaluation. Different structures of silk-fibroin-poly-electrolyte complex (SFPEC) scaffolds had been designed by varying hole distance and hole diameter, with reference to existing literature. The size of scaffolds were maintained at 5 [Formula: see text] 5 mm2. Current study evaluates the effect of cryogenic temperature on mechanical properties (corelated to degradation) of scaffold. Six parameters related to scaffold degradation: heat transfer, deformation gradient, stress, strain, strain tensor, and displacement gradient were analyzed for three different cooling rates (- 5 K/min, - 2 K/min, and - 1 K/min). Scaffold degradation had been evaluated in the presence of water and four different concentrations of cryoprotectant solution. Heat distribution at various points (points_base, point_wall and point_core) on the region of interest (ROI) was found similar for different cooling rates of the system. Thermal stress was found developing proportional to cooling rate, which leads to minimal variation in thermal stress over time. Strain tensor was found gradually decreasing due to attenuating response of deformation gradient. In addition to that, dipping down of cryogenic temperature had prohibited the movement of molecules in the crystalline structure which had restricting the displacement gradient. It was found that uniform distribution of desired heat at different cooling rates has the ability to minimize the responses of other scaffold degradation parameters. It was found that the rates of change in stress, strain, and strain tensor were minimal at different concentrations of cryoprotectant. The present study had predicted the degradation behavior of PEC scaffold under cryogenic temperature on the basis of explicit mechanical properties.

Next-generation protein-based materials capture and preserve projectiles from supersonic impacts

Extreme energy-dissipating materials are essential for a range of applications. The military and police force require ballistic armour to ensure the safety of their personnel, while the aerospace industry requires materials that enable the capture, preservation and study of hypervelocity projectiles. However, current industry standards display at least one inherent limitation, such as weight, breathability, stiffness, durability and failure to preserve captured projectiles. To resolve these limitations, we have turned to nature, using proteins that have evolved over millennia to enable effective energy dissipation. Specifically, a recombinant form of the mechanosensitive protein talin was incorporated into a monomeric unit and crosslinked, resulting in a talin shock-absorbing material (TSAM). When subjected to 1.5 km s-1 supersonic shots, TSAMs were shown to absorb the impact and capture and preserve the projectile.

A photoactive injectable antibacterial hydrogel to support chemo-immunotherapeutic effect of antigenic cell membrane and sorafenib by near-infrared light mediated tumor ablation

Intravenously administered nanocarriers suffer from off-target distribution, pre-targeting drug leakage, and rapid clearance, limiting their efficiency in tumor eradication. To bypass these challenges, an injectable hydrogel with time- and temperature-dependent viscosity enhancement behavior and self-healing property are reported to assist in the retention of the hydrogel in the tumor site after injection. The cancer cell membrane (CCM) and sorafenib are embedded into the hydrogel to elicit local tumor-specific immune responses and induce cancer cell apoptosis, respectively. In addition, hyaluronic acid (HA) coated Bi₂S₃ nanorods (BiH) are incorporated within the hydrogel to afford prolonged multi-cycle local photothermal therapy (PTT) due to the reduced diffusion of the nanorods to the surrounding tissues as a result of HA affinity toward cancer cells. The results show the promotion of immunostimulatory responses by both CCM and PTT through the release of inflammatory cytokines from immune cells, which allows localized and complete ablation of the breast tumor in an animal model by a single injection of the hydrogel. Moreover, the BiH renders strong antibacterial activity to the hydrogel, which is crucial for the clinical translation of injectable hydrogels as it minimizes the risk of infection in the post-cancer lesion formed by PTT-mediated cancer therapy.

Rheological and Self-Healing Behavior of Hydrogels Synthesized from l-Lysine-Functionalized Alginate Dialdehyde

Alginate dialdehyde and l-lysine-functionalized alginate dialdehyde were prepared to provide active aldehyde and l-lysine sites along the alginate backbone, respectively. Different concentrations of substrates and the reduction agent were added, and their influence on the degree of l-lysine substitution was evaluated. An amination reduction reaction (with l-lysine) was conducted on alginate dialdehyde with a 31% degree of oxidation. The NMR confirmed the presence of l-lysine functionality with the degree of substitution of 20%. The structural change of the polymer was observed via FTIR spectroscopy, confirming the formation of Schiff base covalent linkage after the crosslinking. The additional l-lysine sites on functionalized alginate dialdehyde provide more crosslinking sites on the hydrogel, which leads to a higher modulus storage rate than in the original alginate dialdehyde. This results in dynamic covalent bonds, which are attributed to the alginate derivative-gelatin hydrogels with shear-thinning and self-healing properties. The results suggested that the concentration and stoichiometric ratio of alginate dialdehyde, l-lysine-functionalized alginate dialdehyde, and gelatin play a fundamental role in the hydrogel's mechanical properties.

Solidification of Gelatine Hydrogels by Using a Cryoplatform and Its Validation through CFD Approaches

In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using a cryoplatform.

Dual encapsulation of β-carotene by β-cyclodextrin and chitosan for 3D printing application

Dual encapsulation of β-carotene (CAT) by β-cyclodextrin (CCLD) and chitosan (CS) are prepared via self-assembly process by special addition order and concentration. CCLD and CS alone could not effectively stabilize CAT, while CAT could be encapsulated in cavity of CCLD and the inclusion complex could be further strengthened by CS, due to hydrogen-bonding between CCLD and CS via groups including NH₂ and OH. The dispersion system based on dual encapsulation of CAT had outstanding shear-thinning behavior, proper pseudoplastic properties, satisfactory yield stress, excellent thermal stability and great thixotropy, illustrating high potential for 3D printing. 3D printing of CAT-encapsulated system with high-content CS on paper and bread proves its excellent extrudability and printability, with possible potential in nutrition personalization. The designed host encapsulation structure by CCLD and CS plays a guiding role in incorporating functional materials including bioactives, probiotics, enzymes, vitamins, etc., and provides a reference in innovative food technology.

Coordination with zirconium: A facile approach to improve the mechanical properties and thermostability of gelatin hydrogel

The poor mechanical property and thermostability restricted applications of gelatin hydrogel. Herein, a facile and inexpensive approach of immerging cooling induced gelatin hydrogels into Zr(SO₄)₂ dilute solution was applied to overcome these shortages. After this treatment, the micropores in hydrogel decreased to tens of microns while the water content slightly decreased. XPS results revealed that the coordination bonds formed between amino or carboxyl groups of gelatins and Zr⁴⁺. After immerging in 0.06 M Zr⁴⁺ solution, mechanical tests showed that the elastic modulus, compressive modulus and compressive strength of hydrogel were about 400, 1192 and 476 kPa, respectively, which were approximate 100, 11 and 5 times larger than those of pure gelatin. The DSC data indicated that the thermoreversible temperature of triple helix structure in gelatin was improved from about 30 °C to 55 °C. More importantly, the rheological temperature sweep test revealed that hydrogels with 0.06 M Zr⁴⁺ treatment can maintain the hydrogel state without melting even at 80 °C. CCK-8 tests and Calcein-AM/PI double-stain experiments demonstrated Zr⁴⁺ coordination was non-cytotoxic. These promising data indicated this nontoxic method was efficient and had potential to fabricate gelatin related materials for further application.

Characterization of Tuna Gelatin-Based Hydrogels as a Matrix for Drug Delivery

The skin of yellowfin tuna is one of the fishery industry solid residues with the greatest potential to add extra value to its circular economy that remains yet unexploited. Particularly, the high collagen content of fish skin allows generating gelatin by hydrolysis, which is ideal for forming hydrogels due to its biocompatibility and gelling capability. Hydrogels have been used as drug carriers for local administration due to their mechanical properties and drug loading capacity. Herein, novel tuna gelatin hydrogels were designed as drug vehicles with two structurally different antitumoral model compounds such as Doxorubicin and Crocin to be administrated locally in tissues with complex human anatomies after surgical resection. The characterization by gel permeation chromatography (GPC) of purified gelatin confirmed their heterogeneity composition, exhibiting three major bands that correspond to the β and α chains along with high molecular weight species. In addition, the Fourier Transform Infrared (FT-IR) spectra of gelatin probed the secondary structure of the gelatin showing the simultaneous existence of α helix, β sheet, and random coil structures. Morphological studies at different length scales were performed by a multi-technique approach using SAXS/WAXS, AFM and cryo-SEM that revealed the porous network formed by the interaction of gelatin planar aggregates. In addition, the sol-gel transition, as well as the gelation point and the hydrogel strength, were studied using dynamic rheology and differential scanning calorimetry. Likewise, the loading and release profiles followed by UV-visible spectroscopy indicated that the novel gelatin hydrogels improve the drug release of Doxorubicin and Crocin in a sustained fashion, indicating the structure-function importance in the material composition.

Synthesis of nanocapsules blended polymeric hydrogel loaded with bupivacaine drug delivery system for local anesthetics and pain management

Local anesthetics are used clinically for the control of postoperative pain management. This study aimed to develop chitosan (CS) with genipin (GP) hydrogels as the hydrophilic lipid shell loaded poly(ε-caprolactone) (PC) nanocapsules as the hydrophobic polymeric core composites (CS-GP/PC) to deliver bupivacaine (BPV) for the prolongation of anesthesia and pain relief. The swelling ratio, in vitro degradation, and rheological properties enhancement of CS-GP/PC polymeric hydrogel. The incorporation of PC nanocapsules into CS-GP hydrogels was confirmed by SEM, FTIR, and XRD analysis. Scanning electron microscopy results demonstrated that the CS-GP hydrogels and CS-GP/PC polymeric hydrogels have a porous structure, the pore dimensions being non-uniform with diameters between 25 and 300 μm. The in vitro drug release profile of CS-GP/PC polymeric hydrogel has been achieved 99.2 ± 1.12% of BPV drug release in 36 h. Cellular viability was evaluated using the CCK-8 test on 3T3 fibroblast cells revealed that the obtained CS-GP/PC polymeric hydrogel with BPV exhibited no obvious cytotoxicity. The CS-GP/PC polymeric hydrogel loaded with BPV showed significant improvement in pain response compared to the control group animals for at least 7 days. When compared with BPV solution, CS-GP hydrogel and CS-GP/PC polymeric hydrogel improved the skin permeation of BPV 3-fold and 5-fold in 24 h, respectively. In vitro and in vivo results pointed out PC nanocapsules loaded CS-GP hydrogel can act as effective drug carriers, thus prolonging and enhancing the anesthetic effect of BPV. Histopathological results demonstrated the excellent biodegradability and biocompatibility of the BPV-loaded CS-GP/PC polymeric hydrogel system on 7, 14, and 21 days without neurotoxicity.

HIGHLIGHTS

Preparation and characterization of CS-GP/PC polymeric hydrogel system.

BPV-loaded CS-GP/PC exhibited prolonged in vitro release in PBS solution.

Cytotoxicity of BPV-loaded CS-GP/PC polymeric hydrogel against fibroblast (3T3) cells.

Development of CS-GP/PC a promising skin drug-delivery system for local anesthetic BPV.

Extraction and Characterization of Gelatin from Skin By-Products of Seabream, Seabass and Rainbow Trout Reared in Aquaculture

The expansion of fish filleting, driven by the increasing demand for convenience food, concomitantly generates a rising amount of skinning by-products. Current trends point to a growing share of aquaculture in fish production, so we have chosen three established aquaculture species to study the properties of gelatin extracted from their skin: rainbow trout, commonly filleted; and seabass and seabream, marketed whole until very recently. In the first case, trout skin yields only 1.6% gelatin accompanied by the lowest gel strength (96 g bloom), while yield for the other two species exceeds 6%, and gel strength reaches 181 and 229 g bloom for seabass and seabream, respectively. These results are in line with the proportion of total imino acids analyzed in the gelatin samples. Molecular weight profiling shows similarities among gelatins, but seabass and seabream gelatins appear more structured, with higher proportion of β-chains and high molecular weight aggregates, which may influence the rheological properties observed. These results present skin by-products of seabream, and to a minor extent seabass, as suitable raw materials to produce gelatin through valorization processes.

Ascorbic acid-loaded polyvinyl alcohol/cellulose nanofibril hydrogels as precursors for 3D printed materials

We proposed a simple method to process hydrogels containing polyvinyl alcohol and cellulose nanofibrils (PVA/CNF) to prepare volumetric architectures by direct ink writing (DIW). The presence of CNF in the aqueous PVA suspensions conferred rheology profiles that were suitable for extrusion and solidification in pre-designed shapes. The viscoelastic behavior of the hybrid inks enabled precise control on processability and shape retention, for instance, as demonstrated in multilayered lattice structures of high fidelity. After lyophilization, the obtained 3D-printed hydrogels presented a very high porosity, with open and interconnected pores, allowing a high-water uptake capacity (up to 1600%). The mechanical strength of the composite 3D-printed materials matched those of soft tissues, opening opportunities for skin applications. As such, drug-loaded samples revealed a controlled and efficient delivery of an antioxidant (ascorbic acid) in PBS buffer media at 23 °C (~80% for 8 h). Altogether, PVA/CNF hydrogels were introduced as suitable precursors of 3D-lattice geometries with excellent physical and mechanical characteristics.

Reinforcement of Alginate-Gelatin Hydrogels with Bioceramics for Biomedical Applications: A Comparative Study

This study states the preparation of novel ink with potential use for bone and cartilage tissue restoration. 3Dprint manufacturing allows customizing prostheses and complex morphologies of any traumatism. The quest for bioinks that increase the restoration rate based on printable polymers is a need. This study is focused on main steps, the synthesis of two bioceramic materials as WO₃ and Na₂Ti₆O₁₃, its integration into a biopolymeric-base matrix of Alginate and Gelatin to support the particles in a complete scaffold to trigger the potential nucleation of crystals of calcium phosphates, and its comparative study with independent systems of formulations with bioceramic particles as Al₂O₃, TiO₂, and ZrO₂. FT-IR and SEM studies result in hydroxyapatite's potential nucleation, which can generate bone or cartilage tissue regeneration systems with low or null cytotoxicity. These composites were tested by cell culture techniques to assess their biocompatibility. Moreover, the reinforcement was compared individually by mechanical tests with higher results on synthesized materials Na₂Ti₆O₁₃ with 35 kPa and WO₃ with 63 kPa. Finally, the integration of these composite materials formulated by Alginate/Gelatin and bioceramic has been characterized as functional for further manufacturing with the aid of novel biofabrication techniques such as 3D printing.