Deformation and fracture behavior of physical gelatin gel systems

Composite Hydrogel Sealants for Annulus Fibrosus Repair

Intervertebral disc (IVD) herniation is a leading cause of disability and lower back pain, causing enormous socioeconomic burdens. The standard of care for disc herniation is nucleotomy, which alleviates pain but does not repair the annulus fibrosus (AF) defect nor recover the biomechanical function of the disc. Existing bioadhesives for AF repair are limited by insufficient adhesion and significant mechanical and geometrical mismatch with the AF tissue, resulting in the recurrence of protrusion or detachment of bioadhesives. Here, we report a composite hydrogel sealant constructed from a composite of a three-dimensional (3D)-printed thermoplastic polyurethane (TPU) mesh and tough hydrogel. We tailored the fiber angle and volume fraction of the TPU mesh design to match the angle-ply structure and mechanical properties of native AF. Also, we proposed and tested three types of geometrical design of the composite hydrogel sealant to match the defect shape and size. Our results show that the sealant could mimic native AF in terms of the elastic modulus, flexural modulus, and fracture toughness and form strong adhesion with the human AF tissue. The bovine IVD tests show the effectiveness of the composite hydrogel sealant for AF repair and biomechanics recovery and for preventing herniation with its heightened stiffness and superior adhesion. By harnessing the combined capabilities of 3D printing and bioadhesives, these composite hydrogel sealants demonstrate promising potential for diverse applications in tissue repair and regeneration.

Competition between slicing and buckling underlies the erratic nature of paper cuts

By enabling the dissemination and storage of information, paper has been central to human culture for more than a millennium. Its use is, however, associated with a common injury: the paper cut. Surprisingly, the physics underpinning a flexible sheet of paper slicing into soft tissues remains unresolved. In particular, the unpredictable occurrence of paper cuts, often restricted to a limited thickness range, has not been explained. Here we visualize and quantify the motion, deformation, and stresses during paper cuts, uncovering a remarkably complex relationship between cutting, geometry, and material properties. A model based on the hypothesis that a competition between slicing and buckling controls the probability of initiating a paper cut is developed and successfully validated. This explains why paper with a specific thickness is most hazardous (65µm, corresponding, e.g., to dot matrix paper) and suggests a probabilistic interpretation of irregular occurrence of paper cuts. Stimulated by these findings, we finally show how a recyclable cutting tool can harness the surprising power of paper.

Wound Healing Activity of Topical Herbal Gels Containing Barringtonia acutangula Fruit Extract: In silico and In vivo Studies

The current study describes the efficacy of B. acutangula fruit extract in wound healing via incorporation within topical gels. B. acutangula fruit extract was produced by solvent extraction method. The bioactive extract was incorporated within Carbopol 940-based topical gels, which were applied topically over the excision and incision wounds. The change in healing process was observed till 20 days. The percentages of closure of excision wound area were 92.89 % and 93.43 %, when treated with topical herbal gels containing B. acutangula fruit extract of 5 % and 10 %, respectively. The tensile strengths of incision area in rats treated with topical herbal gels containing 5 % and 10 % methanol extract of B. acutangula fruits were found to be 25±5.12 g and 30±4.10 g, respectively. The wound healing activity of topical herbal gels containing B. acutangula fruit extract in rats was found to be significant when compared with that of the reference standard and untreated groups. In addition, in silico studies suggested about good skin permeability and binding to the proteins responsible for delaying wound healing. It can be concluded that this topical herbal gels containing B. acutangula fruit extract could be used clinically for the treatment of wounds.

Characterization of drying-induced changes in moduli and internal stresses in a constrained gel using laser vibrometry

Hydrogels, water-saturated polymer networks find widespread use in soft robotics, biomedical, pharmaceutical and food industries. Both solid and water constituents of hydrogels are sensitive to external stimuli such as temperature, humidity, osmolarity, and light. For instance, common hydrogels swell or shrink in the presence of chemical potential gradient between the sample and surrounding environment. Corresponding changes in internal water content lead to significant changes in mechanical properties of hydrogels. Besides, internal stresses build up if the gel samples are constrained during swelling or dehydration. In the present research, we utilize modal analyses technique on drying hydrogels to identify dehydration-induced changes in elastic moduli and internal stresses. In particular, natural frequencies and damping ratios of the first two axisymmetric transverse vibration modes are measured on clamped gelatin disks using non-contact laser vibrometry at various water loss states. Experimental modal frequencies are then compared to the predictions of a pre-stressed thick plate model. The evolutions of elastic moduli and internal stresses for water losses up to 80% are identified. The broadband loss capacity of gelatin is also determined from the measured modal damping ratios. Highly transient mechanical response observed on the gelatin disks further demonstrates the need for non-contact and rapid mechanical characterization of hydrogels. As illustrated in this work, vibration and wave-based techniques are promising candidates to fulfill that need.

Biomechanics, Energetics, and Structural Basis of Rupture of Fibrin Networks

Fibrin provides the main structural integrity and mechanical strength to blood clots. Failure of fibrin clots can result in life-threating complications, such as stroke or pulmonary embolism. The dependence of rupture resistance of fibrin networks (uncracked and cracked) on fibrin(ogen) concentrations in the (patho)physiological 1-5 g L-1 range is explored by performing the ultrastructural studies and theoretical analysis of the experimental stress-strain profiles available from mechanical tensile loading assays. Fibrin fibers in the uncracked network stretched evenly, whereas, in the cracked network, fibers around the crack tip showed greater deformation. Unlike fibrin fibers in cracked networks formed at the lower 1-2.7 g L-1 fibrinogen concentrations, fibers formed at the higher 2.7-5 g L-1 concentrations align and stretch simultaneously. Cracked fibrin networks formed in higher fibrinogen solutions are tougher yet less extensible. Statistical modeling revealed that the characteristic strain for fiber alignment, crack size, and fracture toughness of fibrin networks control their rupture resistance. The results obtained provide a structural and biomechanical basis to quantitatively understand the material properties of blood plasma clots and to illuminate the mechanisms of their rupture.

Effects of acetic, malic, and citric acids on the large deformation behaviors of fish gelatin gels

This research was aimed to quantify the effects of acetic acid, malic acid, and citric acid (0, 0.5, 1.0, and 2.0 g/100 g H2 O) on the stress-strain responses of fish gelatin (FG) gels (2, 4, and 6.67 g/100 g H2 O) under uniaxial compression up to 68% of deformation. The first-order Ogden model fitted quite well for the compression responses of FG gels (R2  = 0.9909-0.9997). Protons from the acids played a key role on weakening the FG gel structures (gel rigidity, μ, decreased 11%-27%), as the μ values and pH values of FG gels were linearly correlated (R2  = 0.8240-0.9748), regardless of the acid type. The addition of an acid also resulted in a significant increase (p < .002) in the strain hardening capacity (α) of gels with 2 g FG/100 g H2 O. Both μ and α values of FG gels with higher gelatin concentrations were less affected by an acid partly due to their stronger buffering effects. The μ and α values of FG gels as affected by acids could not be fully explained based upon the pH changes, implying that the effects of acetate, malate, and citrate ions on the gel structure could not be ignored.

Crack propagation and arrests in gelatin hydrogels are linked to tip curvatures

Gelatin hydrogels are attractive scaffold materials for tissue engineering applications as they provide motifs for cell attachment, undergo large deformations, and are tunable. Low toughness and brittle fractures however limit their use in load bearing applications. An investigation of crack tip processes and mechanisms of crack propagation is warranted to link fracture properties with material microstructure. We cross-linked gelatin using glutaraldehyde to obtain low cross-linked control hydrogels and used an additional cross-linker, methylglyoxal, to fabricate MGO hydrogels with higher cross-links. We quantified fractures in the gelatin hydrogels from both groups using pure shear notch tests and characterized strain fields near the crack tip using 2-D digital image correlation. We used a numerical method based on Taylor's series expansion to measure the crack tip curvatures in the hydrogels. This method captures tip curvatures better than the parabolic method routinely used in studies. Results from our study show that cracks in gelatin hydrogels underwent frequent arrests during propagation through the specimen width in both groups. MGO hydrogels had 85% enhanced fracture toughness and a significantly higher number of stalls compared to the control group. Crack initiations following stalls in the sample correlated with low tip curvatures in both hydrogel groups. We also show that mechanical stretching blunts the crack tip before crack propagation; the degree of blunting was independent of the cross-link density and elastic modulus of the gelatin hydrogels. These results show a link between crack growth and the tip curvature in cross-linked gelatin hydrogels, and offer potential insights for the development of tougher hydrogels.

A device for studying fluid-induced cracks under mixed-mode loading conditions using x-ray tomography

We introduce an innovative instrument designed to investigate fluid-induced fractures under mixed loading conditions, including uniaxial tension and shear stress, in gels and similar soft materials. Equipped with sensors for measuring force, torque, and fluid pressure, the device is tailored for compatibility with x-ray tomography scanners, enabling non-invasive 3D analysis of crack geometries. To showcase its capabilities, we conducted a study examining crack-front segmentation in a hydrogel subjected to air pressure and a combination of tension and shear stress.

Evaluation of Sufu Fermented Using Mucor racemosus M2: Biochemical, Textural, Structural and Microbiological Properties

The quality and safety of sufu fermented using Mucor racemosa M2 was studied and compared with naturally fermented sufu. After 90 days post-fermentation, both naturally fermented and inoculated fermented sufu reached the maturity standard of sufu, and the degree of protein hydrolysis of natural sufu (WP/TP: 34% ± 1%; AAN/TN: 33% ± 1%) was slightly higher than that of the inoculated sufu (WP/TP: 28.2% ± 0.4%; AAN/TN: 27% ± 1%). The hardness and adhesiveness of inoculated sufu (Hadness: 1063 g ± 211 g; Adhesiveness: -80 g ± 47 g) were significantly greater than those of natural sufu (Hadness: 790 g ± 57 g; Adhesiveness: -23 g ± 28 g), and the internal structure of natural sufu was denser and more uniform than that of inoculated sufu. A total of 50 aroma compounds were detected in natural and inoculated sufu. The total number of bacterial colonies in naturally fermented sufu was significantly higher than that in inoculated sufu, and the pathogenic bacteria in both types of fermented sufu were lower than the limit of pathogenic bacteria required in fermented soybean products. The content of biogenic amines in sufu was determined by high performance liquid chromatography (HPLC), and the results showed that the content of biogenic amines (Putrescine, Cadaverine, Histamine, Tyramine, etc.) in naturally fermented sufu was significantly higher than that in inoculated fermented sufu. Especially the histamine content, after 90 days of fermentation, was found to be 64.95 ± 4.55 for inoculated fertilization and 44.24 ± 0.71 for natural fertilization. Overall, the quality of inoculated sufu was somewhat better than that of natural sufu, and the M2 strain can be used to ferment sufu.

Microfluidic Organ-on-A-chip: A Guide to Biomaterial Choice and Fabrication

Organ-on-A-chip (OoAC) devices are miniaturized, functional, in vitro constructs that aim to recapitulate the in vivo physiology of an organ using different cell types and extracellular matrix, while maintaining the chemical and mechanical properties of the surrounding microenvironments. From an end-point perspective, the success of a microfluidic OoAC relies mainly on the type of biomaterial and the fabrication strategy employed. Certain biomaterials, such as PDMS (polydimethylsiloxane), are preferred over others due to their ease of fabrication and proven success in modelling complex organ systems. However, the inherent nature of human microtissues to respond differently to surrounding stimulations has led to the combination of biomaterials ranging from simple PDMS chips to 3D-printed polymers coated with natural and synthetic materials, including hydrogels. In addition, recent advances in 3D printing and bioprinting techniques have led to the powerful combination of utilizing these materials to develop microfluidic OoAC devices. In this narrative review, we evaluate the different materials used to fabricate microfluidic OoAC devices while outlining their pros and cons in different organ systems. A note on combining the advances made in additive manufacturing (AM) techniques for the microfabrication of these complex systems is also discussed.

Monitoring cavitation dynamics evolution in tissue mimicking hydrogels for repeated exposures via acoustic cavitation emissions

A 700 kHz histotripsy array is used to generate repeated cavitation events in agarose, gelatin, and polyacrylamide hydrogels. High-speed optical imaging, a broadband hydrophone, and the narrow-band receive elements of the histotripsy array are used to capture bubble dynamics and acoustic cavitation emissions. Bubble radii, lifespan, shockwave amplitudes are noted to be measured in close agreement between the different observation methods. These features also decrease with increasing hydrogel stiffness for all of the tested materials. However, the evolutions of these properties during the repeated irradiations vary significantly across the different material subjects. Bubble maximum radius initially increases, then plateaus, and finally decreases in agarose, but remains constant across exposures in gelatin and polyacrylamide. The bubble lifespan increases monotonically in agarose and gelatin but decreases in polyacrylamide. Collapse shockwave amplitudes were measured to have different-shaped evolutions between all three of the tested materials. Bubble maximum radii, lifespans, and collapse shockwave amplitudes were observed to express evolutions that are dependent on the structure and stiffness of the nucleation medium.

Insight into the mechanism of fracture properties modulated by microstructure in the myofibrillar protein and polysaccharide gel systems

The objective of this study was to investigate the mechanism of fracture properties modulated by microstructure in the myofibrillar protein (MP) and polysaccharides gel systems. Compare to the modified starch, the dietary fiber significantly improved the fracture stress and reduced the fracture strain at same concentration. The treatment with 2% dietary fiber had the highest value of fracture stress and the lowest value of fracture strain, which were 259 g and 1.12 respectively. From the skeleton structure, the Raman spectroscopy result showed that dietary fiber addition significantly reduced the intensity at 2945 cm−1, which suggested that the aggregation of hydrophobic groups was improved. The SEM showed that the treatment with 2% dietary fiber had the highest fractal dimension value of 1.7772 and the lowest lacunary value of 0.258. From the filling structure, the paraffin section showed that the polysaccharides were just simply trapped in MP gel networks and formed numerous large volumes and no-elastic of cavities. The principal component analysis suggested that the compactness of three-dimensional gel networks determined fracture stress of composite gel. The no- no-elastic of cavities formed by modified starch and dietary fiber resulted in the reduction of fracture strain. These results would promote the development of innovative nutritional meat product formulation with satisfied textural property.

Graphical Abstract

3D Printed gelatin film with Garcinia atroviridis extract

Active packaging, such as edible film with antibacterial properties, can help extend the shelf life of food. The research aimed to develop a 3D printed gelatin edible film by using glycerol and Garcinia atroviridis extract (GAE). Mechanical properties of gelatin gel, physical, mechanical, and antimicrobial properties of edible film with glycerol and GAE were determined. Water solubility, total colour difference, and elongation of break of gelatin edible film increased as glycerol concentration increased (0-25% w/w), whereas tensile strength and Young's modulus value decreased from 26.5 to 4.64 MPa and 3.04 to 0.13 MPa, respectively. On the other hand, increasing GAE from 1 to 4% (w/w) increases elongation at break from 40.83 to 98.27%, while decreasing edible film tensile strength and gelatin gel hardness value from 8.94 to 6.21 MPa and 1848.67 to 999.67 g, respectively. Using 20% (w/w) glycerol and 4% (w/w) GAE, the best 3D printed film with low tensile strength (6.21 MPa), high elongation at break (98.27%), and antibacterial activity against S. aureus with 7.23 mm zone of inhibition was developed. It seems to have a great potentiality as an active packaging material for 3D printed gelatin edible film.

Cavitation nucleation and its ductile-to-brittle shape transition in soft gels under translational mechanical impact

Cavitation bubbles in the human body, when subjected to impact, are being increasingly considered as a possible brain injury mechanism. However, the onset of cavitation and its complex dynamics in biological materials remain unclear. Our experimental results using soft gels as a tissue simulant show that the critical acceleration (a_cr) at cavitation nucleation monotonically increases with increasing stiffness of gelatin A/B, while a_cr for agarose and agar initially increases but is followed by a plateau or even decrease after stiffness reach to ∼100 kPa. Our image analyses of cavitation bubbles and theoretical work reveal that the observed trends in a_cr are directly linked to how bubbles grow in each gel. Gelatin A/B, regardless of their stiffness, form a localized damaged zone (tens of nanometers) at the gel-bubble interface during bubble growth. In contrary, the damaged zone in agar/agarose becomes significantly larger (> 100 times) with increasing shear modulus, which triggers the transition from formation of a small, damaged zone to activation of crack propagation. STATEMENT OF SIGNIFICANCE: We have studied cavitation nucleation and bubble growth in four different types of soft gels (i.e., tissue simulants) under translational impact. The critical linear acceleration for cavitation nucleation has been measured in the simulants by utilizing a recently developed method that mimics acceleration profiles of typical head blunt events. Each gel type exhibits significantly different trends in the critical acceleration and bubble shape (e.g., A gel-specific sphere-to-saucer transition) with increasing gel stiffness. Our theoretical framework, based on the concepts of a damaged zone and crack propagation in each gel, explains underlying mechanisms of the experimental observations. Our in-depth studies shed light on potential links between traumatic brain injuries and cavitation bubbles induced by translational acceleration, the overlooked mechanism in the literature.

Colloidal hydrogels made of gelatin nanoparticles exhibit fast stress relaxation at strains relevant for cell activity

Viscoelastic properties of hydrogels such as stress relaxation or plasticity have been recognized as important mechanical cues that dictate the migration, proliferation, and differentiation of embedded cells. Stress relaxation rates in conventional hydrogels are usually much slower than cellular processes, which impedes rapid cellularization of these elastic networks. Colloidal hydrogels assembled from nanoscale building blocks may provide increased degrees of freedom in the design of viscoelastic hydrogels with accelerated stress relaxation rates due to their strain-sensitive rheology which can be tuned via interparticle interactions. Here, we investigate the stress relaxation of colloidal hydrogels from gelatin nanoparticles in comparison to physical gelatin hydrogels and explore the particle interactions that govern stress relaxation. Colloidal and physical gelatin hydrogels exhibit comparable rheology at small deformations, but colloidal hydrogels fluidize beyond a critical strain while physical gels remain primarily elastic independent of strain. This fluidization facilitates fast exponential stress relaxation in colloidal gels at strain levels that correspond to strains exerted by cells embedded in physiological extracellular matrices (10-50%). Increased attractive particle interactions result in a higher critical strain and slower stress relaxation in colloidal gels. In physical gels, stress relaxation is slower and mostly independent of strain. Hence, colloidal hydrogels offer the possibility to modulate viscoelasticity via interparticle interactions and obtain fast stress relaxation rates at strains relevant for cell activity. These beneficial features render colloidal hydrogels promising alternatives to conventional monolithic hydrogels for tissue engineering and regenerative medicine. STATEMENT OF SIGNIFICANCE: In the endeavor to design biomaterials that favor cell activity, research has long focused on biochemical cues. Recently, the time-, stress-, and strain-dependent mechanical properties, i.e. viscoelasticity, of biomaterials has been recognized as important factor that dictates cell fate. We herein present the viscoelastic stress relaxation of colloidal hydrogels assembled from gelatin nanoparticles, which show a strain-dependent fluidization at strains relevant for cell activity, in contrast to many commonly used monolithic hydrogels with primarily elastic behavior.

Effect of random fiber networks on bubble growth in gelatin hydrogels

In hydrodynamics, the event of dynamic bubble growth in a pure liquid under tensile pressure is known as cavitation. The same event can also be observed in soft materials (e.g., elastomers and hydrogels). However, for soft materials, bubble/cavity growth is either defined as cavitation if the bubble growth is elastic and reversible or as fracture if the cavity growth is by material failure and irreversible. In any way, bubble growth can cause damage to soft materials (e.g., tissue) by inducing high strain and strain-rate deformation. Additionally, a high-strength pressure wave is generated upon the collapse of the bubble. Therefore, it is crucial to identify the critical condition of spontaneous bubble growth in soft materials. Experimental and theoretical observations have agreed that the onset of bubble growth in soft materials requires higher tensile pressure than pure water. The extra tensile pressure is required since the cavitating bubble needs to overcome the elastic and surface energy in soft materials. In this manuscript, we developed two models to study and quantify the extra tensile pressure for different gelatin concentrations. Both the models are then compared with the existing cavitation onset criteria of rubber-like materials. Validation is done with the experimental results of threshold tensile pressure for different gelatin concentrations. Both models can moderately predict the extra tensile pressure within the intermediate range of gelatin concentrations (3-7% [w/v]). For low concentration (∼1%), the network's non-affinity plays a significant role and must be incorporated. On the other hand, for higher concentrations (∼10%), the entropic deformation dominates, and the strain energy formulation is not adequate.

Mechanically Induced Cavitation in Biological Systems

Cavitation bubbles form in soft biological systems when subjected to a negative pressure above a critical threshold, and dynamically change their size and shape in a violent manner. The critical threshold and dynamic response of these bubbles are known to be sensitive to the mechanical characteristics of highly compliant biological systems. Several recent studies have demonstrated different biological implications of cavitation events in biological systems, from therapeutic drug delivery and microsurgery to blunt injury mechanisms. Due to the rapidly increasing relevance of cavitation in biological and biomedical communities, it is necessary to review the current state-of-the-art theoretical framework, experimental techniques, and research trends with an emphasis on cavitation behavior in biologically relevant systems (e.g., tissue simulant and organs). In this review, we first introduce several theoretical models that predict bubble response in different types of biological systems and discuss the use of each model with physical interpretations. Then, we review the experimental techniques that allow the characterization of cavitation in biologically relevant systems with in-depth discussions of their unique advantages and disadvantages. Finally, we highlight key biological studies and findings, through the direct use of live cells or organs, for each experimental approach.

Effect of gelatin concentration on the characterizations and hemocompatibility of polyvinyl alcohol-gelatin hydrogel

BACKGROUND

The design and fabrication of hemocompatible and low-toxicity formulations remains a challenging task. Hydrogels are of considerable importance for biomedical applications since they are highly compatible with living tissue, both in vivo and in vitro.

OBJECTIVE

The present study aimed to develop and evaluate the characterizations and in vitro hemocompatibility of a hydrogel using polyvinyl alcohol and gelatin with different concentrations.

METHODS

The gelling process was realized by cross-linking the polyvinyl alcohol and gelatin. The morphological and structural examinations of the synthetic hydrogels were done by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The swelling behavior of the prepared hydrogels in water was evaluated. Prothrombin time, activated partial thromboplastin time, and thrombin time were measured, and a hemolysis test was done to evaluate the hemocompatibility of prepared hydrogels.

RESULTS

The increase of the gelatin concentration in polyvinyl gelatin hydrogel increases the porosity and enhances the absorptivity of the prepared hydrogel. The measured hematological parameters indicated enhancement of hemocompatibility as the gelatin concentration was increased in the prepared hydrogel.

CONCLUSIONS

The results obtained from this study confirm that gelatin was able to improve the properties of the polyvinyl alcohol-gelatin hydrogel and enhance the hemocompatibility. Thus, the prepared hydrogel could be used in a variety of biomedical applications.

3D printed soft surgical planning prototype for a biliary tract rhabdomyosarcoma

Biliary tract rhabdomyosarcoma is a soft tissue malignant musculoskeletal tumor which is located in the biliary tract. Although this tumor represents less than 1% of the total amount of childhood cancers, when localized, a >70% overall 5-year survival rate, the resection is clinically challenging and complications might exist during the biliary obstruction. Although surgery remains a mainstay, complete tumor resection is generally difficult to achieve without mutilation and severe long-term sequelae. Therefore, manufacturing multi-material 3D surgical planning prototypes of the case provides a great opportunity for surgeons to learn beforehand what they can expect. Additionally, practicing before the operation enhances the probability of success. That is why different compositions of materials have been characterized to match the mechanical properties of the liver. To do this, Dynamic Mechanical Analysis (DMA) tests and Shore hardness tests have been carried out. Amongst the material samples produced, 6%wt PVA (poly vinyl alcohol)/1%wt PHY (Phytagel)-1FT (Freeze-Thaw cycles) and 1%wt agarose appear as the best options for mimicking the liver tissue in terms of viscoelasticity. Regarding the Shore hardness, the best solution is 1%wt agarose. Additionally, a surgical planning prototype using this last material mentioned was manufactured and validated using a CT (Computed Tomography) scanner. In most of the structures the difference between the 3D model and the organ in terms of dimensions is less than 3.35 mm, which represents a low dimensional error, around 1%. On the other hand, the total manufacturing cost of the 3D physical model was €513 which is relatively low in comparison with other technologies.

Valorization of marine-derived biowaste to develop chitin/fish gelatin products as bioactive carriers and moisture scavengers

Marine-derived biowaste was valorized to develop chitin/fish gelatin porous materials with the aim of being used as moisture scavengers and bioactive carriers. Chitin was extracted from squid pens, abundant and available biowastes from fishery industry, through a sustainable process and the environmental assessment was carried out. Besides the valorization of biowaste, it is worth noting that the use of this specific biowaste allows the avoidance of discoloration and demineralization processes to extract chitin and, thus, a lower consumption of resources, both chemicals and energy, in comparison to the conventional chitin extraction from crustacean shells. Consequently, this alternative source of chitin brings economic and environmental benefits. In addition to the reduction of food waste disposal, the incorporation of squid pen-extracted chitin into fish gelatin formulations led to the conversion of a biowaste into a value-added product. In this regard, chitin was employed as a reinforcing agent in order to improve the mechanical behavior of fish gelatin materials. It is worth noting that good compatibility between gelatin and chitin was achieved since no chitin aggregation was observed. Furthermore, more defined pores were obtained after chitin addition. Additionally, tetrahydrocurcumin was incorporated into the formulation as a bioactive and its release was analyzed during three days. It was observed that samples prepared with chitin and THC showed potential as active porous materials for bioactive delivery.

Coordination of Covalent Cross-Linked Gelatin Hydrogels via Oxidized Tannic Acid and Ferric Ions with Strong Mechanical Properties

The design of gelatin-based hydrogels with high mechanical strength, high gelation temperature, and a rapid self-healing property still presents a challenge to researchers. In the present study, single cross-linked gelatin-oxidized tannic acid (SC-GT/OTA) hydrogels were fabricated through covalent cross-linking between gelatin and tannic acid (TA) oxidized by using sodium periodate (NaIO₄). Double cross-linked gelatin-OTA-FeCl₃·6H₂O (DC-GT/OTA/Fe^III) hydrogels were also created using metal coordination bonds formed between the catechol groups present in OTA and Fe^III in ferric chloride. As a result, the maximum gelling temperature of the SC-GT/OTA hydrogel (37 °C) was considerably higher than that of the pure gelatin hydrogel (15.4 °C). Moreover, the maximum values of compressive stress of SC-GT/OTA hydrogels increased significantly by almost seven times the original value as the molar ratio of NaIO₄ to TA increased from 3:1 to 5:1. When the molar ratio of NaIO₄ to TA was maintained at the constant of 4:1, the storage modulus values of DC-GT/OTA/Fe^III hydrogels with the Fe^III-to-TA molar ratio of 1.5:1 were three to 4 orders of magnitude higher than those of SC-GT/OTA hydrogels in the whole angular frequency range. The double cross-linked gelatin hydrogels developed in this research can be used widely in agriculture and material science fields.

Fabrication and Characterization of Starch Nanohydrogels via Reverse Emulsification and Internal Gelation

Biopolymer-based nanohydrogels have great potential for various applications, including in food, nutraceutical, and pharmaceutical industries. Herein, starch nanohydrogels were prepared for the first time via reverse emulsification coupled with internal gelation. The effects of starch type (normal corn, potato, and pea starches), amylose content, and gelation time on the structural, morphological, and physicochemical properties of starch nanohydrogels were investigated. The diameter of starch nanohydrogel particles was around 100 nm after 12 h of retrogradation time. The relative crystallinity and thermal properties of starch nanohydrogels increased gradually with an increasing amylose content and gelation time. The swelling behavior of starch nanohydrogels was dependent upon the amylose content, and the swelling ratios were between 2.0 and 14.0, with the pea starch nanogels exhibiting the lowest values and the potato starch nanogels exhibiting the highest values.

Viscoplastic fracture transition of a biopolymer gel

Physical gels are swollen polymer networks consisting of transient crosslink junctions associated with hydrogen or ionic bonds. Unlike covalently crosslinked gels, these physical crosslinks are reversible thus enabling these materials to display highly tunable and dynamic mechanical properties. In this work, we study the polymer composition effects on the fracture behavior of a gelatin gel, which is a thermoreversible biopolymer gel consisting of denatured collagen chains bridging physical network junctions formed from triple helices. Below the critical volume fraction for chain entanglement, which we confirm via neutron scattering measurements, we find that the fracture behavior is consistent with a viscoplastic type process characterized by hydrodynamic friction of individual polymer chains through the polymer mesh to show that the enhancement in fracture scales inversely with the squared of the mesh size of the gelatin gel network. Above this critical volume fraction, the fracture process can be described by the Lake-Thomas theory that considers fracture as a chain scission process due to chain entanglements.

3D Printed Organ Models for Surgical Applications

Medical errors are a major concern in clinical practice, suggesting the need for advanced surgical aids for preoperative planning and rehearsal. Conventionally, CT and MRI scans, as well as 3D visualization techniques, have been utilized as the primary tools for surgical planning. While effective, it would be useful if additional aids could be developed and utilized in particularly complex procedures involving unusual anatomical abnormalities that could benefit from tangible objects providing spatial sense, anatomical accuracy, and tactile feedback. Recent advancements in 3D printing technologies have facilitated the creation of patient-specific organ models with the purpose of providing an effective solution for preoperative planning, rehearsal, and spatiotemporal mapping. Here, we review the state-of-the-art in 3D printed, patient-specific organ models with an emphasis on 3D printing material systems, integrated functionalities, and their corresponding surgical applications and implications. Prior limitations, current progress, and future perspectives in this important area are also broadly discussed.

Preparation of a Strong Gelatin-Short Linear Glucan Nanocomposite Hydrogel by an in Situ Self-Assembly Process

Gelatin hydrogels exhibit excellent biocompatibility, nonimmunogenicity, and biodegradability, but they have limited applications in the food and medical industries because of their poor mechanical properties. Herein, we first developed an in situ self-assembly process for the preparation of gelatin-short linear glucan (SLG) nanocomposite hydrogels with enhanced mechanical strength. The microstructure, dynamic viscoelasticity, compression behavior, and thermal characteristics of the gelatin-SLG nanocomposite hydrogels were determined using scanning electron microscopy (SEM), dynamic rheological experiments, compression tests, and texture profile analysis tests. The SEM images revealed that nanoparticles were formed by the in situ self-assembly of SLG in the gelatin matrix and that the size of these nanoparticles ranged between 200 and 600 nm. The pores of the nanocomposite hydrogels were smaller than those of the pure gelatin hydrogels. Transmission electron microscopy images and X-ray diffraction further confirmed the presence of SLG nanoparticles with spherical shapes and B-type structures. Compared with pure gelatin hydrogels, the nanocomposite hydrogels exhibited improved mechanical behavior. Notably, the hardness and maximum values of the compressive stress of gelatin-SLG nanocomposites containing 5% SLG increased by about 2-fold and 3-fold, respectively, compared to the corresponding values of pure gelatin hydrogels.

A rapid and simple UPLC-MS/MS method using collagen marker peptides for identification of porcine gelatin

Gelatin, which is mainly derived from bovine and porcine sources, has been used in many foods and pharmaceutical products. To ensure the compliance of food products with halal regulations, reliable analytical methods are very much required. In this study, one unique marker peptide for porcine gelatins was selected to develop an UPLC-MS/MS multiple reaction monitoring method. The capability of this method to identify porcine materials was demonstrated by analyzing in-house-made gelatins containing different amounts of porcine gelatins and commercial gelatin products. The adulteration of porcine gelatin could be sensitively detected at a low level of 0.04%. When combined with HPLC and mass spectrometry, this method is an accurate and sensitive quantitative method to identify porcine gelatins. Thus, the strategy can be used to verify halal authenticity of gelatin.

Gelatin, which is mainly derived from bovine and porcine sources, has been used in many foods and pharmaceutical products.