Search Results (2,200)

Background/Objectives: Within the spectrum of lactic acid bacteria, Lacticaseibacillus casei and Lactobacillus johnsonii are of particular technological and nutritional significance. Protein fortification of fermented dairy systems offers dual benefits: it improves product quality while enhancing probiotic resilience. Supplementary proteins supply bioavailable nitrogen and peptides that stimulate bacterial metabolism and contribute to a viscoelastic gel matrix that buffers cells against gastric acidity and bile salts. The aim of this study was to clarify the functional potential of such formulations by assessing probiotic survival under in vitro digestion simulating oral, gastric, and intestinal phases. Methods: Sheep milk was fermented with L. casei 431 or L. johnsonii LJ in the presence of whey protein isolate (WPI), soy protein isolate (SPI), or pea protein isolate (PPI) at concentrations of 1.5% and 3.0%. Physicochemical parameters (pH, titratable acidity, color, syneresis), organoleptic properties, and microbiological counts were evaluated. The viability of L. casei and L. johnsonii was determined at each digestion stage, and probiotic survival rates were calculated. Results: Samples with L. johnsonii consistently exhibited lower pH values compared to L. casei. Across both bacterial strains, the addition of 1.5% protein isolate more effectively limited syneresis than 3.0%, regardless of protein type. Samples fortified with WPI at 1.5% (JW1.5) and 3.0% (JW3.0) were rated highest by the panel, demonstrating smooth, homogeneous textures without grittiness. The greatest bacterial survival (>70%) was observed in WPI-fortified samples (JW1.5, JW3.0) and in SPI-fortified JS3. Conclusions: Protein isolates of diverse origins are suitable for the enrichment of fermented sheep milk, with 1.5% supplementation proving optimal. Such formulations maintained desirable fermentation dynamics and, in most cases, significantly improved the survival of L. casei and L. johnsonii under simulated gastrointestinal conditions, underscoring their potential in the development of functional probiotic dairy products. Full article

Experimental analysis of the viscoelastic properties of natural polymers over different testing durations and response time scales yields complementary insights into their static and dynamic mechanical behavior. Within this context, Brillouin spectroscopy has emerged as a contactless, non-invasive and label-free tool for the mechanical characterization of materials. In this review article, we provide a comprehensive overview of recent advances in Brillouin spectroscopy techniques applied to various natural polymers, including proteins, carbohydrates, and polysaccharides. We discuss the principles of Brillouin scattering and their application in investigating the mechanical properties of natural polymers. Additionally, we explore future perspectives and challenges. This review aims to provide researchers and practitioners with a comprehensive understanding of the capabilities and limitations of Brillouin spectroscopy for the mechanical characterization of natural polymers, promoting new advances in this interdisciplinary field. Full article

Fish gelatins are increasingly recognized as sustainable biopolymers for food, packaging, and biomedical applications; however, their functional performance often requires improvement. In this study, the effects of transglutaminase (TG) modification on the physicochemical and structural properties of trout (T) and sea bass (SB) gelatins were systematically investigated. TG treatment enhanced gel strength in a species- and concentration-dependent manner, with trout increasing from 100 g (control) to 108 g at 0.04% TG and SB reaching a maximum of 163 g at 0.01% TG. Rheological measurements confirmed improved viscoelastic behavior, particularly in trout samples (G′ > G″). Emulsifying activity was optimized at 0.02–0.04% TG in trout, while excessive cross-linking reduced interfacial activity; nevertheless, emulsion stability was improved in both species. Foaming capacity and stability reached 195% and 148%, respectively, in trout, whereas higher TG concentrations led to reductions in SB foaming performance. Scanning electron microscopy revealed denser and more homogeneous networks in TG-modified gels, correlating with their enhanced rigidity. Transparency remained high, while zeta potential shifted toward more negative values, indicating improved colloidal stability. FTIR, UV–Vis, and DSC analyses confirmed conformational rearrangements and thermal stabilization after cross-linking. Minor decreases in oil-binding capacity and slight color changes were also observed. Overall, TG cross-linking significantly enhanced the functional and structural properties of fish gelatins in a source-dependent manner, supporting their potential as versatile and sustainable biopolymers for diverse industrial applications. Full article

Magnetic hydrogels are stimulus-responsive hydrogels with rapid response when placed in a magnetic field. Their properties include those of conventional hydrogels such as biocompatibility, viscoelasticity, and a high content of water, with the addition of magnetic actuation, magnetothermal conductivity, and magnetic resonance conferred by the magnetic particles. Their use in the biomedical field is constantly growing, with various applications such as drug delivery, hyperthermia treatment, theranostic, and tissue engineering. Since the research field of magnetic hydrogels is very dynamic, it is important to review the literature regularly to highlight the most recent insights of the field. In this review, we focused on the latest advances of magnetic hydrogels and give a large overview on their types, fabrication, properties, and applications in hyperthermia, drug delivery, wound healing, MRI, sensors, and tissue engineering (neural, cartilage, bone, and cardiac tissues). We concluded this review with challenges and future developments of magnetic hydrogels. Full article

Room-temperature self-healing polyurethanes (PUs) generally show limited mechanical properties. In order to improve the mechanical properties of PUs without sacrificing their self-healing ability, in this study, different amounts of halloysite clay filler were added. Thus, intrinsically self-healing PUs were synthesized using polycarbonate diol polyol, aliphatic diisocyanate, 1,4-butanediol, and different amounts (0.5–10 wt.%) of thermally treated halloysite. During synthesis, the halloysite clay was added to the polyol. The structural, thermal, viscoelastic, and mechanical properties of the resulting halloysite-filled PUs were evaluated. All halloysite-filled PUs retained their room-temperature self-healing capability while exhibiting improved mechanical strength. The PU with 0.5 wt.% halloysite (E0.5) showed the most balanced performance, with well-dispersed halloysite nanotubes intercalated within the soft segments, enhancing chain mobility and soft segment ordering. Higher halloysite loadings (1–3 wt.%) led to increased mechanical properties but also some round clay particle agglomeration and surface migration, leading to limited halloysite–polyurethane interactions. The addition of more than 3 wt.% halloysite did not result in further improvements in mechanical properties. The findings of this study provide new insight into the filler–polymer interaction mechanism and establish a foundation for the design of multifunctional PUs with both autonomous self-repair and enhanced mechanical performance. Full article

This study examines how diabetes mellitus and physiological aging influence the nanomechanical behavior of rat rib cortical bone using combined static and dynamic nanoindentation. Ribs from young control, old, and streptozotocin-induced diabetic rats were analyzed to quantify both intrinsic and frequency-dependent mechanical properties. Static nanoindentation revealed markedly higher hardness and elastic modulus in the diabetic group (0.47 ± 0.22 GPa and 9.53 ± 3.03 GPa, respectively) compared to controls (0.11 ± 0.03 GPa and 3.21 ± 0.51 GPa; p < 0.001). The modulus-to-hardness ratio, an indicator of fracture toughness, was reduced from 30.34 in controls to 20.45 in diabetics, suggesting increased stiffness but greater brittleness. Dynamic nanoindentation (0–4.5 Hz) demonstrated significant aging-related changes in the storage and loss moduli (p < 0.001), while the loss factor (tan δ < 1) and viscosity remained similar across groups, indicating predominantly solid-like behavior. These results show that diabetes stiffens bone tissue through matrix-level alterations, whereas aging primarily affects its viscoelastic damping capacity. The combined static–dynamic nanoindentation protocol provides a robust framework for distinguishing disease- and age-related bone degradation at the tissue scale. Translationally, the findings help explain why bones in diabetic or elderly individuals may fracture despite normal mineral density, underscoring the need to assess bone quality beyond conventional densitometry. Full article

We present a novel formulation of the Rayleigh–Plesset equation to describe stable gas bubble dynamics in viscoelastic media, using bubble volume variation, rather than radius, as the primary variable of the resulting nonlinear ordinary differential equation. This formulation incorporates the linear Kelvin–Voigt model as the constitutive relation for the surrounding fluid, capturing both viscous and elastic contributions, to track the oscillations of a gas bubble subjected to an ultrasonic field over time. The proposed model is solved numerically, subjected to a convergence analysis, and validated by comparisons with theoretical and experimental results from the literature. We systematically investigate the nonlinear oscillations of a single spherical gas bubble in various viscoelastic environments, each modeled with varying levels of rheological complexity. The influence of medium properties, specifically shear elasticity and viscosity, is examined in detail across both linear and nonlinear regimes. This work improves our understanding of stable cavitation dynamics by emphasizing key differences from Newtonian fluid behavior, resonance frequency, phase shifts, and oscillation damping. Elasticity has a pronounced effect in low-viscosity media, whereas viscosity emerges as the dominant factor modulating the amplitude of oscillations in both the linear and nonlinear regimes. The model equation developed here provides a robust tool for analyzing how viscoelastic properties affect bubble dynamics, contributing to improved the prediction and control of stable cavitation phenomena in complex media. Full article

Magnetorheological elastomers (MREs) are composed of soft silicone rubber, carbonyl iron particles (CIPs), and various additives. This study designs and fabricates a novel hybrid-mode MRE isolator that can operate in both compression and shear modes simultaneously. Experimental and modeling investigations are conducted to examine the dynamic mechanical properties of the hybrid-mode MRE isolator under varying excitation frequencies, displacement amplitudes, and magnetic field strengths. The equivalent stiffness, energy dissipation, and equivalent damping of the MRE isolator are determined. Experimental results reveal that the hybrid-mode MRE isolator exhibits a pronounced MR effect by utilizing a hybrid magnetic field generation system, with all three parameters significantly increasing as the magnetic field strength increases. However, as the excitation frequency increases, the equivalent stiffness and energy dissipation increase, while the equivalent damping decreases. Based on the experimental findings, a compression–shear hybrid fractional-derivative parametric (CSHF) model is proposed to describe the impact of different operating conditions on the dynamic viscoelastic properties of the MRE isolator. A comparative analysis of the experimental results and model predictions indicates that the proposed mechanical model can accurately describe the dynamic mechanical characteristics of the hybrid-mode MRE isolator. Full article

The development of biodegradable films with antioxidant properties offers a promising approach to food preservation. This study focused on creating and characterising mango starch-based films enriched with mango peel extract (MPE) at concentrations of 0, 1, and 2%, using peels from mangoes (Mangifera indica var. Corazon) at organoleptic maturity, obtained as residual byproducts (peel and seed) for active food packaging applications. An MPE extraction yield of 35.57 ± 2.74% was achieved using ultrasound-assisted extraction (UAE), confirming its rich phenolic content and antioxidant activity as a natural alternative to synthetic preservatives. Rheological analysis revealed that the films exhibited pseudoplastic behavior, with complex viscosity reducing as angular frequency increased. Incorporating MPE at concentrations up to 1% enhanced the films’ viscoelastic properties, while a 2% addition significantly altered their frequency and temperature dependence. The rheological modeling showed that the fractional Maxwell model with two springpots described the films more accurately than the generalized Maxwell model. This approach offered a clearer understanding of their viscoelastic response, especially under changes in frequency and temperature. Mechanical characterization indicated that adding MPE improved film strength while reducing solubility. Although film thickness remained unchanged, increasing MPE concentration led to greater opacity and darker coloration. These changes offer advantages in food packaging by enhancing UV protection and reducing oxidative degradation. Crucially, the incorporation of MPE significantly increased the phenolic content and antioxidant capacity of the films, as confirmed by ABTS assays. These findings strongly support the potential of MPE-based films for active packaging, providing a sustainable and functional alternative for preserving light-sensitive food products. Among the tested formulations, films with 1% MPE demonstrated the most effective balance of rheological stability, mechanical strength, and antioxidant capacity. Full article

Background/Objectives: Local delivery of gene therapy products through the airways shows great promise for the treatment of a number of serious lung diseases, but its effectiveness is hampered by the mucus layer protecting the lung epithelium in the trachea and bronchi. Methods: To overcome this barrier, we engineered carbon dots (CDs) with mucus penetrating properties. Results: The CDs were synthesized by solvothermal treatment of citric acid and branched polyethyleneimine, and functionalized with maleamic acid groups to create cationic mucoinert nanoparticles with tunable charge. We characterized their interactions with a mucus model through turbidity and transport measurements, and assessed their impact on the viscoelastic properties of the biopolymer. We then demonstrated that the carriers are effective at delivering pDNA to a variety of cell models in vitro. In particular, mucus-producing Calu-3 cells cultured at the air–liquid interface (ALI) were used as a discriminating model to evaluate intracellular delivery of the genetic cargo through a thick layer of mucus at the cell surface. Conclusions: The functionalization of CDs with maleamic acid groups resulted in a 1000- to 10,000-fold increase in transfection efficiency in the mucus-producing model, offering new opportunities for lung gene therapy. Full article

Consistent volumetric flow control is essential in extrusion-based additive manufacturing, particularly when printing viscoelastic materials with complex rheological properties. This study proposes a control framework incorporating simplified rheological dynamics via a Kelvin–Voigt model that integrates nonlinear dynamic modeling, an unknown input observer (UIO), and a closed-loop PID controller to regulate material flow in a motorized electro-pneumatic extrusion system. A comprehensive state-space model is developed, capturing both mechanical and rheological dynamics. The UIO estimates unmeasurable internal states—specifically, syringe plunger velocity—which are critical for real-time flow regulation. Simulation results validate the observer’s accuracy, while experimental trials with a curing silicone resin confirm that the system can achieve steady extrusion and maintain stable linewidth once transient disturbances settle. The proposed system leverages a dual-mode actuation mechanism—combining pneumatic buffering and motor-based adjustment—to achieve responsive and robust control. This architecture offers a compact, sensorless solution well-suited for high-precision applications in bioprinting, electronics, and soft robotics, and provides a foundation for intelligent flow regulation under dynamic material behaviors. Full article

This study aims to evaluate the effects of repeated mechanical recycling on the properties of a novel aliphatic polyketone composite reinforced with 15 wt% and 30 wt% glass fibers (PK15GF and PK30GF), providing insights into its potential for sustainable engineering applications. The investigation focuses on three main aspects: changes in melt flow index (MFI) and viscosity, the influence of glass fiber content on thermal and mechanical stability, and the retention of structural integrity and crystallinity under multiple processing cycles. Composites, commercially available since 2019, were subjected to single- and five-cycle recycling with 100% reprocessed content. Comprehensive characterization—including tensile testing, Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Fourier Transform Infrared Spectroscopy (FT-IR), Melt-Flow Index (MFI), Differential Thermal Analysis (DTA), and mechanical tensile testing—revealed filler-dependent alterations in morphology, thermal stability, and crystallinity. MFI decreased from 100.56 to 42.63 g/10 min for PK15GF, indicating pronounced chain scission, recombination, and crosslinking, whereas PK30GF decreased only from 89.00 to 59.76 g/10 min. FT-IR spectra confirmed greater crosslinking in PK15GF, while DSC and DMA demonstrated smaller T_g and ΔHm variations in PK30GF (T_g +0.45 °C, ΔHm −13.93 J·g⁻¹) versus PK15GF (T_g +1.13 °C, ΔHm −69.24 J·g⁻¹). These findings reveal that higher glass fiber content mitigates degradation, preserves structural integrity, and maintains thermal and viscoelastic stability, establishing clear correlations between filler content, mechanical performance, and recyclability. Overall, this work provides mechanistic insights into degradation pathways and demonstrates the potential of glass fiber-reinforced aliphatic polyketones for sustainable, high-performance engineering and automotive applications. Full article

Understanding adsorption and interfacial properties of surface-active agents at interfaces is crucial to the formation and stability of colloidal systems such as emulsions and foams. In this work, interfacial tension and viscoelasticity of saponin at the β-pinene/water interface were studied using drop tensiometry and dilational rheology measurement. For comparison, saponin at the air/water interface was also evaluated. Both saponin and β-pinene are bio-based, eco-friendly, and abundant in plants, trees, and agricultural wastes. Results showed that dynamic interfacial tensions σ(t) of saponin adsorbed at β-pinene/water and air/water interfaces could be well described by the Ward and Tordai model, suggesting that the saponin adsorption kinetics at both interfaces are controlled by a kinetically limited mechanism. The equilibrium interfacial pressure π_e data prior to critical micelle concentration (cmc) were adequately fitted by the Gibbs adsorption isotherm. At the β-pinene/water interface, a higher cmc and a larger area per molecule, but a lower π_e, were observed compared to the air/water interface. Interestingly, the dilational moduli of saponin at β-pinene/water increased with increasing oscillating frequency, but with less significant frequency dependence than their counterparts at the air/water interface. The dilational moduli of saponin at β-pinene/water passed through a minimum with increasing saponin bulk concentration, while the air/water interface exhibited a strikingly different trend in terms of concentration dependence and a higher magnitude for the dilational moduli. The correlation between adsorption behaviors and dilational properties of saponin at the two interfaces is discussed. Fundamental knowledge gained from this study will be beneficial for the rational development of new biocompatible emulsions and foam products for more sustainable applications. Full article

Dry eye disease (DED) is a multifactorial ocular surface disorder that significantly affects vision and quality of life. While artificial tears are the standard first-line therapy, their effectiveness is limited by the complex pathophysiology of DED. This study evaluated DayDrop^® Triple Action, a novel formulation combining hyaluronic acid (HA), ectoine, and carboxymethylcellulose (CMC), designed to enhance tear film stability and ocular surface protection. Physicochemical and rheological properties were assessed, including viscosity, pseudoplasticity, and viscoelastic behaviour under dynamic conditions, along with ectoine release over 24 h. An in vitro allergic conjunctivitis model using conjunctival fibroblasts exposed to a pro-allergic cytokine cocktail was employed to examine immunomodulatory effects. DayDrop^® Triple Action demonstrated high viscosity with pronounced pseudoplasticity and stable viscoelasticity, supporting improved mucoadhesion. The formulation provided sustained ectoine release and exhibited a positive immunomodulatory effect, likely linked to ectoine’s preferential hydration mechanism, which stabilizes membranes and reduces inflammatory signalling. These findings suggest that DayDrop^® Triple Action integrates viscoelastic optimization, osmoprotection, and targeted anti-inflammatory action, offering a promising non-pharmacological strategy for managing DED and allergic ocular surface disorders. Full article

Concrete materials undergo a series of physical and chemical changes under high temperature, leading to the degradation of mechanical properties. This study investigates basalt fiber-reinforced concrete (BFRC) through high-temperature testing using the split Hopkinson pressure bar (SHPB) apparatus. Impact compression tests were conducted on specimens after exposure to elevated temperatures to analyze the effects of varying fiber content, temperature levels, and impact rates on the mechanical behaviors of BFRC. Based on fractional calculus theory, a dynamic constitutive equation was established to characterize the viscoelastic properties and high-temperature damage of BFRC. The results indicate that the dynamic compressive strength of BFRC decreases significantly with increasing temperature but increases gradually with higher impact rates, demonstrating fiber-toughening effects, thermal degradation effects, and strain rate strengthening effects. The proposed constitutive model aligns well with the experimental data, effectively capturing the dynamic mechanical behaviors of BFRC after high-temperature exposure, including its transitional mechanical characteristics across elastic, viscoelastic, and viscous states. The viscoelastic behaviors of BFRC are fundamentally attributed to the synergistic response of its multi-phase composite system across different scales. Basalt fibers enhance the material’s elastic properties by improving the stress transfer mechanism, while high-temperature exposure amplifies its viscous characteristics through microstructural deterioration, chemical transformations, and associated thermal damage. Full article