[Viscoelasticity-based point of care coagulation diagnostics in the context of resuscitation room management of severely injured and bleeding trauma patients : Diagnostics and treatment of trauma-induced coagulopathy]. / Viskoelastizitätsbasierte "Point-of-care"-Gerinnungsdiagnostik im Kontext des Schockraummanagements von blutenden Traumapatienten : Diagnostik und Therapie der traumainduzierten Koagulopathie.

Uncontrolled bleeding with associated trauma-induced coagulopathy (TIC) remains the leading cause of preventable death after severe trauma. Meanwhile, TIC is recognized as a separate clinical entity with substantial impact on downstream morbidity and mortality. In clinical practice severely injured and bleeding patients are often still being treated according to established damage control surgery (DCS) procedures with surgical bleeding control and empirical transfusion of classical blood products in predefined ratios in the sense of damage control resuscitation (DCR); however, algorithms are also available, which have been constructed from established viscoelasticity-based point of care (POC) diagnostic procedures and target value-oriented treatments. The latter enables a timely qualitative assessment of coagulation function from whole blood at bedside and provides rapid and clinically useful information on the presence, development and dynamics of the coagulation disorder. The early implementation of viscoelasticity-based POC procedures in the context of resuscitation room management of severely injured and bleeding patients was uniformly associated with reductions in potentially harmful blood products, especially overtransfusions, and an overall improvement in outcome including survival. The present article reviews the clinical questions around the use of viscoelasticity-based procedures as well as recommendations for the early and acute management of bleeding trauma patients taking the current literature into account.

Management of partially absorbed white soft cataract post penetrating injury to eye.

Background: A measurable burden to the emergency ophthalmology department is represented by ocular trauma in pediatric patients. Traumatic cataracts still result in visual disability despite great advancements in diagnostic and treatment methods. Cataract surgery with intraocular lens (IOL) implantation aids in the improvement of visual acuity in such cases. Duration of trauma is an important prognostic factor for recovery of visual acuity before amblyopia sets in young patients with penetrating ocular injury. Purpose: This video deals with the management of a case of partially absorbed traumatic cataract in a scenario of an old and neglected penetrating injury. This case had a corneal scar, ruptured anterior lens capsule, and posterior synechiae formation between the posterior pigmented epithelium of the iris and the lens capsule. Synopsis: In a case of penetrating ocular injury, one should always suspect violation of posterior lens capsule, weakened or broken zonules and retained intraocular foreign body. In this case, a circular capsulorhexis is difficult to attain. After staining the capsule with trypan blue dye, viscoelastic substance is instilled in the anterior chamber to have good control over the rhexis and to avoid rhexis run out. In case the rhexis runs off to the equator, a pair of Vannas scissors is used to cut the extended flap. The cataract is partially absorbed, white and soft in nature and is easily mobilized from the bag and eaten up via phacoaspiration. Before implantation of posterior chamber intraocular lens (PCIOL) in the sulcus, posterior synechiae are released by swiping a cyclodialysis spatula in the sulcus area. Visual axis is cleared by giving nicks in the posterior capsule to remove the central dense posterior plaque. Automated anterior vitrectomy is done and a three-piece PCIOL is implanted safely in the ciliary sulcus. Retained viscoelastic substance is washed, intracameral antibiotic is instilled, and the anterior chamber is subsequently formed via stromal wound hydration. Highlights: Through this video, we tried to show how one should proceed with phacoaspiration with intraocular lens implantation in a case of traumatic cataract post penetrating injury in a sequential manner. Video Link: https://youtu.be/20DbYUn_Fd8.

Mechanism and Effects of Cellular Creep in a Microfluidic Filter.

Biomicroparticles such as proteins, bacterium, and cells are known to be viscoelastic, which significantly affects their performance in microfluidic applications. However, the exact effects and the quantitative study of cellular viscoelastic creep within different applications remain unclear. In this study, the cellular-deforming evolution within a filter unit was studied using a multiphysics numerical model. A general cellular creep deformation process of viscoelastic particle trapping in pores was revealed. Two featured variables, namely, the maximum surface displacement and the volumetric strain, were identified and determined to quantitatively describe the evolution. The effects of flow conditions and physical characteristics of the microparticles were studied. Furthermore, a Giardia concentration experiment was conducted using an integrated hydraulic filtration system with a porous membrane. The experimental results agreed well with the numerical analysis, indicating that, compared to pure elastic particles, it is more difficult to release cellular material matters including cells, chemical synthetic particles, and microbes from trapping due to their time-accumulated creep deformation.

Microrheology of Pseudomonas aeruginosa biofilms grown in wound beds.

A new technique was used to measure the viscoelasticity of in vivo Pseudomonas aeruginosa biofilms. This was done through ex vivo microrheology measurements of in vivo biofilms excised from mouse wound beds. To our knowledge, this is the first time that the mechanics of in vivo biofilms have been measured. In vivo results are then compared to typical in vitro measurements. Biofilms grown in vivo are more relatively elastic than those grown in a wound-like medium in vitro but exhibited similar compliance. Using various genetically mutated P. aeruginosa strains, it is observed that the contributions of the exopolysaccharides Pel, Psl, and alginate to biofilm viscoelasticity were different for the biofilms grown in vitro and in vivo. In vitro experiments with collagen containing medium suggest this likely arises from the incorporation of host material, most notably collagen, into the matrix of the biofilm when it is grown in vivo. Taken together with earlier studies that examined the in vitro effects of collagen on mechanical properties, we conclude that collagen may, in some cases, be the dominant contributor to biofilm viscoelasticity in vivo.

Evaluation of a single-shot of a high-density viscoelastic solution of hyaluronic acid in patients with symptomatic primary knee osteoarthritis: the no-dolor study.

BACKGROUND: Pronolis®HD mono 2.5% is a novel, one-shot, high-density sterile viscoelastic solution, recently available in Spain, which contains a high amount of intermediate molecular weight hyaluronic acid (HA), highly concentrated (120 mg in 4.8 mL solution: 2.5%). The objective of the study was to analyze the efficacy and safety of this treatment in symptomatic primary knee osteoarthritis (OA). METHODS: This observational, prospective, multicenter, single-cohort study involved 166 patients with knee OA treated with a single-shot of Pronolis®HD mono 2.5% and followed up as many as 24 weeks. RESULTS: Compared with baseline, the score of the Western Ontario and McMaster Universities Arthritis Osteoarthritis Index (WOMAC) pain subscale reduced at the 12-week visit (primary endpoint, median: 9 interquartile range [IQR]: 7-11 versus median: 4; IQR: 2-6; p < 0.001). The percentage of patients achieving > 50% improvement in the pain subscale increased progressively from 37.9% (at 2 weeks) to 66.0% (at 24 weeks). Similarly, WOMAC scores for pain on walking, stiffness subscale, and functional capacity subscale showed significant reductions at the 12-week visit which were maintained up to the 24-week visit. The EuroQol visual analog scale score increased after 12 weeks (median: 60 versus 70). The need for rescue medication (analgesics/nonsteroidal anti-inflammatory drugs) also decreased in all post-injection visits. Three patients (1.6%) reported local adverse events (joint swelling) of mild intensity. CONCLUSIONS: In conclusion, a single intra-articular injection of the high-density viscoelastic gel of HA was associated with pain reduction and relief of other symptoms in patients with knee OA. TRIAL REGISTRATION: ClinicalTrial# NCT04196764.

Evaporation-controlled dripping-onto-substrate (DoS) extensional rheology of viscoelastic polymer solutions.

Extensional flow properties of polymer solutions in volatile solvents govern many industrially-relevant coating processes, but existing instrumentation lacks the environment necessary to control evaporation. To mitigate evaporation during dripping-onto-substrate (DoS) extensional rheology measurements, we developed a chamber to enclose the sample in an environment saturated with solvent vapor. We validated the evaporation-controlled DoS device by measuring a model high molecular weight polyethylene oxide (PEO) in various organic solvents both inside and outside of the chamber. Evaporation substantially increased the extensional relaxation time [Formula: see text] for PEO in volatile solvents like dichloromethane and chloroform. PEO/chloroform solutions displayed an over 20-fold increase in [Formula: see text] due to the formation of an evaporation-induced surface film; evaporation studies confirmed surface features and skin formation reminiscent of buckling instabilities commonly observed in drying polymer solutions. Finally, the relaxation times of semi-dilute PEO/chloroform solutions were measured with environmental control, where [Formula: see text] scaled with concentration by the exponent [Formula: see text]. These measurements validate the evaporation-controlled DoS environment, and confirm that chloroform is a good solvent for PEO, with a Flory exponent of [Formula: see text]. Our results are the first to control evaporation during DoS extensional rheology, and provide guidelines establishing when environmental control is necessary to obtain accurate rheological parameters.

Sculpting tissues by phase transitions.

Biological systems display a rich phenomenology of states that resemble the physical states of matter - solid, liquid and gas. These phases result from the interactions between the microscopic constituent components - the cells - that manifest in macroscopic properties such as fluidity, rigidity and resistance to changes in shape and volume. Looked at from such a perspective, phase transitions from a rigid to a flowing state or vice versa define much of what happens in many biological processes especially during early development and diseases such as cancer. Additionally, collectively moving confluent cells can also lead to kinematic phase transitions in biological systems similar to multi-particle systems where the particles can interact and show sub-populations characterised by specific velocities. In this Perspective we discuss the similarities and limitations of the analogy between biological and inert physical systems both from theoretical perspective as well as experimental evidence in biological systems. In understanding such transitions, it is crucial to acknowledge that the macroscopic properties of biological materials and their modifications result from the complex interplay between the microscopic properties of cells including growth or death, neighbour interactions and secretion of matrix, phenomena unique to biological systems. Detecting phase transitions in vivo is technically difficult. We present emerging approaches that address this challenge and may guide our understanding of the organization and macroscopic behaviour of biological tissues.

Endocytic proteins with prion-like domains form viscoelastic condensates that enable membrane remodeling.

Membrane invagination and vesicle formation are key steps in endocytosis and cellular trafficking. Here, we show that endocytic coat proteins with prion-like domains (PLDs) form hemispherical puncta in the budding yeast, Saccharomyces cerevisiae These puncta have the hallmarks of biomolecular condensates and organize proteins at the membrane for actin-dependent endocytosis. They also enable membrane remodeling to drive actin-independent endocytosis. The puncta, which we refer to as endocytic condensates, form and dissolve reversibly in response to changes in temperature and solution conditions. We find that endocytic condensates are organized around dynamic protein-protein interaction networks, which involve interactions among PLDs with high glutamine contents. The endocytic coat protein Sla1 is at the hub of the protein-protein interaction network. Using active rheology, we inferred the material properties of endocytic condensates. These experiments show that endocytic condensates are akin to viscoelastic materials. We use these characterizations to estimate the interfacial tension between endocytic condensates and their surroundings. We then adapt the physics of contact mechanics, specifically modifications of Hertz theory, to develop a quantitative framework for describing how interfacial tensions among condensates, the membrane, and the cytosol can deform the plasma membrane to enable actin-independent endocytosis.

Enhanced microscopic dynamics in mucus gels under a mechanical load in the linear viscoelastic regime.

Mucus is a biological gel covering the surface of several tissues and ensuring key biological functions, including as a protective barrier against dehydration, pathogen penetration, or gastric acids. Mucus biological functioning requires a finely tuned balance between solid-like and fluid-like mechanical response, ensured by reversible bonds between mucins, the glycoproteins that form the gel. In living organisms, mucus is subject to various kinds of mechanical stresses, e.g., due to osmosis, bacterial penetration, coughing, and gastric peristalsis. However, our knowledge of the effects of stress on mucus is still rudimentary and mostly limited to macroscopic rheological measurements, with no insight into the relevant microscopic mechanisms. Here, we run mechanical tests simultaneously to measurements of the microscopic dynamics of pig gastric mucus. Strikingly, we find that a modest shear stress, within the macroscopic rheological linear regime, dramatically enhances mucus reorganization at the microscopic level, as signaled by a transient acceleration of the microscopic dynamics, by up to 2 orders of magnitude. We rationalize these findings by proposing a simple, yet general, model for the dynamics of physical gels under strain and validate its assumptions through numerical simulations of spring networks. These results shed light on the rearrangement dynamics of mucus at the microscopic scale, with potential implications in phenomena ranging from mucus clearance to bacterial and drug penetration.

A Biosynthetic Hybrid Spidroin-Amyloid-Mussel Foot Protein for Underwater Adhesion on Diverse Surfaces.

Strong underwater adhesives are attractive materials for biomedical healing and underwater repair, but their success in applications has been limited, owing to challenges with underwater setting and with balancing surface adhesion and cohesion. Here, we applied synthetic biology approaches to overcome these challenges through design and synthesis of a novel hybrid protein consisting of the zipper-forming domains of an amyloid protein, flexible spider silk sequences, and a dihydroxyphenylalanine (DOPA)-containing mussel foot protein (Mfp). This partially structured, hybrid protein can self-assemble into a semi-crystalline hydrogel that exhibits high strength and toughness as well as strong underwater adhesion to a variety of surfaces, including difficult-to-adhere plastics, tendon, and skin. The hydrogel allows selective debonding by oxidation or iron-chelating treatments. Both the material design and the biosynthetic approach explored in this study will inspire future work for a wide range of hybrid protein-based materials with tunable properties and broad applications.

Ultra-light poly(lactic acid)/SiO2 aerogel composite foam: A fully biodegradable and full life-cycle sustainable insulation material.

In this study, a fully biodegradable ultra-light poly(lactic acid)/silicon dioxide (PLA/SiO2) aerogel nanocomposite with ultra-low thermal conductivity was successfully fabricated. PLA used was a produced from lactic acid, where the lactic acid has been produced from carbohydrates. The rheological properties of PLA were enhanced by diphenylmethane diisocyanate (MDI). The foaming properties, cell density, cell size uniformity, mechanical properties and thermal conductivity and thermal diffusivity of PLA were further improved by SiO2 aerogel, and finally the ultra-low density foamed material was prepared by supercritical CO2. The density of PLA foam can be as low as 0.02 g/cm3 and the thermal conductivity as low as 0.02628 W/m·K. The PLA-based composites can be used in many fields such as thermal insulation, vibration damping and packaging, and can be fully biodegradable and sustainable throughout their life cycle, which meets the global trend of energy saving and emission reduction.

Photoresponsive Viscoelastic Solutions Based on Chiral Wormlike Micelles in Mixed Solutions Containing an Amphiphile Derived from Rosin.

A novel rosin-based photoresponsive anionic amphiphile, sodium N-azophenyl maleopimaric acid imide carboxylate (AzoMPCOONa), has been successfully synthesized. Its molecular structure was characterized by 1H and 13C NMR and mass spectrometry (MS). The photoisomerization of AzoMPCOONa was evaluated by ultraviolet (UV)-visible spectrometry and 1H NMR. The structure of AzoMPCOONa could be converted between the trans and cis isomers by irradiation with UV/visible light. Importantly, a fascinating photoresponsive viscoelastic solution was prepared by mixing AzoMPCOONa and cetyltrimethylammonium bromide (CTAB). The properties of the photoresponsive viscoelastic solution were further investigated by rheology, circular dichroism (CD), and cryogenic transmission electron microscopy (cryo-TEM). Initially, the AzoMPCOONa/CTAB system was a gel-like solution composed of entangled wormlike micelles possessing the right-handed chiral structure. After UV irradiation for 10 min, the gel-like solution transformed into a slightly viscous solution, its zero-shear viscosity dramatically reduced by 2 orders of magnitude, and the aggregates were converted into rod-like micelles and spherical micelles. In addition, the right-handed chiral structure of the aggregates disappeared. These dramatic changes in the viscosity and the aggregate structure can be attributed to the photoisomerization of the azobenzene group in AzoMPCOONa, which led to changes in the molecular geometry and the packing parameter of the AzoMPCOONa/CTAB system. Interestingly, the right-handed chiral structure of wormlike micelles also is photoresponsive. The results reveal the superiority of forest resources for preparing viscoelastic solutions.

Pastable, Adhesive, Injectable, Nanofibrous, and Tunable (PAINT) Biphasic Hybrid Matrices as Versatile Therapeutic Carriers.

A critical challenge in many pharmaceutical fields is developing versatile adjuvant devices that can reduce the off-target delivery of therapeutic materials to target lesions. Herein, a biphasic hybrid fibrous system that can manipulate the spatial and temporal delivery of various therapeutic agents to target lesions by integrating multiple distinct systems and technologies such as fluffy coaxial electrospun polycaprolactone (PCL)/polystyrene (PS) fibers, cyclohexane-mediated leaching to remove PS layers selectively, amine display on PCL fibers, conjugation of naturally occurring adhesive gallol molecules onto hyaluronic acid (HA-g), and electrostatically complexing the aminated PCL fibers with the gallol-conjugated HA. In the context of "paintable" systems on target lesions, the resulting system is called a PAINT matrix (abbreviated according to the initial letter of its features: pastable, adhesive, injectable, nanofibrous, and tunable). Its viscoelastic property, which was attributed by coalescing aminated PCL fibers with viscous HA-g, enabled it to be noninvasively injected and fit into any cavity in the body with various morphologies, manually pasted on tissue surfaces, and adhered onto moisture-rich surfaces to ensure the secure delivery of therapeutics toward the target lesions. The PAINT matrix efficiently supplied immunomodulatory human neural stem cells (hNSCs) at rat hemisectioned spinal cord injury (SCI) sites and promoted both locomotive and sensory recovery in SCI models, presumably by protecting hNSCs against host immunosurveillance. The PAINT matrix will be broadly utilized for efficiently delivering therapeutics to difficult-to-reach target lesions by direct infusion or conventional biomaterial-mediated approaches due to their locations, wet surfaces, or complicated ambient environments.

Chondrus crispus treated with ultrasound as a polysaccharides source with improved antitumoral potential.

Ultrasound-assisted extraction was used to recover gelling biopolymers and antioxidant compounds from Chondrus crispus with improved biological potential. The optimal processing conditions were evaluated using a Box-Behnken design, and the impact on the biological and thermo-rheological properties of the carrageenan fraction and on the bioactive features of the soluble extracts were studied. The optimum extraction parameters were defined by extraction time of ~34.7 min; solid liquid ratio of ~2.1 g/100 g and ultrasound amplitude of ~79.0% with a maximum power of 1130 W. The dependent variables exhibited maximum carrageenan yields (44.3%) and viscoelastic modulus (925.9 Pa) with the lowest gelling temperatures (38.7 °C) as well as maximum content of the extract in protein (22.4 mg/g), gallic acid (13.4 mg/g) and Trolox equivalents antioxidant capacity (182.4 mg TEAC/g). Tested hybrid carrageenans exhibited promising biological activities (% of growth inhibition around 91% for four human cancer cellular lines: A549; A2780; HeLa 229; HT-29).

Emulsifying capacity of peanut polysaccharide: Improving interfacial property through the co-dissolution of protein during extraction.

The co-dissolution of residual protein from byproduct (PPSI) was employed to improve the interfacial property of peanut polysaccharide (PPS). Protein content in the PPSI and PPS were 16.89% and 2.58%, respectively. The convent bonding and intermolecular interaction maintained the complex structure in PPSI. More protein promoted the shift from linear chain conformation to spherical particle, weakened surface charge, induced stronger intermolecular attraction and wettability, which facilitated interfacial adsorption of PPSI. Concomitantly, the linear chain after adsorbing the O/W interface was observed in PPSI-polystyrene, promoting the cross-linking between adsorption layers and thereby forming the elastic interfacial film. Consequently, the emulsion borne smaller size. Subsequently, the particles in continuous phase moved to the adsorption layer via intermolecular interaction and then formed a gel, enhancing stability against oil coalescence, the thermal and refrigerated treatments. Additionally, the acidified (pH 3.0) PPSI further strengthened the emulsion structure and improved its creaming and freeze-thaw stability.

Self-Healing, Self-Adhesive Silk Fibroin Conductive Hydrogel as a Flexible Strain Sensor.

Flexible and wearable hydrogel strain sensors have attracted tremendous attention for applications in human motion and physiological signal monitoring. However, it is still a great challenge to develop a hydrogel strain sensor with certain mechanical properties and tensile deformation capabilities, which can be in conformal contact with the target organ and also have self-healing properties, self-adhesive capability, biocompatibility, antibacterial properties, high strain sensitivity, and stable electrical performance. In this paper, an ionic conductive hydrogel (named PBST) is rationally designed by proportionally mixing polyvinyl alcohol (PVA), borax, silk fibroin (SF), and tannic acid (TA). SF can not only be a reinforcement to introduce an energy dissipation mechanism into the dynamically cross-linked hydrogel network to stabilize the non-Newtonian behavior of PVA and borax but it can also act as a cross-linking agent to combine with TA to reduce the dissociation of TA on the hydrogel network, improving the mechanical properties and viscoelasticity of the hydrogel. The combination of SF and TA can improve the self-healing ability of the hydrogel and realize the adjustable viscoelasticity of the hydrogel without sacrificing other properties. The obtained hydrogel has excellent stretchability (strain > 1000%) and shows good conformal contact with human skin. When the hydrogel is damaged by external strain, it can rapidly self-repair (mechanical and electrical properties) without external stimuli. It shows adhesiveness and repeatable adhesiveness to different materials (steel, wood, PTFE, glass, iron, and cotton fabric) and biological tissues (pigskin) and is easy to peel off without residue. The obtained PBST conductive hydrogel also has a wide strain-sensing range (>650%) and reliable stability. The hydrogel adhered to the skin surface can monitor large strain movements such as in finger joints, wrist joints, knee joints, and so on and detect swallowing, smiling, facial bulging and calming, and other micro-deformation behaviors. It can also distinguish physical signals such as light smile, big laugh, fast and slow breathing, and deep and shallow breathing. Therefore, the PBST conductive hydrogel material with multiple synergistic functions has great potential as a flexible wearable strain sensor. The PBST hydrogel has antibacterial properties and good biocompatibility at the same time, which provides a safety guarantee for it as a flexible wearable strain sensor. This work is expected to provide a new way for people to develop ideal wearable strain sensors.

Comparison of Viscoelastic Substance Injection Versus Air Filling in the Anterior Chamber During Foldable Capsular Vitreous Body (FCVB) Implant Surgery: A Prospective Randomized Controlled Trial.

INTRODUCTION: To compare the outcomes of viscoelastic substance injection with air filling in the anterior chamber during foldable capsular vitreous body (FCVB) implant surgery in patients with severe retinal disease. METHODS: Thirty eyes with severe retinal diseases were randomly divided into two groups. In the viscoelastic group, 0.15-0.2 mL of 1.7% sodium hyaluronate was injected into the anterior chamber after FCVB implantation; in the air group, the anterior chamber was maintained by filling the air after FCVB implant surgery. The eyes of treated patients were examined during a 24-week follow-up appointment. Data, including intraocular pressure (IOP), the difference between preoperative and postoperative IOP, and postoperative complications, were recorded. RESULTS: Data collected from 27 eyes were used in the final analysis. The IOP of the air group was lower than that of the viscoelastic group from the first to third postoperative day (P < 0.01). Moreover, the difference between preoperative and postoperative IOP in the viscoelastic group was significantly smaller than that in the air group from the first to third postoperative day (P < 0.01). After the 1st postoperative week, postoperative IOP values were similar in the two groups (P > 0.05). Postoperative complications in the air group and the viscoelastic group included corneal blood staining (1 eye vs. 0 eyes), transient postoperative diffuse hemorrhage (5 eyes vs. 1 eye), inflammation reaction (9 eyes vs. 4 eyes), and postoperative fibrin exudation (4 eyes vs. 1 eye), respectively. CONCLUSION: The use of viscoelastic substances in the anterior chamber during FCVB implant surgery was associated with less fluctuation in postoperative IOP and could reduce postoperative complications. REGISTRATION NUMBER: ChiCTR-TNC-00000396.

Sodium hyaluronate-g-2-((N-(6-aminohexyl)-4-methoxyphenyl)sulfonamido)-N-hydroxyacetamide with enhanced affinity towards MMP12 catalytic domain to be used as visco-supplement with increased degradation resistance.

The present paper describes the functionalization of sodium hyaluronate (NaHA) with a small molecule (2-((N-(6-aminohexyl)-4-methoxyphenyl)sulfonamido)-N-hydroxyacetamide) (MMPI) having proven inhibitory activity against membrane metalloproteins involved in inflammatory processes (i.e. MMP12). The obtained derivative (HA-MMPI) demonstrated an increased resistance to the in-vitro degradation by hyaluronidase, viscoelastic properties close to those of healthy human synovial fluid, cytocompatibility towards human chondrocytes and nanomolar affinity towards MMP 12. Thus, HA-MMPI can be considered a good candidate as viscosupplement in the treatment of knee osteoarticular disease.

The influence of alkaline treatment on the mechanical and structural properties of bacterial cellulose.

The unique mechanical properties of hydrated bacterial cellulose make it suitable for biomedical applications. This study evaluates the effect of concentrated sodium hydroxide treatment on the structural and mechanical properties of bacterial cellulose hydrogels using rheological, tensile, and compression tests combined with mathematical modelling. Bacterial cellulose hydrogels show a concentration-dependent and irreversible reduction in shear moduli, compression, and tensile strength after alkaline treatment. Applying a poroelastic biphasic model to through-thickness compressive stress-relaxation tests showed the alkaline treatment to induce no significant change in axial compression, an effect was observed in the radial direction, potentially due to the escape of water from within the hydrogel. Scanning electron microscopy showed a more porous structure of bacterial cellulose. These results show how concentration-dependent alkaline treatment induces selective weakening of intramolecular interactions between cellulose fibres, allowing the opportunity to precisely tune the mechanical properties for specific biomedical application, e.g., faster-degradable materials.

Nonlinear dynamics and acoustic emissions of interacting cavitation bubbles in viscoelastic tissues.

The cavitation-mediated bioeffects are primarily associated with the dynamic behaviors of bubbles in viscoelastic tissues, which involves complex interactions of cavitation bubbles with surrounding bubbles and tissues. The radial and translational motions, as well as the resultant acoustic emissions of two interacting cavitation bubbles in viscoelastic tissues were numerically investigated. Due to the bubble-bubble interactions, a remarkable suppression effect on the small bubble, whereas a slight enhancement effect on the large one were observed within the acoustic exposure parameters and the initial radii of the bubbles examined in this paper. Moreover, as the initial distance between bubbles increases, the strong suppression effect is reduced gradually and it could effectively enhance the nonlinear dynamics of bubbles, exactly as the bifurcation diagrams exhibit a similar mode of successive period doubling to chaos. Correspondingly, the resultant acoustic emissions present a progressive evolution of harmonics, subharmonics, ultraharmonics and broadband components in the frequency spectra. In addition, with the elasticity and/or viscosity of the surrounding medium increasing, both the nonlinear dynamics and translational motions of bubbles were reduced prominently. This study provides a comprehensive insight into the nonlinear behaviors and acoustic emissions of two interacting cavitation bubbles in viscoelastic media, it may contribute to optimizing and monitoring the cavitation-mediated biomedical applications.