Physically cross-linked organo-hydrogels for friction interfaces in joint replacements: design, evaluation and potential clinical applications.

This paper investigates physically crosslinked organo-hydrogels for total hip replacement surgery. Current materials in artificial joints have limitations in mechanical performance and biocompatibility. To overcome these issues, a new approach based on hydrogen bonds between polyvinyl alcohol, poly(2-hydroxyethyl methacrylate), and glycerin is proposed to develop bioactive organo-hydrogels with improved mechanical properties and biocompatibility. This study analyzes local pathological characteristics, systemic toxicity, and mechanical properties of the gels. The results show that the gels possess excellent biocompatibility and mechanical strength, suggesting their potential as an alternative material for total hip replacement surgery. These findings contribute to improving patient outcomes in joint replacement procedures.

Chitosan-based double network hydrogel loading herbal small molecule for accelerating wound healing.

Skin injuries are one of the most common clinical traumas worldwide, and wound dressings are considered to be one of key factors in wound healing. Natural polymer-based hydrogels have been developed as ideal materials for a new generation of dressings due to their excellent biocompatibility and wetting ability. However, the inadequate mechanical performances and lack of efficacy in promoting wound healing have limited the application of natural polymer-based hydrogels as wound dressings. In this work, a double network hydrogel based on natural chitosan molecules was constructed to enhance the mechanical properties, and emodin, a herbal natural product, was loaded into the hydrogel to improve the healing effect of the dressing. The structure of the chitosan-emodin network formed by Schiff base reaction and microcrystalline network of biocompatible polyvinyl alcohol endowed hydrogels with excellent mechanical properties and ensured its integrity as wound dressings. Moreover, the hydrogel showed excellent wound healing properties due to the loading of emodin. The hydrogel dressing could promote cell proliferation, cell migration, and secretion of growth factors. The animal experimental results also demonstrated that the hydrogel dressing facilitated the regeneration of blood vessels and collagen and accelerated wound healing.

Construction and evaluation of a risk prediction model for pulmonary infection-associated acute kidney injury in intensive care units.

Acute kidney injury (AKI) is one of the common complications of pulmonary infections. However, nomograms predicting the risk of early-onset AKI in patients with pulmonary infections have not been comprehensively researched. In this study, 3278 patients with pulmonary infection were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. These patients were randomly divided into training and validation cohorts, with the training cohort used for model building and the validation cohort used for validation. Independent risk factors for patients with pulmonary infection were determined using the least absolute shrinkage and selection operator (LASSO) method and forward stepwise logistic regression, which revealed that 11 independent risk factors for AKI in patients with pulmonary infections were congestive heart failure (CHF), hypertension, diabetes, transcutaneous oxygen saturation (SpO2), 24-h urine output, white blood cells (WBC), serum creatinine (Scr), prothrombin time (PT), potential of hydrogen (PH), vasopressor use, and mechanical ventilation (MV) use. The nomogram was then constructed and validated. The area under the receiver operating characteristic curve (AUC) values of the nomogram were 0.770 (95% CI = 0.789-0.807) in the training cohort and 0.724 (95% CI = 0.754-0.784) in the validation cohort. High AUC values indicated the good discriminative ability of the nomogram, while the calibration curves and Hosmer-Lemeshow test results indicated that the nomogram was well-calibrated. Improvements in net reclassification index (NRI) and integrated discrimination improvement (IDI) values indicate that our nomogram was superior to the Simplified Acute Physiology Score (SAPS) II scoring system, and the decision-curve analysis (DCA) curves indicate that the nomogram has good clinical application. We established a risk-prediction model for AKI in patients with pulmonary infection, which has good discriminative power and is superior to the SAPS II scoring system. This model can provide clinical reference information for patients with this type of disease in the intensive care unit.

Preparation of stretchable and self-healable dual ionically cross-linked hydrogel based on chitosan/polyacrylic acid with anti-freezing property for multi-model flexible sensing and detection.

As a kind of promising material for flexible wearable electronics, conductive hydrogels have attracted extensive interests of researchers for their inherent merits such as superior mechanical properties, biocompatibility, and permeability. Herein, we constructed a new type of highly stretchable, anti-freezing, self-healable, and conductive hydrogel based on chitosan/polyacrylic acid. The large amount of ions inside the network had five functions for the proposed hydrogel, including excellent mechanical behaviors, high conductivity, self-recovery, self-healing and anti-freezing capability. Consequently, the proposed hydrogel possessed tunable stretchability (1190-1550%), tensile strength (0.96-2.56 MPa), toughness (5.7-14.7 MJ/m3), superior self-healing property (self-healing efficiency up to 83.7%), high conductivity (4.58-5.76 S/m), and excellent anti-freezing capability. To our knowledge, the self-healable hydrogel with balanced tensile strength, toughness, conductivity, and low-temperature tolerance can hardly be achieved till now. Furthermore, the conductive hydrogels exhibited high sensitivity (gauge factor up to 10.8) in a broad strain window (0-1000%) and could detect the conventional motion signals of human body such as bending of a knuckle, swallowing, and pressure signal at both room temperature and -20 °C. Moreover, the hydrogels could also be fabricated as flexible detectors to identify different temperatures, different kinds of solutions, and different concentrations of the solution.

An extremely tough and ionic conductive natural-polymer-based double network hydrogel.

Hydrogels are widely used in fields such as drug delivery, tissue regeneration, soft robotics and flexible smart electronic devices, yet their application is often limited by unsatisfactory mechanical behaviors. Among the various improvement strategies, double network (DN) hydrogels from synthetic polymers demonstrated impressive mechanical properties, while those from natural polymers were usually inferior. Here, a novel DN hydrogel composed fully of natural polymers exhibiting remarkable mechanical properties and conductivity is prepared by simply soaking a virgin gellan gum/gelatin composite hydrogel in a mixed solution of Na2SO4 and (NH4)2SO4. This hydrogel exhibits a tunable Young's modulus (0.08 to 42.6 MPa), good fracture stress (0.05 to 7.5 MPa), good fracture stretch (1.4 to 7.1), high fracture toughness (up to 27.7 kJ m-2), and high ionic conductivity (up to 11.4 S m-1 at f = 1 kHz). The improvement in the mechanical properties of the DN gel is attributed to the chain-entanglement crosslinking points introduced by SO42- in the gelatin network and the electrostatic interaction crosslinking points introduced by Na+ in the gellan gum network. The high ionic conductivity of the DN gel is attributed to the infiltration of the DN gel in a salt solution of high concentration. The developed gellan gum/gelatin DN hydrogel has shown a new pathway towards strengthening natural-polymer-based DN hydrogels and towards potential applications in biomedical engineering and flexible electronic devices.

Fully physically cross-linked double network hydrogels with strong mechanical properties, good recovery and self-healing properties.

Combining a hydrophobic interaction crosslinked curdlan as the first network and hydrophobic interaction crosslinked polyacrylamide as the second network, we have fabricated a curdlan/HPAAm double network (DN) hydrogel using a one-pot method. The resulting DN hydrogel exhibited good mechanical properties, i.e. an elastic modulus of 103 kPa, a tensile fracture strength of 0.81 MPa, a tensile stretch of 25.3 and a compressive stress of 62.5 MPa when the compressive strain increased up to 99%. The DN gel could withstand ten compression tests under 90% compressive strain without observable damage. The DN gel demonstrated 84% stiffness recovery and 97% toughness recovery after the deformed samples were relaxed and stored at 95 °C for 4 h. The stiffness and fracture stress of the DN gel were enhanced after sterilization treatment at 120 °C. Furthermore, the gels exhibited 52% self-healing of fracture stretch after the samples were cut and brought into contact at 95 °C for 4 h. The self-recovery and self-healing properties of the DN gel both originated from the first curdlan network via the reformation of hydrophobic interactions and the second HPAAm network via reformation of the broken hydrophobic associations.

Tough and Stretchable Dual Ionically Cross-Linked Hydrogel with High Conductivity and Fast Recovery Property for High-Performance Flexible Sensors.

As a kind of typical soft and wet material, hydrogel has been increasingly investigated as another way to develop flexible electronics. However, the traditional hydrogel with poor strain and strength performance cannot meet the requirements for stretchable electronics; fabricating a stretchable hydrogel with balanced tensile strength, toughness, and conductivity is still a big challenge. Herein, a new type of physically cross-linked hydrogel with poly(acrylamide-co-acrylic acid)-Fe3+ and chitosan-SO42- dual ionic networks via facile free radical polymerization and soaking processes is developed to fabricate excellent high-performance flexible sensors. The abundant Fe3+ and SO42- ions in the hydrogel can not only construct tough and strong dual ionic networks but also give the hydrogel high conductivity. Consequently, the optimal hydrogel possesses high tensile strength (∼5.1 MPa), large strain capacity (∼1225%), elasticity (∼1.13 MPa), high toughness (∼32.1 MJ/m3), and high conductivity (3.04 S/m at f = 0.1M), as well as rapid self-recovery property. Furthermore, the hydrogel conductor has high stretching sensitivity with a gauge factor of 6.0 at strain of 700% and was able to detect conventional motions of the human body such as the motions of the knuckle, speaking, and swallowing, which indicates that our ionic conductive hydrogels can be used to fabricate excellent high-performance flexible sensors.

Ultrastiff, Tough, and Healable Ionic-Hydrogen Bond Cross-Linked Hydrogels and Their Uses as Building Blocks To Construct Complex Hydrogel Structures.

We report the ultrastiff and tough poly(acrylamide- co-acrylic acid)/Na-alginate/Fe3+ (P(AM- co-AA)/Na-alginate/Fe3+) hydrogel via the formation of hybrid ionic-hydrogen bond cross-linking networks. The optimal P(AM- co-AA)/Na-alginate/Fe3+ hydrogel possessed super high elastic modulus (∼24.6 MPa), tensile strength (∼10.4 MPa), compression strength (∼44 MPa), and toughness (∼4800 J/m2). The P(AM- co-AA)/Na-alginate/Fe3+ hydrogel was highly stable and maintained its superior mechanical properties in 0.5-2 M NaCl solution, aqueous solution with pH ranging from 4 to 10. The ionic cross-linking networks of the P(AM- co-AA)/Na-alginate/Fe3+ hydrogels can be locally and selectively dissociated by treating with aqueous NaOH solution with pH of 13 for 1 min and reformed by locally adding the additional Fe3+ solutions, making the hydrogels healable and cohesive. The healed hydrogels from the cutting surfaces can bear a tensile strength of up to 7.1 MPa. Various complex hydrogel structures can be constructed by using the P(AM- co-AA)/Na-alginate/Fe3+ hydrogels as building blocks via the adhesion of as-prepared hydrogels.