Rheological Properties of Gel Foam Co-Stabilized with Nanoparticles, Xanthan Gum, and Multiple Surfactants

Gel foam has the advantages of gel and foam and shows good prospects for applications in the fields of fire prevention and extinguishing. Rheology has a significant impact on the application of gel foam, but there is little related research. In the present study, hydrophilic silica nanoparticles (NPs) and water-soluble polymer xanthan gum (XG) were combined with fluorocarbon surfactant (FS-50) and hydrocarbon surfactant (APG0810) to create gel foam. The foaming ability and foam drainage were evaluated. The gel foam's rheology, including its flow behavior and viscoelasticity, was systematically investigated. The results show that the foaming of the FS-50/APG0810 mixture decreases but the foam drainage increases in the presence of NPs and/or XG. All of the foams belong to the category of non-Newtonian fluids with shear thinning behavior. The flow curves of the foams are consistent with the Cross model. The presence of XG/NPs enhanced the foam viscoelasticity of the FS-50/APG0810 mixture. The silica NPs showed a better ability to enhance foam viscoelasticity but a worse ability to stabilize the foam compared to XG. This research can offer theoretical support for the industrial usage of gel foam.

Diagnostic outcome and safety of plugged liver biopsy in high-risk patients: a systematic review and meta-analysis

BACKGROUND

Percutaneous liver biopsy is the gold standard test for the assessment of liver disease. In patients with coagulopathy, ascites, post-transplantation, and hypervascular tumors, biopsy is associated with increased risk of adverse events (AEs). Transjugular liver biopsy (TJLB) is recommended in these conditions but is expensive and unavailable at many centers. Plugged liver biopsy (PLB) provides an alternate diagnostic modality in these high-risk cases.

PURPOSE

To analyze the pooled diagnostic outcome and safety of PLB in high-risk cases.

MATERIAL AND METHODS

A literature search of various databases from January 1990 to July 2022 was conducted for studies evaluating the outcome of PLB in high-risk cases. The primary outcomes were pooled sample adequacy and AEs. Pooled event rates across studies were expressed with summative statistics.

RESULTS

A total of 17 studies (2329 patients) were included in the meta-analysis. The pooled proportion of sample adequacy was 98.9% (95% confidence interval [CI]=98.2-99.6). Severe AEs, major bleeding, and minor AEs were seen in 0.7% (95% CI=0.1-1.3), 0.4% (95% CI=0.1-0.8), and 11.5% (95% CI=2.4-20.6) of the patients. There was only one reported mortality, giving a pooled incidence of 0.0002% (95% CI=0.0-0.0038). Compared to TJLB (5 studies, n = 336), there was no difference in either sample adequacy (odds ratio [OR]=2.34, 95% CI=0.83-6.58) or risk of serious AEs (OR=0.47, 95% CI=0.173-1.31).

CONCLUSION

PLB can be safely performed on patients with coagulopathy and/or ascites with high sample adequacy rates and low incidence of AEs and mortality.

Heat Transfer Performance of Gel Foam Layer with Nanoparticles Doping under a Radiative Heat Flux

The risk of fire in the chemical industry's production process is fatal. Gel foam has been widely employed in petroleum storage tanks, oil pools, and other petrochemical equipment for fire extinguishing and thermal protection. Recently, nanoparticles have been doped into gel foam to enhance thermal stability and insulation. However, heat transfer behaviors of the gel foam layer containing nanoparticles are still missing. In this study, a numerical heat transfer model of a gel foam layer containing silica nanoparticles under a radiative heat flux was established. Through simulation, the changes in foam thickness and temperature distribution were analyzed. The effects of the maximum heating temperature, initial gas content, nanoparticle size, and concentration on the thermal insulation behavior of the gel foam layer were systematically studied. The results showed that the thermal stability and insulation performance of the three-phase gel foam layer decreased with the increase in the initial gas content and particle size. Increasing the nanoparticle concentration could enhance the foam's thermal stability and insulation performance. The results provide guidance for a designing gel foam with high thermal protection performance.

Superfast-Expanding Porous Hydrogels: Pushing New Frontiers in Converting Chemical Potential into Useful Mechanical Work

Superabsorbent polymer gels can absorb large amounts of water (100-1000× their dry weight). For the past 50 years, many scientists such as de Gennes have proposed to extract mechanical work from gel expansion/contraction, which could pave the way for "artificial muscles". However, slow rates of gel expansion have limited these efforts: macroscale (∼cm) gels take over 24 h to expand to their equilibrium size. Gels can be made to expand faster if their characteristic length scale is reduced, e.g., by making a macroscopic gel porous. Still, gels that are both superabsorbent and able to expand rapidly have not yet been realized. Here, we create gels at the macroscale (∼cm or larger) that are porous, highly robust, superabsorbent and expand much faster than any gels thus far. Our approach involves the in situ foaming of a monomer solution (acrylic acid and acrylamide) using a double-barreled syringe that has acid and base in its two barrels. Gas (CO₂) is generated at the mixing tip of the syringe by the acid-base reaction, and gas bubbles are stabilized by an amphiphilic polymer in one of the barrels. The monomers are then polymerized by ultraviolet (UV) light to form the gel around the bubbles, and the material is dried under ambient conditions to give a porous solid. When this dry gel is added to water, it absorbs water at a rate of 20 g/g·s until an equilibrium is achieved at ∼300× its weight. In the process, each gel dimension increases by ∼20%/s until its final dimensions are more than 3× larger. Such rapid and appreciable expansion can be easily observed by the eye, and remarkably, the swollen gel is robust enough to be picked up by hand. SEM images reveal a porosity of >90% and an interconnected network of pores. The gels are responsive to pH, and a full cycle of expansion (in regular water) and contraction (at pH 10 or in ethanol) can be completed within about 60 s. We use gel expansion to rapidly lift weights against gravity, resulting in ∼0.4 mJ of work being done over 40 s, which translates to a power density of 260 mW/kg. This ability to harness the chemical potential energy from the gel to do useful mechanical work could enable new designs for mechano-chemical engines─and potentially for artificial muscles.

The effect of transcatheter bronchial artery embolization in five patients with bronchial artery aneurysm

Introduction

Due to its rarity and the lack of animal models for this disease, the etiology of bronchial artery aneurysm (BAA) is poorly understood.

Aim

To investigate the effect of transcatheter artery embolization (TAE) with coils, spherical polyvinyl alcohol (PVA), and gel foam in patients with BAA.

Material and methods

From June 2015 to November 2018, 5 patients diagnosed with BAA with massive hemoptysis after undergoing bronchial arteriography and receiving TAE therapy in the Department of Interventional Radiology were enrolled in this study. Post-embolization angiography was used to demonstrate total occlusion of the BAAs and bronchiectatic engorged vessels. The patients’ follow-up was conducted 1–16 months after TAE.

Results

All 5 patients were cured by the TAE treatment, during which PVA, coils, and gel foam were applied. The patients also received successful TAE via a microcatheter. Hemoptysis disappeared in all patients. No special or severe complications occurred, and no patient experienced a recurrence during the follow-up.

Conclusions

Overall, TAE is the best choice for patients with hemoptysis and BAA due to its effectivity and reliability. Thorough and complete embolization of the bleeding arteries is the key to successful treatment. Though PVA and coils are the most common materials for embolization, gel foam strips can also be applied.

Risedronate-Loaded Macroporous Gel Foam Enriched with Nanohydroxyapatite: Preparation, Characterization, and Osteogenic Activity Evaluation Using Saos-2 Cells

The application of minimally invasive surgical techniques in the field of orthopedic surgery has created a growing need for new injectable synthetic materials that can be used for bone grafting. In this work, novel injectable thermosensitive foam was developed by mixing nHAP powder with a thermosensitive polymer with foaming power (Pluronic F-127) and loaded with a water-soluble bisphosphonate drug (risedronate) to promote osteogenesis. The foam was able to retain the porous structure after injection and set through temperature change of PF-127 solution to form gel inside the body. The effect of different formulation parameters on the gelation time, porosity, foamability, injectability, and in vitro degradation in addition to drug release from the prepared foams were analyzed using a full factorial design. The addition of a co-polymer like methylcellulose or sodium alginate into the foam was also studied. Results showed that the prepared optimized thermosensitive foam was able to gel within 1 min at 37°C, and sustain the release of drug for 72 h. The optimized formulation was further tested for any interactions using DSC and IR, and revealed no interactions between the drug and the used excipients in the prepared foam. Furthermore, the ability of the pre-set foam to support osteoblastic-like Saos-2-cell proliferation and differentiation was assessed, and revealed superior function on promoting cellular proliferation as confirmed by fluorescence microscope compared to the plain drug solution. The activity of the foam treated cells was also assessed by measuring the alkaline phosphatase activity and calcium deposition, and confirmed that the cellular activity was greatly enhanced in foam treated cells compared to those treated with the plain drug solution only. The obtained results show that the prepared risedronate-loaded thermosensitive foam would represent a step forward in the design of new materials for minimally invasive bone regeneration.