Liquid metal bath as conformable soft electrodes for target tissue ablation in radio-frequency ablation therapy

Conversion of the bronchial tree into a conforming electrode to ablate the lung nodule in a porcine model

BACKGROUND

Radiofrequency ablation (RFA) is one of the treatment options for lung nodules. However, the need for exact delivery of the rigid metal electrode into the center of the target mass often leads to complications or suboptimal results. To overcome these limitations, a concept of conforming electrodes using a flexible material has been tested in this study.

METHODS

A bronchoscopy-guided RFA (CAROL) under a temperature-controlled mode was tested in in-vivo and ex-vivo porcine lungs. Gallium-based liquid metal was used for turning the bronchial tree into temporary RF electrodes. A customized bronchoscopy-guided balloon-tipped guiding catheter (CAROL catheter) was used to make the procedure feasible under fluoroscopy imaging guidance. The computer simulation was also performed to gain further insight into the ablation results. Safety was also assessed including the liquid metal remaining in the body.

RESULTS

The bronchial electrode injected from the CAROL catheter was able to turn the target site bronchial air pipe into a temporally multi-tined RF electrode. The mean volume of Gallium for each effective CAROL was 0.46 ± 0.47 ml. The ablation results showed highly efficacious and consistent results, especially in the peripheral lung. Most bronchial electrodes were also retrieved by either bronchoscopic suction immediately after the procedure or by natural expectoration thereafter. The liquid metal used in these experiments did not have any significant safety issues. Computer simulation also supports these results.

CONCLUSION

The CAROL ablation was very effective and safe in porcine lungs showing encouraging potential to overcome the conventional approaches.

Liquid metal biomaterials for biomedical imaging

Liquid metals (LMs) not only retain the basic properties of metallic biomaterials, such as high thermal conductivity and high electrical conductivity, but also possess flexibility, flowability, deformability, plasticity, good adhesion, and so on. Therefore, they open many possibilities of extending soft metals into biomedical sciences including biomedical imaging. One of the special properties of LMs is that they can provide a controllable material system in which the electrical, thermal, mechanical, and chemical properties can be controlled on a large scale. This paper reviews the preparation and characteristics of LM-based biomaterials classified into four categories: LM micro/nanoparticles, surface modified LM droplets, LM composites with inorganic substances, and LM composites with organic polymers. Besides, considering the most important requirement for biomaterials is biocompatibility, the paper also analyzes the toxicity results of various LM biomaterials when used in the biomedical area, from different levels including body weight measurement, histology evaluation, and blood biochemistry tests. Next, the applications of LMs in X-ray, CT, MRI, photoacoustic imaging, and molecular imaging are introduced in detail. And finally, the challenges and opportunities of their application in medical imaging are also discussed.

Soft liquid metal nanoparticles achieve reduced crystal nucleation and ultrarapid rewarming for human bone marrow stromal cell and blood vessel cryopreservation

High warming rates during cryopreservation are crucial and essential for successful vitrification. However, realizing a faster warming rate in low-concentration cryoprotective agents appears to be challenging for conventional warming process through convective heat transfer. Herein, we developed a liquid metal (LM) nanosystem that can act as a spatial source to significantly enhance the warming rates with near-infrared laser irradiation during the warming process. The synthetic Pluronic F127-liquid metal nanoparticles (PLM NPs) displayed multiple performances with uniform particle size, superior photothermal conversion efficiency (52%), repeatable photothermal stability, and low cytotoxicity. Particularly, it is more difficult for the liquid PLM NPs with less surface free energy to form crystal nucleation than other solid NPs such as gold and Fe₃O₄, which is beneficial for the cooling process during cryopreservation. The viability of human bone marrow-derived mesenchymal stem cells postcryopreservation reached 78±3%, which is threefold higher than that obtained by the conventional warming method (25±6%). Additionally, the cells postcryopreservation maintained their normal attachment, proliferation, surface marker expression, and intact multilineage differentiation properties. Moreover, the results of mouse tails including blood vessel cryopreservation showed a relatively improved intact structure when using PLM NP rewarming compared with the results of conventional warming. The new LM nanosystem provides a universal platform for cryopreservation that is expected to have potential for widespread applications including bioengineering, cell-based medicine, and clinical translation. STATEMENT OF SIGNIFICANCE: In this study, we fabricated soft liquid metal nanoparticles with high photothermal conversion efficiency, repeatable photothermal stability, and low cytotoxicity. Particularly, soft liquid metal nanoparticles with less surface free energy and suppression effects of ice formation were first introduced to mediate cryopreservation. Superior ice-crystallization inhibition is achieved as a result of less crystal nucleation and ultrarapid rewarming during the freezing and warming processes of cryopreservation, respectively. Collectively, cryopreservation of human bone marrow stromal cells (HBMSCs) and mouse tails including blood vessels can be successfully performed using this new nanoplatform, showing great potential in the application of soft nanoparticles in cryopreservation.

Novel contrast media based on the liquid metal gallium for in vivo digestive tract radiography: a feasibility study

The barium sulfate has been playing an important role as the contrast medium in gastrointestinal radiography and disease diagnosis. However, its application has been gradually reduced due to the limitation of its imaging effect and the progress of other imaging techniques. Here, the liquid metal gallium was proposed as an improved contrast agent, which was applied in the in vivo digestive tract radiography of the mice for the first time. Under the CT scanning, the gallium produced excellent contrast effect intuitively. According to the records of discharge time, the tissue sections of organs, the survival state and body weight, the liquid metal was proven to be capable and safe for gastrointestinal radiography. Further, the mixture of the gallium and the barium sulfate has been tested, which showed better performance in both contrast and detail. Therefore, with the characteristics of better imaging contrast effect and acceptable safety, the gallium and its mixture with the barium sulfate might be useful as potential candidates for digestive tract contrast agent in animal experiments, even possibly as alternative contrast agents for clinical use.

Shape tunable gallium nanorods mediated tumor enhanced ablation through near-infrared photothermal therapy

To date, photothermal sensitizers include organic and inorganic nanomaterials for biomedical applications. However, the impediments of low biodegradability and potential toxicity hinder their further applications in clinics. Liquid metal nanospheres show superior photothermal effects under near-infrared laser irradiation, in addition, a transformation in shape can be triggered, which also promotes biodegradability that helps to avoid potential systemic toxicity. Here, we fabricated tunable liquid metal nanoparticles having sphere-shaped to rod-shaped characteristics, resulting in good biocompatibility, favorable photothermal conversion efficiency, and targeting capability to tumors. The synthesis strategy is easy to achieve through one-step sonication. We systematically evaluated the photothermal properties of these liquid metal nanoparticles as well as their destructive effects on tumors in a quantitative way both in vitro and in vivo under laser exposure. Results have shown for the first time in mice that gallium nanorods, regulated and controlled through the production of GaO(OH), displayed outstanding photothermal conversion efficiency and exhibited distinct temperature elevation compared to gallium nanospheres and gallium-indium alloy nanorods. These shape transformable and biocompatible gallium nanorods establish the basis for the future laser ablation of tumors to achieve enhanced therapeutic outcomes. This shape tunability of a smart nano-liquid metal directly contributes to enhanced photothermal therapy in mice and opens new opportunities for potential applications with tumor therapy and imaging.

Liquid Metal Enabled Electrobiology: A New Frontier to Tackle Disease Challenges

In this article, a new conceptual biomedical engineering strategy to tackle modern disease challenges, called liquid metal (LM) enabled electrobiology, is proposed. This generalized and simple method is based on the physiological fact that specially administrated electricity induces a series of subsequent desired biological effects, either shortly, transitionally, or permanently. Due to high compliance within biological tissues, LM would help mold a pervasive method for treating physiological or psychological diseases. As highly conductive and non-toxic multifunctional flexible materials, such LMs can generate any requested electric treating fields (ETFields), which can adapt to various sites inside the human body. The basic mechanisms of electrobiology in delivering electricity to the target tissues and then inducing expected outputs for disease treatment are interpreted. The methods for realizing soft and conformable electronics based on LM are illustrated. Furthermore, a group of typical disease challenges are observed to illustrate the basic strategies for performing LM electrobiology therapy, which include but are not limited to: tissue electronics, brain disorder, immunotherapy, neural functional recovery, muscle stimulation, skin rejuvenation, cosmetology and dieting, artificial organs, cardiac pacing, cancer therapy, etc. Some practical issues regarding electrobiology for future disease therapy are discussed. Perspectives in this direction for incubating a simple biomedical tool for health care are pointed out.