Biocompatibility and preclinical experiments of a Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes

Abstract

BACKGROUND: The increasing prevalence of minimally invasive surgery has placed higher demands on high-frequency electrosurgical equipment. Imported minimally invasive tungsten alloy electrodes offer high cutting precision, low tissue adhesion, and good biocompatibility, but their high cost limits their widespread application. Therefore, conducting biocompatibility and preclinical animal studies on Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes can provide a scientific basis for the research and development of Chinese-made minimally invasive electrodes. OBJECTIVE: To evaluate the biocompatibility and preclinical safety of Chinese-made 3D-printed tungsten alloy needle-shaped electrodes. METHODS: (1) Biocompatibility: L-929 cells were co-cultured with extracts from Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes at different concentrations (100%, 50%, 25%, and 12.5%), and the cytotoxicity of the materials was assessed using the MTT assay. Intradermal stimulation experiments were performed on New Zealand white rabbits to evaluate the skin irritation of the Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes. Skin sensitization was evaluated in albino guinea pigs. (2) Preclinical animal experiments: 36 SD rats were randomly divided into three groups (n=12 per group): 304 stainless steel electrode group, imported minimally invasive tungsten alloy needle electrode group, and Chinese-made 3D-printed minimally invasive tungsten alloy needle electrode group. The corresponding electrodes were used to cut subcutaneous tissue and abdominal wall muscle, and the incisions were sutured. The amount of adherent material on the electrode surface, intraoperative blood loss, and smoke formation were recorded. At 14 days postoperatively, wound healing, fat liquefaction, and histological morphology of the incision were observed. RESULTS AND CONCLUSION: (1) MTT assay showed that the cell survival rate in the extract group of Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes was higher than 80%, indicating no obvious cytotoxicity. Intradermal stimulation and sensitization tests showed no significant skin irritation or sensitization reaction. (2) Compared with the 304 stainless steel electrode group, the Chinese-made 3D-printed minimally invasive tungsten alloy needle electrode group had reduced electrode surface adhesion, increased intraoperative blood loss and smoke formation (P < 0.05). There were no significant differences between the Chinese-made and imported tungsten alloy needle electrode groups in terms of electrode surface adhesion, intraoperative blood loss, and smoke formation (P > 0.05). There were no significant differences among the three groups in wound healing, fat liquefaction, and incision adverse reactions (P > 0.05). Hematoxylin-eosin staining showed mild inflammatory cell infiltration in all three groups, consistent with normal wound repair pathology, with no abnormal immune reaction or delayed healing. (3) The results indicate that Chinese-made 3D-printed minimally invasive tungsten alloy needle electrodes have good biocompatibility and safety, with overall performance comparable to imported tungsten needle electrodes.

1. Introduction

With the development of minimally invasive surgical techniques, high-frequency electrosurgical equipment has been widely used in clinical operations, offering advantages such as rapid cutting, reduced blood loss, simple operation, low cost, and broad applicability [1-3]. As the core component of high-frequency electrosurgical equipment, the surgical electrode's performance directly affects surgical precision and safety. Among various materials, stainless steel has good biocompatibility and is easy to process, making it one of the most widely used surgical electrode materials [4-5]. However, the commonly used 304 stainless steel electrode, despite its good electrical conductivity, has significant drawbacks in practice: the electrode tip diameter is relatively large (typically >1 mm), making precise tissue cutting difficult in delicate procedures such as thyroidectomy and otolaryngological microsurgery. Moreover, under high temperatures, tissue carbonization and adhesion on the electrode surface can occur, increasing the risk of secondary injury and potentially causing abnormal current conduction, thereby affecting surgical safety. Clinical complications in minimally invasive surgery are directly related to electrode performance deficiencies [4], highlighting the technical bottlenecks of existing materials. Therefore, developing new electrode materials to reduce electrode adhesion and enhance precision is crucial for advancing high-frequency electrodes in minimally invasive surgery. Medical metal materials currently used clinically include stainless steel, titanium alloys, cobalt-based alloys, as well as precious metals such as gold, silver, and tungsten, and shape memory alloys [6-7].

Compared with traditional stainless steel, tungsten alloys are considered ideal electrode materials due to their high melting point (3,410 °C), low thermal expansion coefficient (4.5×10-6/K), and excellent mechanical strength [8-10]. Tungsten alloys exhibit good corrosion resistance and surface stability, closely related to their high melting point [11]. Additionally, tungsten has a low electron work function and is often used as electrical contact material in high-voltage circuit breakers resistant to arc erosion [12]. Furthermore, tungsten possesses good biocompatibility [13], chemical inertness, and corrosion resistance [9,14], making it a promising candidate for surgical electrodes.