An Ultrasonically Powered Implantable Microprobe for Electrolytic Ablation

Abstract

electrolytic ablation (eA) is a promising nonthermal tumor ablation technique that destroys malignant cells through induction of a locoregional pH change. eA is typically performed by inserting needle electrodes inside the tumor followed by application of direct current (Dc), thus inducing electrolysis and creating localized pH changes around the electrodes. in this paper, we report an ultrasonically powered implantable eA microprobe that may increase the clinical relevance of eA by allowing wireless control over device operation (capability to remotely turn the device on and off) and providing flexibility in treatment options (easier to administer fractionated doses over a longer period). the wireless eA microprobe consists of a millimeter-sized piezoelectric ultrasonic receiver, a rectifier circuit, and a pair of platinum electrodes (overall size is 9 × 3 × 2 mm 3). once implanted through a minimally invasive procedure, the microprobe can stay within a solid tumor and be repeatedly used as needed. Ultrasonic power allows for efficient power delivery to mm-scale devices implanted deep within soft tissues of the body. The microprobe is capable of producing a direct current of 90 µA at a voltage of 5 V across the electrodes under low-intensity ultrasound (~200 mW/cm 2). the Dc power creates acidic (pH < 2) and alkaline (pH > 12.9) regions around the anode and the cathode, respectively. The pH change, measured using tissue-mimicking agarose gel, extends to 0.8 cm 3 in volume within an hour at an expansion rate of 0.5 mm 3 /min. The microprobe-mediated EA ablative capability is demonstrated in vitro in cancer cells and ex vivo in mouse liver.

Implantable Cisplatin Synthesis Microdevice for Regional Chemotherapy

“…We utilized the ultrasonic powering for the microdevice since it offers a long-range and omni-directional operation, making it suitable for operating the microdevice within deeply seated tumors, such as ovarian cancer, as illustrated in Figure 1. [15][16][17] We confirmed the cisplatin generation by the microdevice and investigated the effects of various operating parameters on the synthesis process. Moreover, we demonstrated the effect of microdevicesynthesized cisplatin with an in vitro murine breast cancer cells, as well as ex vivo liver tissue.…”

“…Ultrasonic Powering: The previously reported ultrasonic powering methods were utilized. [15][16][17] The transmitting system consisted of a 2 mm thick PZT-5A plate (75 × 75 × 1 mm 3 ; PZT-5A; Piezo Inc.), a signal generator (MDO3054, Tektronix), and an RF amplifier (1040, ENI). The acoustic intensity of the applied ultrasound was measured using a fiber-optic hydrophone (Precision Acoustics, UK).…”

“…The ultrasonically induced electrolysis-only group could kill the cancer cell due to electrolytic ablation, which is related to our previous work. [17] However, the cisplatin synthesis group could induce much higher efficacy than the electrolytic ablation by ≈33% more cell death (p value < 0.01). We also observed slight cell death under the UV LED irradiance; however, it was not significant.…”

Advances in the Electrochemical Treatment of Cancers and Tumors: Exploring the Current Trends, Advancements, and Mechanisms of Electrolytic Tumor Ablation

“…Another leap forward in the application of EChT is the creation of an ultrasonically powered implantable electrolytic ablation microprobe that allows for the wireless control over treatment times. [17] The microprobe, which consists of a millimeter-sized piezoelectric ultrasonic receiver, a rectifier circuit, and a pair of platinum electrodes sized 9 × 3 × 2 mm 3 , can be implanted in a tumor through a minimally invasive procedure and is capable of applying a direct current of 90 mA at a voltage of 5 V under 200 mW/cm2 ultrasound. These tests were conducted in vitro using HMT3522 S1 breast cancer cell cultures spanning 4 test groups (see Figure 4).…”

“…*p < 0.05, **p < 0.01, ***p < 0.001. Adapted with permission from Ref [17]. in accordance with a Creative Commons 4.0 license; Copyright (2020) The Authors Creative.…”