Drugs such as anticancer can be effective while minimizing side effects if they reach the affected area at an appropriate concentration. Therefore, measurements of the amount of drug delivered to the tissue are required to evaluate the efficacy of the drug. However, real-time monitoring of drugs in specific tissues without affecting the living body is difficult. To achieve drug concentration monitoring in vivo, our group have been developing a new drug analytical method using atmospheric pressure low-temperature plasma. In this method, the drug molecules disorbed and protonated by plasma are analyzed by a mass spectrometer. For analyzing drug concentration in vivo, a plasma injection probe is developed. This probe is fabricated by incorporating a miciro mini plasma jet in a syringe needle. In this study, an anticancer drug containing biological simulated samples were analyzed by inserting the device.

A micro mini plasma jet was fabricated by spiraling copper electrodes around a hollow optical fiber. The outer diameter of the plasma jet was 700 µm. The plasma injection probe was fabricated by integrating this plasma jet into a 16G injection needle.  The biological simulated samples were prepared by mixing purified water with agar powder and fluorouracil, which is used as an anticancer drug, at 100 ppm, 500 ppm, and 1000 ppm, respectively, and solidifying the mixture. During analysis, a plasma injection probe was inserted 15 mm into the samples, and the helium plasma was irradiated inside the sample . To increase the efficiency of protonation hydrogen gas was added to the plasma generation gas at a ratio of 0 to 5%. 

As a result, a fluorouracil derived mass signal was observed. This result confirms that the plasma injection probe can be analyzed drug molecules inside the biological simulated sample. In the presentation, analysis results for each drug concentration and the relationship between the ratio of the hydrogen gas and the signal intensity will be reported.