Green and effective synthesis of gold nanoparticles as an injectable fiducial marker for real-time image gated proton therapy

Abstract

Fiducial markers are crucial for reducing damage to surrounding healthy tissues in real-time image gated proton therapy (RGPT) by boosting geometric accuracy and precision. This study aims to develop an injectable fiducial marker based on gold nanoparticles (Au NPs) synthesized by a green ethanol reduction method, as well as to determine the factors that affect their injectability and imaging capability. Au NPs synthesized in the ethanol-only system had an improved injectability (through 18 G and 21 G needles) and their imaging performance was almost identical to current fiducial markers used in the clinic. The reducing capacity of the ethanol system was significantly enhanced through the introduction of sodium alginate. Meanwhile, the addition of sodium alginate could also control the size of Au NPs, ranging from 21. 8 to 14.1 nm. The product alg-Au NPs with smaller sizes enabled an injectability up to 100% even through 25 G needles with an extrusion force less than 17 N, which is superior for the injection of high-concentration Au NPs. A better imaging performance of alg-Au NPs was also verified in the X-ray visualization test. The work describes the green synthesis of Au NPs via the high-efficiency reducing system ethanol/alginate without the use of toxic reducing, capping, or stabilizing agents. The alg-Au NPs were found to exhibit promise as a fiducial marker for RGPT based on the injectability and imaging test.