Harnessing vinylferrocene microgel-based photonic interferometers for clinical X-ray sensing

X-rays play an essential role in modern tumor radiotherapy. Precise X-ray dosimetry is crucial for tumor radiotherapy to maximize therapeutic efficacy while minimizing normal tissue damage. Compared to traditional X-ray physical dosimeters, hydrogels are strong candidates for detecting X-ray doses due to their excellent tissue equivalence, ease of chemical modification, tunable sizes and low costs. However, most of these sensors are time-consuming, dose rate dependent, and irreversible. Additionally, they require sophisticated device readout systems and skilled personnel. To overcome these shortcomings, this study focuses on developing a hydrogel photonic material that is capable of sensing X-rays.

In this paper, we first synthesize a series of poly(N-isopropylacrylamide-co-vinylferrocene) microgels (PVFc MG) with a variety of microstructures by modulating chemical compositions and synthetic strategies. Subsequently, Au-PVFc MG-Au photonic interferometers are generated by sandwiching PVFc MG monolayer between two Au metal layers. After depositing the X-ray-irradiated Fe²⁺ solution, the optical signals of the Au-PVFc MG-Au interferometer redshift due to the swelling of the microgel. As a result, the optimized interferometer exhibits a fast and linear response in the dose range of 0.1-20 Gy, a sensitivity of ∼4 nm/Gy, 95% of accuracy and dose-rate independence (0.847-5.085 Gy/min). It can return to its initial state in the presence of ascorbic acid, showing excellent reversible sensing capability. This work provides a promising platform for precise clinical X-ray dose monitoring in radiotherapy.

This study explores the use of vinylferrocene microgel-based photonic interferometers for detecting clinical X-ray doses. The sensing capabilities of the Au-PVFc MG-Au interferometers can be enhanced by modifying the chemical compositions and structures of the microgels. The underlying response mechanism is examined in detail. When applied in clinical X-ray dose sensing, these interferometers demonstrate exceptional performance, surpassing previous reports in terms of response time, linear responsivity, accuracy, reversibility, and dose rate independence.