Boateng Francis, Ngwa Wilfred
1 Department of Biomedical Engineering and Biotechnology, University of Massachusetts, Lowell, MA, USA.
2 Department of Physics and Applied Physics, University of Massachusetts, Lowell, MA, USA.
Br J Radiol. 2017 Jun;90(1074):20170069. doi: 10.1259/bjr.20170069. Epub 2017 May 4.
To investigate the dosimetric impact of slow vs burst release of gold nanoparticles (GNPs) from biodegradable brachytherapy spacers loaded with GNPs, which has been proposed to increase therapeutic efficacy during brachytherapy application with in situ dose painting.
Mathematical models were developed based on experimental data to study the release of GNPs from a spacer designed with poly(lactic-co-glycolic acid) polymer. The models addressed diffusion controlled-release process and poly(lactic-co-glycolic acid) degradation kinetics that were used to determine GNP concentration profiles in tumour and the corresponding dose enhancement.
The results show a significant delay of GNP diffusion in the tumour in comparison to burst release assumed in previous studies. The model for diffusion controlled-release process and the model for combined processes of both diffusion and polymer degradation indicated that it may take about 25 and 45 days, respectively, for all GNPs to release from the spacer. Based on tumour concentration profiles, a significant dose enhancement factor (>2) could be attained at a tumour distance of 5 mm from a spacer loaded with 2-, 5- and 10-nm GNP sizes.
The results highlight the need to account for the slow release of GNPs from spacers and polymer biodegradation in research development of the GNP-eluting spacers. The findings suggest the use of radioisotopes with longer half-lives, such as iodine-125, in comparison with others with shorter half-lives such as Pd-103 and Cs-131. Advances in knowledge: The study provides a scientific platform and basis for research development of GNP-eluting spacers that can be used during brachytherapy to boost dose to tumour subvolumes, towards enhancing therapeutic efficacy. It concludes that the use of iodine-125 would be more feasible.
研究载有金纳米颗粒（GNPs）的可生物降解近距离放射治疗间隔物中，金纳米颗粒缓慢释放与突发释放对剂量学的影响，该方法已被提议用于在近距离放射治疗应用中通过原位剂量描绘提高治疗效果。
基于实验数据建立数学模型，以研究金纳米颗粒从聚（乳酸 - 乙醇酸）聚合物设计的间隔物中的释放情况。这些模型考虑了扩散控制释放过程和聚（乳酸 - 乙醇酸）降解动力学，用于确定肿瘤中的金纳米颗粒浓度分布以及相应的剂量增强情况。
结果表明，与先前研究中假设的突发释放相比，肿瘤中金纳米颗粒的扩散有显著延迟。扩散控制释放过程模型以及扩散和聚合物降解联合过程模型表明，所有金纳米颗粒从间隔物中释放可能分别需要约25天和45天。根据肿瘤浓度分布，在距装载2纳米、5纳米和10纳米金纳米颗粒尺寸的间隔物5毫米的肿瘤距离处，可获得显著的剂量增强因子（>2）。
结果强调在金纳米颗粒洗脱间隔物的研究开发中，需要考虑间隔物中金纳米颗粒的缓慢释放和聚合物生物降解。研究结果表明，与半衰期较短的其他放射性同位素（如钯 - 103和铯 - 131）相比，应使用半衰期较长的放射性同位素，如碘 - 125。知识进展：该研究为金纳米颗粒洗脱间隔物的研究开发提供了科学平台和基础，该间隔物可在近距离放射治疗期间用于提高肿瘤亚体积的剂量，以增强治疗效果。研究得出结论，使用碘 - 125将更可行。
