Department of Chemistry and Biochemistry, ‡BIO5 Institute, and §Department of Biomedical Engineering, University of Arizona , Tucson, Arizona 85721, United States.
ACS Appl Mater Interfaces. 2018 Feb 7;10(5):4953-4960. doi: 10.1021/acsami.7b15943. Epub 2018 Jan 24.
β-particle emitting radionuclides are useful molecular labels due to their abundance in biomolecules. Detection of β-emission from H, S, and P, important biological isotopes, is challenging due to the low energies (E ≤ 300 keV) and short penetration depths (≤0.6 mm) in aqueous media. The activity of biologically relevant β-emitters is usually measured in liquid scintillation cocktail (LSC), a mixture of energy-absorbing organic solvents, surfactants, and scintillant fluorophores, which places significant limitations on the ability to acquire time-resolved measurements directly in aqueous biological systems. As an alternative to LSC, we developed polystyrene-core, silica-shell nanoparticle scintillators (referred to as nanoSCINT) for quantification of low-energy β-particle emitting radionuclides directly in aqueous solutions. The polystyrene acts as an absorber for energy from emitted β-particles and can be loaded with a range of hydrophobic scintillant fluorophores, leading to photon emission at visible wavelengths. The silica shell serves as a hydrophilic shield for the polystyrene core, enabling dispersion in aqueous media and providing better compatibility with water-soluble analytes. While polymer and inorganic scintillating microparticles are commercially available, their large size and/or high density complicates effective dispersion throughout the sample volume. In this work, nanoSCINT nanoparticles were prepared and characterized. nanoSCINT responds to H, S, and P directly in aqueous solutions, does not exhibit a change in scintillation response between pH 3.0 and 9.5 or with 100 mM NaCl, and can be recovered and reused for activity measurements in bulk aqueous samples, demonstrating the potential for reduced production of LSC waste and reduced total waste volume during radionuclide quantification. The limits of detection for 1 mg/mL nanoSCINT are 130 nCi/mL for H, 8 nCi/mL for S, and <1 nCi/mL for P.
β-发射放射性核素由于在生物分子中丰富而成为有用的分子标签。由于在水介质中的能量低（E ≤ 300 keV）和穿透深度短（≤0.6 毫米），检测 H、S 和 P 等重要生物同位素的 β 发射非常具有挑战性。由于生物相关 β-发射器的活性通常在液体闪烁鸡尾酒（LSC）中进行测量，LSC 是一种吸收能量的有机溶剂、表面活性剂和闪烁荧光染料的混合物，这对直接在水生物系统中进行时间分辨测量的能力有很大的限制。作为 LSC 的替代物，我们开发了聚苯乙烯核/二氧化硅壳纳米粒子闪烁体（称为 nanoSCINT），用于直接在水溶液中定量测定低能量 β-发射放射性核素。聚苯乙烯作为发射β-粒子的能量吸收体，可以负载一系列疏水性闪烁荧光染料，从而在可见光波长处发射光子。二氧化硅壳作为聚苯乙烯核的亲水性屏蔽物，使纳米粒子在水介质中分散，并与水溶性分析物更好地兼容。虽然聚合物和无机闪烁微球可商购，但它们的尺寸大和/或高密度使它们在整个样品体积中难以有效分散。在这项工作中，制备和表征了 nanoSCINT 纳米粒子。nanoSCINT 直接在水溶液中响应 H、S 和 P，在 pH 3.0 至 9.5 之间或在 100 mM NaCl 中不显示闪烁响应的变化，并且可以在批量水样品中回收和重复用于活性测量，这表明在放射性核素定量分析中减少 LSC 废物的产生和总废物量的潜力。对于 1 mg/mL nanoSCINT，H 的检测限为 130 nCi/mL，S 的检测限为 8 nCi/mL，P 的检测限低于 1 nCi/mL。
