Department of Bioengineering, University of California, Riverside, CA 92521, USA.
Nanotechnology. 2017 Jan 20;28(3):035101. doi: 10.1088/1361-6528/28/3/035101. Epub 2016 Dec 14.
Light-activated theranostic materials offer a potential platform for optical imaging and phototherapeutic applications. We have engineered constructs derived from erythrocytes, which can be doped with the FDA-approved near infrared (NIR) chromophore, indocyanine green (ICG). We refer to these constructs as NIR erythrocyte-mimicking transducers (NETs). Herein, we investigated the effects of changing the NETs mean diameter from micron- (≈4 μm) to nano- (≈90 nm) scale, and the ICG concentration utilized in the fabrication of NETs from 5 to 20 μM on the resulting absorption and scattering characteristics of the NETs. Our approach consisted of integrating sphere-based measurements of light transmittance and reflectance, and subsequent utilization of these measurements in an inverse adding-doubling algorithm to estimate the absorption (μ ) and reduced scattering (μ ') coefficients of these NETs. For a given NETs diameter, values of μ increased over the approximate spectral band of 630-860 nm with increasing ICG concentration. Micron-sized NETs produced the highest peak value of μ when using ICG concentrations of 10 and 20 μM, and showed increased values of μ ' as compared to nano-sized NETs. Spectral profiles of μ ' for these NETs showed a trend consistent with Mie scattering behavior for spherical objects. For all NETs investigated, changing the ICG concentration minimally affected the scattering characteristics. A Monte Carlo-based model of light distribution showed that the presence of these NETs enhanced the fluence levels within simulated blood vessels. These results provide important data towards determining the appropriate light dosimetry parameters for an intended light-based biomedical application of NETs.
光激活治疗性材料为光学成像和光疗应用提供了一个潜在的平台。我们设计了源自红细胞的构建体，可以掺杂美国食品和药物管理局批准的近红外（NIR）发色团吲哚菁绿（ICG）。我们将这些构建体称为近红外红细胞模拟换能器（NETs）。在此，我们研究了改变 NETs 的平均直径从微米（≈4 μm）到纳米（≈90 nm）以及在制造 NETs 时 ICG 浓度从 5 μM 到 20 μM 对 NETs 的吸收和散射特性的影响。我们的方法包括基于积分球的光透射率和反射率测量，以及随后将这些测量值用于逆加-倍增算法中，以估计这些 NETs 的吸收（μ）和减少散射（μ'）系数。对于给定的 NETs 直径，随着 ICG 浓度的增加，μ在大约 630-860nm 的光谱带内增加。当使用 10 和 20 μM 的 ICG 浓度时，微米大小的 NETs 产生了最高的 μ峰值，并且与纳米大小的 NETs相比，μ'值增加。这些 NETs 的 μ'光谱曲线显示出与球形物体 Mie 散射行为一致的趋势。对于所有研究的 NETs，改变 ICG 浓度对散射特性的影响最小。基于蒙特卡罗的光分布模型表明，这些 NETs 的存在增强了模拟血管内的荧光水平。这些结果为确定 NETs 预期基于光的生物医学应用的适当光剂量学参数提供了重要数据。
