Solid lipid nanoparticles (SLNs) have shown great capabilities for drug delivery and are therefore attractive theranostic candidates when labelled with an imaging contrast agent. This work aims to create the first SLNs labelled for photoacoustic (PA) imaging by encapsulating a specially designed and near-infrared absorbing BODIPY dye (BY-aniline-Palm) into SLNs of dexamethasone palmitate. A one-pot formulation protocol enabled us to replace the prodrug with the BY-aniline-Palm label in various proportions up to 100%. Increasing the dye content resulted in complex but gradual transformations of the SLNs in terms of optical absorption and PA spectra, and the formation of aggregates at high concentration. A comprehensive and quantitative PA spectrometric study revealed a photoacoustic generation efficiency (PGE) that was spectrally varying and notably greater than 1. A joint spectral decomposition of the absorption and PA spectra into the sum of three Gaussian functions displayed a per-band evolution of the PGE when the concentration of BY-aniline-Palm varied and showed an interplay between the bands with a constant spectrum area. Finally, a novel quantitative PA spectroscopic approach, involving measurements at three different ambient temperatures, demonstrated that the remarkable PGE values arose from a significant thermo-elastic expansion of the SLNs during PA signal generation independently of the absorption band. This study highlights that labeled SLNs are promising agents for PA imaging and also unveils complex transformations that can occur in such nanosystems with a dye prone to aggregation.

中文翻译：

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用浓度递增的光声 NIR BODIPY 标记的治疗诊断固体脂质纳米颗粒中的定量光声光谱变换


固体脂质纳米颗粒 （SLN） 已显示出强大的药物递送能力，因此当用成像造影剂标记时，它们是有吸引力的治疗诊断候选者。这项工作旨在通过将专门设计的近红外吸收 BODIPY 染料 （BY-苯胺-Palm） 封装到棕榈酸地塞米松的 SLN 中，创建第一个标记用于光声 （PA） 成像的 SLN。一锅法配方方案使我们能够用不同比例的 BY-苯胺-Palm 标记替换前药，最高可达 100%。增加染料含量导致 SLN 在光吸收和 PA 光谱方面发生复杂但逐渐的转变，并在高浓度下形成聚集体。一项全面的定量 PA 光谱研究揭示了光声产生效率 （PGE），该效率在光谱上是可变的，并且明显大于 1。将吸收光谱和 PA 光谱联合分解为三个高斯函数之和，显示当 BY-苯胺-Palm 的浓度变化时，PGE 的每波段演变，并显示具有恒定光谱面积的波段之间的相互作用。最后，一种新颖的定量 PA 光谱方法，涉及在三种不同环境温度下的测量，表明显着的 PGE 值是由 SLN 在 PA 信号产生过程中独立于吸收带的显着热弹性膨胀引起的。这项研究强调标记的 SLN 是 PA 成像的有前途的试剂，并且还揭示了在这种具有易聚集染料的纳米系统中可能发生的复杂转变。