Cyclodextrins are a well-established system which form inclusion complexes with many guest molecules. This property can be easily exploited to develop drug delivery systems. Additionally, carbon dots (CD) are a low-toxic photoluminescent product which have been used as luminescent tags. The combination of cyclodextrins and carbon dots allows obtaining a new nanoplatform, a biocompatible material, with both capabilities, increasing as well the internalization by the cells of the CD, induced by the cyclodextrins. In the present work, we have modified the surface of carbon dots obtained from citric acid and glutathione with β and γ cyclodextrins. After a morphological and spectroscopic characterization, we concluded that the luminescence quantum yield and absorption molar coefficient of the derivatized and unmodified carbon dots was the same. These findings, together with the spectroscopic detection of active cyclodextrins, those bond to the CD able to interact with a guest molecule, allowed determination of the ratios: cyclodextrins/CD, active cyclodextrins/CD and an estimation of the CD molecular mass. Furthermore, the biocompatibility of the new materials was evaluated through cytotoxicity and cell-penetrance assays revealing that the materials were non cytotoxic up to 0.1 mg/mL. Moreover, the biocompatible developed nanoplatform penetrates in the cells maintaining the material's intrinsic fluorescence, thus constituting an adequate photoluminescent-tag with high-contrast for cell imaging. This work provides a new and easy method to combine cyclodextrins and carbon dots into a biocompatible material which can be used as nanoplatform both as drug delivery system and as photoluminescent tag in cell imaging. Likewise, this paper shows how to characterize the number of cyclodextrins and active cyclodextrins per CD, having an average stoichiometric relation of 1:1 for guest molecule – CD. Additionally, the minimum molecular mass of the unmodified CD was indirectly obtained, yielding about 1.6–1.9 kDa.

中文翻译：

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用环糊精对碳点进行表面修饰作为潜在的生物相容性光致发光传递/生物成像纳米平台


环糊精是一种成熟的系统，可与许多客体分子形成包合物。可以很容易地利用这一特性来开发药物输送系统。此外，碳点（CD）是一种低毒的光致发光产品，已被用作发光标签。环糊精和碳点的组合可以获得一种新的纳米平台，一种生物相容性材料，具有这两种功能，并增加由环糊精诱导的CD细胞的内化。在目前的工作中，我们用β和γ环糊精对从柠檬酸和谷胱甘肽获得的碳点的表面进行了修饰。经过形态和光谱表征后，我们得出结论，衍生化和未改性的碳点的发光量子产率和吸收摩尔系数是相同的。这些发现与活性环糊精的光谱检测一起，那些与CD键合的能够与客体分子相互作用的环糊精，可以确定比率：环糊精/CD、活性环糊精/CD以及CD分子质量的估计。此外，通过细胞毒性和细胞渗透率测定评估了新材料的生物相容性，结果表明这些材料在浓度高达 0.1 mg/mL 的情况下是无细胞毒性的。此外，生物相容性开发的纳米平台渗透到细胞中，保持材料的固有荧光，从而构成足够的具有高对比度的光致发光标签，用于细胞成像。这项工作提供了一种新的、简单的方法，将环糊精和碳点组合成生物相容性材料，该材料可用作纳米平台，既可用作药物输送系统，也可用作细胞成像中的光致发光标签。 同样，本文展示了如何表征每个 CD 的环糊精和活性环糊精的数量，客体分子 - CD 的平均化学计量关系为 1:1。此外，间接获得了未修饰 CD 的最小分子量，约为 1.6–1.9 kDa。