Rub Pakkath Sajid Abdul, Chetty Shashank Shankar, Selvarasu Praneetha, Vadivel Murugan Arumugam, Kumar Yogesh, Periyasamy Latha, Santhakumar Muthukamalam, Sadras Sudha Rani, Santhakumar Kirankumar
Zebrafish Genetics Laboratory, Department of Genetic Engineering, Sree Ramaswamy Memorial (SRM) Institute of Science and Technology, SRM Nagar, Kattankulathur, Tamil Nadu 603203, India.
ACS Biomater Sci Eng. 2018 Jul 9;4(7):2582-2596. doi: 10.1021/acsbiomaterials.7b00943. Epub 2018 Jun 6.
Heteroatom-doped carbon dots (C-dots) have captured widespread research interest owing to high fluorescence and biocompatibility for multimodal bioimaging applications. Here, we exemplify a rapid, facile synthesis of ethylenediamine (EDA)-functionalized transition metal ion (Mn, Fe, Co, and Ni)-doped C-dots via one-pot microwave (MW)-assisted pyrolysis at 800 W within 6 min using (lemon) extract as a carbon source. During MW pyrolysis, the precursor extract undergoes simultaneous carbonization and doping of metal ions onto C-dot surfaces in the presence of EDA. The EDA-functionalized transition metal ion-doped C-dots (i.e., Mn/C, Fe/C, Co/C, and Ni/C-dots) are collectively termed as TMCDs. The water-soluble TMCDs exhibited a size of 3.2 ± 0.485 nm and were enriched with amino and oxo functionalities and corresponding metal-oxide traces on the surfaces, as revealed from Fourier transfer infrared and X-ray photoelectron spectroscopy analyses. Interestingly, TMCDs demonstrated excitation-wavelength-dependent emission with brighter photoluminescence (PL) at 460 nm. Compared to pristine C-dots with a PL quantum yield (QY) of 48.31% and a fluorescence lifetime of 3.6 ns, the synthesized Mn/C, Fe/C, Co/C, and Ni/C-dots exhibited PL QY values of 35.71, 41.72, 75.07, and 50.84% as well as enhanced fluorescence lifetimes (τ) of 9.4, 8.6, 9.2, and 8.9 ns, respectively. The TMCDs significantly exhibited enhanced biocompatibility in human colon cancer cells (SW480) for fluorescence bioimaging and showed ferromagnetic and superparamagnetic behavior with vibrant -contrast ability. Interestingly, the maximum longitudinal () relaxivity of 0.341 mM s was observed for Mn/C-dots in comparison to that of 3.1-3.5 mM s of clinically used Gd-DTPA magnetic resonance (MR)-contrast agent in vitro (1.5 T). Similarly, the maximum longitudinal relaxivity () of 0.356 mM s was observed for Ni/C-dots (1.5 T) with respect to 4.16 ± 0.02 mM s attained for Gd-DTPA in vivo (8.45 T). Thus, the rapid, energy-efficient MW-assisted pyrolysis presents lemon extract derived, EDA-functionalized TMCDs with enhanced PL and efficient contrast as potential magneto-fluorescent nanoprobes for dual-modality bioimaging applications.
杂原子掺杂的碳点（C点）因其高荧光性和生物相容性，在多模态生物成像应用中引起了广泛的研究兴趣。在此，我们展示了一种快速、简便的合成方法，以乙二胺（EDA）功能化的过渡金属离子（Mn、Fe、Co和Ni）掺杂的C点，通过在800W功率下6分钟内的一锅微波（MW）辅助热解，使用（柠檬）提取物作为碳源。在MW热解过程中，前体提取物在EDA存在下同时进行碳化和金属离子掺杂到C点表面。EDA功能化的过渡金属离子掺杂的C点（即Mn/C、Fe/C、Co/C和Ni/C点）统称为TMCDs。水溶性TMCDs的尺寸为3.2±0.485nm，表面富含氨基和羰基官能团以及相应的金属氧化物痕迹，这通过傅里叶变换红外光谱和X射线光电子能谱分析得以揭示。有趣的是，TMCDs表现出激发波长依赖性发射，在460nm处具有更亮的光致发光（PL）。与PL量子产率（QY）为48.31%、荧光寿命为3.6ns的原始C点相比，合成的Mn/C、Fe/C、Co/C和Ni/C点的PL QY值分别为35.71%、41.72%、75.07%和50.84%，荧光寿命（τ）分别增强至9.4ns、8.6ns、9.2ns和8.9ns。TMCDs在人结肠癌细胞（SW480）中进行荧光生物成像时显著表现出增强的生物相容性，并表现出铁磁性和超顺磁性行为，具有出色的对比能力。有趣的是，与体外（1.5T）临床使用的钆喷酸葡胺磁共振（MR）造影剂的3.1 - 3.5mM⁻¹s⁻¹相比，Mn/C点在体外观察到的最大纵向（r1）弛豫率为0.341mM⁻¹s⁻¹。同样，对于Ni/C点（1.5T），相对于体内（8.45T）钆喷酸葡胺达到的4.16±0.02mM⁻¹s⁻¹，观察到的最大纵向弛豫率（r1）为0.356mM⁻¹s⁻¹。因此，快速、节能的MW辅助热解呈现出柠檬提取物衍生的、EDA功能化的TMCDs，具有增强的PL和高效的磁共振对比，作为用于双模态生物成像应用的潜在磁荧光纳米探针。
