Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore, 117583.
NUS, Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, 117456.
ACS Appl Mater Interfaces. 2020 Mar 18;12(11):12549-12556. doi: 10.1021/acsami.0c00672. Epub 2020 Mar 6.
Upconversion nanoparticles (UCNPs) have been used effectively as light transducers to convert near-infrared irradiation to short-wavelength emissions for photoactivation in deep tissues. UCNPs with single/multiple emissions under excitation at a single wavelength can be used for simultaneous activation of single or multiple photosensitive molecules only; an ideal multifunctional UCNP nanoplatform should not only have the ability to load multiple molecules but also should activate them at the right time with the right dose when necessary, depending upon the application for which it is used. The control of many biological processes requires complex (simultaneous or subsequent) photoactivation at different time points. Subsequent photoactivation requires UCNPs with orthogonal fluorescence emissions, which can be controlled independently. So far, there are only a few reports about UCNPs with orthogonal emissions. Synthesis of these orthogonal emission nanoparticles is complicated and tedious because nanoparticles with multiple shells need to be synthesized, and different lanthanide ions need to be doped into different shells. Also, there is no flexibility for changing the doped ions and emission profile after the nanoparticles are produced. Here, we have demonstrated a versatile method to modularly assemble individual UCNPs into UCNP clusters (UCNPs-C) with adjustable emissions. The synthesis is much easier, and there is a lot of flexibility in changing the particle size, shape, doped ions, and emission profile. We have demonstrated the use of such UCNPs-C for color encoding at the nanoscale. We further designed orthogonal photoactivatable UCNPs-C (OP-UCNPs-C), which can be independently activated under 980 nm excitation for red emission and 808 nm excitation for UV/blue emission. These OP-UCNPs-C were used for independent activation of processes for cell imaging (980 nm) and drug delivery (808 nm). In comparison to the traditional nonprogrammed activation, a programmed controlled imaging and drug delivery process could guarantee highly targeted and enhanced cell death of cancerous cells.
上转换纳米粒子（UCNPs）已被有效地用作光转换器，将近红外辐射转换为短波长发射，以在深层组织中进行光激活。在单一波长的激发下具有单一/多种发射的 UCNPs 只能用于单一或多种光敏分子的同时激活；理想的多功能 UCNP 纳米平台不仅应具有负载多种分子的能力，而且还应根据其用途在需要时以适当的剂量和时间激活它们。许多生物过程的控制需要在不同时间点进行复杂（同时或随后）的光激活。随后的光激活需要具有正交荧光发射的 UCNPs，其可以独立控制。到目前为止，仅有少数关于具有正交发射的 UCNPs 的报道。这些正交发射纳米粒子的合成复杂而繁琐，因为需要合成具有多层的纳米粒子，并且需要将不同的镧系元素离子掺杂到不同的壳层中。此外，在纳米粒子制成后，改变掺杂离子和发射谱的灵活性受到限制。在这里，我们展示了一种将单个 UCNPs 组装成具有可调发射的 UCNP 簇（UCNPs-C）的通用方法。该合成方法更容易，并且在改变颗粒尺寸、形状、掺杂离子和发射谱方面具有很大的灵活性。我们已经证明了这种 UCNPs-C 在纳米尺度上的颜色编码的用途。我们进一步设计了正交光可激活的 UCNPs-C（OP-UCNPs-C），其可以在 980nm 激发下独立激活以产生红色发射，在 808nm 激发下独立激活以产生 UV/蓝色发射。这些 OP-UCNPs-C 用于独立激活细胞成像（980nm）和药物输送（808nm）过程。与传统的非编程激活相比，编程控制的成像和药物输送过程可以保证对癌细胞的高度靶向和增强的细胞死亡。
