Department of Chemistry 'Giacomo Ciamician', University of Bologna, Bologna, Italy.
Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2016 Jan-Feb;8(1):139-50. doi: 10.1002/wnan.1351. Epub 2015 May 27.
Fluorescent nanoparticles (NPs) are unique contrast agents for bioimaging. Examples of molecular-based fluorescent NPs with brightness similar or superior to semiconductor quantum dots have been reported. These ultra-bright NPs consist of a silica or polymeric matrix that incorporate the emitting dyes as individual moieties or aggregates and promise to be more biocompatible than semiconductor quantum dots. Ultra-bright materials result from heavy doping of the structural matrix, a condition that entails a close mutual proximity of the doping dyes. Ground state and excited state interactions between the molecular emitters yield aggregation-caused quenching (ACQ) and proximity-caused quenching (PCQ). In combination with Föster resonance energy transfer (FRET) ACQ and PCQ originate collective phenomena that produce amplified quenching of the nanoprobes. In this focus article, we discuss strategies to achieve ultra-bright nanoprobes avoiding ACQ and PCQ also exploiting aggregation-induced emission (AIE). Amplified quenching, on the other hand, is also proposed as a strategy to design stimuli-responsive fluorogenic probes through disaggregation-induced emission (DIE) in alternative to AIE. As an advantage, DIE consents to design stimuli-responsive materials starting from a large variety of precursors. On the contrary, AIE is characteristic of a limited number of species. Examples of stimuli-responsive fluorogenic probes based on DIE are discussed.
荧光纳米粒子（NPs）是生物成像的独特对比剂。已经有报道称，一些分子基荧光 NPs 的亮度与半导体量子点相当或更优。这些超亮 NPs 由硅或聚合物基质组成，将发射染料作为单个部分或聚集体掺入其中，并有望比半导体量子点更具生物相容性。超亮材料是通过对结构基质进行重度掺杂产生的，这种情况需要掺杂染料的紧密相互接近。分子发射器的基态和激发态相互作用产生聚集引起的猝灭（ACQ）和临近引起的猝灭（PCQ）。与Förster 共振能量转移（FRET）结合，ACQ 和 PCQ 产生集体现象，从而放大纳米探针的猝灭。在这篇重点文章中，我们讨论了避免 ACQ 和 PCQ 的超亮纳米探针的设计策略，同时还利用聚集诱导发光（AIE）来实现。另一方面，放大猝灭也被提议作为一种通过解聚集诱导发射（DIE）设计刺激响应荧光探针的策略，而不是 AIE。作为一个优势，DIE 允许从大量的前体开始设计刺激响应材料。相反，AIE 是少数几种物质的特征。讨论了基于 DIE 的刺激响应荧光探针的例子。
