Nanogels containing AIE Active Molecules
Since the introduction of the concept of aggregation-induced emission (AIE) in 2001, many research groups have become involved in AIE research. Aggregation-induced emission luminogens (AIEgens) have emerged as a novel type of advanced material with excellent performance in various fields. Much effort has been devoted to determining the AIE mechanism(s) by theoreticians and experimentalists. Restriction of intramolecular motion has been recognized as the general working mechanism of AIE, but the mechanims of some AIE systems still remain unclear [1]. AIE, a novel photophyscial phenomena where the aggregate formation enhances the light emission, has drawn great attention because it provides a fantastic platform for the development of these useful luminescent materials. Numerous AIE luminogens (AIEgens) with tunable color and high quantum yields have been reported and used in diverse applications from optics and electronics to energy and bioscience [2].
Luminescence is a useful process. In nature, living organisms such as lampyridae, anglerfish and ctenophore emit bright bioluminescence to attract the opposite sex, catch food or defend against attackers, keeping their species viable [3]. Inspired by nature, human beings have utilized luminescent materials in lighting devices, information displays, and biomedical engineering, creating a colorful life [3]. Technological demands have generated an even greater interest in the study and development of new luminescent materials [3]. Fundamental investigations on organic luminescence have generally been carried out in dilute solutions, where abundant solvent molecules impede the intermolecular interactions between luminophore molecules [3].
However, in the real world, luminophores are often used in solid state, for example, as thin films in organic light-emitting diodes (OLEDs) [3]. Conventional luminophores for medical diagnosis tend to form aggregates in aqueous solutions due to the high hydrophobicity of their emitting centers (often aromatic rings) [3]. Understanding light emission in the aggregate state is thus of great importance for their practical application [3].
Chromophore aggregation generally exerts two effects on luminescence processes, aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) [3]. These two effects are diametrically opposed to each other [3]. Which one prevails in a particular system depends strongly on chromophore structure and packing interaction [3]. A facile and efficient approach for design and synthesis of organic fluorescent nanogels has been developed by using a pre-synthesized polymeric precursor. This strategy is achieved by two key steps: (i) precise synthesis of core–shell star-shaped block copolymers with crosslinkable AIEgen-precursor (AIEgen: aggregation induced emission luminogen) as pending groups on the inner blocks; (ii) gelation of the inner blocks by coupling the AIEgen-precursor moieties to generate AIE-active spacers, and thus, fluorescent nanogel [4].
Bioresponsive nanogels with a crosslinked three-dimensional structure and an aqueous environment that undergo physical or chemical changes including swelling and dissociation in response to biological signals such as mild acidity, hyperthermia, enzymes, reducing agents, reactive oxygen species (ROS), and adenosine-5ʹ-triphosphate (ATP) present in tumor microenvironments or inside cancer cells have emerged as an appealing platform for targeted drug delivery and cancer therapy [5]. Also, compared with other bio-imaging techniques, fluorescent imaging displayed more advantages of high sensitivity, easy operation, and cost-effectiveness.1minus;3 Using fluorescent imaging techniques to trace cellular processes over a long period of time is significant for biological or medical researchers because they provide some important information about cell transplantation, migration, division, fusion, and lysis [6].
I am planning to finish writing the “Synthetic method of Nanogels containing AIE Active Molecules” part of my thesis by May 9th 2021, the second part “Main features of Nanogels containing AIE Active Molecules” will be done by May 23rd 2021 and the last part “Applications and uses of Nanogels with AIE property in the biomedical field” will be done no later than June 6th.
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