A self-healing supramolecular hydrogel with temperature-responsive fluorescence based on an AIE luminogen

A Fluorescent Hydrogel with AIE Emission for Dehydration-Visualizable Wearable Sensors

Hydrogel-based wearable sensors eventually experience dehydration, which negatively impacts their function, leading to decreased sensitivity. Monitoring the real-time water retention rate and sensing performance of wearable flexible sensors without dismantling them remains a significant difficulty. In this study, a molecule having aggregation-induced emission (AIE) properties in an aqueous environment has been developed and produced, which can combine with anionic guar gum and acrylic acid to create an AIE hydrogel. Wearable sensing electronic devices have the capability to track motion signals at various joints of the human body. Additionally, they can effectively and visually monitor dehydration status during extended periods of operation. The fluorescence intensity of the hydrogel is primarily influenced by the level of aggregation of luminous monomers inside the network. This level of aggregation is predominantly governed by the hydrogel's water retention rate. Hence, the extended duration of hydrogel dehydration can be manifested through alterations in their fluorescence characteristics, which are employed for strain sensing. This approach enables users to assess the water retention of hydrogels with greater efficiency, eliminating the requirement for disassembling them from the completed electrical gadget. In summary, the use of AIE-based fluorescent hydrogels will advance the progress of intelligent wearable electronics.

Tetraphenylethene-modified polysiloxanes: Synthesis, AIE properties and multi-stimuli responsive fluorescence

Herein, polysiloxane-based aggregation-induced emission (AIE) polymers and rubbers were prepared which display interesting multi-stimuli responsive fluorescence. TPE-modified polydimethylsiloxanes (PDMS-TPE) as polysiloxane-based AIE polymers were synthesized through Heck reaction of bromo-substituted tetraphenylethene (TPE-Br) and vinyl polysiloxanes. As expected, TPE moiety endows the modified polysiloxane with typical AIE behavior. However, limited by the long polymer chains, the aggregation process of PDMS-TPE shows obvious differences compared with the small molecule TPE-Br. The fluorescence of PDMS-TPE in THF/H2O starts to increase when the H2O fraction (fw) is 70% while TPE-Br is nearly non-luminous until the fw is up to 99%. The fluorescence intensity ratio (I/I0) of PDMS-TPE in the aggregated state and dispersed state is over 1300, greater than that of TPE-Br (I/I0 = 380). More importantly, the exceptional thermal motion of Si-O-Si chains and AIE characteristic of TPE moiety work together, enabling PDMS-TPE to show specific temperature-dependent fluorescence with a wider response range of room temperature to 190°C, which is distinguished from TPE-Br. And such fluorescence responsiveness possess good fatigue-resistance. Furthermore, fluorescent silicone rubbers, r-PDMS-TPE were prepared by using PDMS-TPE as additive of the base gum. They display interesting solvent-controllable fluorescence and higher tensile strength (4.42 MPa) than the control sample without TPE component (1.96 MPa). Notably, a unique stretching-enhanced emission (SEE) phenomenon is observed from these TPE-modified silicone rubbers. When being stretched, the rubbers' fluorescent emission intensity could increase by 143%.

In vitro and in vivo anti-inflammatory properties of an active fucoidan fraction from Sargassum fusiforme and a fraction-based hydrogel

In a previous study, we separated an active fucoidan (JHCF4) from acid-processed Sargassum fusiforme, then analyzed and confirmed its structure. In the present study, we investigated the potential anti-inflammatory properties of JHCF4 and a JHCF4-based hydrogel in vitro and in vivo. JHCF4 reliably inhibited nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages, with an IC50 of 22.35 μg/ml. Furthermore, JHCF4 attenuated the secretion of prostaglandin E2, tumor necrosis factor-α, interleukin (IL)-1β, and IL-6, indicating that JHCF4 regulates inflammatory reactions. In addition, JHCF4 downregulated iNOS and COX-2 and inhibited the activation of the MAPK pathway. According to further in vivo analyses, JHCF4 significantly reduced the generation of reactive oxygen species (ROS), NO production, and cell death in an LPS-induced zebrafish model, suggesting that JHCF4 exhibits anti-inflammatory effects. Additionally, a JHCF4-based hydrogel was developed, and its properties were evaluated. The hydrogel significantly decreased inflammatory and nociceptive responses in carrageenan (carr)-induced mouse paws by reducing the increase in paw thickness and decreasing neutrophil infiltration in the basal and subcutaneous layers of the toe epidermis. These results indicate that JHCF4 exhibits potential anti-inflammatory activity in vitro and in vivo and that JHCF4-based hydrogels have application prospects in the cosmetic and pharmaceutical fields.

A supramolecular assembly strategy towards organic luminescent materials

Supramolecular organic luminescent materials with different dimensionalities usually exhibit different optical properties as well as their potential applications in various fields. Recent reports showed that non-covalent interactions are useful tools to obtain diverse luminescent materials due to their dynamicity and reversibility, including π-π stacking, host-guest interactions, hydrophobic effects, hydrogen bonding, electrostatic effects and so on. In this review, we summarized recent progress in zero-, one-, two-, three-dimensional and disordered organic luminescent materials using the aforementioned strategies, in order to provide a solution for designing luminescent materials with specific structures and morphologies. The relationship between assembly behavior and luminescent properties is discussed in detail, along with the existing difficulties hindering the development of supramolecular assembly systems and future research directions.

Fast and Reversibly Humidity-Responsive Fluorescence Based on AIEgen Proton Transfer

The construction of humidity-responsive fluorescent materials with reversibility, specificity, and sensitivity is of great importance for the development of information encryption, fluorescence patterning, and sensors. Nevertheless, to date, the application of these materials has been limited by their slow response rate and nonspecificity. Herein, a humidity-responsive fluorescence system was designed and assembled to achieve a rapid, reversible, and specific moisture response. The system comprised tetra-(4-pyridylphenyl)ethylene (TPE-4Py) as a fluorescent proton acceptor with an aggregation-induced emission (AIE) effect and poly(acrylic acid) (PAA) as a proton donor with an efficient moisture-capturing ability. The fluorescence color and intensity rapidly changed with increasing relative humidity (RH) because of TPE-4Py protonation, and TPE-4Py deprotonation resulted in recovery of the original fluorescence color in low-humidity environments. The proton transfer between the pyridyl group in TPE-4Py and the carboxyl group in PAA was reversible and chemically stable, and the humidity-responsive fluorescence system showed a high response/recovery speed, an obvious color change, good reversibility, and an outstanding specific moisture response. Because of these advantages, diverse applications of this humidity-responsive fluorescence system in transient fluorescent patterning and the encryption of information were also developed and demonstrated.

Configuration-Dependent Liquid Crystal and Gel Behaviors of Tetraphenylethene-Containing Main-Chain Copolyesters

The construction of aggregation-induced emission-active (AIE-active) gelators with liquid crystal properties remains a challenge. Moreover, it is still unclear for the effect of AIE configuration on liquid crystal, gel and AIE behaviors in one system. Herein, two main-chain liquid crystalline copolyester gelators with a single configuration of AIEgen TPE, mesogen biphenyl and pendent amide groups have been synthesized through melt polycondensation. Both copolyesters display smectic phase, while E-P20 possesses a wider temperature range of liquid crystal and a narrower layer distance owing to the more serious nonlinear "defect" of Z-TPE than E-TPE units. In addition, E-P20 and Z-P20 can form AIE-active gels with the minimum gelation concentration (MGC) values of 10 wt% and 4 wt% in ethyl acetate mainly via hydrogen bond between the pendent amide groups, respectively. These AIE-active gels show potential applications in temperature sensor, information storage, and so on. This article is protected by copyright. All rights reserved.

Zinc (II) and AIEgens: The "Clip Approach" for a Novel Fluorophore Family. A Review

Aggregation-induced emission (AIE) compounds display a photophysical phenomenon in which the aggregate state exhibits stronger emission than the isolated units. The common term of "AIEgens" was coined to describe compounds undergoing the AIE effect. Due to the recent interest in AIEgens, the search for novel hybrid organic-inorganic compounds with unique luminescence properties in the aggregate phase is a relevant goal. In this perspective, the abundant, inexpensive, and nontoxic d10 zinc cation offers unique opportunities for building AIE active fluorophores, sensing probes, and bioimaging tools. Considering the novelty of the topic, relevant examples collected in the last 5 years (2016-2021) through scientific production can be considered fully representative of the state-of-the-art. Starting from the simple phenomenological approach and considering different typological and chemical units and structures, we focused on zinc-based AIEgens offering synthetic novelty, research completeness, and relevant applications. A special section was devoted to Zn(II)-based AIEgens for living cell imaging as the novel technological frontier in biology and medicine.

Aggregation-Induced Emission Fluorescent Gels: Current Trends and Future Perspectives

The development of fluorescent gels, if not the current focus, is at the center of recent efforts devoted to the invention of a new generation of gels. Fluorescent gels have numerous properties that are intrinsic to the gel structure, with additional light-emitting properties making them attractive for different applications. This review focuses on current studies associated with the development of fluorescent gels using aggregation-induced emission fluorophores (AIEgens) to ultimately suggest new directions for future research. Here, we discuss major drawbacks of the methodologies used frequently for the fabrication of fluorescent gels using traditional fluorophores compared to those using AIEgens. The fabrication strategies to develop AIE-based fluorescent gels, including physical mixing, soaking, self-assembly, noncovalent interactions, and permanent chemical reactions, are discussed thoroughly. New and recent findings on developing AIE-active gels are explained. Specifically, physically prepared AIE-based gels including supramolecular, ionic, and chemically prepared AIE-based gels are discussed. In addition, the intrinsic fluorescent properties of natural gels, known as clustering-triggered fluorescent gel, and new and recent relevant findings published in peer-reviewed journals are explained. This review also revealed the biomedical applications of AIE-based fluorescent hydrogels including drug delivery, biosensors, bioimaging, and tissue engineering. In conclusion, the current research situation and future directions are identified.

Research Progress Review of Preparation and Applications of Fluorescent Hydrogels

The fluorescent gel with good flexibility and biocompatibility has attracted more and more attention due to its excellent optical properties. In this paper, the research progresses in preparation methods and applications of fluorescent gels are reviewed. In addition, the preparation methods of self-assembly and polymerization of fluorescent gel are also introduced. In this paper, it should be noted that some outstanding research about the fluorescent gels used in sensors, bio-imaging probes, drug delivery, and other application fields is summarized. This work provides useful reference information for further exploration and study of fluorescent hydrogels.