Multicolor fluorescent polymeric hydrogels (MFPHs) are three‐dimensionally crosslinked hydrophilic polymer networks with tunable emission color. Different from the classic fluorescent materials that are used primarily in dry solid states or solutions, MFPHs exist as highly water‐swollen quasi‐solids. They thus present many promising properties of both solids and solution, including tissue‐like mechanical properties, an intrinsic soft and wet nature, fabulous biocompatibility, along with a responsive volume, shape, and fluorescence color change. These advantageous properties hold great potential in many applications such as sensing, bioimaging, information encoding, encryption, biomimetic actuators, and soft robotics. This Review gives an in‐depth overview of recent progress in the field of MFPHs, with a particular focus on the diverse construction methods and important demonstrated applications. Current challenges and future perspectives on MFPHs are also discussed.

Exosomes are membrane-enclosed phospholipid extracellular vesicles. In spite of their great promise as noninvasive biomarkers for cancer diagnosis, sensitive detection of exosomes is still challenging. Herein, the detection of exosomes was changed to the detection of DNA after recognition of exosomes with its aptamers. CD63 aptamer and EpCAM aptamer were used for the detection of MCF-7 cell-secreted exosome. The recognition process was amplified through the movements of a three-dimensional DNA walker. And then, Exonuclease III- assisted electrochemical ratiometric sensor was applied for further signal amplification. Under optimal conditions, the detection limit of 1.3 × 104 particles/mL was obtained with excellent selectivity. Furthermore, clinical application test for the detection of exosomes in human serum was also verified.

In this study, rapid loss of relativistic radiation belt electrons at low L * values (2.4-3.2) during a strong geomagnetic storm on 22 June 2015 is investigated along with five possible loss mechanisms. Both the particle and wave data are obtained from the Van Allen Probes. Duskside H + band electromagnetic ion cyclotron (EMIC) waves were observed during a rapid decrease of relativistic electrons with energy above 5.2 MeV occurring outside the plasmasphere during extreme magnetopause compression. Lower He + composition and enriched O + composition are found compared to typical values assumed in other studies of cyclotron resonant scattering of relativistic electrons by EMIC waves. Quantitative analysis demonstrates that even with the existence of He + band EMIC waves, it is the H + band EMIC waves that are likely to cause the depletion at small pitch angles and strong gradients in pitch angle distributions of relativistic electrons with energy above 5.2 MeV at low L values for this event. Very low frequency wave activity at other magnetic local time can be favorable for the loss of relativistic electrons at higher pitch angles. An illustrative calculation that combines the nominal pitch angle scattering rate due to whistler mode chorus at high pitch angles with the H + band EMIC wave loss rate at low pitch angles produces loss on time scale observed at L = 2.4-3.2. At high L values and lower energies, radial loss to the magnetopause is a viable explanation.

Fluorescence resonance energy transfer (FRET) between a quantum dot as donor and an organic fluorophore as acceptor has been widely used for detection of nucleic acids and proteins. In this paper, we developed a new method, characterized by 605-nm quantum dot (605QD) fluorescence intensity increase and corresponding Cy5 fluorescence intensity decrease, to detect adenosine triphosphate (ATP). The new method involved the use of three different oligonucleotides: 3'-biotin-modified DNA that binds to streptavidin-conjugated 605QD; 3'-Cy5-labelled DNA; and a capture DNA consisting of an ATP aptamer and a sequence which could hybridize with both 3'-biotin-modified DNA and 3'-Cy5-labelled DNA. In the absence of the target ATP, the capture DNA binds to 3'-biotin-modified DNA and 3'-Cy5-labelled DNA, bringing quantum dot and Cy5 into close proximity for greater FRET efficiency. When ATP is introduced, the release of the 3'-Cy5-labelled DNA from the hybridization complex took place, triggering 605QD fluorescence intensity increase and corresponding Cy5 fluorescence intensity decrease. Taken together, the virtue of FRET pair 605QD/Cy5 and the property of aptamer-specific conformation change caused by aptamer-ATP interaction, combined with the fluorescence intensity change of both 605QD and Cy5, provide prerequisites for simple and convenient ATP detection.

A tetrahedron-like PEG macromonomer-based fluorescent hydrogel was fabricated by a facile method.

Aggregation-induced emission (AIE) and antenna effect (AE) are two important luminescence behaviors. Connecting them into polymers is a promising but challenging work, which can supply opportunities for luminescence materials with extensive applications. In this work, AIE-active Eu3+-coordinated polymers (Poly-Eu-1, -2, -3, and -4) have been synthesized, and the efficient AE was verified. This finding presents a facile approach to obtain the Ln3+-based solid luminescence materials due to the synergistic effect from AIE and AE. Also, benefiting from the film-processing ability and water solubility, Poly-Eu-1, -2, -3, and -4 could be employed with different application purposes. In the solution phase, they can be used as sensitive optical probes to detect trace amounts of H2O and D2O, and the limit of detection (LOD) of Poly-Eu-2 toward D2O in H2O is determined to be 7.8 ppm. This discovery is a novel strategy for the construction of D2O optical sensors with a totally intervention-free style.

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Advanced materials with high performance and distinctive function are one of the main driving forces for the development of human society. The selection of appropriate materials and adequately utilizing their features to apply them in a specific area rationally are of great significance but remain challenging. Herein, an aggregation‐induced emission (AIE)‐active nanocomposite (NC) hydrogel is developed by introducing a pH‐responsive AIE luminogen (AIEgen) into a Laponite XLS/polyacrylamide‐based NC hydrogel (Laponite is a trademark of the company BYK Additives Ltd.). The AIEgen can protonate to interact with the negatively charged clay through the electrostatic interaction, which results in a drastic fluorescence enhancement due to the restriction of intramolecular motion by the rigid clay to the protonated AIEgen. This behavior facilitates the input of fluorescent information with a high contrast ratio in the hydrogel by acid stimulation. Moreover, by utilizing the excellent resilience of the hydrogel, hierarchically inputting and displaying the information in the original and stretched states of the hydrogel film is realized, which achieves information‐storage expansion and dual‐encryption via switching between stretching and restoring the film. This work showcases fully and synergistically utilizing the superiorities of various advanced materials to achieve superior applications and should guide the future development of advanced materials in emerging areas.