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.