Responsive Nanogel Probe for Ratiometric Fluorescent Sensing of pH and Strain in Hydrogels

In this study a new pH-responsive nanogel probe containing a complementary nonradiative resonance energy transfer (NRET) fluorophore pair is investigated and its ability to act as a versatile probe of network-related changes in three hydrogels demonstrated. Fluorescent sensing using NRET is a powerful method for studying relationships between Angstrom length-scale structure and macroscopic properties of soft matter. Unfortunately, inclusion of NRET fluorophores into such materials requires material-specific chemistry. Here, low concentrations of preformed nanogel probes were included into hydrogel hosts. Ratiometric photoluminescence (PL) data for the gels labeled with the nanogel probes enabled pH-triggered swelling and deswelling to be studied as well as Ca2+-triggered collapse and solute release. PL measurements during compression of a nanogel probe-labeled nanocomposite gel demonstrated mechanochromic behavior and strain sensing. The new nanogel probes have excellent potential for investigating the internal structures of gels and provide a versatile ratiometric fluorescent platform for studying pH and strain

Observing GLUT4 Translocation in Live L6 Cells Using Quantum Dots

The glucose transporter 4 (GLUT4) plays a key role in maintaining whole body glucose homeostasis. Tracking GLUT4 in space and time can provide new insights for understanding the mechanisms of insulin-regulated GLUT4 translocation. Organic dyes and fluorescent proteins were used in previous studies for investigating the traffic of GLUT4 in skeletal muscle cells and adipocytes. Because of their relative weak fluorescent signal against strong cellular autofluorescence background and their fast photobleaching rate, most studies only focused on particular segments of GLUT4 traffic. In this study, we have developed a new method for observing the translocation of GLUT4 targeted with photostable and bright quantum dots (QDs) in live L6 cells. QDs were targeted to GLUT4myc specifically and internalized with GLUT4myc through receptor-mediated endocytosis. Compared with traditional fluorescence dyes and fluorescent proteins, QDs with high brightness and extremely photostability are suitable for long-term single particle tracking, so individual GLUT4-QD complex can be easily detected and tracked for long periods of time. This newly described method will be a powerful tool for observing the translocation of GLUT4 in live L6 cells

Composite hydrogels of polyacrylamide and crosslinked pH-responsive micrometer-sized hollow particles

Polyacrylamide composite hydrogels containing micrometer-sized pH-responsive hollow particles have tuneable mechanical properties that are governed by percolation.</p

Effects of casting process on microstructures and flow stress behavior of Mg–9Gd–3Y–1.5Zn–0.8Zr semi-continuous casting billets

Mg–9Gd–3Y–1.5Zn–0.8Zr alloys own high strength, good heat and corrosion resistance. However, it is difficult for the fabrication of large-scale billets, due to the poor deformation ability and strong hot-crack tendency. This work investigated the casting process on the microstructures and flow stress behaviors of the semi-continuous casting billets for the fabrication of large-scale Mg–9Gd–3Y–1.5Zn–0.8Zr billets. The casting process (electromagnetic intensity and casting speed) shows outstanding effects on the microstructures and flow stress behavior of the billets. The billets with the specific casting process (I = 68 A, V = 65 mm/min) exhibit uniform microstructures and good deformation uniformity

How gold nanoparticles can be used to probe the structural changes of a pH-responsive hydrogel

Incorporating gold nanoparticles within a pH-responsive hydrogel enables the surface plasmon resonance signal and metal-induced fluorescence quenching to be used to study local network structure and probe gel swelling remotely.</p

Hydrogel Composites Containing Sacrificial Collapsed Hollow Particles as Dual Action pH-Responsive Biomaterials

In this study hydrogel composites are investigated that contain sacrificial pH-responsive collapsed hollow particles (CHPs) entrapped within a poly­(acrylamide) (PAAm) network. The CHPs were prepared using a scalable (mainly) water-based method and had a bowl-like morphology that was comparable to that of red blood cells. The CHPs were constructed from poly­(methyl methacrylate-<i>co</i>-methacrylic acid), which is a pH-responsive copolymer. The PAAm/CHP composite morphology was probed with optical microscopy, CLSM and SEM. These data showed the CHPs were dispersed throughout the PAAm network. Inclusion of the CHPs within the gel composites increased the modulus in a tunable manner. The CHPs fragmented at pH values greater than the p<i>K</i>_<i>a</i> of the particles, and this process decreased the gel modulus to values similar to that of the parent PAAm hydrogel. CHPs containing a model drug were used to demonstrate pH-triggered release from PAAm/CHP and the release kinetics obeyed Fickian diffusion. The composite gels had low cytotoxicity as evidenced by Live/Dead and MTT assays. The hydrogel composites showed dual action pH-triggered softening with simultaneous drug release which occurred without a volume increase. The hydrogel composites may have potential application as enteric gels or for intra-articular drug delivery

Rotationally symmetrical spoof-plasmon antenna for polarization-independent radiation enhancement

Plasmon antennas allow subwavelength confinement and enhancement of electromagnetic fields at the “hotspot” where the radiation efficiency of emitters can be substantially enhanced. Such enhancement, however, is often polarization dependent. Consequently, the radiation behaviors (e.g., radiation pattern and polarization states) of the emitter placed at the hotspot are also modified significantly. Enhancing the radiation efficiency without altering the original radiation pattern and polarization state of the emitter is highly desired for many sought-after applications involving chiral emitters but remains a challenging task, especially at low frequencies. To this end, spoof-plasmon antennas with fourfold and sixfold rotational symmetries are designed and realized experimentally. These plasmon antennas support polarizationindependent localized plasmon resonances, which can significantly enhance the local density of photonic states at the structural center without changing the polarization state of the emitter. As a typical example, the structure with sixfold rotational symmetry is coupled with a half-wave dipole antenna. The measurement results show that the far-field radiation pattern of the dipole antenna is maintained with the radiation efficiency enhanced by more than 2 orders of magnitude, irrespective of the dipole orientation.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionThis work is supported, in part, by the National Science Foundation of China under Grants No. 61871127 and No. U21A20459, the 111 Project under Grant No. 111-2-05, and the Fund for International Cooperation and Exchange of the National Natural Science Foundation of China Grant No. 61761136007. Y.L. received funding from the Singapore Ministry of Education [Grant No. MOE2018-T2-2-189(S)], an A*Star AME IRG grant (Grant No. A20E5c0095) and Programmatic Funds (Grant No. A18A7b0058), and the National Research Foundation Singapore Competitive Research Program (Grants No. NRF220 CRP22-2019-0006 and No. NRF-CRP23-2019-0007)