Near infrared (NIR) photothermal pattern on conductive polymer film enables unique approaches to harvest large‐area cell sheets with various patterns without the use of patterned culture dish. The ...NIR photothermal pattern is generated from a patterned optical lens (POL), which creates a dynamic near IR light pattern and the corresponding photothermal pattern (PTP) on the polymer film. The POL is prepared from transparent polydimethylsiloxane designed to generate various light patterns. The PTPs allow a noninvasive harvest of cultured cells as an intact living cell sheet with a high harvesting efficiency (ηcell > 100). Various PTPs are generated by the diffraction of NIR light through POLs having different micropatterns, which afford cell sheets with a desired pattern without changing the original cell morphology at cultured state. Furthermore, a large‐area living cell sheet is obtained with a detached area larger than 19 cm2, which is the largest living cell sheet up to date. Further optical engineering of the harvesting system allows multiple productions of cell sheets with one dose of light. It is possible to harvest cell sheets not only from human fibroblast cells but also from human adipose‐derived stem cells, indicating that the method can be applied to engineer various cells.
Through a dynamic control of near infrared light diffraction, the photothermal patterns are generated onto the poly(3,4‐ethylenedioxythiophene) surface with various patterns such as line, square, and hexagonal. This optical method can harvest not only the patterned and large‐area cell sheets but also multiple cell sheets at once.
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•Sensitivity of graphene-based chemical sensors can be improved with nanoparticles decorations.•Ag2S nanoparticles-decorated graphene exhibited ~660% increase in response to ...acetone.•DFT calculations showed higher binding energies between Ag2S and small-chain ketones.
Decorating graphene with nanoparticles is an effective method for improving gas selectivity and sensitivity of graphene-based chemical sensors. We report herein the enhancement of the gas selectivity and improved response of a graphene-based chemical sensor by decorating the graphene with synthesized Ag2S nanoparticles. To synthesize uniformly sized Ag2S nanoparticles, we used the ultrasonic irradiation method, and then the synthesized Ag2S nanoparticles were decorated onto graphene uniformly, by using a simple spin coating method. Gas responses of the resulting chemical sensor were tested for volatile organic compounds (VOCs) such as acetone, ethanol, and hexane. While no noticeable gas response changes were obtained for ethanol and hexane vapors, a dramatic increase of ~660% resulted from exposure of the sensor to acetone vapor. In order to determine the mechanism behind the excellent acetone response of graphene decorated with Ag2S nanoparticles, density functional theory (DFT) calculations were performed, and showed higher binding energies and electron transfer between Ag2S and acetone than between Ag2S and the other VOCs. This result indicated that decorating graphene with nanoparticles displaying a high binding energy for the target gas is an efficient way to improve the gas selectivity and response levels of graphene-based chemical sensors.
Conducting polymers that absorb three primary colors, red, green, and blue (RGB), were introduced with a yellow electrochromic polymer (Y) for the preparation of black electrochromic devices. Red ...poly(3-hexylthiophene) (P3HT) and blue poly(3,4-ethylenedioxythiophene) (PEDOT) were coated on one side of the electrode as a cathodically coloring electrochromic (EC) layer, while green poly(aniline-N-butylsulfonate) (PANBS) and yellow EC poly{1,3-bis(9′,9′-dihexylfluoren-20-yl)azulenyl-alt-2″,7″-(9″,9″-dihexylfluorenyl} (PDHFA) were coated on the opposite electrode to complete a complementary EC device. The yellow PDHFA layer effectively compensated for absorption below 450 nm and above the 600 nm region, which was lacking in the RGB electrode. The resultant RGBY ECD provided a black color near the CIE black with L*, a*, and b* values of 32, −1.1, and 3.7, respectively, covering a broad absorption in the visible range in the colored state. The state of the black EC device was maintained, even after the electricity was turned off for 200 h, showing stable memory effect.
The ubiquitin-proteasome system and the autophagy-lysosome system are two major intracellular proteolytic pathways in eukaryotes. Although several biochemical mechanisms underlying the crosstalk ...between them have been suggested, little is known about the effect of enhanced proteasome activity on autophagic flux. Here, we found that upregulation of proteasome activity, which was achieved through the inhibition of USP14, significantly impaired cellular autophagic flux, especially at the autophagosome-lysosome fusion step. UVRAG appeared to function as a crucial checkpoint for the proper progression of autophagic flux. Although proteasome activation through USP14 inhibition facilitated the clearance of microtubule-associated protein tau (MAPT) and reduced the amount of its oligomeric forms, the same conditions increased the formation of inclusion bodies from nonproteasomal substrates such as huntingtin with long polyglutamine repeats. Our results collectively indicate that USP14 may function as a common denominator in the compensatory negative feedback between the two major proteolytic processes in the cell.
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•Inactivation of USP14 results in downregulation of autophagic flux•USP14 inhibition accelerates UVRAG degradation•Inhibition of USP14 enhances proteasomal degradation of tau/MAPT•USP14 is a common denominator of UPS and autophagy
Kim et al. present evidence that the ubiquitin-proteasome system and autophagy are in a compensatory negative-feedback connection through USP14, a proteasome-associated deubiquitinating enzyme. USP14 inhibition results in elevation of proteasome activity and facilitation of tau degradation in the cell, while it delays the cellular autophagic flux.
Microelectronic devices can directly communicate with biology, as electronic information can be transmitted via redox reactions within biological systems. By engineering biology's native redox ...networks, we enable electronic interrogation and control of biological systems at several hierarchical levels: proteins, cells, and cell consortia. First, electro-biofabrication facilitates on-device biological component assembly. Then, electrode-actuated redox data transmission and redox-linked synthetic biology allows programming of enzyme activity and closed-loop electrogenetic control of cellular function. Specifically, horseradish peroxidase is assembled onto interdigitated electrodes where electrode-generated hydrogen peroxide controls its activity. E. coli's stress response regulon, oxyRS, is rewired to enable algorithm-based feedback control of gene expression, including an eCRISPR module that switches cell-cell quorum sensing communication from one autoinducer to another-creating an electronically controlled 'bilingual' cell. Then, these disparate redox-guided devices are wirelessly connected, enabling real-time communication and user-based control. We suggest these methodologies will help us to better understand and develop sophisticated control for biology.
The local heating of poly(3,4‐ethylenedioxythiophene) (PEDOT) by a photothermal effect directed by near‐infrared (NIR) light induces unfolding of absorbed collagen triple helices, yielding soluble ...collagen single‐helical structures. This dissociation of collagens allowed the harvesting of a living idiomorphic cell sheet, achieved upon irradiation with NIR light (λ=808 nm). The PEDOT layer was patterned and cells were successfully cultured on the patterned substrate. Cell sheets of various shapes mirroring the PEDOT pattern could be detached after a few minutes of irradiation with NIR light. The PEDOT patterns guided not only the entire shape of the cell sheets but also the spreading direction of the cells in the sheets. This photothermally induced dissociation of collagen provided a fast non‐invasive harvesting method and tailor‐made cell‐sheet patterns.
A live cell sheet is harvested by the dissociation of adsorbed collagens on a poly(3,4‐ethylenedioxythiophene) (PEDOT) surface by a photothermal method employing near‐IR (NIR) radiation. Irradiation with NIR light induces unfolding of the collagen triple helices leading to the spatially controlled detachment of a patterned cell sheet with intact cell morphology.
Pheomelanin has been implicated in the increased susceptibility to UV-induced melanoma for people with light skin and red hair. Recent studies identified a UV-independent pathway to melanoma ...carcinogenesis and implicated pheomelanin's pro-oxidant properties that act through the generation of reactive oxygen species and/or the depletion of cellular antioxidants. Here, we applied an electrochemically-based reverse engineering methodology to compare the redox properties of human hair pheomelanin with model synthetic pigments and natural eumelanin. This methodology exposes the insoluble melanin samples to complex potential (voltage) inputs and measures output response characteristics to assess redox activities. The results demonstrate that both eumelanin and pheomelanin are redox-active, they can rapidly (sec-min) and repeatedly redox-cycle between oxidized and reduced states, and pheomelanin possesses a more oxidative redox potential. This study suggests that pheomelanin's redox-based pro-oxidant activity may contribute to sustaining a chronic oxidative stress condition through a redox-buffering mechanism.
A highly fluorescent triazine‐bridged polymer, poly(diphenylamino‐s‐triazine)‐co‐(2‐methoxy‐5‐propyloxysulfonate‐1,4‐phenylene vinylene) (DTMSPV), is synthesized from Wittig polycondensation of a ...triazine monomer with a water‐soluble p‐phenylene vinylene monomer. The fluorescent amphiphilic polymer in aqueous solution self‐assembled into nanoassemblies of micelle‐like nanostructure (MS) and π stacking nanostructure (πS), which have average sizes of 93 to 270 nm, depending on the concentration of DTMSPV. The micelle‐like nanostructure of DTMSPV (MS) shows blue emission at 457 and 488 nm with a high emission quantum yield (ΦE) of 31% in aqueous solution. On the other hand, the ΦE of π stacking structures (πS), formed in a highly concentrated solution, is lower than the MS. The MS exhibits fluorescence quenching as well as color change from blue to green/yellow, depending on the kinds of metal ions. The metal ion sensitivity is larger in the order of the main group ions (Na+, K+) < dicationic transition metal ions (Zn2+, Cd2+, Pb2+, Cu2+, Pd2+) < trivalent transition metal ions (Fe3+, Ru3+), with an exception of Al3+. In particular, the fluorescence of MS is dramatically quenched with color change to yellow in response to Al3+ concentrations. The selectivity and sensitivity of MS to Al3+ are unusually high even in the presence of competitive metal ions, which can be attributed to the specific interaction of triazine units with Al3+.
A highly fluorescent conjugated polyelectrolyte (DTMSPV) with high fluorescence quantum yield is syntheiszed for Al3+ sensing in aqueous solutions. The DTMSPV with dual metal binding sites is self‐assembled into stable fluorescent nanostructures in aqueous solution. DTMSPV micelle‐like structure (DTMSPV‐MS) is sensitive and selective to Al3+, showing a color change from blue to yellow. Al3+ in water is easily eliminated by filtration of precipitates formed by the complexation of the triazine units of the polymer and Al3+.
Electron transfer in biology occurs with individual or pairs of electrons, and is often mediated by catechol/o‐quinone redox couples. Here, a biomimetic polysaccharide‐catecholic film is fabricated ...in two steps. First, the stimuli‐responsive polysaccharide chitosan is electrodeposited as a permeable film. Next, the chitosan‐coated electrode is immersed in a solution containing catechol and the electrode is biased to anodically‐oxidize the catechol. The oxidation products covalently graft to the chitosan films as evidenced by electrochemical quartz crystal microbalance (EQCM) studies. Cyclic voltammetry (CV) measurements demonstrate that the catechol‐modified chitosan films are redox‐active although they are non‐conducting and cannot directly transfer electrons to the underlying electrode. The catechol‐modified chitosan films serve as a localized source or sink of electrons that can be transferred to soluble mediators (e.g., ferrocene dimethanol and Ru(NH3) 6Cl3). This electron source/sink is finite, can be depleted, but can be repeatedly regenerated by brief (30 s) electrochemical treatments. Further, the catechol‐modified chitosan films can i) amplify currents associated with the soluble mediators, ii) partially‐rectify these currents in either oxidative or reductive directions (depending on the mediator), and iii) switch between regenerated‐ON and depleted‐OFF states. Physical models are proposed to explain these novel redox properties and possible precedents from nature are discussed.
Catechol‐quinone redox couples are commonly used in biology to transfer electrons. A biomimetic film is fabricated by grafting catechol onto the aminopolysaccharide chitosan to impart redox properties. Specifically, the catechol‐modified chitosan films can amplify and partially rectify mediator currents, and also offer switching capabilities. Possible biological precedents for redox‐active films are discussed.
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