Crosslinking-induced anion transport control for enhancing linearity in organic synaptic devices.

Numerous studies on neuromorphic computing systems and their associated synaptic devices have been reported for the efficient processing of complex data. Among them, organic electrochemical transistors (OECTs) have attracted considerable attention owing to their advantages such as low cost, high scalability, and facile electrical modulation. However, the requirement of supplementary processing for ionic transport control to actualize or enhance synaptic attributes necessitates a compromise between their inherent benefits. Here, we developed a simple method, photoinduced crosslinking, which can control the structure of conjugated polymers in OECTs to improve ionic transport control. Crosslinked polymers increase the ion doping efficiency and allow sequential anion movements, which leads to high linearity in OECTs. The fabricated device also exhibited enhanced synaptic properties such as a long retention time, wide dynamic range, and high recognition accuracy. This innovative approach opens up new possibilities for the construction of next-generation artificial synapses.

Unveiling the Role of Side Chain for Improving Nonvolatile Characteristics of Conjugated Polymers-Based Artificial Synapse.

Interest has grown in services that consume a significant amount of energy, such as large language models (LLMs), and research is being conducted worldwide on synaptic devices for neuromorphic hardware. However, various complex processes are problematic for the implementation of synaptic properties. Here, synaptic characteristics are implemented through a novel method, namely side chain control of conjugated polymers. The developed devices exhibit the characteristics of the biological brain, especially spike-timing-dependent plasticity (STDP), high-pass filtering, and long-term potentiation/depression (LTP/D). Moreover, the fabricated synaptic devices show enhanced nonvolatile characteristics, such as long retention time (≈102 s), high ratio of Gmax/Gmin, high linearity, and reliable cyclic endurance (≈103 pulses). This study presents a new pathway for next-generation neuromorphic computing by modulating conjugated polymers with side chain control, thereby achieving high-performance synaptic properties.

Solvent-assisted sulfur vacancy engineering method in MoS2 for a neuromorphic synaptic memristor.

Recently, two-dimensional transition metal dichalcogenides (TMDs) such as molybdenum disulfide (MoS2) have attracted great attention due to their unique properties. To modulate the electronic properties and structure of TMDs, it is crucial to precisely control chalcogenide vacancies and several methods have already been suggested. However, they have several limitations such as plasma damage by ion bombardment. Herein, we introduced a novel solvent-assisted vacancy engineering (SAVE) method to modulate sulfur vacancies in MoS2. Considering polarity and the Hansen solubility parameter (HSP), three solvents were selected. Sulfur vacancies can be modulated by immersing MoS2 in each solvent, supported by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses. The SAVE method can further expand its application in memory devices representing memristive performance and synaptic behaviors. We represented the charge transport mechanism of sulfur vacancy migration in MoS2. The non-destructive, scalable, and novel SAVE method controlling sulfur vacancies is expected to be a guideline for constructing a vacancy engineering system of TMDs.

Realizing Electronic Synapses by Defect Engineering in Polycrystalline Two-Dimensional MoS2 for Neuromorphic Computing.

Neuromorphic computing based on two-dimensional transition-metal dichalcogenides (2D TMDs) has attracted significant attention recently due to their extraordinary properties generated by the atomic-thick layered structure. This study presents sulfur-defect-assisted MoS2 artificial synaptic devices fabricated by a simple sputtering process, followed by a precise sulfur (S) vacancy-engineering process. While the as-sputtered MoS2 film does not show synaptic behavior, the S vacancy-controlled MoS2 film exhibits excellent synapse with remarkable nonvolatile memory characteristics such as a high switching ratio (∼103), a large memory window, and long retention time (∼104 s) in addition to synaptic functions such as paired-pulse facilitation (PPF) and long-term potentiation (LTP)/depression (LTD). The synaptic device working mechanism of Schottky barrier height modulation by redistributing S vacancies was systemically analyzed by electrical, physical, and microscopy characterizations. The presented MoS2 synaptic device, based on the precise defect engineering of sputtered MoS2, is a facile, low-cost, complementary metal-oxide semiconductor (CMOS)-compatible, and scalable method and provides a procedural guideline for the design of practical 2D TMD-based neuromorphic computing.

Targeting senescent retinal pigment epithelial cells facilitates retinal regeneration in mouse models of age-related macular degeneration.

Although age-related macular degeneration (AMD) is a multifactorial disorder with angiogenic, immune, and inflammatory components, the most common clinical treatment strategies are antiangiogenic therapies. However, these strategies are only applicable to neovascular AMD, which accounts for less than 20% of all AMD cases, and there are no FDA-approved drugs for the treatment of dry AMD, which accounts for ~ 80% of AMD cases. Here, we report that the elimination of senescent cells is a potential novel therapeutic approach for the treatment of all types of AMD. We identified senescent retinal pigment epithelium (RPE) cells in animal models of AMD and determined their contributions to retinal degeneration. We further confirmed that the clearance of senescent RPE cells with the MDM2-p53 inhibitor Nutlin-3a ameliorated retinal degeneration. These findings provide new insights into the use of senescent cells as a therapeutic target for the treatment of AMD.

Quantitative proteomic analysis of aqueous humor from patients with drusen and reticular pseudodrusen in age-related macular degeneration.

BACKGROUND: To identify novel biomarkers related to the pathogenesis of dry age-related macular degeneration (AMD), we adopted a human retinal pigment epithelial (RPE) cell culture model that mimics some features of dry AMD including the accumulation of intra- and sub-RPE deposits. Then, we investigated the aqueous humor (AH) proteome using a data-independent acquisition method (sequential window acquisition of all theoretical fragment ion mass spectrometry) for dry AMD patients and controls. METHODS: After uniformly pigmented polarized monolayers of human fetal primary RPE (hfRPE) cells were established, the cells were exposed to 4-hydroxy-2-nonenal (4-HNE), followed by Western blotting, immunofluorescence analysis and ELISA of cells or conditioned media for several proteins of interest. Data-dependent acquisition for identification of the AH proteome and SWATH-based mass spectrometry were performed for 11 dry AMD patients according to their phenotypes (including soft drusen and reticular pseudodrusen [RPD]) and 2 controls (3 groups). RESULTS: Increased intra- and sub-RPE deposits were observed in 4-HNE-treated hfRPE cells compared with control cultures based on APOA1, cathepsin D, and clusterin immunoreactivity. Additionally, the differential abundance of proteins in apical and basal chambers with or without 4-HNE treatment confirmed the polarized secretion of proteins from hfRPE cells. A total of 119 proteins were quantified in dry AMD patients and controls by SWATH-MS. Sixty-five proteins exhibited significantly altered abundance among the three groups. A two-dimensional principal component analysis plot was generated to identify typical proteins related to the pathogenesis of dry AMD. Among the identified proteins, eight proteins, including APOA1, CFHR2, and CLUS, were previously considered major components or regulators of drusen. Three proteins (SERPINA4, LUM, and KERA proteins) have not been previously described as components of drusen or as being related to dry AMD. Interestingly, the LUM and KERA proteins, which are related to extracellular matrix organization, were upregulated in both RPD and soft drusen. CONCLUSIONS: Differential protein expression in the AH between patients with drusen and RPD was quantified using SWATH-MS in the present study. Detailed proteomic analyses of dry AMD patients might provide insights into the in vivo biology of drusen and RPD.

Association Between Soluble CD14 in the Aqueous Humor and Hyperreflective Foci on Optical Coherence Tomography in Patients With Diabetic Macular Edema.

Purpose: To investigate the associations between soluble CD14 (sCD14), a cytokine released by microglia and macrophages, and hyperreflective foci (HF) and various characteristics of spectral-domain optical coherence tomography (SD-OCT) in diabetic macular edema (DME). Methods: Sixty-nine eyes from 51 patients with DME and 28 eyes from 28 control subjects were studied. sCD14 levels in the aqueous humor (AH) were measured using ELISA before bevacizumab injection (IVB), and the associations between sCD14 and visual acuity, the number of HF, retinal volume, and the DME pattern were assessed. Results: sCD14 levels were higher in DME patients than in the control subjects (29.9 ± 41.6 pg/mL versus 8.1 ± 3.6 pg/mL, P < 0.001). sCD14 levels in diffuse edema were higher than those in focal edema (50.0 ± 65.3 pg/mL versus 19.8 ± 14.7 pg/mL, P = 0.039). The number of HF in the inner retina of patients with diffuse edema was significantly higher than that in patients with focal edema (4.4 ± 2.3 vs. 2.6 ± 2.1, P = 0.001), but no difference was found in the outer retina (5.8 ± 3.4 vs. 5.0 ± 3.9, P = 0.25). According to multivariate analyses, elevated sCD14 levels were associated with an increased inner nuclear layer volume and the total number of HF in all retinal layers on SD-OCT. Reduction of DME following IVB was correlated with reduction in the number of HF in a subset of eyes followed longitudinally in the study (n = 30). Conclusions: DME patients with diffuse edema exhibit higher sCD14 levels in the AH and more HF in the inner retina than patients with focal edema, indicating severe inflammation. The strong correlation between sCD14 and HF in the inner retina suggests that the HF observed on SD-OCT may be due to activated microglia in DME.