Development of a miniaturized, reconnectable, and implantable multichannel connector.

Objective. Connectors for implantable neural prosthetic systems provide several advantages such as simplification of surgery, safe replacement of implanted devices, and modular design of the implant systems. With the rapid advancement of technologies for neural implants, miniaturized multichannel implantable connectors are also required. In this study, we propose a reconnectable and area-efficient multichannel implantable connector.Approach. A female-to-female adapter was fabricated using the thermal-press bonding of micropatterned liquid crystal polymer films. A bump inside the adapter enabled a reliable electrical connection by increasing the contact pressure between the contact pads of the adapter and the inserted cable. After connection, the adapter is enclosed in a metal case sealed with silicone elastomer packing. With different sizes of the packings, leakage current tests were performed under accelerated conditions to determine the optimal design for long-term reliability. Repeated connection tests were performed to verify the durability and reconnectability of the fabricated connector. The connector was implanted in rats, and the leakage currents were monitored to evaluate the stability of the connectorin vivo. Main results. The fabricated four- and eight-channel implantable connectors, assembled with the metal cases, had a diameter and length of 6 and 17 mm, respectively. Further, the contact resistances of the four- and eight-channel connectors were 53.2 and 75.2 mΩ, respectively. The electrical contact remained stable during repeated connection tests (50 times). The fabricated connectors with packings having 125%, 137%, and 150% volume ratios to the internal space of the metal case failed after 14, 88, and 14 d, respectively, in a 75 °C saline environment. In animal tests with rats, the connector maintained low leakage current levels for up to 92 d.Significance. An implantable and reconnectable multichannel connector was developed and evaluated. The feasibility of the proposed connector was evaluated in terms of electrical and mechanical characteristics as well as sealing performance. The proposed connector is expected to have potential applications in implantable neural prosthetic systems.

Correction: Ha, Y. et al. Hemispherical Microelectrode Array for Ex Vivo Retinal Neural Recording. Micromachines 2020, 11, 538.

The authors would like to make the following changes to the published paper [...].

Hemispherical Microelectrode Array for Ex Vivo Retinal Neural Recording.

To investigate the neuronal visual encoding process in the retina, researchers have performed in vitro and ex vivo electrophysiological experiments using animal retinal tissues. The microelectrode array (MEA) has become a key component in retinal experiments because it enables simultaneous neural recording from a population of retinal neurons. However, in most retinal experiments, it is inevitable that the retinal tissue is flattened on the planar MEA, becoming deformed from the original hemispherical shape. During the tissue deforming process, the retina is subjected to mechanical stress, which can induce abnormal physiological conditions. To overcome this problem, in this study, we propose a hemispherical MEA with a curvature that allows retinal tissues to adhere closely to electrodes without tissue deformation. The electrode array is fabricated by stretching a thin, flexible polydimethylsiloxane (PDMS) electrode layer onto a hemispherical substrate. To form micro patterns of electrodes, laser processing is employed instead of conventional thin-film microfabrication processes. The feasibility for neural recording from retinal tissues using this array is shown by conducting ex vivo retinal experiments. We anticipate that the proposed techniques for hemispherical MEAs can be utilized not only for ex vivo retinal studies but also for various flexible electronics.

Robustaflavone Isolated from Nandina domestica Using Bioactivity-Guided Fractionation Downregulates Inflammatory Mediators.

Nandina domestica (Berberidaceae) has been used in traditional medicine for the treatment of cough. This plant is distributed in Korea, Japan, China, and India This study aimed to investigate the anti-inflammatory phytochemicals obtained from the N. domestica fruits. We isolated a biflavonoid-type phytochemical, robustaflavone (R), from N. domestica fruits through bioactivity-guided fractionation based on its capacity to inhibit inflammation. The anti-inflammatory mechanism of R isolated from N. domestica has not yet been studied. In the present study, we evaluated the anti-inflammatory activities of R using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. We have shown that R reduces the production of nitric oxide (NO), pro-inflammatory cytokine interleukin-1 beta (IL-1ß), and IL-6. Western blot analysis showed that R suppresses the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and downregulates the expression of LPS-induced nuclear factor-kappa B (NF-κB) and the phosphorylation of extracellular-regulated kinases (pERK 1/2). Moreover, R inhibited IL-8 release in LPS-induced human colonic epithelial cells (HT-29). These results suggest that R could be a potential therapeutic candidate for inflammatory bowel disease (IBD).

Disappearance of contralateral dominant neural activity of auditory cortex after single-sided deafness in adult rats.

Hearing loss in mature ears can cause functional reorganization of the auditory cortex. The functional reorganization is speculated to negatively affect the outcome of hearing rehabilitation. Therefore, once hearing loss occurs, it is important to provide auditory input before extensive reorganization in the auditory pathways. We investigated the neural plasticity in auditory cortex after single-sided deafness (SSD) in an adult rat model. The animals were divided into two groups: a normal hearing (NH) and the SSD group. The neural recordings of the SSD group were conducted at different time points (2, 4, 6 and 8 weeks) after cochlear ablation. The multi-unit activity was discriminated on the sum of spikes, peak amplitude, onset latency, peak latency, and responsive area based on the peak amplitude. The auditory cortical reorganization was observed after SSD. The contralateral dominance of peak amplitude and latency that normally occur in NH group were not present in the SSD group, replaced by higher amplitude and faster response in ipsilateral cortex. According to serial recordings at different time points after SSD, different phases in the response of the auditory cortex were speculated. Compared with normal hearing, alteration of contralateral dominance was observed because of the functional reorganization of the auditory cortex after SSD.

Response time measurements in the iOS app-based Token Test, the Brief Token Test in the elderly.

AIM: A pen and paper Token Test utilizing binary scoring of accuracy-inaccuracy in responses evaluates linguistic functions including verbal comprehension. However, the test might not be sensitive enough to detect the aging effect on performance in normal older adults unless the test utilizes a multidimensional scoring system. We hypothesized that the measurement of response time (RT) instead of accuracy would be a feasible way to measure deterioration of verbal comprehension as a function of age in this linguistically vulnerable population. METHODS: Data were acquired from 174 community-dwelling normal older adults (147 females and 27 males, mean age 75.9 ± 6.13 years, range 65-94 years). In order to automatically quantify accuracies and RT, we developed an iOS app-based Token Test, comprising of four subtests (24 items, 6 items in each subtest), and administered it to each participant. RESULTS: RT of the second, third and fourth subtests (P<0.001, P<0.01, P<0.05, respectively) and the average RT across all four subtests (P<0.01) had significant partial correlation coefficients with age. The results of the multiple linear regression analyses showed that the models for RT and average RT analyses of the three subtests (2, 3 and 4) included the age variable. CONCLUSION: RT measurement of the iOS app-based Token Test could be highly useful and convenient to better detect abnormalities in linguistic efficiency. RT measurement in the Token Test could be used as a screening tool for linguistic slowing in the elderly population.

Rational design, synthesis, and characterization of deep blue phosphorescent Ir(III) complexes containing (4'-substituted-2'-pyridyl)-1,2,4-triazole ancillary ligands.

On the basis of the results of frontier orbital considerations, 4-substituted-2'-pyridyltriazoles were designed to serve as ancillary ligands in 2-phenylpyridine main ligand containing heteroleptic iridium(III) complexes that display deep blue phosphorescence emission. The iridium(III) complexes, Ir1-Ir7, prepared using the new ancillary ligands, were found to display structured, highly quantum efficient (Φp = 0.20-0.42) phosphorescence with emission maxima in the blue to deep blue 448-456 nm at room temperature. In accord with predictions based on frontier orbital considerations, the complexes were observed to have emission properties that are dependent on the electronic nature of substituents at the C-4 position of the pyridine moiety of the ancillary ligand. Importantly, placement of an electron-donating methyl group at C-4' of the pyridine ring of the 5-(pyridine-2'-yl)-3-trifluoromethyl-1,2,4-triazole ancillary ligand leads to an iridium(III) complex that displays a deep blue phosphorescence emission maximum at 448 nm in both the liquid and film states at room temperature. Finally, an OLED device, constructed using an Ir-complex containing the optimized ancillary ligand as the dopant, was found to emit deep blue color with a CIE of 0.15, 0.18, which is close to the perfect goal of 0.15, 0.15.