Surface-enhanced Raman spectroscopy long-range detection investigation based on the alternating coupling of a surface plasmonic array and dielectric waveguide.

Surface-enhanced Raman spectroscopy (SERS) is widely used to detect low-concentration samples in biology, medicine, etc. We design and theoretically investigate a SERS sensor with a surface plasmonic array coupled alternately with a dielectric waveguide. The effect of the incident angle on the coupling efficiency of an evanescent field is systematically studied. The results show that the maximum evanescent field coupling efficiency can be obtained at an incident angle of 66°. The proposed SERS sensor has a transmission length of 1.027 cm and a high enhancement performance with an enhancement factor of 1.574×104 at a wavelength of 633 nm. The integration of this SERS sensor with a metal array and a dielectric waveguide prevents the direct illumination of the sample molecules by the excited light. Furthermore, the long-range nondestructive detection of the SERS signals of the low-concentration sample molecules can be achieved.

Sparse phase retrieval using a physics-informed neural network for Fourier ptychographic microscopy.

In this paper, we report a sparse phase retrieval framework for Fourier ptychographic microscopy using the recently proposed principle of physics-informed neural networks. The phase retrieval problem is cast as training bidirectional mappings from the measured image space with random noise and the object space to be reconstructed, in which the image formation physics and convolutional neural network are integrated. Meanwhile, we slightly modify the mean absolute error loss function considering the signal characteristics. Two datasets are used to validate this framework. The results indicate that the proposed framework is able to reconstruct sparsely sampled data using a small aperture overlapping rate without additional data driving whereas conventional methods cannot.

[SERS Enhancement Factor Analysis and Experiment of Carbon Nanotube Arrays Coated by Ag Nanoparticles].

To intuitive and accurate quantitatively analyze Raman enhancement of surface enhanced Raman scattering substrate structure, three-dimensional composite structure of silver nanoparticles modified vertically aligned carbon nanotube array is produced by magnetron sputtering and thermal annealing process; Relevant experiments using Rhodamine 6G (R6G) solution as the molecular probes are conducted to analyze surface enhanced Raman enhancement factor (EF), combining with confocal Raman microscopy systems. The result of scanning electron microscopy (SEM) shows that a large number of silver nanoparticles are attached onto the tips and sidewalls of the ordered carbon nanotubes array uniformly. EF of the sample which was produced 30 min annealing time and 450 degrees C annealing temperature evaluates to 2.2 x 10(3), and the reasons for the low EF are analyzed: on the one hand, thickness of silver film sputtered on vertically aligned carbon nanotube array is non-uniform, leading to distribution of silver nanoparticles is uneven after annealing, so that the value of sample roughness is too large, EF value is low; on the other hand, the excitation light source is not the advantage wavelength of silver nanoparticles in the experiments.

Silver-decorated aligned CNT arrays as SERS substrates by high temperature annealing.

A feasible way to synthesize a surface-enhanced Raman scattering (SERS) substrate has been developed, where Ag nanoparticles (AgNPs) of different size and morphology are assembled on the surface and sidewalls of the aligned carbon nanotube (CNT) arrays via magnetron sputtering and high-temperature annealing. Our results show that the optimized substrate is performed by annealing temperature at 450 °C for 30 min. The state of the obtained AgNPs makes a significant contribution to the high sensitivity of SERS to R6G molecules, and the substrate has an enhancement factor (EF) on the order of ~10¹°. Meanwhile, the Ag/CNT arrays keep a good reproducibility with the average RSD values being less than 0.01 for all major Raman peaks. The temporal stability of our substrates has been also appeared, which indicates that the Ag/CNT arrays can be used as stable substrates for the production of enhanced SERS signals for up to three months under ambient conditions.

Three-dimensional multi-walled carbon nanotube arrays coated by gold-sol as a surface-enhanced Raman scattering substrate.

We demonstrated a three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrate consisting of large area carbon nanotube (CNT) arrays coated by gold-sol nanoparticles. A low-cost, simple process is used to prepare Au-decorated 3D CNT arrays. The SERS enhancement from the 3D CNT arrays, and two-dimensional (2D) CNT films substrates coated by different size gold-sol nanoparticles, was experimentally verified with Rhodamine 6G as the probe analyte. The experiments showed that the 3D CNT arrays substrate has a higher Raman enhancement compared with 2D CNT arrays substrate and planar glass substrate, due to the large specific surface area of CNT arrays and more gold nanoparticles on the CNT arrays sidewalls, which contribute the electromagnetic field and Raman intensity. Meanwhile, the 3D structure could enhance the excitation light trapping in CNT arrays, consequently increasing the light interaction with Au nanoparticles.

Development of neural correlates of linear motion in the rat vestibular nucleus.

The capability of the central vestibular system in utilizing cues arising from the inner ear determines the ability of animals to acquire the sense of head orientations in the three-dimensional space and to shape postural movements. During development, neurons in the vestibular nucleus (VN) show significant changes in their electrophysiological properties. An age-dependent enhancement of membrane excitability is accompanied by a progressive increase in firing rate and discharge regularity. The coding of horizontal and vertical linear motions also exhibits developmental refinement in VN neurons. Further, modification of cell surface receptors, such as glutamate receptors, of developing VN neurons are well-orchestrated in the course of maturation, thereby regulating synaptic efficacy and spatial coding capacity of these neurons in local circuits. Taken together, these characteristic features of VN neurons contribute to developmental establishment of space-centered coordinates within the brain.

[Three-dimensional vertically aligned CNTs coated by Ag nanoparticles for surface-enhanced Raman scattering].

In order to make surface-enhanced Raman scattering (SERS) substrates contained more "hot spots" in a three-dimensional (3D) focal volume, and can be adsorbed more probe molecules and metal nanoparticles, to obtain stronger Raman spectral signal, a new structure based on vertically aligned carbon nanotubes (CNTs) coated by Ag nanoparticles for surface Raman enhancement is presented. The vertically aligned CNTs are synthesized by chemical vapor deposition (CVD). A silver film is first deposited on the vertically aligned CNTs by magnetron sputtering. The samples are then annealed at different temperature to cause the different size silver nanoparticles to coat on the surface and sidewalls of vertically aligned CNTs. The result of scanning electron microscopy(SEM) shows that Ag nanoparticles are attached onto the sidewalls and tips of the vertically aligned CNTs, as the annealing temperature is different , pitch size, morphology and space between the silver nanoparticles is vary. Rhodamine 6G is served as the probe analyte. Raman spectrum measurement indicates that: the higher the concentration of R6G, the stronger the Raman intensity, but R6G concentration increase with the enhanced Raman intensity varies nonlinearly; when annealing temperature is 450 °C, the average size of silver nanoparticles is about 100 to 120 nm, while annealing temperature is 400 °C, the average size is about 70 nm, and the Raman intensity of 450 °C is superior to the annealing temperature that of 400 °C and 350 °C.

Anti-Hyperuricemia Activity and Potential Mechanisms of Medicinal Mushroom Activity: A Review of Preclinical Studies.

Hyperuricemia (HUA) is characterized by abnormally elevated levels of serum uric acid, the product of purine metabolism. The primary symptom of HUA is gout; however, asymptomatic HUA is associated with complications such as hypertension, kidney disease, cardiovascular disease, and metabolic syndrome. The activation of xanthine oxidase (XO), a pivotal enzyme in uric acid biosynthesis, is coupled with extensive reactive oxygen species generation, leading to inflammatory responses, and triggers the development of HUA and its complications. In clinical practice, XO inhibitors are primarily used to treat HUA; however, their prolonged use is accompanied by serious adverse effects. Mushrooms and their bioactive constituents have shown promising anti-HUA activities in both in vitro and in vivo studies, including inhibition of urate production, modulation of renal urate transporters, enhancement of intestinal uric acid excretion, and antioxidant, anti-inflammatory, and antimetabolic syndrome properties. Clinical trials are necessary to validate the beneficial effects and safety of mushrooms in preventing or alleviating HUA and attenuating the associated complications. This review presents contemporary insights into the pathogenesis of HUA, the bioactive components of mushrooms, their therapeutic potential, and the underlying mechanisms involved in ameliorating HUA.

Topography of inferior olivary neurons that encode canal and otolith inputs.

Vestibular information arising from rotational head movement and that from translational head movement are detected respectively by the semicircular canal and otolith organ in the inner ear. Spatiotemporal cues are in turn processed by the vestibulo-olivo-cerebellar pathway for sensorimotor coordination, but the role of the inferior olive (IO) in this pathway remains unclear. To address whether rotational and translational movements are differentially represented in the IO, we studied the distribution pattern of IO neurons recruited into the circuitry following selective activation of receptor hair cells of the horizontal semicircular canal or the utricle in adult rats. Neurons in the beta nucleus of IO (IOß) and dorso-medial cell column of IO were responsive to horizontal translation, but not rotation. Notably, otolith-related neurons were observable largely in the rostral IOß. In contrast, the subnucleus A of IO (IOA), subnucleus C of IO (IOC), and dorsal cap of Kooy (IOK) were responsive to horizontal rotation, but not translation. In the IOA, these canal-related neurons were clustered in the medial portion of the subnucleus. In the IOC, canal-related neurons were skewed towards the rostral half. In the IOK, canal-related neurons were found throughout the subnucleus. These indicate that the distributions of canal- and otolith-related neurons encoding horizontal motions are clearly segregated in the IO. These discrete IO subnuclei therefore provide a topographic map for temporal and adaptive operations of sensorimotor coordination and spatial reference.

28-day oral safety evaluation of extracellular polysaccharopeptides produced in submerged culture from the turkey tail medicinal mushroom Trametes versicolor (L.:Fr.) Pilát LH-1 in mice.

Turkey tail medicinal mushroom, Trametes versicolor (TV), is a species with a variety of pharmacological activities. Its intracellular polysaccharopeptides are widely commercialized. Recently, we found a novel TV strain LH-1 in Taiwan and demonstrated that the extracellular polysaccharopeptide (ePSP) of LH-1 obtained from submerged culture exhibits significant immunomodulatory activity. In this in vivo study, we further evaluated the safety of orally administered LH-1 ePSP using both male and female ICR mice. The LH-1 ePSP was orally administered to mice at levels of 0 (water), 100 (low dose), 500 (medium dose), or 1000 mg/kg/day (high dose) for 28 days. Clinical observations, growth, food consumption, histopathological examination, and clinical biochemical analyses revealed no adverse effects of LH-1 ePSP in mice. There were no significant differences in the results of target organ weights, hematological analyses, and urinalysis examination among groups. However, male mice that ingested high doses of LH-1 ePSP tended to have decreased lung weights and platelet numbers. In conclusion, the results of the present study suggested that oral administration of LH-1 ePSP for 28 days is accompanied by no obvious signs of toxicity. The lack of toxicity supports the potential use of LH-1 ePSP as a food or dietary supplement.

Superwicking Functionality of Femtosecond Laser Textured Aluminum at High Temperatures.

An advanced superwicking aluminum material based on a microgroove surface structure textured with both laser-induced periodic surface structures and fine microholes was produced by direct femtosecond laser nano/microstructuring technology. The created material demonstrates excellent wicking performance in a temperature range of 23 to 120 °C. The experiments on wicking dynamics show a record-high velocity of water spreading that achieves about 450 mm/s at 23 °C and 320 mm/s at 120 °C when the spreading water undergoes intensive boiling. The lifetime of classic Washburn capillary flow dynamics shortens as the temperature increases up to 80 °C. The effects of evaporation and boiling on water spreading become significant above 80 °C, resulting in vanishing of Washburn's dynamics. Both the inertial and visco-inertial flow regimes are insignificantly affected by evaporation at temperatures below the boiling point of water. The boiling effect on the inertial regime is small at 120 °C; however, its effect on the visco-inertial regime is essential. The created material with effective wicking performance under water boiling conditions can find applications in Maisotsenko cycle (M-cycle) high-temperature heat/mass exchangers for enhancing power generation efficiency that is an important factor in reducing CO2 emissions and mitigation of the global climate change.

Developmental maturation of ionotropic glutamate receptor subunits in rat vestibular nuclear neurons responsive to vertical linear acceleration.

We investigated the maturation profile of subunits of ionotropic glutamate receptors in vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the vertical plane. The otolithic origin of Fos expression in these neurons was confirmed as a marker of functional activation when labyrinthectomized and/or stationary control rats contrasted by showing sporadically scattered Fos-labeled neurons in the vestibular nuclei. By double immunohistochemistry for Fos and one of the receptor subunits, otolith-related neurons that expressed either alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate or N-methyl-d-aspartate subunits were first identified in the medial vestibular nucleus, spinal vestibular nucleus and Group x by postnatal day (P)7, and in the lateral vestibular nucleus and Group y by P9. No double-labeled neurons were found in the superior vestibular nucleus. Within each vestibular subnucleus, these double-labeled neurons constituted approximately 90% of the total Fos-labeled neurons. The percentage of Fos-labeled neurons expressing the GluR1 or NR2A subunit showed developmental invariance in all subnuclei. For Fos-labeled neurons expressing the NR1 subunit, similar invariance was observed except that, in Group y, these neurons decreased from P14 onwards. For Fos-labeled neurons expressing the GluR2, GluR2/3, GluR4 or NR2B subunit, a significant decrease was found by the adult stage. In particular, those expressing the GluR4 subunit showed a two- to threefold decrease in the medial vestibular nucleus, spinal vestibular nucleus and Group y. Also, those expressing the NR2B subunit showed a twofold decrease in Group y. Taken together, the postsynaptic expression of ionotropic glutamate receptor subunits in different vestibular subnuclei suggests that glutamatergic transmission within subregions plays differential developmental roles in the coding of gravity-related vertical spatial information.

[Neuronal plasticity of otolith-related vestibular system].

This review focuses on our effort in addressing the development and lesion-induced plasticity of the gravity sensing system. After severance of sensory input from one inner ear, there is a bilateral imbalance in response dynamics and spatial coding behavior between neuronal subpopulations on the two sides. These data provide the basis for deranged spatial coding and motor deficits accompanying unilateral labyrinthectomy. Recent studies have also confirmed that both glutamate receptors and neurotrophin receptors within the bilateral vestibular nuclei are implicated in the plasticity during vestibular compensation and development. Changes in plasticity not only provide insight into the formation of a spatial map and recovery of vestibular function but also on the design of drugs for therapeutic strategies applicable to infants or vestibular disorders such as vertigo and dizziness.

Corticofugal modulation of acoustically induced Fos expression in the rat auditory pathway.

To investigate the corticofugal modulation of acoustic information ascending through the auditory pathway of the rat, immunohistochemical techniques were used to study the functional expression of Fos protein in neurons. With auditory stimulation at different frequencies, Fos expression in the medial geniculate body (MGB), inferior colliculus (IC), superior olivary complex, and cochlear nucleus was examined, and the extent of Fos expression on the two sides was compared. Strikingly, we found densely Fos-labeled neurons in all divisions of the MGB after both presentation of an auditory stimulus and administration of a gamma-aminobutyric acid type A (GABA(A)) antagonist (bicuculline methobromide; BIM) to the auditory cortex. The location of Fos-labeled neurons in the ventral division (MGv) after acoustic stimulation at different frequencies was in agreement with the known tonotopic organization. That no Fos-labeled neurons were found in the MGv with acoustic stimuli alone suggests that the transmission of ascending thalamocortical information is critically governed by corticofugal modulation. The dorsal (DCIC) and external cortices (ECIC) of the IC ipsilateral to the BIM-injected cortex showed a significantly higher number of Fos-labeled neurons than the contralateral IC. However, no difference in the number of Fos-labeled neurons was found between the central nucleus of the IC on either side, indicating that direct corticofugal modulation occurs only in the ECIC and DCIC. Further investigations are needed to assess the functional implications of the morphological differences observed between the descending corticofugal projections to the thalamus and the IC.

Integrated Surface-Enhanced Raman Spectroscopy (SERS) Chip Based on a Total Reflection Liquid Core Waveguide.

This study proposes a surface-enhanced Raman scattering (SERS) chip integrated with a liquid core waveguide. Due to the total reflection, the chip suppresses the leaky waveguide mode and enables a long propagation distance for SERS signal collection. A 10 nM rhodamine 6G Raman signal was obtained using a QE65000 portable microspectrometer at a low excitation power intensity of 14.5 W/cm2. The proposed SERS chip was also used to detect the SERS spectrum of a silkworm DNA solution, the structural information of which was clearly shown. In addition, due to the lower excitation power density, damage to the structure of the biomolecule was avoided.

Oral Citrulline Mitigates Inflammation and Jejunal Damage via the Inactivation of Neuronal Nitric Oxide Synthase and Nuclear Factor-κB in Intestinal Ischemia and Reperfusion.

BACKGROUND: Intestinal ischemia and reperfusion (I/R) is a life-threatening emergency accompanied by inflammation and organ damage. We compared the mechanisms and the effects of arginine, citrulline, and glutamine on inflammation and intestinal damage. MATERIALS AND METHODS: Male Wistar rats underwent 60 minutes of superior mesenteric artery occlusion and either 3 (I/R3) or 24 (I/R24) hours of reperfusion and were orally administered vehicle, arginine, citrulline, or glutamine 15 minutes before reperfusion and at 3, 9, and 21 hours of reperfusion. RESULTS: I/R3 rats experienced jejunal damage and apoptosis, and I/R24 rats had liver dysfunction compared with normal rats (one-way ANOVA, P < .05). Arginine and citrulline administrations improved jejunal morphology, and citrulline and glutamine administrations alleviated the loss of jejunal mass in I/R3 rats. I/R3-increased circulating nitrate/nitrite (NOx), tumor necrosis factor-α, and interleukin-6 were significantly decreased by citrulline, glutamine and citrulline, and arginine, glutamine, and citrulline, respectively. These amino acids decreased plasma NOx and interferon-γ in I/R24, decreased jejunal neuronal nitric oxide synthase (NOS) protein in I/R3 rats, and alleviated jejunal apoptosis in I/R3 and I/R24 rats. In addition, the jejunal phosphorylated to total nuclear factor-κB (NF-κB) ratio was decreased by arginine and citrulline in I/R24 rats. CONCLUSION: Oral administration of arginine, citrulline, and glutamine may alleviate systemic inflammation, jejunal apoptosis, and neuronal NOS in intestinal I/R. Citrulline may further attenuate jejunal damage by preserving jejunal mass, partially via the inactivation of NOS and the NF-κB pathway. In conclusion, oral citrulline may have more benefits than arginine and glutamine in mitigating intestinal ischemia and reperfusion-induced adverse effects.

Maturation of glutamatergic transmission in the vestibulo-olivary pathway impacts on the registration of head rotational signals in the brainstem of rats.

The recognition of head orientation in the adult involves multi-level integration of inputs within the central vestibular circuitry. How the different inputs are recruited during postnatal development remains unclear. We hypothesize that glutamatergic transmission at the vestibular nucleus contributes to developmental registration of head orientations along the vestibulo-olivary pathway. To investigate the maturation profile by which head rotational signals are registered in the brainstem, we used sinusoidal rotations on the orthogonal planes of the three pairs of semicircular canals. Fos expression was used as readout of neurons responsive to the rotational stimulus. Neurons in the vestibular nucleus and prepositus hypoglossal nucleus responded to all rotations as early as P4 and reached adult numbers by P21. In the reticular formation and inferior olive, neurons also responded to horizontal rotations as early as P4 but to vertical rotations not until P21 and P25, respectively. Neuronal subpopulations that distinguish between rotations activating the orthogonally oriented vertical canals were identifiable in the medial and spinal vestibular nuclei by P14 and in the inferior olivary subnuclei IOß and IOK by P25. Neonatal perturbation of glutamate transmission in the vestibular nucleus was sufficient to derange formation of this distribution in the inferior olive. This is the first demonstration that developmental refinement of glutamatergic synapses in the central vestibular circuitry is essential for developmental registration of head rotational signals in the brainstem.

Quantitative study of the coexpression of Fos and N-methyl-D aspartate (NMDA) receptor subunits in otolith-related vestibular nuclear neurons of rats.

The expression of NMDA receptor subunits (NR1 and NR2A/B) was demonstrated immunocytochemically in otolith-related neurons within the vestibular nuclear complex and its subnuclei of conscious Sprague-Dawley adult rats. All experimental animals were subjected to constant velocity off-vertical axis rotation (OVAR). The rotating gravity vector during OVAR sequentially activates hair cells on all sectors of the utricular maculae; neurons so activated within the vestibular nuclei were denoted by the expression of Fos protein. Control animals, i.e., labyrinthectomized rats subjected to OVAR and normal rats that remained stationary, showed only a few sporadically scattered labeled neurons. In the brainstem of normal rats subjected to OVAR, a high density of Fos-immunoreactive (Fos-ir) neurons was found in the vestibular nuclear complex (namely, spinal vestibular nucleus, SpVe; medial vestibular nucleus, Mve; superior vestibular nucleus, SuVe) and subnuclei (namely, group x and group y), whereas a lower density was found in the lateral vestibular nucleus (LVe). A double-immunofluorescence study indicated that both NR1 and NR2A/B subunits were highly expressed in Fos-ir neurons within the vestibular nuclei. Fos/NR1 or Fos/NR2A/B double-labeled neurons constitute over three-quarters of the total number of Fos-ir neurons in SpVe, MVe, LVe, SuVe, and groups x and y. Our findings suggest that NMDA-type ionotropic glutamate receptors play a key role in the OVAR-induced neuronal activation of the vestibular nuclei, thus providing a morphological basis for further study of glutamatergic central otolith neurons and their involvement in sensorimotor regulation and autonomic functions of rats.

Fos expression in otolith-related brainstem neurons of postnatal rats following off-vertical axis rotation.

To determine the critical time of responsiveness of developing otolith organ-related brainstem neurons and their distribution, Fos protein expression in response to off-vertical axis rotations (OVAR) was mapped in conscious Sprague Dawley rats from P5 to adulthood. OVAR was used to activate sequentially all utricular hair cells per 360 degrees revolution. We detected the coding of horizontal head positions in otolith organ-related neurons within the vestibular nucleus as early as P7. In the vestibular nuclear complex and its subgroups, the density of Fos-immunoreactive (Fos-ir) neurons increased steadily with age and reached the adult level by P21. In both labyrinthectomized rats subjected to OVAR and normal rats kept stationary, labeled neurons were found sporadically in the aforementioned brain regions in each age group, confirming that Fos labeling observed in neurons of normal experimental rats subjected to OVAR was due to otolith organ stimulation. Whereas OVAR-induced Fos-ir neurons were also first observed in vestibular-related brain areas, such as the prepositus hypoglossal nucleus, gigantocellular reticular nucleus, and locus coeruleus, of normal experimental rats at P7, those in the inferior olive were observed only from P14 onward. This indicates the unique maturation time of inferior olivary neurons in gravity-related spatial coding. In general, age-dependent increase in OVAR-induced Fos-ir neurons was observed in brain areas that received otolith inputs. The locus coeruleus was exceptional in that prominent OVAR-induced Fos-ir neuronal number did not change with maturation, and this was well above the low but significant number of Fos-ir neurons in control preparations. Taken together, our results suggest that neuronal subpopulations within the developing network of the horizontal otolith system provide an anatomical basis for the postnatal development of otolith organ-related sensorimotor functions. J. Comp. Neurol. 470:282-296, 2004.

Microchannel-based surface-enhanced Raman spectroscopy for integrated microfluidic analysis.

We have demonstrated a microchannel-based, surface-enhanced Raman spectroscopy (SERS) sensing approach for integrated microfluidic analysis developed using standard micro-fabrication technology. Our approach allows high-sensitivity SERS sensing with a comparatively low-excitation optical power intensity and large cross-sectional microchannel for biological cell analysis. Utilizing a microchannel with a cross section of 100 × 70 µm(2), we achieved a detection limit smaller than 10 nM for rhodamine 6G at an excitation power intensity of 132 W/cm(2), avoiding any possible heating effects on the sample under investigation. There is great potential for further improvement in the sensitivity of this microchannel-based SERS detection.