Multifocal meta-fiber based on the fractional Talbot effect.

Multi-focusing of light is a crucial capability for photonic devices that can be effectively achieved by precisely modulating the phase delay on the incident wavefront. However, integrating functional structures into optical fibers for remote light focusing remains challenging due to the complex device design and limited fabrication approaches. Here, we present the design and fabrication of metalens array on the end-face of a tailored single-mode step-index fiber for focusing light field into closely packed focal spot array. The metalenses are configured based on the fractional Talbot effect and benefit a modular design capability. Light passing through the optical fiber can be focused into different focal planes. With a synergistic 3D laser nanoprinting technique based on two-photon polymerization, high-quality meta-fibers are demonstrated for focusing light parallelly with a uniform numerical aperture (NA) as high as approximately 0.77. This may facilitate various applications such as optical trapping, generation of sophisticated beam profiles, and boosting light coupling efficiencies.

Gut microbiota is causally associated with poststroke cognitive impairment through lipopolysaccharide and butyrate.

BACKGROUND: Poststroke cognitive impairment (PSCI) is prevalent in stroke patients. The etiology of PSCI remains largely unknown. We previously found that stroke induces gut microbiota dysbiosis which affects brain injury. Hereby, we aimed to investigate whether the gut microbiota contributes to the pathogenesis of PSCI. METHODS: 83 stroke patients were recruited and their cognitive function were measured by Montreal Cognitive Assessment (MoCA) scores 3 months after stroke onset. The peripheral inflammatory factor levels and gut microbiota compositions of the patients were analyzed. Fecal microbiota transplantation from patients to stroke mice was performed to examine the causal relationship between the gut microbiota and PSCI. The cognitive function of mice was evaluated by Morris water maze test. RESULTS: 34 and 49 stroke patients were classified as PSCI and non-PSCI, respectively. Compared with non-PSCI patients, PSCI patients showed significantly higher levels of gut Enterobacteriaceae, lipopolysaccharide (LPS) and peripheral inflammation markers. Consistently, stroke mice that received microbiota from PSCI patients (PSCI mice) presented a higher level of Enterobacteriaceae, intestinal Toll-like receptor-4 (TLR4) expression, circulating LPS, LPS-binding protein (LBP) and inflammatory cytokines, and a lower level of fecal butyrate, severer intestine destruction and cognitive impairment than mice that received microbiota from nPSCI patients (nPSCI mice). In addition, we observed exacerbations in blood-brain barrier (BBB) integrity, microglial activation, neuronal apoptosis in the CA1 region of the hippocampus, and Aß deposition in the thalamus of PSCI mice in comparison with nPSCI mice. Intraperitoneal injection of LPS after stroke caused similar pathology to those seen in PSCI mice. Supplementation with sodium butyrate (NaB) via drinking water rescued these detrimental changes in PSCI mice. CONCLUSIONS: Our data indicate a cause-effect relationship between gut microbiota and PSCI for the first time, which is likely mediated by inflammation-regulating metabolites including LPS and butyrate.

3D high precision laser printing of a flat nanofocalizer for subwavelength light spot array.

Here, we demonstrate a flat nanofocalizer for converging light field into a uniform subwavelength light spot array based on the fractional Talbot effect by developing a direct laser writing technique with 3D fabrication precision. The fractional Talbot effect endows the device with the merits of high compression ratio and modular design capability for transforming a plane wave into arrayed light focal spots. By combining a synergistic laser printing technique, we introduce a buffer layer for improving the fabrication precision of structural height in favor of accurately manipulating the phase delay. For a given light wavelength at 750 nm, by precisely producing a nanofocalizer consisting of periodic unit elements with the dimensions of 300(width)×600(length)×585(height)nm, we have achieved 5×6 light spot array with modular design, while the full width at half-maximum of a single focused light spot can be reduced to ∼0.82λ. Our research may pave the way for realizing subwavelength optical devices capable of being readily integrated to existing optical systems.

Cholestyramine resin administration alleviated cerebral ischemic injury in obese mice by improving gut dysbiosis and modulating the bile acid profile.

Obesity is a risk factor for cerebrovascular diseases. Accumulating evidence has revealed that gut dysbiosis plays an important role in the pathophysiology of cerebrovascular diseases. However, little is known about the role of gut dysbiosis in stroke in obesity. In this study, we established a rodent middle cerebral artery occlusion (MCAO) model to investigate whether obesity-induced gut dysbiosis exacerbates cerebral ischemic injury and the role of the bile salt sequestrant cholestyramine resin (CR) in gut microbiota and stroke outcome in obese mice. Long-term 45% high-fat diet (HFD) diet (8 weeks) induced an obesity phenotype and caused gut dysbiosis, resulting in a larger infarct volume and higher serum levels of inflammatory cytokines after stroke, compared to those in the lean counterparts. LC-MS/MS and GC analysis revealed that obese mice with stroke developed an obviously perturbed bile acid (BA) profile characterized by higher levels of deoxycholic acid and its conjugated forms, and lower levels of butyrate in the cecal content. CR administration improved the obesity-induced dysbiotic microbiome, attenuated ischemic brain injury and modulated the stroke-perturbed BA profile. Furthermore, fecal microbiota transplantation (FMT) experiments revealed that the impact of obesity on stroke and the neuroprotective effects of CR were mediated by gut microbiota. In conclusion, Obesity induces gut dysbiosis, worsens stroke outcomes, and perturbs the BA profile. The dysbiotic microbiome is an important linkage between obesity and stroke. CR confers metabolic benefits and neuroprotective effects in obesity, perhaps by modulating gut microbial composition and BA metabolism.

Low Serum Superoxide Dismutase Is Associated With a High Risk of Cognitive Impairment After Mild Acute Ischemic Stroke.

Background: Post-stroke cognitive impairment (PSCI) is a common complication after stroke, but effective therapy is limited. Identifying potential risk factors for effective intervention is warranted. We investigated whether serum superoxide dismutase (SOD) levels were related to cognitive impairment after mild acute ischemic stroke (AIS) by using a prospective cohort design. Methods: A total of 187 patients diagnosed with mild AIS (National Institutes of Health Stroke Scale ≤ 8) were recruited. Serum SOD, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and interleukin-6 (IL-6) levels were measured, and cognitive assessments (Mini-Mental State Examination, MMSE; Montreal Cognitive Assessment, MoCA) were performed in the early phase (within 2 weeks). These indexes and assessments were repeated at 3 months after onset. MoCA < 22 was defined as early cognitive impairment (CI-E) within 2 weeks and late cognitive impairment (CI-L) at 3 months after stroke. Results: In a survey, 105 of 187 (56.1%) patients were identified as CI-E after mild AIS. Lower serum SOD associated with higher inflammatory biomarkers (ESR, CRP, and IL-6) and worse cognitive scores was observed in CI-E patients. In a survey, 39 of 103 (37.9%) stroke patients who completed the 3-month follow-up were identified as CI-L. Serum SOD was consistently lower in CI-L patients at baseline and 3 months and positively associated with cognitive scores. In adjusted analyses, low serum SOD at baseline was independently associated with high risks of CI-E and CI-L, with odds ratios (ORs) of 0.64 and 0.33 per standard deviation increase in serum SOD, respectively. Multiple-adjusted spline regression models showed linear associations between serum SOD and CI-E (P = 0.044 for linearity) and CI-L (P = 0.006 for linearity). Moreover, 35.2% (19/54) of CI-E patients cognitively recovered during the 3-month follow-up. In multivariable analysis, SOD was identified as a protective factor for cognitive recovery after stroke (OR 1.04, 95% CI: 1.01-1.08, P = 0.024). Conclusion: We demonstrate that low serum SOD is associated with a high risk of cognitive impairment after mild AIS, indicating SOD may be a potential modifiable factor for PSCI.

Effect of enteral nutrition on the intestinal microbiome and risk of death in ischemic stroke patients.

BACKGROUND: Studies have shown that the intestinal microbiome of stroke patients is significantly altered and that the degree of microbiota disturbance correlates with prognosis. Enteral nutrition (EN) can reshape the intestinal microbiome and is important for stroke patients with dysphagia. We aimed to describe the intestinal microbiome in patients with ischemic cerebral infarction receiving standard EN. METHODS: First, 17 healthy controls (HCs), 54 stroke patients with oral feeding (ON), and 50 stroke patients with EN were matched to investigate the changes in the intestinal microbiota with EN in the first week after admission and dynamic changes in the EN group in the second week. Second, we investigated the relationship between the intestinal microbiome and clinical characteristics in a larger sample of participants receiving EN (n = 147). Survival analysis was performed using Cox proportional hazards regression. The composition and structure of the intestinal microbiota were analyzed by 16S rRNA sequencing. RESULTS: Compared with the HC and ON groups, patients with EN exhibited significantly different compositions of the intestinal microbiota in the first week, including enrichment of the opportunistic pathogen Enterococcus and depletion of bacteria such as Lachnospiraceae, and Ruminococcus, which were further depleted in the second week. An increase in Parvimonas and Comamonas abundances was associated with an increased risk of 180-day mortality. CONCLUSIONS: The intestinal microbiota in ischemic stroke patients receiving EN is significantly altered, and specific strains of bacteria may be associated with prognosis and clinical indicators.

Dysbiosis of Gut Microbiota Is an Independent Risk Factor of Stroke-Associated Pneumonia: A Chinese Pilot Study.

Background and Purpose: Identifying risks of stroke-associated pneumonia (SAP) is important for clinical management. We aimed to evaluate the association between gut microbiome composition and SAP in patients with acute ischemic stroke (AIS). Methods: A prospective observational study was conducted, and 188 AIS patients were enrolled as the training cohort. Fecal and serum samples were collected at admission. SAP was diagnosed by specialized physicians, and disease severity scores were recorded. Fecal samples were subjected to 16S rRNA V4 tag sequencing and analysed with QIIME and LEfSe. Associations between the most relevant taxa and SAP were analysed and validated with an independent cohort. Fecal short-chain fatty acid (SCFA), serum D-lactate (D-LA), intestinal fatty acid-binding protein (iFABP) and lipopolysaccharide binding protein (LBP) levels were measured. Results: Overall, 52 patients (27.7%) had SAP in the training cohort. The gut microbiome differed between SAP and non-SAP patients; specifically, Roseburia depletion and opportunistic pathogen enrichment were noted in SAP patients, as confirmed in the validation cohort (n=144, 28 SAP [19.4%]). Based on multivariate analysis, Roseburia was identified as a protective factor against SAP in both cohorts (training, aOR 0.52; 95% CI, 0.30-0.90; validation, aOR 0.44; 95% CI, 0.23-0.85). The combination of these taxa into a microbial dysbiosis index (MDI) revealed that dysbiosis increased nearly 2 times risk of SAP (training, aOR 1.95; 95% CI, 1.19-3.20; validation, aOR 2.22; 95% CI, 1.15-4.26). Lower fecal SCFA levels and higher serum D-LA levels were observed in SAP patients. Furthermore, SAP was an independent risk factor of 30-day death and 90-day unfavorable outcome. Conclusion: We demonstrate that a microbial community with depleted Roseburia and enriched opportunistic pathogens is associated with increased risk of SAP among AIS patients. Gut microbiota screening might be useful for identifying patients at high risk for SAP and provide clues for stroke treatment.

Ultra-high quality factor metallic micro-cavity based on concentric double metal-insulator-metal rings.

We propose and numerically investigate a novel ultra-high quality (Q) factor metallic micro-cavity based on concentric double metal-insulator-metal (MIM) rings (CDMR). In this CDMR cavity, because of the angular momentum matching, the strong coupling occurs between the same order modes of the inner and outer rings with huge resonance frequency difference. Consequently, the energy distribution between in the inner and outer rings presents enormous difference. Especially, for the quasi-in-phase CDMR modes, the energy is confined in the inner ring mainly, which suppresses the radiation loss greatly and results in ultra-narrow resonance dips and ultra-high Q factors. The full width at half-maximum (FWHM) of this CDMR cavity can be less than 2 nm and the Q factor can be higher than 300. Moreover, the character of this CDMR metallic micro-cavity can be modulated by varying the gap width between the two MIM rings. Our CDMR metallic micro-cavity provides a new perspective to design the advanced optical cavity with high Q factor and small mode volumes.