MORPHOFUNCTIONAL EVALUATION OF MACULAR-FOVEAL CAPILLARIES: A Comparative Optical Coherence Tomography Angiography and Microperimetry Study.

PURPOSE: To analyze the macular function of eyes with macular-foveal capillaries (MFC), a condition characterized by the absence of the foveal avascular zone (FAZ), identified by optical coherence tomography angiography. METHODS: Eight eyes with MFC at optical coherence tomography angiography and normal visual acuity were consecutively recruited. Eight eyes of healthy subjects were enrolled as healthy controls. All eyes underwent optical coherence tomography, optical coherence tomography angiography, best-correct visual acuity, low-luminance visual acuity, contrast sensitivity measurement, colour vision tests, and both mesopic and scotopic microperimetry. RESULTS: Best-corrected visual acuity, low-luminance visual acuity, contrast sensitivity, and colour vision tests did not differ between the two groups. At mesopic microperimetry, both foveal retinal sensitivity and mean mesopic retinal sensitivity of the central 1° were statistically inferior in MFC versus control eyes (P < 0.0001 and P < 0.0001, respectively). At scotopic microperimetry, a dense foveal scotoma, normally present in control eyes, was completely lacking in MFC eyes. Scotopic foveal retinal sensitivity was statistically superior in MFC versus control eyes (P = 0.009). CONCLUSION: The absence of the foveal dense scotoma in scotopic conditions underlines that the foveal rod-free zone is not present when capillaries are present in this area. An anomalous foveal distribution of photoreceptors, with both rods and cones present in this area, may be postulated in MFC eyes.

Repeatability and Reproducibility of Foveal Avascular Zone Area Measurement on Normal Eyes by Different Optical Coherence Tomography Angiography Instruments.

PURPOSE: To compare the foveal avascular zone (FAZ) area measurements produced by different optical coherence tomography angiography (OCTA). METHODS: Healthy enrolled volunteers underwent OCTA using 2 different devices: Spectralis HRA+OCTA (Heidelberg Engineering, Heidelberg, Germany) and RS-3000 Advance (Nidek, Gamagori, Japan). Two graders measured FAZ in both superficial (SCP) and deep (DCP) retinal capillary plexuses. The SCP and DCP en face images were visualized automatically segmenting 2 separate slabs defined by the arbitrary segmentation lines created by the software of each OCT device. One grader repeated each measure twice. RESULTS: Fifty-nine eyes were included. The mean FAZ was 0.33 ± 0.09 mm2 at the SCP and 0.57 ± 0.17 mm2 at the DCP measured with RS-3000 versus 0.30 ± 0.08 and 0.35 ± 0.08 mm2, respectively, measured with Spectralis. The measurements of the 2 devices were significantly different (p < 0.0001). The intraoperator agreement was excellent at the SCP (intraclass correlation coefficient, ICC: 0.97 with Spectralis and 0.96 with RS-3000). At the DCP, it was good with Spectralis and fair with RS-3000 (ICC: 0.85 and 0.64, respectively). The interoperator agreement was excellent for Spectralis and good for RS-3000 at the SCP (ICC: 0.97 and 0.93, respectively). It was good at the DCP with both devices (ICC: 0.74 with RS-3000 and 0.81 with Spectralis). CONCLUSIONS: FAZ measurements obtained with different OCTA devices differ. These findings should be considered in follow-up studies of patients with retinal vascular diseases.

Three-dimensional biofabrication of an aragonite-enriched self-hardening bone graft substitute and assessment of its osteogenicity in vitro and in vivo.

A self-hardening three-dimensional (3D)-porous composite bone graft consisting of 65 wt% hydroxyapatite (HA) and 35 wt% aragonite was fabricated using a 3D-Bioplotter®. New tetracalcium phosphate and dicalcium phosphate anhydrous/aragonite/gelatine paste formulae were developed to overcome the phase separation of the liquid and solid components. The mechanical properties, porosity, height and width stability of the end products were optimised through a systematic analysis of the fabrication processing parameters including printing pressure, printing speed and distance between strands. The resulting 3D-printed bone graft was confirmed to be a mixture of HA and aragonite by X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The compression strength of HA/aragonite was between 0.56 and 2.49 MPa. Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in vitro. The osteogenicity of HA/aragonite was evaluated in vitro by alkaline phosphatase assay using human umbilical cord matrix mesenchymal stem cells, and in vivo by juxtapositional implantation between the tibia and the anterior tibialis muscle in rats. The results showed that the scaffold was not toxic and supported osteogenic differentiation in vitro. HA/aragonite stimulated new bone formation that bridged host bone and intramuscular implants in vivo. We conclude that HA/aragonite is a biodegradable and conductive bone formation biomaterial that stimulates bone regeneration. Since this material is formed near 37°C, it will have great potential for incorporating bioactive molecules to suit personalised application; however, further study of its biodegradation and osteogenic capacity is warranted. The study was approved by the Animal Ethical Committee at Tongji Medical School, Huazhong University of Science and Technology (IACUC No. 738) on October 1, 2017.

Cellulose nanofibrils and silver nanowires active coatings for the development of antibacterial packaging surfaces.

An active ink composed of cellulose nanofibrils and silver nanowires was deposited on flexible and transparent polymer films using the bar coating process, achieving controlled thicknesses ranging from 200 nm up to 2 µm. For 350 nm thick coating on polyethylene terephthalate films, high transparency (75.6% transmittance) and strong reduction of bacterial growth equal to 89.3% and 100% was noted respectively against Gram-negative Escherichia Coli and Gram-positive Staphylococcus Aureus bacteria using AATCC contact active standard test. Retained antibacterial activity was found with films produced by reverse gravure roll-to-roll process, showing the promising capability of this antibacterial solution to be deployed industrially. Finally, the same ink was also deposited on polylactic acid substrate to investigate barrier properties: for 350 nm thick coating, a reduction of 49% of oxygen transmission rate (dry conditions) and 47% reduction of water vapor transmission rate was noted, proving the enhanced barrier properties of the coatings.

Vertically Aligned Graphene Prepared by Photonic Annealing for Ultrasensitive Biosensors.

Graphene exhibits excellent physical, electronic, and chemical properties that are highly desirable for biosensing applications. However, most graphene biosensors are based on graphene lying flat on a substrate and therefore do not utilize its maximum specific surface area for ultrasensitive detection. Herein, we report the novel use of photonic annealing on a flexographically printed graphene-ethyl cellulose composite to produce vertically aligned graphene (VAG) biosensors for ultrasensitive detection of algal toxins in drinking water. These VAG structures, which maximized the specific surface area of graphene, were formed by partial removal of the polymeric binder upon applying intense pulsed light on the printed graphene. A label-free and low-cost VAG biosensor based on a non-faradaic electrochemical impedance spectroscopy technique was fabricated. The biosensor exhibited a limit of detection of 1.2 ng/L for microcystin-LR in local tap water. Such an ultrasensitive VAG biosensor is suitable for low-cost mass production using an integrated roll-to-roll flexographic printing with rapid photonic annealing technique.

Early retinal and choroidal OCT and OCT angiography signs of inflammation after uncomplicated cataract surgery.

PURPOSE: To evaluate, by means of optical coherence tomography (OCT) and OCT angiography (OCTA), early retinal, choroidal and macular perfusion changes induced by a local inflammatory reaction secondary to uncomplicated cataract surgery. METHODS: Selected eyes undergoing cataract surgery were enrolled in a prospective study. OCT and OCTA were performed before cataract surgery (T0) and at day: 1 (T1), 7 (T7), 30 (T30) and 90 (T90). Inner (IR) and outer retinal (OR) volumes, choroidal volume, hyper-reflective retinal spots (HRS) in IR and OR changes were measured at OCT. Macular perfusion was analysed in superficial (SCP), intermediate (ICP) and deep retinal capillary plexuses (DCP). RESULTS: Nine eyes of nine selected patients were consecutively enrolled. Mean IR volume changed after surgery (p=0.0001), increasing progressively from 4.391±0.231 mm³ at T0 to 4.573±0.241 mm³ at T30, p=0.0002. Both mean OR and choroidal volume increased, mainly at T30, but not significantly (p=0.4360 and p=0.2300, respectively). Mean HRS changed during follow-up, increasing at first in IR and later in OR (at T1 and T7, respectively, both p<0.0001). Macular ICP and DCP perfusion increased at T1, whereas macular SCP perfusion did not change. At T90, all OCT and OCTA parameters had almost reached baseline levels. CONCLUSIONS: The increase of HRS at first in IR and later in OR seems to confirm their inflammatory nature. Early OCTA changes (underline) underscore a selective susceptibility of DCP and ICP to a localised inflammatory reaction induced by cataract surgery.

The association between diabetes and cataract among 42,469 community-dwelling adults in six low- and middle-income countries.

BACKGROUND: Cataract is a major cause of visual impairment in people with diabetes, yet a paucity of data is available in low- and middle-income countries (LMICs) on this comorbidity. Thus we assessed the association between diabetes and cataract in 6 LMICs. METHODS: Cross-sectional, community-based data from the Study on Global Ageing and Adult Health (SAGE) was analyzed (n = 42,469 aged ≥18 years). Five years information on self-reported diagnosis of cataract was collected. Three definitions for cataract were used: (a) Self-reported diagnosis and/or past 12-month symptoms; (b) Solely self-reported diagnosis; and (c) Surgical treatment for cataract in the past five years. Diabetes was based on self-reported diagnosis. Multivariable logistic regression was conducted to assess the associations. RESULTS: Overall, the prevalence of diabetes was 3.1% (95%CI = 2.7-3.5%) and that of cataract based on the three different definitions was: (a) 13.3% (95%CI = 12.4-14.3%); (b) 4.4% (95%CI = 3.9-4.8%), (c) 1.7% (95%CI = 1.5-2.0%). After adjustment the association was significantly elevated: (a) OR = 2.10 (95%CI = 1.59-2.76); (b) OR = 2.62 (95%CI = 2.00-3.42); (c) OR = 2.80 (95%CI = 1.78-4.40). These associations were particularly pronounced among those aged <50 years. CONCLUSIONS: A strong association between diabetes and cataract was observed in LMICs. Considering the impact on health and quality of life and the limited treatment options especially for cataract it is mandatory to promote the prevention through bi-directional screening and treatment.

Spray-Coating Thin Films on Three-Dimensional Surfaces for a Semitransparent Capacitive-Touch Device.

Here, we formulate low surface tension (∼30 mN/m) and low boiling point (∼79 °C) inks of graphene, single-wall carbon nanotubes and conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and demonstrate their viability for spray-coating of morphologically uniform ( Sq ≈ 48 ± 3 nm), transparent conducting films (TCFs) at room temperature (∼20 °C), which conform to three dimensional curved surfaces. Large area (∼750 cm2) hybrid PEDOT:PSS/graphene films achieved an optical transmission of 67% in the UV and 64% in the near-infrared wavelengths with a conductivity of ∼104 S/m. Finally, we demonstrate the spray-coating of TCFs as an electrode on the inside of a poly(methyl methacrylate) sphere, enabling a semitransparent (around 360°) and spherical touch sensor for interactive devices.

The effect of graphite and carbon black ratios on conductive ink performance.

Conductive inks based on graphite and carbon black are used in a host of applications including energy storage, energy harvesting, electrochemical sensors and printed heaters. This requires accurate control of electrical properties tailored to the application; ink formulation is a fundamental element of this. Data on how formulation relates to properties have tended to apply to only single types of conductor at any time, with data on mixed types of carbon only empirical thus far. Therefore, screen printable carbon inks with differing graphite, carbon black and vinyl polymer content were formulated and printed to establish the effect on rheology, deposition and conductivity. The study found that at a higher total carbon loading ink of 29.4% by mass, optimal conductivity (0.029 Ω cm) was achieved at a graphite to carbon black ratio of 2.6 to 1. For a lower total carbon loading (21.7 mass %), this ratio was reduced to 1.8 to 1. Formulation affected viscosity and hence ink transfer and also surface roughness due to retention of features from the screen printing mesh and the inherent roughness of the carbon components, as well as the ability of features to be reproduced consistently.

Nanotextured Surface on Flexographic Printed ZnO Thin Films for Low-Cost Non-Faradaic Biosensors.

In this work, the formation of a nanotextured surface is reported on flexographic printed zinc oxide thin films which provide an excellent platform for low-cost, highly sensitive biosensing applications. The ability to produce nanotextured surfaces using a high-throughput, roll-to-roll production method directly from precursor ink without any complicated processes is commercially attractive for biosensors that are suitable for large-scale screening of diseases at low cost. The zinc oxide thin film was formed by printing a zinc acetate precursor ink solution and annealing at 300 °C. An intricate nanotexturing of the film surface was achieved through 150 °C drying process between multiple prints. These surface nanostructures were found to be in the range of 100 to 700 nm in length with a width of 58 ± 18 nm and a height of between 20 and 60 nm. Such structures significantly increase the surface area to volume ratio of the biosensing material, which is essential to high sensitivity detection of diseases. Nonfaradaic electrochemical impedance spectroscopy measurements were carried out to detect the pp65-antigen of the human cytomegalovirus using the printed device, which has a low limit of detection of 5 pg/mL.

Direct patterning of gold nanoparticles using flexographic printing for biosensing applications.

In this paper, we have presented the use of flexographic printing techniques in the selective patterning of gold nanoparticles (AuNPs) onto a substrate. Highly uniform coverage of AuNPs was selectively patterned on the substrate surface, which was subsequently used in the development of a glucose sensor. These AuNPs provide a biocompatible site for the attachment of enzymes and offer high sensitivity in the detection of glucose due to their large surface to volume ratio. The average size of the printed AuNPs is less than 60 nm. Glucose sensing tests were performed using printed carbon-AuNP electrodes functionalized with glucose oxidase (GOx). The results showed a high sensitivity of 5.52 µA mM(-1) cm(-2) with a detection limit of 26 µM. We have demonstrated the fabrication of AuNP-based biosensors using flexographic printing, which is ideal for low-cost, high-volume production of the devices.

Short-Term Intra-Subject Variation in Exhaled Volatile Organic Compounds (VOCs) in COPD Patients and Healthy Controls and Its Effect on Disease Classification.

Exhaled volatile organic compounds (VOCs) are of interest for their potential to diagnose disease non-invasively. However, most breath VOC studies have analyzed single breath samples from an individual and assumed them to be wholly consistent representative of the person. This provided the motivation for an investigation of the variability of breath profiles when three breath samples are taken over a short time period (two minute intervals between samples) for 118 stable patients with Chronic Obstructive Pulmonary Disease (COPD) and 63 healthy controls and analyzed by gas chromatography and mass spectroscopy (GC/MS). The extent of the variation in VOC levels differed between COPD and healthy subjects and the patterns of variation differed for isoprene versus the bulk of other VOCs. In addition, machine learning approaches were applied to the breath data to establish whether these samples differed in their ability to discriminate COPD from healthy states and whether aggregation of multiple samples, into single data sets, could offer improved discrimination. The three breath samples gave similar classification accuracy to one another when evaluated separately (66.5% to 68.3% subjects classified correctly depending on the breath repetition used). Combining multiple breath samples into single data sets gave better discrimination (73.4% subjects classified correctly). Although accuracy is not sufficient for COPD diagnosis in a clinical setting, enhanced sampling and analysis may improve accuracy further. Variability in samples, and short-term effects of practice or exertion, need to be considered in any breath testing program to improve reliability and optimize discrimination.