On the barrier properties of the cornea: a microscopy study of the penetration of fluorescently labeled nanoparticles, polymers, and sodium fluorescein

Overcoming the natural defensive barrier functions of the eye remains one of the greatest challenges of ocular drug delivery. Cornea is a chemical and mechanical barrier preventing the passage of any foreign bodies including drugs into the eye, but the factors limiting penetration of permeants and nanoparticulate drug delivery systems through the cornea are still not fully understood. In this study, we investigate these barrier properties of the cornea using thiolated and PEGylated (750 and 5000 Da) nanoparticles, sodium fluorescein, and two linear polymers (dextran and polyethylene glycol). Experiments used intact bovine cornea in addition to bovine cornea de-epithelialized or tissues pretreated with cyclodextrin. It was shown that corneal epithelium is the major barrier for permeation; pretreatment of the cornea with β-cyclodextrin provides higher permeation of low molecular weight compounds, such as sodium fluorescein, but does not enhance penetration of nanoparticles and larger molecules. Studying penetration of thiolated and PEGylated (750 and 5000 Da) nanoparticles into the de-epithelialized ocular tissue revealed that interactions between corneal surface and thiol groups of nanoparticles were more significant determinants of penetration than particle size (for the sizes used here). PEGylation with polyethylene glycol of a higher molecular weight (5000 Da) allows penetration of nanoparticles into the stroma, which proceeds gradually, after an initial 1 h lag phase

Biomedical applications of hydrogels: a review of patents and commercial products

Hydrogels have become very popular due to their unique properties such as high water content, softness, flexibility and biocompatibility. Natural and synthetic hydrophilic polymers can be physically or chemically cross-linked in order to produce hydrogels. Their resemblance to living tissue opens up many opportunities for applications in biomedical areas. Currently, hydrogels are used for manufacturing contact lenses, hygiene products, tissue engineering scaffolds, drug delivery systems and wound dressings. This review provides an analysis of their main characteristics and biomedical applications. From Wichterle’s pioneering work to the most recent hydrogel-based inventions and products on the market, it provides the reader with a detailed introduction to the topic and perspective on further potential developments

Water Fingering Into an Oil-Wet Porous Medium Saturated with Oil At Connate Water Saturation Digitation de l'eau dans un milieu poreux mouillable à l'huile saturée en eau connée

The effect that connate water has on fingers of water penetrating into an oil-wet porous medium is examined. In this context, the connate water appears to have no influence on the width of fingers, but instead causes the fingers to be more irregular than fingers in similar experiments without connate water. The surface wettability, in contrast, does have a marked effect on finger widths. On examine dans cet article les effets de l'eau connée sur la digitation de l'eau dans un milieu poreux mouillable à l'huile. Dans ce contexte l'eau connée ne semble avoir aucune influence sur la largeur des digitations mais rend ces dernières plutôt plus irrégulières que dans le cas des expériences effectuées en absence d'eau connée. Par contre, la mouillabilité de la surface a un effet important sur la largeur des digitations

Water Fingering Into an Oil-Wet Porous Medium Saturated with Oil At Connate Water Saturation

The effect that connate water has on fingers of water penetrating into an oil-wet porous medium is examined. In this context, the connate water appears to have no influence on the width of fingers, but instead causes the fingers to be more irregular than fingers in similar experiments without connate water. The surface wettability, in contrast, does have a marked effect on finger widths

Radial Fingering in a Porous Medium

The theory of immiscible radial displacement in a Hele-Shaw cell is extended to the case of a porous medium contained between two closely-spaced parallel plates, and experiments are described for the displacement of glycerine by paraffin oil in such a system. Data are presented for the number of fingers, the breakthrough time, and the glycerine recovery, for a range of flowrates varying through three orders of magnitude. Good agreement between theory and experiment is observed

Radial Fingering in a Porous Medium Digitation radiale dans un milieu poreux

The theory of immiscible radial displacement in a Hele-Shaw cell is extended to the case of a porous medium contained between two closely-spaced parallel plates, and experiments are described for the displacement of glycerine by paraffin oil in such a system. Data are presented for the number of fingers, the breakthrough time, and the glycerine recovery, for a range of flowrates varying through three orders of magnitude. Good agreement between theory and experiment is observed. La théorie s'appliquant aux déplacements radiaux dans les cellules Hele-Shaw a été étendue à un système qui consiste en une couche mince de milieux poreux encapsulée entre deux plaques en verre. Dans cet article, on examine les déplacements de la glycérine par de l'huile de paraffine. En faisant varier le débit de l'huile de paraffine dans un intervalle de trois ordres de grandeur, on a étudié les variables telles que le nombre de digitations, le temps de percée et le taux de récupération de la glycérine. On a observé un bon accord entre la théorie et les résultats expérimentaux

The Sound of One Eye Clapping: Tapping an Accurate Rhythm With Eye Movements

As eye-controlled interfaces becomes increasingly viable, there is a need to better understand fundamental humancomputer interaction capabilities between a human and a computer via an eye tracking device. Prior research has explored the maximum rate of input from a human to a computer, such as key-entry rates in eye-typing tasks, but there has been little or no work to determine capabilities and limitations with regards to delivering gaze-mediated commands at precise moments in time. This paper evaluates four different methods for converting real-time eye movement data into control signals—two fixationbased methods and two saccade-based methods. An experiment compares musicians ’ ability to use each method to trigger the playing of sounds at precise times, and examined how quickly musicians are able to move their eyes to trigger correctly-timed, evenly-paced rhythms. The results indicate that fixation-based eye-control algorithms provide better timing control than saccade-based algorithms, and that people have a fundamental performance limitation for tapping out eye-controlled rhythms that lies somewhere between two and four beats per second