Related Experiment Video
Updated: Jul 28, 2026
07:22
Using a Laminating Technique to Perform Confocal Microscopy of the Human Sclera
Published on: May 6, 2016
Diffusion of high molecular weight compounds through sclera.
J Ambati1, C S Canakis, J W Miller
1Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston 02114, USA.
Investigative Ophthalmology & Visual Science
|February 7, 2001
Summary
Scleral permeability to large molecules decreases with size, with molecular radius being a key factor. This suggests transscleral delivery of immunoglobulins to the eye
Area of Science:
- Ophthalmology
- Biomaterials Science
- Drug Delivery
Background:
- The sclera acts as a significant barrier to drug delivery to the posterior eye.
- Understanding scleral permeability is crucial for developing effective ocular therapies.
Purpose of the Study:
- To quantify the in vitro permeability of sclera for high molecular weight compounds.
- To establish the relationship between scleral permeability and molecular size and shape.
Main Methods:
- Rabbit sclera was used in a two-chamber diffusion apparatus to measure permeability.
- Fluorescence spectrophotometry assessed permeability to sodium fluorescein, FITC-labeled proteins, and FITC dextrans (4-150 kDa).
- Electron microscopy and hydration studies evaluated experimental effects on scleral integrity.
Main Results:
- Scleral permeability decreased with increasing molecular weight and radius.
- Molecular radius predicted permeability better than molecular weight.
- Sclera was more permeable to globular proteins than linear dextrans of similar molecular weights.
- Rabbit scleral permeability mirrored human data but exceeded bovine sclera.
Conclusions:
- Large molecules like IgG permeate the sclera via porous diffusion through its fiber matrix.
- Transscleral delivery of immunoglobulins and other large molecules to the choroid and retina is potentially feasible.
More Related Videos
10:33A Method for Determination and Simulation of Permeability and Diffusion in a 3D Tissue Model in a Membrane Insert System for Multi-well Plates
Published on: February 23, 2018
07:12Spatio-Temporal In Vivo Imaging of Ocular Drug Delivery Systems using Fiberoptic Confocal Laser Microendoscopy
Published on: September 27, 2021
Related Concept Videos
01:12Diffusion
Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
01:21Diffusion
Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
01:25Physiological Barriers
Physiological barriers are semi-permeable cellular structures restricting drug diffusion into intracellular compartments and tissues. There are six types of physiological barriers: blood endothelial, cell membrane, blood-brain, blood-cerebrospinal fluid (CSF), blood-placenta, and blood-testis barriers.
The blood endothelial barrier is the most porous of these. It allows all small ionized, un-ionized, and lipophilic molecules to pass through the endothelial lining into the interstitial space...
The blood endothelial barrier is the most porous of these. It allows all small ionized, un-ionized, and lipophilic molecules to pass through the endothelial lining into the interstitial space...
01:24Cellular Membranes and Drug Transport
Drugs must traverse multiple biological barriers, such as multi-layered skin, single-layered intestinal epithelium, and the plasma membrane, to reach their target sites within the body. The plasma membrane, a highly structured composite of phospholipids, carbohydrates, and proteins, is the cell's protective boundary, facilitating selective substance exchange.
Phospholipids arrange themselves into a bilayer, with hydrophilic heads oriented outward and hydrophobic tails facing inward.
Phospholipids arrange themselves into a bilayer, with hydrophilic heads oriented outward and hydrophobic tails facing inward.
01:17Passive Diffusion: Overview and Kinetics
Passive diffusion is a critical process that allows small lipophilic drugs to cross the cell membrane along a concentration gradient. This mechanism's efficiency depends on four primary factors: the membrane's surface area, the drug's lipid-water partition coefficient, the concentration gradient, and the membrane's thickness.
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...
01:23Ophthalmic Drug Delivery Systems
Ophthalmic drug delivery faces major limitations due to poor absorption across the corneal membrane. This process is primarily driven by diffusion and is influenced by two main factors: the physicochemical properties of the drug and tear drainage. Most ophthalmic drugs, such as pilocarpine, epinephrine, atropine, and local anesthetics, are weak bases. They are typically formulated at an acidic pH to enhance chemical stability. However, this leads to high ionization, reducing their ability to...