A new method for measuring free drug concentration: retinal tissue as a biosensor

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Controlled drug release systems are crucial for targeted therapy.
• Assessing drug concentration and carrier biocompatibility in living tissue is challenging.
• Existing methods may lack the sensitivity or real-time feedback needed for complex biological systems.

Purpose of the Study:

• To establish a novel biosensor method using isolated rat retinas.
• To quantify free drug concentrations in biological tissue during controlled release.
• To evaluate the biocompatibility of polymeric drug carriers and nanostructures.

Main Methods:

• Utilized the light-induced electrical response of retinal rods as a biosensor.
• Measured the photoresponse kinetics, specifically time to peak (tp), influenced by 3-isobutyl-1-methylxanthine (IBMX) concentration.
• Employed transretinal electroretinography (ERG) in aspartate-treated rat retinas for sensitive measurements.
• Developed a calibration curve correlating tp with IBMX concentration for drug quantification.
• Assessed polymer biocompatibility by observing rod function in the presence of carrier materials.

Main Results:

• Established a reproducible, polynomial relationship between tp and IBMX concentration.
• Demonstrated that equilibrium drug concentrations were reached within 6-9 minutes.
• Quantified released IBMX from biocompatible polymers with accuracy in the 10-300 microM range.
• Showed that rod function stability indicates carrier biocompatibility.

Conclusions:

• The isolated rat retina serves as an effective biosensor for drug release studies.
• The method allows for accurate, real-time determination of drug concentrations in retinal tissue.
• This approach facilitates rapid screening of polymer biocompatibility for drug delivery applications.
• Calibration is essential for each retina and temperature to ensure measurement accuracy.