One-step enzyme immunochromatographic assay for theophylline

Area of Science:

• Clinical Chemistry
• Biotechnology
• Assay Development

Background:

• Enzyme immunochromatography offers visual quantification of theophylline in whole blood.
• Existing two-step protocols present convenience limitations.

Purpose of the Study:

• To develop a simplified, one-step enzyme immunochromatographic assay for theophylline.
• To introduce and describe the concept of an internal delay reaction for assay improvement.

Main Methods:

• A one-step protocol combining capillary migration and color generation was developed.
• Ascorbic acid was employed as a signal inhibitor to temporarily delay color development.
• The internal delay reaction mechanism was investigated.

Main Results:

• The one-step assay successfully integrates previously separate steps.
• Ascorbic acid effectively delays enzymatic color product formation.
• The internal delay reaction enables a practical, quantitative visual assay.

Conclusions:

• A convenient one-step enzyme immunochromatographic assay for theophylline in whole blood has been established.
• The internal delay reaction strategy enhances assay simplicity and practicality.
• This method provides a user-friendly approach for visual theophylline measurement.