Antibody-Based Biosensor Can Monitor Drug Levels

New biosensor can detect methotrexate, theophylline, and quinine in the blood.

In most cases, optimal patient outcomes and disease control can only result if adequate doses of the right medications are administered. Healthcare providers may prescribe a dose of a medication that should be effective, but may not elicit beneficial effects for certain patients due to changes in metabolism and genetics.

For patients with HIV or cancer, drug concentration in the blood can be a matter of life and death. However, drug monitoring requires specific equipment and provisions that may not be feasible in many countries throughout the world.

A group of investigators have created novel antibody-based biosensors that monitor drug concentrations in the blood. These biosensors could be used to assist healthcare providers in developing countries who may not have the proper resources, as well as patients in their own homes, according to a study published by Angewandte Chemie.

This novel biosensor was developed from 3 components: a protein that can bind to the drug; the light-producing enzyme luciferase; and a fluorescent tagging molecule, SNAP-tag.

The tagging molecule carries florescence that causes luciferase to bind even when there is no drug present, which causes a reaction with bioluminescent resonance energy transfer (BRET) that produces red light. According to the study, the authors replaced the binding protein with an antibody created against the target drug.

When the biosensor detects the target drug in the blood or saliva, it binds to the drug rather than the SNAP-tag ligand. When the ligand is displaced, the BRET reaction is changed to create blue light.

Antibodies have a natural ability to identify and bind to foreign molecules to warn the immune system, so they do not need to be engineered to do so. Additionally, the authors report that creating antibodies that identify small molecules is fairly routine, which means that the biosensors can be easily modified to detect various molecules.

This method allows patients to monitor the information themselves without undergoing tests in a laboratory. Current methods are complex, expensive, and may even reduce the quality of life for patients who must remain within or near hospitals, according to the study.

Placing the antibody within the biosensor has led to a pipeline of biosensors that can detect numerous drugs in blood samples. The authors specifically assessed the efficacy of methotrexate, theophylline, and quinine, and found the biosensor was accurate.

Next steps include optimizing the sensitivity of the biosensor so it can detect low concentrations of drugs or biomolecules in the blood, the study concluded.