# Antibody-Based Array for Tacrolimus Immunosuppressant Monitoring with Planar Plastic Waveguides Activated with an Aminodextran-Lipase Conjugate

## TL;DR

Researchers developed a new biosensor using modified plastic surfaces to detect very low levels of the immunosuppressant drug tacrolimus.

## Contribution

A novel surface modification technique using an aminodextran-lipase conjugate enables sensitive detection of tacrolimus.

## Key findings

- The ADLC modification allows for efficient conjugation of small molecules like tacrolimus.
- The biosensor achieved a detection limit of 0.02 ng/mL and a wide dynamic range.
- The method is fast, simple, and reproducible for point-of-care applications.

## Abstract

Cyclic olefin copolymers (COC; e.g., Zeonor, Topas, Arton,
etc.)
are materials with outstanding properties for developing point-of-care
systems; however, the lack of functional groups in their native form
makes their application challenging. This work evaluates different
strategies to functionalize commercially available Zeonor substrates,
including oxygen plasma treatment, photochemical grafting, and direct
surface amination using an amino dextran-lipase conjugate (ADLC).
The modified surfaces were characterized by contact angle measurements,
Fourier transform infrared-attenuated total reflection analysis, and
fluorescence assays based on evanescent wave excitation. The bioaffinity
activation through the ADLC approach results in a fast, simple, and
reproducible approach that can be used further to conjugate carboxylated
small molecules (e.g., haptens). The usefulness of this approach has
been demonstrated by the development of a heterogeneous fluorescence
immunoassay to detect tacrolimus (FK506) immunosuppressant drug using
an array biosensor platform based on evanescence wave laser excitation
and Zeonor-ADLC substrates. Surface modification with ADLC-bearing
FK506 provides a 3D layer that efficiently leads to a remarkably low
limit of detection (0.02 ng/mL) and IC50 (0.9 ng/mL) together with
a wide dynamic range (0.07–11.3 ng/mL).