# Preparation of Nanoparticle-Immobilized Gold Surfaces for the Reversible Conjugation of Neurotensin Peptide

## TL;DR

This paper describes a method to create gold surfaces with nanoparticles for reversible attachment of a neurotensin peptide, enabling reusable biosensor platforms.

## Contribution

A novel approach using PEG-based nanoparticles for reversible peptide conjugation on gold surfaces is introduced.

## Key findings

- PEG6K-diMA-based nanoparticles formed a smooth, monolayer coating of 80–120 nm on gold surfaces.
- Disulfide bonds enabled reversible conjugation of the neurotensin peptide, with surface restoration after DTT treatment.
- The modified gold surface showed potential for reusability in detecting biomarkers via binding to NTSR2 antibodies.

## Abstract

Polymer coatings as thin films stand out as a commonly used strategy to modify biosensor surfaces for improving detection performance; however, nonspecific biomolecule interactions and the limited degree of ligand conjugation on the surface have necessitated the development of innovative methods for surface modification. To this end, methacrylated tethered telechelic polyethylene glycol (PEG-diMA) chains of three different molecular weights (2, 6, and 10 kDa) were synthesized herein and used for obtaining thiolated nanoparticles (NPs) upon adding excess amounts of a tetra-thiol crosslinker. Characterized according to their size, surface charge, morphology, and thiol amounts, these nanoparticles were immobilized on gold surfaces that mimicked gold-coated mass sensor platforms. The PEG-based nanoparticles, prepared especially by PEG6K-diMA polymers, were shown to result in the preparation of a monolayer and smooth coating of 80–120 nm thickness. Cysteine-modified NTS(8–13) peptide (RRPYIL) was conjugated to thiolated NP with reversible disulfide bonds and it was demonstrated that its cleavage with a reducing agent such as dithiothreitol (DTT) restores the NP-immobilized gold surface for at least two cycles. Together with its binding studies to NTSR2 antibodies, it was revealed that the peptide-conjugated NP-modified gold surface could be employed as a model for a reusable sensor surface for the detection of biomarkers of same or different types.