Introduction

Reconfiguration of chemical sensors, meaning the capacity to adapt the sensor to new target analytes, is potentially game changing and would enable rapid and cost-effective reactions to dynamic changes occurring at different levels, although this is still a challenge. Here, we report on a reconfigurable label-free optical sensor leveraging versatile immobilization of a metal ion chelating agent on a nanostructured porous silica (PSiO₂) optical transducer for the detection of different biomolecules.

Method

PSiO₂ scaffolds were functionalized with a modified silane, GLYMO-IDA, preliminarily derived from a condensation reaction between 3-glycidoxypropyltrimethoxysilane (GLYMO) and iminodiacetic acid (IDA). When exposed to aqueous solutions of metal ions (e.g., Zn²⁺, Ni²⁺, Cu²⁺, Fe³⁺), GLYMO-IDA exhibits the ability to chelate them. The as-modified silane was employed as a receptor for biomolecules, leveraging the metal ions as pivotal points. The metal ion on GLYMO-IDA was easily switched by treating the PSiO₂ samples with a complexing agent.

Results

Successful functionalization of PSiO₂ scaffolds with the artificial receptors for various biomolecules was corroborated via UV-VIS spectroscopy and XPS analysis. After switching the metal ions from Cu²⁺ to Zn²⁺, the sensor was used in carnosine detection tests, proving its ability, in both configurations, to detect the target in a concentration range between 0.1 and 1 mM. Alternatively, by switching Cu²⁺ with Fe³⁺ ions, the sensor was successfully used for adenosine triphosphate (ATP) detection. A satisfactory sample-to-sample reproducibility was obtained (RSD: ~15%), along with an excellent repeatability (RSD: 2.5%) and stability (30 days).

Conclusions

A reconfigurable sensing platform was developed, and sensor reconfiguration was achieved by switching the metal ions from Cu²⁺ to Zn²⁺ and testing its ability to detect the dipeptide carnosine. Additionally, by switching Cu²⁺ with Fe³⁺ ions, the sensor was able to detect the target ATP, demonstrating effective reconfiguration of the sensor with the proposed surface chemistry.