Metal-Organic Framework-Based Biosensors for Enzyme-Linked Assays

Abstract

This study investigates the use of europium and terbium-based metal-organic frameworks (MOFs) as biosensors for monitoring DNA amplification in LAMP processes, with a specific focus on detecting phosphate compounds like deoxynucleotide triphosphates (dNTPs) and pyrophosphate (PPi). The findings demonstrate that Eu(BTC) and TbEu(BTC) MOFs can effectively differentiate between dNTPs and PPi in an isothermal amplification buffer (Tris buffer, pH = 8.8), due to their rigid crystalline structures that ensure stable fluorescence. TbEu(BTC) is particularly advantageous as it allows self-calibration, minimising errors associated with suspension concentration when distributed in plate wells. Since dNTPs and PPi are converted during DNA amplification, these sensors are suitable for evaluating optimal LAMP conditions, including the concentrations of P. malariae DNA templates, magnesium, and BST 2.0 polymerase. The study also aims to enhance the practicality and environmental compatibility of these phosphate sensors through aqueous synthesis and hydrogel encapsulation of the MOFs. In-situ encapsulation with agarose gel improved sensitivity to dNTPs, and optimising synthesis conditions further enhanced the sensor's performance. The addition of PVP coating increased resistance to DNA strand interference.The sensitivity of the sensor can be maintained over a period of three weeks. These findings suggest further exploration of alternative materials to improve performance and cost efficiency. Furthermore, glucose sensing and real-time monitoring were achieved by incorporating glucose oxidase (GOx) into PCN222(Fe), a highly stable iron-modified MOF that acts as a hydrogen peroxidase mimic. The PCN222(Fe)@GOx complex was identified as a promising candidate for glucose detection due to its optimised pore size and catalytic activity, capable of detecting glucose at concentrations as low as 10 μM. The development of the alginate hydrogel-encapsulated PCN222(Fe)@GOx facilitates continuous monitoring with reliable activity and a rapid response time, making it well-suited for applications in cell cultivation and bio-agriculture. Overall, this research highlights the potential of lanthanide MOFs and PCN222(Fe)@GOx in biosensing applications and identifies future directions for improvement and practical use.