A visual logic alarm sensor for diabetic patients towards diabetic polyneuropathy based on a metal–organic framework functionalized by dual-cation exchange

Abstract

Considering that diabetic polyneuropathy (DPN) is a severe complication caused by vitamin B12 (VB12) deficiency in diabetic patients, in this work, a visual logic alarm sensor for diabetic patients towards DPN is creatively proposed to realize the prevention and early diagnosis of DPN. An anionic structure, {[NH₂(CH₃)₂]·[In(pdca)₂]}_n (In-MOF; H₂pdca = 2,5-pyridinedicarboxylic acid), is synthesized successfully by the direct solvothermal method. In-MOF features two-dimensional (2D) infinite layers containing triangular and hexagonal windows with dimethylamine counterions in supramolecular channels. Based on the ion-exchange strategy, the fluorescence of Tb³⁺ (λ_545 nm) and Ru(bpy)₃²⁺ (λ_585 nm) is simultaneously introduced into the In-MOF through dual-cation exchange for constructing a precise self-calibrating fluorescent sensor towards methylmalonic acid (MMA), a potential marker of VB12 deficiency in urine. Based on the different fluorescence behaviors of Tb³⁺ and Ru(bpy)₃²⁺ towards MMA, a molecular half-subtractor logic gate consisting of INHIBIT and XOR gates is designed. After performing binary subtraction operations, the calculation result (1,0) will trigger the alarm to warn diabetic patients of the probable deficiency of VB12 in their body and the output can be visualized by the naked eye intuitively. This work is the first attempt to functionalize an anionic MOF by dual-cation exchange, and it also proposes a new strategy for the early diagnosis and prevention of DPN based on a luminescent MOF and molecular logic gates.