Serum Albumin Inspired Self-Assembly/Disassembly of a Fluorogenic Nanoprobe for Real-Time Monitoring and Quantification of Urinary Albumin with Live Cell Imaging Application

Abstract

Abnormal levels (high/low) of urinary human serum albumin (HSA) are associated with a number of diseases and thus act as an essential biomarker for quick therapeutic monitoring and biomedical diagnosis, entailing the urgent development of an effective chemosensor to quantify the albumin levels. Herein, we have rationally designed and developed a small fluorogenic molecular probe, (Z)-2-(5-((8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9-yl) methylene)-4-oxo-2-thioxothiazolidin-3-yl) acetic acid (HJRA) with a twisted intramolecular charge transfer (TICT) property, which can easily self-assemble into nonfluorescent nanoaggregates in aqueous solution. However, HJRA nanoaggregates can selectively bind with serum albumin proteins (HSA/BSA) in ∼100% PBS medium, thereby facilitating the disassembly of nanoaggregates into monomers, exhibiting a clear turn-on red fluorescent response toward HSA and BSA. Analysis of the specific binding mechanism between HJRA and HSA using a site-selective fluorescence displacement assay and molecular docking simulations indicates that a variety of noncovalent interactions are responsible for the disassembly of nanoaggregates with the concomitant trapping of the HJRA monomer at site I in HSA, yielding a substantial red emission caused by the inhibition of intramolecular rotation of HJRA probe inside the hydrophobic cavity of HSA. The limit of detection (LOD) determined by the 3σ/slope method was found to be 1.13 nM, which is substantially below the normal HSA concentration level in healthy urine, signifying the very high sensitivity of the probe toward HSA. The comparable results and quick response toward quantification of HSA in urine by HJRA with respect to the Bradford method clearly point toward the superiority of this method compared to the existing ones and may lead to biomedical applications for HSA quantification in urine. It may also find potential application in live-cell imaging of HSA.

BODIPY(aryl)iodonium salts in the efficient synthesis of diversely functionalized BODIPYs and selective detection of serum albumin

“…which can lead to cardiovascular and renal damage. 66,67 The LOD values obtained for the four BODIPY derivatives show their efficacy as good serum protein indicators.…”

A self-assembled nanoprobe based on Schiff base for the rapid and selective detection of serum albumin with cell imaging applications

“…From this fluorescence titration study, we have calculated the dissociation constant ( K d ) between DBNHC and BSA by utilising the following equation: 40 …”

“…36,37 Recently, it has been shown that self-assembly based nanoprobes have displayed some distinct advantages for protein sensing because of their high photostability, biocompatibility, flexibility in chemical design and fine-tuning of optical properties. [38][39][40] For instance, a selfassembled probe exhibits no or very weak fluorescence due to the aggregation caused quenching (ACQ) effect, but when the probe responds to the target analytes by undergoing disassembly, it will emit strong fluorescence. 41 However, a very few number of fluorescent probes have been reported for detection of proteins in virtue of different strategies including polymer nanoparticles 38,42 or affinity ligand-based aggregate disassembly 40,[43][44][45] and metal nanoparticle displacement.…”

“…[38][39][40] For instance, a selfassembled probe exhibits no or very weak fluorescence due to the aggregation caused quenching (ACQ) effect, but when the probe responds to the target analytes by undergoing disassembly, it will emit strong fluorescence. 41 However, a very few number of fluorescent probes have been reported for detection of proteins in virtue of different strategies including polymer nanoparticles 38,42 or affinity ligand-based aggregate disassembly 40,[43][44][45] and metal nanoparticle displacement. 46,47 Thus, keeping these things in mind, we have devoted our attention towards the synthesis of probe ((E)-2-(2,4-dihydroxybenzylidene)-N-(naphthalen-1-yl)hydrazine-1-carbothio-amide) (hereafter designated as DBNHC) that can easily self-assemble into nonfluorescent nanoaggregates in aqueous solution which can selectively bind with bovine serum albumin (BSA), facilitating the disassembly of nanoaggregates into monomers, exhibiting an observable turn-on cyan green fluorescent response towards BSA in biological environments.…”

“…38–40 For instance, a self-assembled probe exhibits no or very weak fluorescence due to the aggregation caused quenching (ACQ) effect, but when the probe responds to the target analytes by undergoing disassembly, it will emit strong fluorescence. 41 However, a very few number of fluorescent probes have been reported for detection of proteins in virtue of different strategies including polymer nanoparticles 38,42 or affinity ligand-based aggregate disassembly 40,43–45 and metal nanoparticle displacement. 46,47…”