Construction of efficient “on-off-on” fluorescence aptasensor for ultrasensitive detection of prostate specific antigen via covalent energy transfer between g-C3N4 quantum dots and palladium triangular plates

doi:10.1016/j.aca.2020.01.009

Analytica Chimica Acta

Volume 1104, 1 April 2020, Pages 53-59

https://doi.org/10.1016/j.aca.2020.01.009 Get rights and content

Highlights

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Pd TPs were synthesized under solvothermal conditions and acted as effective fluorescent quencher.
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The Pd TPs-PA behaved as signal reporter for constructing a FL aptasensor.
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The aptasensor was applied for PSA detection with low detection limit and high specificity.

Abstract

Development of ultra-sensitive and high specific aptasensors is important for early diagnosis of prostate cancer. Herein, ultrasensitive detection of prostate specific antigen (PSA) aptasensor was realized based on the “on-off-on” model via fluorescence (FL) covalent energy transfer between g-C₃N₄ quantum dot (g-CNQDs) and palladium triangular plates (Pd TPs). Specifically, the Pd TPs were primarily linked with PSA aptamer (PA) as the reporter probe, followed by attaching them onto the g-CNQDs surfaces, causing the highly enlarged FL quenching rate (ca. 75%). After the introduction of PSA, the FL intensities recovered again because of the distinctively stronger affinity of PA to PSA than that of g-CNQDs. The bond of pyridine N with Pd was identified as efficient energy transfer pathway through the X-ray photoelectron spectroscopy (XPS) and FL measurements. The surface plasmon resonance (SPR) experiments certified the remarkably different affinity of PA towards g-CNQDs and PSA. The as-constructed FL aptasensor can accurately quantify PSA with wide linear range of 10 pg mL⁻¹-50 ng mL⁻¹ and ultra-low limit of detection (LOD, 4.2 pg mL⁻¹), indicating the promising applications in clinical assay and biological detection.

Graphical abstract

Introduction

Fluorescent technique has received increasing interest in environmental and biological analysis, due to its operational simplicity, high sensitivity and real-time detection [[1], [2], [3]]. Fluorescence (FL) covalent energy transfer is recognized as a reliable and sensitive analytical assay, which can effectively transmit photoexcitation energy from a donor fluorophore to an acceptor [[4], [5], [6]].

Traditional FL donors mainly refer to organic dyes, whose applications are seriously limited by low signal/background ratio, high cost and photobleaching effect [[7], [8], [9]]. Therefore, it is imperative to explore advanced fluorophores with low-cost and high sensitivity. Compared to conventional fluorophore, graphitic carbon nitride quantum dots (g-CNQDs) can act as effective FL donors to construct biosensing platforms for biomolecules detection, thanks to their superior optical and electrical properties [10,11] such as high absorptivity, improved brightness and photostability [[12], [13], [14]].

The sensitivity of g-CNQDs-based biosensors greatly depends on the fluorescence quenching ability of energy acceptors [15]. More importantly, carbon nanomaterials (e.g. graphene) are commonly used as FL quencher for their high FL quenching ability [16,17]. Nevertheless, their non-specific adsorption severely restricts their commercial applications in practice [7].

Recently, many researchers focus on Au or Ag nanoparticles (NPs) [[18], [19], [20]], but the different distances between the quencher and the phosphor inevitably cause unstable quenching effects [21]. As one of noble metal materials, Pd NPs are considered as an ideal quencher because of their extremely high extinction coefficient and broad energy bandwidth [22,23]. The smaller Pd NPs displayed broad optical absorption range and active surface states [7]. Besides, two-dimensional Pd nanoplates had dramatically enlarged specific surface area relative to bulk Pd crystals, which provided enriched sites for post bio-modification, confirming them as the rational electron and energy receptor in photoluminescence progress [24].

Prostate cancer is a kind of malignancy occurred in the prostate gland, which is the common cancer with morbidity ranked the second out of various cancers among men in the world [[25], [26], [27]]. In early diagnosis of prostate cancer, prostate specific antigen (PSA) is the most important biomarker indicator, and thereby its specific, sensitive and quantitative detection are of very significance [[28], [29], [30]].

Herein, Pd triangular plates (Pd TPs) were firstly prepared under hydrothermal conditions, which were sequentially modified with PSA aptamer (PA), accompanied by quenching the FL of g-CNQDs via the coordination bond between Pd TPs and the pyridine N of g-CNQDs. Then, the FL recovered again in the presence of PSA by weakening the linkage between PA and g-CNQDs to release Pd TPs from the g-CNQDs. Finally, the as-constructed aptasensor was explored for detection of PSA in serum samples.

Section snippets

Preparation of g-CNQDs and Pd TPs

The g-CNQDs were synthesized by thermal polymerization of melamine based on the previous work with minor modification [31]. Briefly, g-C₃N₄ powder was obtained by heating melamine in a tube furnace, and then the powder (30 mg) was dispersed into the mixture of 30 mL of ethanol and 3 ml of 0.5 M KOH, followed by heating at 180 °C for 16 h in Teflon-lined stainless-steel autoclave. The resulting suspension was filtered by using a mixed cellulose ester membrane with 0.22 μm pores and dialyzed to

Characterization of g-CNQDs and Pd TPs

The structural and surface features of the typical samples were critically investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) [[32], [33], [34]]. As illustrated in Fig. 1A, plenty of tiny nanoparticles with uniform sizes are dispersed well across the total cross-section. The high-resolution TEM (HRTEM) image (Fig. 1B) reveals the high crystalline structures with a lattice spacing distance of 0.21 nm. This value agrees well with that of g-C₃N₄ in

Conclusions

In summary, a novel FL aptasensor for ultrasensitive and selective detection of PSA was developed based on the covalent energy transfer between the g-CNQDs and Pd TPs. For this protocol, well-defined Pd TPs were initially prepared under hydrothermal conditions and the g-CNQDs severed as the FL emitter. The FL and XPS measurements synchronously demonstrated the covalent bond between the pyridine N of g-CNQDs and Pd TPs, which was the effective energy transfer pathway, harvesting a 75% quenching

CRediT authorship contribution statement

Hui-Min Wang: Data curation, Investigation, Writing - original draft. Xiao-Qin Huang: Data curation. Ai-Jun Wang: Data curation. Xiliang Luo: Investigation. Wei-Dong Liu: Investigation. Pei-Xin Yuan: Writing - review & editing. Jiu-Ju Feng: Funding acquisition, Supervision, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This research was supported by Natural Science Foundation of Zhejiang Province (No. Q19B050016 and LY18B050003) and Basic Public Welfare Research Project of Zhejiang Province (No. LGG18E010001 and LGG19B050001).

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Construction of efficient “on-off-on” fluorescence aptasensor for ultrasensitive detection of prostate specific antigen via covalent energy transfer between g-C3N4 quantum dots and palladium triangular plates

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Preparation of g-CNQDs and Pd TPs

Characterization of g-CNQDs and Pd TPs

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgment

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Construction of efficient “on-off-on” fluorescence aptasensor for ultrasensitive detection of prostate specific antigen via covalent energy transfer between g-C₃N₄ quantum dots and palladium triangular plates