THCH as electron donor in controlled-release system for procalcitonin analysis based on Bi2Sn2O7 photoanode

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Highlights

  • This split-type sensor separates the two processes of antigen-antibody specific recognition and photoelectric conversion.

  • THCH as extra electron donor is released through the controlled-release strategy.

  • CdS sensitized Bi2Sn2O7 forms a heterojunction as the matrix to provide basic PEC response effectively.

  • The biosensor for sensitive detection PCT exhibited the detection limit of 0.17 pg/mL.

Abstract

A split-type photoelectrochemical (PEC) sensor for procalcitonin (PCT) detection was successfully prepared. This split-type sensor adopted controlled-release strategy, which separated the two processes of antigen-antibody specific recognition and photoelectric conversion, so that the two processes can be performed independently. In addition, CdS sensitized Bi2Sn2O7 is combined for the first time to form a heterojunction as the matrix to provide the basic PEC response, which could effectively absorb visible-light, and reduced electron-hole pair recombination, ensured the stability of the sensor. Distinctly important, the skillfully process was performed in a 96-well plate where the specific reaction was completed proceeded between antigen and antibody. For improving sensitivity of the sensor, acetylcholinesterase (ACHE) connected to SiO2 nanospheres (SiO2 NSs) modified by second antibody (Ab2-ACHE@SiO2 NSs) was designed, the thiocholine (THCH) can be released when acetylthiocholine iodide (ATCH) exists, and the THCH as an electron donor could enhance PEC response. The proposed PEC immunoassay with high-performance photosensitive materials, and the smart electron donor released strategy have a wide detection liner range from 0.0005 to 100 ng/mL with a low detection limit of 0.17 pg/mL, also provide great clinical diagnostic potential for other target proteins.

Introduction

In the world, a large proportion of patients occupying a mass of medical resources are suffering from sepsis [[1], [2], [3]]. Sepsis is a disease caused by bacterial or fungi, and the incidence of sepsis has increased year by year since the 21st century [4]. Sepsis is mainly divided into three stages according to the degree of inflammation: sepsis, severe sepsis, septic shock. Patients with early sepsis have mild symptoms, and early treatment with antibiotics can be used to achieve effective cure, but if no measures are taken, septic shock can be achieved in just a few hours. At this stage, the patient will have severe shock, and the mortality rate is as high as 70 % [5]. Therefore, if sepsis can be detected early and treated promptly, the mortality of sepsis will be greatly reduced. Procalcitonin (PCT) is the more accurate biomarker for the diagnosis of sepsis so far, and can effectively distinguish between sepsis and other types of infections [4]. Thus, if the concentration of PCT in the body is detected quickly and accurately, the development stage of sepsis can be ascertained, which can help the patient to be treated accurately in time. Also antibiotic was used in moderation to reduce the waste of intensive care unit resources, moreover, prevented from abusing to increase its resistance [6,7].

As a yet, many methods have been developed for the detection of PCT, such as electrochemiluminescence immunoassay [8], chemiluminescence immunoassay [9], fluorescence assay [10] and radioimmunoassay [11]. However, the development of these methods do not go with a swing. Therefore, novel and accurate method for PCT detection is urgently needed. Photoelectrochemical (PEC) immunosensor is an extremely rapid detection technique in recent years due to its special high-efficiency photoelectric conversion units [12], in which it converts into an electric signal by absorbing light signal, the unique signal conversion mode prompts the low background signal for high sensitivity [13,14]. In view of this, a split-type PEC sensor is studied with high sensitivity, great accurate, and satisfactory stability for PCT detection by controlled-release method.

In this work, a novel PEC sensor based on a unique Bi2Sn2O7/CdS nanocomposite photoactive conversion unit, and controlled-release strategy of signal amplification was prepared. These two parts are completely separated [15] via 96-well plate, thus, the amplification and stability of the photocurrent signal were achieved successfully. And the selection of photoactive materials Bi2Sn2O7/CdS was proposed for the first time. Recently, bismuth-based metallic salt materials are particularly prominent in inorganic photoelectric materials due to their first-rate photoelectric properties and good absorption in visible light range, such as Bi2O3 [16], BiVO4 [17], BiYWO6 [18], Bi2WO6 [19]. In the process of studying these materials, Bi2Sn2O7 was found to be extremely impressive, however, only a single inorganic material cannot meet the needs of sensitivity and stability of photoelectric immunosensor materials, therefore, the combination of CdS (photo sensitizer, ∼2.4 eV) matching the band gap of Bi2Sn2O7 (∼2.76 eV) is introduced to form heterojunction [20]. Based on this, Bi2Sn2O7 and CdS are combined to form a heterojunction that will make both stimulated by a photon to form stronger built-in electric field, which promotes the formation and separation of the carrier, as well as prevents the recombination of electron-hole, thus, the signal intensity and stability were increased [21]. Secondly, we innovated a specific reaction carried out in an individual 96-well plate, second antibody (Ab2) was connected to functional carrier SiO2 nanosphere (SiO2 NSs), and with a specific surface for specific recognition of target PCT (Ag), also acetylcholinesterase (ACHE) is used decorated with SiO2 NSs, which is used to catalyze form thiocholine (THCH) [22] after adding its substrate acetylthiocholine iodide (ATCH). The solution containing THCH generated in the microplate is transferred to the detection electrolyte solution, which could act as electron donor [23] for the photo-generated holes of the photoactive materials [24,25], thereby it greatly limited the recombination of the electron-hole pairs, and improved photocurrent [26]. The PEC immunosensor we proposed owns a great photocurrent response due to the dual signal amplification strategy, good stability, and extremely high sensitivity. Based on the above advantages, the sandwich PEC immunoassay can accurate monitor PCT, and has potential development space in clinical medicine.

Section snippets

Synthesis of Bi2Sn2O7

Bi2Sn2O7 was prepared according to the previous report with some changings [27]. To begin, 0.90 g of SnCl4·5H2O was dispersed in 20 mL ultrapure water with stirring for 15 min under room temperature. Subsequently, the pH of the above solution was transformed to 6 by alkaline solution (NaOH, 4 M). After centrifugation, the obtained precipitate and 1.94 g of Bi(NO3)3·5H2O were co-dispersed into 40 mL ultrapure water under vigorously stirring. The pH of the resulting suspension was transformed

Characterization of synthesized materials

The lattice structure of the basic Bi2Sn2O7 material was characterized by XRD patterns (Fig. 1A), which proved that the crystal structures of Bi2Sn2O7 was more successful and contains no other impurities. In addition, XPS image (Fig. 1B) also proved the purity of this material, further verifying the successful synthesis of Bi2Sn2O7. Fig. S2 showed the XPS peaks of Bi and Sn elements, the particular XPS peaks of 1021.3 eV and 1044.25 eV in Fig. S2A fit well with Bi 2p, proving the +3 valence

Conclusion

A split-type immunosensor based on electron donor controlled-release strategy was successfully prepared. The significant advantage of this split-type sensor was that it separated the two processes of immunoreaction and PEC measurement, eliminating the interfering with each other. The outstanding electrode used for signal testing was modified with inorganic material heterojunction, and the THCH as electron donors were completely controlled released in 96-well plate, owing a very low detection

CRediT authorship contribution statement

Dongquan Leng: Conceptualization, Data curation, Writing - original draft. Jingshuai Li: Methodology, Data curation. Rui Xu: Methodology, Data curation. Lei Liu: Methodology, Writing - review & editing. Xuejing Liu: Methodology, Writing - review & editing. Dawei Fan: Writing - review & editing. Huan Wang: Formal analysis, Project administration. Qin Wei: Supervision, Funding acquisition, Formal analysis. Huangxian Ju: Formal analysis.

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.

Acknowledgements

We gratefully acknowledge the financial support of the National Key Scientific Instrument and Equipment Development Project of China (No. 21627809), National Natural Science Foundation of China (No. 21777056), Special Foundation for Taishan Scholar Professorship of Shandong Province, Jinan Scientific Research Leader Workshop Project (2018GXRC024, 2018GXRC021), the Innovation Team Project of Colleges and Universities in Jinan (No. 2019GXRC027). All of the authors express their sincere thanks.

Dongquan Leng is a master student in school of chemistry and chemical engineering, University of Jinan. His current researchers are photoelectrochemical sensor and nanomaterials.

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Dongquan Leng is a master student in school of chemistry and chemical engineering, University of Jinan. His current researchers are photoelectrochemical sensor and nanomaterials.

Jingshuai Li is a doctor student in school of chemistry and chemical engineering, University of Jinan. His current researchers are electrochemical sensor and nanomaterials.

Rui Xu is a doctor student in school of chemistry and chemical engineering, University of Jinan. Her current researchers are photoelectrochemical sensor and nanomaterials.

Lei Liu received the Ph.D. degree from China University of Geosciences (Beijing), Beijing, China. She is a post-doctoral of school of chemistry and chemical engineering at University of Jinan, Shandong, China. Her research interests focus on the construction of nanomaterials for fuel cell and biosensors with diseases, energy and environment applications.

Xuejing Liu received her Ph.D. degree in College of Chemistry from Dalian University of Technology in 2015. From 2015–2018, she worked as a postdoctoral fellow in Dalian Institute of Chemical Physics. At present, she begins to work in School of Chemistry and Chemical Engineering from University of Jinan. Her main interest is in the theoretical investigation of catalyst materials for applications in small molecules activation and conversion, electrocatalytic of water splitting, reduction of CO2 and N2, etc.

Dawei Fan received her Ph. D degree from Lanzhou institute of chemical physics, Chinese academy of sciences. Now, she is an associate professor at University of Jinan. Her main research interests are electrochemical sensors and photoelectrochemical sensors. She has published over 50 articles on analysis, immunosensor and applied successfully for many research projects, such as Angewandte Chemie International Edition, Biosensors & Bioelectronics, Journal of Physical Chemistry C, and ACS Applied Materials & Interfaces.

Huan Wang received Ph.D. degree from China university of Geosciences (Beijing). Now, he is an associate professor at University of Jinan. His main research interests are the determination of electrochemical immunosensor.

Qin Wei, a professor and DSc, has devoted herself to analytical teaching and scientific research. Her main research interests are the determination of protein and nucleic acid by photometry and the electrochemical immunosensor preparation. She has published over one hundred articles on analysis, immunosensor and applied successfully for many research projects, such as Biomaterials, Adv. Funct. Mater., Biosens. Bioelectron., Sens. Actuators B: Chem., Talanta.

Huangxian Ju received his BS, MS and Ph.D. degrees from Nanjing University during 1982–1992. He was a postdoc in Montreal University (Canada) from 1996 to 1997 and a guest professor in three universities of Germany and Ireland in 1999−2000. He became an associate and full professor of Nanjing University in 1993 and 1999. He is currently the director of State Key Laboratory of Analytical Chemistry for Life Science. His research interests focus on analytical biochemistry, biosensing and molecular diagnosis. He has published 616 papers in different journals with SCI h-index of 83 (29,523 citations) and Google Scholar h-index of 91 with more than 29,000 citations.

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