A nanofiber-based biosensor for ultrasensitive detection of serum CRP in melanoma

Purpose: Early detection of melanoma is important to improve survival; however, the technology for accurate early diagnosis is still challenging. This study is to develop a novel polymeric biosensor that could provide superior sensitivity in the detection of potential early biomarkers (e.g., CRP) of melanoma. Experimental Procedure: Our strategy is to construct a highly specific molecular recognition core and a highly responsive transducer made of conductive polypyrrole (PPy) nanofibers. Briefly, a polymeric matrix was produced by polymerization of acrylamide (AM), methylenebisacrylamide (MBAA), N-Isopropylacrylamide (NIPAAm) and CRP/CRP-aptamer complex first. Next, taking advantage of the porous structure of this NIPAAm-AM-CRP-aptamer/CRP polymeric matrix, we synthesized a polypyrrole-based conductive nanofiber structure using copper phthalocyanine-3,49,499,4‴-tetrasulfonic acid tetrasodium salt (CuPT) as a dopant counterion in situ to achieve uniformly dispersed nanofibers within the polymeric network of NIPAAm-AM-CRP-aptamer/CRP. After removing CRP recombinant protein, we were able to obtain a robust CuPT-PPy/NIPAAm-AM polymeric sensor for the detection of CRP with high sensitivity and selectivity. Two-step signal amplification cascades were involved in this CRP-specific polymeric sensor: 1) CRP binding-induced polymeric network shrinkage; 2) shrinkage-triggered conductance change of the polymeric network. Therefore, serum CRP levels could be quantitatively analyzed through monitoring the conductance change caused by polymeric network shrinkage upon aptamer-CRP binding. Results: The limit of detection (LOD) of the polymeric sensor for detection of human recombinant CRP could reach 10^−19 M. The Fourier transform infrared (FT-IR) spectra confirmed the chemical structure of the polymeric network, and the morphology was observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results of FT-IR reveal that CuPT-PPy nanofiber was successfully synthesized in situ. The nanostructure of the nanofibers was clearly observed using SEM and AFM, indicating that the diameter of nanofiber is about 20 nm. This CRP-specific biosensor and a commercial CRP ELISA kit were used to perform side-by-side measurement of serum CRP in melanoma patients. Conclusion: Our results indicated that this CRP-specific conductive polymeric senor is highly sensitive and selective in accurately discriminating melanoma patients from healthy controls. Such a flexible conductive polymeric biosensor may hold great promise as a point-of-care device in the diagnostics of melanoma or other cancers. Citation Format: Zuan-Tao Lin, Yaxi Li, Tianfu Wu. A nanofiber-based biosensor for ultrasensitive detection of serum CRP in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3869.