Microfluidic Biosensor Based on Molybdenum Disulfide (MoS2) Modified Thin-Core Microfiber for Immune Detection of Toxoplasma gondii

Abstract

Toxoplasma gondii (T. gondii) is a zoonotic parasite that is widely distributed and seriously endangers public health and human health. Therefore, accurate and effective detection of T. gondii is crucial. This study proposes a microfluidic biosensor using a thin-core microfiber (TCMF) coated with molybdenum disulfide (MoS₂) for immune detection of T. gondii. The single-mode fiber was fused with the thin-core fiber, and the TCMF was obtained by arc discharging and flame heating. In order to avoid interference and protect the sensing structure, the TCMF was encapsulated in the microfluidic chip. MoS₂ and T. gondii antigen were modified on the surface of TCMF for the immune detection of T. gondii. Experimental results showed that the detection range of the proposed biosensor for T. gondii monoclonal antibody solutions was 1 pg/mL to 10 ng/mL with sensitivity of 3.358 nm/log(mg/mL); the detection of limit was calculated to be 87 fg/mL through the Langmuir model; the dissociation constant and the affinity constant were calculated to be about 5.79 × 10^-13 M and 1.727 × 10¹⁴ M^-1, respectively. The specificity and clinical characteristics of the biosensor was explored. The rabies virus, pseudorabies virus, and T. gondii serum were used to confirm the excellent specificity and clinical characteristics of the biosensor, indicating that the proposed biosensor has great application potential in the biomedical field.

Keywords: microfluidic chip; molybdenum disulfide; optical fiber biosensor; thin-core microfiber; toxoplasma gondii.

Figure 1

Schematic diagram of the TCMF sensor.

Figure 2

(a–c) Fabrication processes of the TCMF. (d) Micrograph of the TCMF.

Figure 3

Transmission spectrum in air of the TCMF.

Figure 4

Structure design diagram of microfluidic chip.

Figure 5

Schematic of modification process over TCMF structure.

Figure 6

Experimental setup for immune sensing of TCMF biosensor.

Figure 7

FESEM images of (a) bare TCMF sensor (b) TCMF sensor after hydroxylation (c) TCMF sensor after silanization (d) TCMF sensor coated with MoS₂.

Figure 8

EDS image of MoS₂ immobilized sensor structure.

Figure 9

(a) Spectral response and (b) the corresponding wavelength shift of surface modification for TCMF biosensor placed in PBS solution.

Figure 10

(a) Spectral response of the TCMF sensor. (b) Relationship between wavelength shift and ambient RI.

Figure 11

(a) Spectral evolution of the sensor to concentration of T. gondii MAb solutions, and (b) the corresponding wavelength shift with time.

Figure 12

(a) Langmuir curve fitting of wavelength shift and T. gondii MAb concentration. (b) Relationship between wavelength shift and logarithmic concentration of T. gondii MAb.

Figure 13

(a) Reproductivity, and (b) stability of the biosensor.

Figure 14

Specificity and clinical tests of the TCMF biosensor for (a) spectral response and (b) wavelength shift.