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

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.

Microfluidic immunosensor based on a graphene oxide functionalized double helix microfiber coupler for anti-Müllerian hormone detection.

A label-free microfluidic immunosensor based on the double helix microfiber coupler (DHMC) coated with graphene oxide (GO) was proposed for the specific detection of anti-Müllerian hormone (AMH). Two single-mode optical fibers were twisted in a parallel direction, the coning machine was used to fuse and taper them, and the high-sensitivity DHMC was obtained. To make a stable sensing environment, it was immobilized in a microfluidic chip. And then, the DHMC was modified by GO and bio-functionalized by the AMH monoclonal antibodies (anti-AMH MAbs) for the specific detection of AMH. The experimental results showed that the detection range of the immunosensor for AMH antigen solutions was 200 fg/mL∼50 µg/mL, the detection of limit (LOD) was ∼235.15 fg/mL, and the detection sensitivity and the dissociation coefficient were ∼3.518 nm/(log(mg/mL)) and ∼1.85 × 10 - 12 M, respectively. The alpha fetoprotein (AFP), des-carboxy prothrombin (DCP), growth stimulation expressed gene 2 (ST2) and AMH serum were used to confirm the excellent specific and clinical properties of the immunosensor, showing that the proposed immunosensor was easy-made and can be potentially applied in the biosensing field.

Optical Vernier sensor based on a cascaded tapered thin-core microfiber for highly sensitive refractive index sensing.

This study proposes a refractive index (RI) sensor using a cascaded tapered thin-core microfiber (TTCMF) based on the Vernier effect. The thin-core fiber was made into a TTCMF by arc discharging and flame heating and then sandwiched between two single-mode fibers (SMFs). The two structures with the same SMF-TTCMF-SMF but slightly different free spectral ranges (FSRs) were cascaded to generate the Vernier effect. The FSR varied with the taper parameters of TTCMF. The RI sensitivities of a single TTCMF sensor, series SMF-TTCMF-SMF sensor, and parallel SMF-TTCMF-SMF sensor were compared and analyzed. Using the Vernier effect in the RI measurement range from 1.3313 to 1.3392, a very high RI sensitivity of -15,053.411n m/R I U was obtained using the series SMF-TTCMF-SMF structure, and -16,723.243n m/R I U using the parallel structure, which were basically consistent with the simulation results. Compared with the RI sensitivity of the single TTCMF sensor, the RI sensitivities of series and parallel sensors were increased by 4.65 times and 5.16 times, respectively. In addition, in the temperature range from 35°C to 65°C, temperature sensitivities of -0.196n m/ ∘ C and -0.0489n m/ ∘ C were obtained using series and parallel structures, respectively; the corresponding temperature cross errors were 1.302×10-5 R I U/ ∘ C and 2.92×10-6 R I U/ ∘ C, respectively. Based on the advantages of high RI sensitivity, simple structure, low-temperature cross sensitivity, and convenient fabrication, the proposed sensors have great potential in biosensing fields.

CTT1 overexpression increases the replicative lifespan of MMS-sensitive Saccharomyces cerevisiae deficient in KSP1.

Ksplp is a nuclear-localized Ser/Thr kinase that is not essential for the vegetative growth of yeast. A global gene function analysis in yeast suggested that Ksplp was involved in the oxidative stress response; however, the underlying mechanism remains unclear. Here, we showed that KSP1-deficient yeast cells exhibit hypersensitivity to the DNA alkylating agent methyl methanesulphonate (MMS), and treatment of the KSP1-deficient strain with MMS could trigger abnormal mitochondrial membrane potential and up-regulate reactive oxygen species (ROS) production. In addition, the mRNA expression level of the catalase gene CTT1 (which encodes cytosolic catalase) and total catalase activity were strongly down-regulated in the KSP1-deleted strain compared with those in wild-type cells. Moreover, the KSP1 deficiency also leads to a shortened replicative lifespan, which could be restored by the increased expression of CTT1. On the other hand, KSP1-overexpressed (KSP1OX) yeast cells exhibited increased resistance towards MMS, an effect that was, at least in part, CTT1 independent. Collectively, these findings highlight the involvement of Ksplp in the DNA damage response and implicate Ksplp as a modulator of the replicative lifespan.