Tomoya Taniguchi

A highly sensitive Amyloid-β detection by cantilever microsensor immobilized with liposome with incorporated cholesterol and phosphatidylcholine lipid with short hydrophobic acyl chains

We improved the sensitivity of NiCr strain gauge cantilever immobilized with liposome to detect Aβ protein with low concentration. In this work, by immobilizing liposome incorporated cholesterol on cantilever, we could detect 50-nM Aβ(1–40). Also, to investigate whether the hydrophobic carbon number of acyl chains of hydrophobic group influences Aβ-membrane interaction, DMPC, DPPC, and DSPC liposomes were immobilized, respectively, on the cantilever surface. The results show that DMPC-Aβ interaction is much larger than DPPC-Aβ and DSPC-Aβ interactions. We expect that the cantilever microsensor can apply to detect the Aβ(1–40) protein in patients of Alzheimers disease (AD) and also Mild Cognitive Impairment (MCI).

Differential Si ring resonators for label-free biosensing

Differential Si ring optical resonator sensors have been fabricated. Their detection sensitivity was 10−3–10−2% for sucrose solution, which corresponds to a sensitivity of ~1.0 ng/ml for prostate-specific antigen (PSA), which is satisfactory for practical use. In the differential sensing the input light is incident to two rings, and one of the outputs is connected to a π phase shifter then the two outputs are merged again. For the differential detection, not only is the common-mode noise canceled, resulting in high sensitivity, but also the temperature stability is much improved. A fluid channel is fabricated so that the detecting liquid flows to the detection ring and the reference liquid flows to the reference ring. We have proposed a method of obtaining a constant sensitivity for the integrated sensors even though the resonance wavelengths of the two rings of the differential sensor are slightly different. It was found that a region exists with a linear relationship between the differential output and the difference in the resonance wavelengths of the two rings. By intentionally differentiating the resonance wavelengths in this linear region, the sensors have a constant sensitivity. Many differential sensors with different ring spaces have been fabricated and the output scattering characteristics were statistically evaluated. As a result, a standard deviation of resonance wavelength σ = 8 × 10−3 nm was obtained for a ring space of 31 µm. From the width of the linear region and the standard deviation, it was estimated from the Gaussian distribution of the resonance wavelength that 93.8% of the devices have the same sensitivity.

Detection of Aβ(1-40) Protein in Human Serum as a Causative Agent of Alzheimer’s Disease by Strain Gauge Cantilever Biosensor Immobilizing Liposome Incorporating Cholesterol

We have successfully measured amyloid beta (Aβ) (1-40) protein added in human serum by a NiCr strain gauge cantilever biosensor immobilized with liposomes incorporating cholesterol. Importantly, we investigated the effect of incorporation of cholesterol in the liposome in order to suppress the interaction between the liposome and many different proteins included in human serum. It was revealed that incorporating cholesterol suppresses the interaction between the proteins other than Aβ in human serum and the liposome. Finally, we detected Aβ(1-40) in human serum with typical chronological behaviors due to Aβ aggregation and fibrillization. Furthermore, as a digital low-pass filtering procedure could reduce external noises, the cantilever sensor immobilized with liposome incorporating cholesterol can detect low-concentrated Aβ in human serum.

Slot ring biosensors using silicon nitride waveguides with small temperature coefficient

We propose the biosensor chip using optical ring resonators. Although the detection of biomarkers for the diagnosis of diseases generally requires high sensitivity of the order of 10-9 g/ml, the detection sensitivity of our device was of the order of 10-7 g/ml. In this paper, we show that 10 or 100 times higher sensitivity than the previous biosensor is accomplished by the following three strategies; (1) using slot-type waveguides, (2) using silicon nitride (SiN) as the waveguide core, (3) improvement of measurement system.