Po-Yen Hsu

Polysilicon wire glucose sensor highly immune to interference

This study investigated the interference elimination ability of a glucose sensor made of polysilicon wire (PSW) with a surface modified by 3-aminopropyltriethoxysilane mixed with polydimethylsiloxane-treated hydrophobic fumed silica nanoparticles plus ultra-violet illumination (γ-APTES+NPs+UV). Glucose sensing of the PSW sensor in the presence of five common interferences such as ascorbic acid (AA), uric acid (UA), acetaminophen (AP), L-cysteine (Lys), and citric acid (CA) was performed. We found that the disturbance caused by the interferences was low for interference-to-glucose concentration ratios up to 600:1 if the PSW surface is modified with γ-APTES+NPs+UV. The outstanding interference immunity of this PSW glucose sensor is believed to be mainly due to the fact that it is a dry-type sensor and the extremely low leakage of the γ-APTES+NPs membrane which allows the PSW to show three orders of magnitude lower leakage current than with the γ-APTES membrane only. In addition to its excellent interference immunity, the PSW glucose sensor with a line width of 100 nm also exhibits a wide linear detection range, an ultra-high sensitivity, an ultra low detection limit, and it can be reused more than a thousand times without much sensitivity degradation.

Polysilicon Wire for the Detection of Label-Free DNA

In this paper, we report the use of polysilicon (poly-Si) wire for label-free DNA sequence detection. Both single-strained (ss) homopolymers, polyadenine [poly(A)], polythymine [poly(T)], polycytosine [poly(C)], and polyguanine [poly(G)], and doublestranded (ds) heteropolymers (one homopolymer with its complement homopolymer), (A-T) [poly(A-T)] and (C-G) [poly(C-G)], were detected. These polymers, with different lengths and concentrations, were dropped onto the poly-Si wire surface, and then the currents flowing through the poly-Si wire channel were determined. The absolute value of the amount of current change ΔI in the channel for ss homopolymers with fixed length and fixed concentration is as follows: poly(T) > poly(C) > poly(G) > poly(A). For ds heteropolymers, it was observed that poly(A-T) has a ΔI that is higher than that of poly(C-G). This study also showed that the poly-Si wire is useful for detecting single- and multiple-base changes in the ss homopolymers as well as single-and multiple-matched-pair changes in ds heteropolymers. A single-pair mismatch in ds poly(C-G) was also investigated in this work.

Gamma-Ray Sterilization Effects in Silica Nanoparticles/γ-APTES Nanocomposite-Based pH-Sensitive Polysilicon Wire Sensors

In this paper, we report the γ-ray sterilization effects in pH-sensitive polysilicon wire (PSW) sensors using a mixture of 3-aminopropyltriethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs) as a sensing membrane. pH analyses showed that the γ-ray irradiation-induced sensitivity degradation of the PSW pH sensor covered with γ-APTES/silica NPs nanocomposite (γ-APTES+NPs) could be restored to a condition even better than prior to γ-ray irradiation by 40-min of post-sterilization room-temperature UV annealing. We found that the trapping charges caused by γ-ray sterilization primarily concentrated in the native oxide layer for the pH sensor covered with γ-APTES, but accumulated in the γ-APTES+NPs layer for the γ-APTES+NPs-covered sensor. It is believed that mixing the PDMS-treated silica NPs into γ-APTES provides many γ-APTES/SiO2 interfaces for the accumulation of trapping charges and for post-sterilization UV oxidation, thus restoring γ-ray-induced sensor degradation. The PDMS-treated silica NPs not only enhance the sensitivity of the pH-sensitive PSW sensors but are also able to withstand the two-step sterilization resulting from γ-ray and UV irradiations. This investigation suggests γ-ray irradiation could be used as a highly-efficient sterilization method for γ-APTES-based pH-sensitive biosensors.

Characteristics of Polysilicon Wire Glucose Sensors with a Surface Modified by Silica Nanoparticles/γ-APTES Nanocomposite

This report investigates the sensing characteristics of polysilicon wire (PSW) glucose biosensors, including thickness characteristics and line-width effects on detection limits, linear range and interference immunity with membranes coated by micropipette/spin-coating and focus-ion-beam (FIB) processed capillary atomic-force-microscopy (C-AFM) tip scan/coating methods. The PSW surface was modified with a mixture of 3-aminopropyl-triethoxysilane (γ-APTES) and polydimethylsiloxane (PDMS)-treated hydrophobic fumed silica nanoparticles (NPs). We found that the thickness of the γ-APTES+NPs nonocomposite could be controlled well at about 22 nm with small relative standard deviation (RSD) with repeated C-AFM tip scan/coatings. The detection limit increased and linear range decreased with the line width of the PSW through the tip-coating process. Interestingly, the interference immunity ability improves as the line width increases. For a 500 nm-wide PSW, the percentage changes of the channel current density changes (ΔJ) caused by acetaminophen (AP) can be kept below 3.5% at an ultra-high AP-to-glucose concentration ratio of 600:1. Simulation results showed that the line width dependence of interference immunity was strongly correlated with the channel electrical field of the PSW biosensor.

Detecting the effect of targeted anti-cancer medicines on single cancer cells using a poly-silicon wire ion sensor integrated with a confined sensitive window

A mold-cast polydimethylsiloxane (PDMS) confined window was integrated with a poly-silicon wire (PSW) ion sensor. The PSW sensor surface inside the confined window was coated with a 3-aminopropyltriethoxysilane (γ-APTES) sensitive layer which allowed a single living cell to be cultivated. The change in the microenvironment due to the extracellular acidification of the single cell could then be determined by measuring the current flowing through the PSW channel. Based on this, the PSW sensor integrated with a confined sensitive window was used to detect the apoptosis as well as the effect of anti-cancer medicines on the single living non-small-lung-cancer (NSLC) cells including lung adenocarcinoma cancer cells A549 and H1299, and lung squamous-cell carcinoma CH27 cultivated inside the confined window. Single human normal cells including lung fibroblast cells WI38, lung fibroblast cells MRC5, and bronchial epithelium cell Beas-2B were tested for comparison. Two targeted anti-NSCLC cancer medicines, Iressa and Staurosporine, were used in the present study. It was found that the PSW sensor can be used to accurately detect the apoptosis of single cancer cells after the anti-cancer medicines were added. It was also found that Staurosporine is more effective than Iressa in activating the apoptosis of cancer cells.

Electrical characterization of single cells using polysilicon wire ion sensor in an isolation window

A polysilicon wire (PSW) sensor can detect the H+ ion density (pH value) of the medium coated on its surface, and different cells produce different extracellular acidification and hence different H+ ion densities. Based on this, we used a PSW sensor in combination with a mold-cast polydimethylsiloxane (PDMS) isolation window to detect the adhesion, apoptosis and extracellular acidification of single normal cells and single cancer cells. Single living human normal cells WI38, MRC5, and BEAS-2B as well as non-small-cell lung cancer (NSCLC) cells A549, H1299, and CH27 were cultivated separately inside the isolation window. The current flowing through the PSW channel was measured. From the PSW channel current change as a function of time, we determined the cell adhesion time by observing the time required for the current change to saturate, since a stable extracellular ion density was established after the cells were completely adhered to the PSW surface. The apoptosis of cells can also be determined when the channel current change drops to zero. We found that all the NSCLC cells had a higher channel current change and hence a lower pH value than the normal cells anytime after they were seeded. The corresponding average pH values were 5.86 for A549, 6.00 for H1299, 6.20 for CH27, 6.90 for BEAS-2B, 6.96for MRC5, and 7.02 for WI38, respectively, after the cells were completely adhered to the PSW surface. Our results show that NSCLC cells have a stronger cell-substrate adhesion and a higher extracellular acidification rate than normal cells.

Polysilicon Nanowire Sensor Devices Based on High-k Dielectric Membrane for pH Sensing and DNA Detection

The pH sensing characteristics of poly-Si nanowires with high-k sensing membranes are investigated. As a result, the sensing membrane of HfO2 exhibits higher sensitivity and better reproducibility test as compared with TEOS SiO2, Al2O3, TiO2 films. The sensor device with HfO2 dielectric membrane reveals a great pH sensitivity of 172.8 nA/pH. In additon, the label-free DNA detection ability of the poly-Si nanowires is also demonstrated. The 10-base-long single-strained homopolymers DNA molecule solution with an ultra-low concentration of 0.01nM can be detected by using HfO2 sensing film. Such a poly-Si nanowires structure with HfO2 sensing membrane is very suitable for future biochemical sensors applications.

Comparison of multiple-polysilicon-nanowire pH-sensors coated with different ALD-deposited high-k dielectric materials

Multiple poly-silicon nanowires (PS-NWs) coated with different high-k dielectric materials, HfO2, Al2O3, and TiO2, were fabricated and their pH sensing characteristics were compared. Sidewall spacer formation technique was used for the PS-NWs fabrication and all the high-k materials were deposited by atomic-layer-deposition (ALD). Following the high-k dielectric deposition, a 3-aminopropyltriethoxysilane (y-APTES) layer was coated as sensing membrane. It is found that the multiple PS-NW sensor coated with HfO2 exhibits the highest sensitivity and best reproducibility for pH sensing.

Improvement of Radiation-Induced Degradation in MOSFET by Using Glass Fiber/Epoxy/Silica Nanoparticles/γ-APTES Composite as Shielding Materials for High-Energy Radiation

Our recent study showed that the trapping charges of the polysilicon wire sensor caused by γ-ray radiation primarily concentrated in the γ-APTES/silica nanoparticles composite layer covered on the sensor. In this chapter, we investigate the shielding effect of the glass fiber/epoxy/silica nanoparticles/γ-APTES composite materials for high-energy radiation in commercially available MOSFET. The use of glass fiber/epoxy/silica nanoparticles/γ-APTES composite plate shielding during irradiation improved the post-irradiated degradation of transfer characteristics by three orders of magnitude for the pMOSFET and half an order of magnitude for the nMOSFET, respectively, as compared to the pMOSFET and nMOSFET with the glass fiber/epoxy or glass fiber/epoxy/silica nanoparticles or without shielding.

Polysilicon wire sensor for biochemical detection with the help of capillary atomic-force-microscopy tip for solution transfer

In this paper, we proposed a polysilicon (poly-Si) wire based biosensor for the detection of glucose and matrix metalloproteinase (MMP) extracted from cancer cells. A focus-ion-beam (FIB) processed capillary atomic-force-microscopy (C-AFM) tip was used to help for transferring trace amount of glucose and MMP solutions onto the exact position of the surface of the poly-Si wire sensor. Glucose solution with different concentrations and MMPs extracted from humans lung adenocarcinoma cells A549 and H1299 were then determined from the current flowing through the poly-Si wire. Due to different amount of hydrogen ions bounded to the poly-Si wire surface when different glucose solutions or MMPs were dropped on the poly-Si wire surface, charge accumulation would occur in the poly-Si wire and causing different current levels been measured. Our experimental data showed that the poly-Si wire sensor is effective and has high sensitivity for glucose and tumor cell MMPs detection when C-AFM tip is used for solution transfer.