Hui Li, Mengyan Li, Wan Y. Shih, Peter I. Lelkes, and Wei-Heng Shih’s latest paper, titled “Cytotoxicity Tests of Water Soluble ZnS and CdS Quantum Dots,” has been published online in Journal of Nanoscience and Nanotechnology.

From the abstract: “Cytotoxicity tests of zinc sulfide (ZnS) and cadmium sulfide (CdS) quantum dots (QDs) synthesized via all-aqueous process with various surface conditions were carried out with human endothelial cells (EA hy926) using two independent viability assays, i.e., by cell counting following Trypan blue staining and by measuring Alamar Blue (AB) fluorescence. The ZnS QDs with all four distinct types of surface conditions were nontoxic at both 1 µM and 10 µM concentrations for at least 6 days. On the other hand, the CdS QDs were nontoxic only at 1 µM, and showed significant cytotoxicity at 10 µM after 3 days in the cell counting assay and after 4 days in the AB fluorescence assay. The CdS QDs with (3-mercaptopropyl)trimethoxysilane (MPS)-replacement plus silica capping were less cytotoxic than those with 3-mercaptopropionic acid (MPA) capping and those with MPS-replacement capping. Comparing the results of ZnS and CdS QDs with the same particle size, surface condition and concentration, it is indicated that the cytotoxicity of CdS QDs and the lack of it in ZnS QDs were probably due to the presence and absence of the toxic Cd element, respectively. The nontoxicity of the aqueous ZnS QDs makes them favorable for in vivo imaging applications.”

The paper can be viewed directly here. [View PDF]

Joseph A. Capobianco, Wan Y. Shih, Gregory P. Adams, Wei-Heng Shih’s latest paper, titled “Label-free Her2 detection and dissociation constant assessment in diluted human serum using a longitudinal extension mode of a piezoelectric microcantilever sensor,” has been published online in Sensors and Actuators B.

From the abstract: “We have investigated real-time, label-free, in situ detection of human epidermal growth factor receptor 2 (Her2) in diluted serum using the first longitudinal extension mode of a lead zirconate-lead titanate (PZT)/glass piezoelectric microcantilever sensor (PEMS) with H3 single-chain variable fragment (scFv) immobilized on the 3-mercaptopropyltrimethoxysilane (MPS) insulation layer of the PEMS surface. We showed that with the longitudinal extension mode, the PZT/glass PEMS consisting of a 1 mm long and 127 _m thick PZT layer bonded with a 75 _m thick glass layer with a 1.8 mm long glass tip could detect Her2 at a concentration of 6–60 ng/ml (or 0.06–0.6 nM) in diluted human serum, about 100 times lower than the concentration limit obtained using the lower-frequency flexural mode of a similar PZT/glass PEMS. We further showed that with the longitudinal mode, the PZT/glass PEMS determined the equilibrium H3–Her2 dissociation constant Kd to be 3.3±0.3×10−8M consistent with the value, 3.2±0.28×10−8M deduced by the surface plasmon resonance method (BIAcore).”

The paper can be viewed directly here. [View PDF]

Xiaotong Gao, Wei-Heng Shih, and Wan Y. Shih’s latest paper, titled “Vibration energy harvesting using piezoelectric unimorph cantilevers with unequal piezoelectric and nonpiezoelectric lengths,” has been published online in Applied Physics Letters.

From the abstract: “We have examined a piezoelectric unimorph cantilever PUC with unequal piezoelectric and nonpiezoelectric lengths for vibration energy harvesting theoretically by extending the analysis of a PUC with equal piezoelectric and nonpiezoelectric lengths. The theoretical approach was validated by experiments. A case study showed that for a fixed vibration frequency, the maximum open-circuit induced voltage which was important for charge storage for later use occurred with a PUC that had a nonpiezoelectric-to-piezoelectric length ratio greater than unity, whereas the maximum power when the PUC was connected to a resistor for immediate power consumption occurred at a unity nonpiezoelectric-to-piezoelectric length ratio.”

The paper can be viewed directly here. [View PDF]

Joseph A. Capobianco, Wei-Heng Shih, Jiann-Horng Leu, Grace Chu-Fang Lo, and Wan Y. Shih’s latest paper, titled “Label Free Detection of White Spot Syndrome Virus Using Lead Magnesium Niobate-Lead Titanate Piezoelectric Microcantilever Sensors,” has been published online in Biosensors and Bioelectronics.

From the abstract: “We have investigated rapid, label free detection of white spot syndrome virus (WSSV) using the first longitudinal extension resonance peak of five lead–magnesium niobate–lead titanate (PMN–PT) piezoelectric microcantilever sensors (PEMS) 1050–700 µm long and 850–485 µm wide constructed from 8 µm thick PMN–PT freestanding films. The PMN–PT PEMS were encapsulated with a 3-mercaptopropyltrimethoxysilane (MPS) insulation layer and further coated with anti-VP28 and anti-VP664 antibodies to target the WSSV virions and nucleocapsids, respectively. By inserting the antibody coated PEMS in a flowing virion or nucleocapsid suspension, label free detection of the virions and nucleocapsids were respectively achieved by monitoring the PEMS resonance frequency shift. We showed that positive label free detection of both the virion and the nucleocapsid could be achieved at a concentration of 100 virions (nucleocapsids)/ml or 10 virions (nucleocapsids)/100 µl, comparable to the detection sensitivity of polymerase chain reaction (PCR). However, in contrast to PCR, PEMS detection was label free, in situ and rapid (less than 30 min), potentially requiring minimal or no sample preparation.”

The paper can be viewed directly here. [View PDF]

Hakki Yegingil, Wan Y. Shih, and Wei-Heng Shih’s latest paper, titled “Probing Model Tumor Interfacial Properties Using Piezoelectric Cantilevers,” has been published online in Review of Scientific Instruments.

From the abstract: “Invasive malignant breast cancers are typically branchy and benign breast tumors are typically smooth. It is of interest to characterize tumor branchiness (roughness) to differentiate invasive malignant breast cancer from noninvasive ones. In this study, we examined the shear modulus (G) to elastic modulus (E) ratio, G/E, as a quantity to describe model tumor interfacial roughness using a piezoelectric cantilever capable of measuring both tissue elastic modulus and tissue shear modulus. The piezoelectric cantilever used had two lead zirconate titanate layers to facilitate all-electrical elastic (shear) modulus measurements using one single device. We constructed model tissues with tumors by embedding one-dimensional (1D) corrugated inclusions and three-dimensional (3D) spiky-ball inclusions made of modeling clay in gelatin. We showed that for smooth inclusions, G/E was 0.3 regardless of the shear direction. In contrast, for a 1D corrugated rough inclusion G/E was 0.3 only when the shear was parallel to corrugation and G/E increased with an increasing angle between the shear direction and the corrugation. When the shear was perpendicular to corrugation, G/E became _0.7. For 3D isotropic spiky-ball inclusions we showed that the G/E depended on the degree of the roughness. Using the ratio s / r of the spike length (s) to the overall inclusion radius (r) as a roughness parameter, we showed that for inclusions with s / r larger than or equal to 0.28, the G/E ratio over the inclusions was larger than 0.7 whereas for inclusions with s / r less than 0.28, the G/E decreased with decreasing s / r to around 0.3 at s / r=0. In addition, we showed that the depth limit of the G/E measurement is twice the width of the probe area of the piezoelectric cantilever.”

The paper can be viewed directly here. [View PDF]