Assembling Vertical Nanogap Arrays with Nanoentities for Highly Sensitive Electrical Biosensing.

Nanogap biosensors have emerged as promising platforms for detecting and measuring biochemical substances at low concentrations. Although the nanogap biosensors provide high sensitivity, low limit of detection (LOD), and enhanced signal strength, it requires arduous fabrication processes and costly equipment to obtain micro/nanoelectrodes with extremely narrow gaps in a controlled manner. In this work, we report the novel design and fabrication processes of vertical nanogap structures that can electrically detect and quantify low-concentration biochemical substances. Approximately 40 nm gaps are facilely created by magnetically assembling antibody-coated nanowires onto a nanodisk patterned between a pair of microelectrodes. Analyte molecules tagged with conductive nanoparticles are captured and bound to nanowires and bridge over the nanogaps, which consequently causes an abrupt change in the electrical conductivity between the microelectrodes. Using biotin and streptavidin as model antibodies and analytes, we demonstrated that our nanogap biosensors can effectively measure the protein analytes with the LOD of ∼18 pM. The outcome of this research could inspire the design and fabrication of nanogap devices and nanobiosensors, and it would have a broad impact on the development of microfluidics, biochips, and lab-on-a-chip architectures.

A new triterpenoid from the stems of Kadsura coccinea with antiproliferative activity.

A series of schiartane C29 nortriterpenoids with 5/5/7/6/5 membered consecutive rings (1‒5) with an unique schinortriterpenoid skeleton including a new, kadcoccilactone V (1), together with four known ones (2‒5) and three known triterpenoids (6‒8) were identified from stems of Kadsura coccinea (Lem.) A. C. Smith. The structures of 1 and known compounds were elucidated by interpretation of 1D and 2D NMR, and HR-ESI-MS data as well as comparing those data in the literature. All the isolated compounds were examined for cytotoxic effects against six human cancer cell lines [(HCT-15 (colon), NUGC-3 (stomach), NCI-H23 (lung), ACHN (renal), PC-3 (prostate), and MDA-MB-231 (breast)]. Among them, compound 6 showed potent cytotoxicity against NCI-H23 (GI50 1.28 µM) and NUGC-3 (GI50 1.28 µM), and significantly inhibited on PC-3, MDA-MB-231, ACHN, HCT-15 with GI50 values around 2.33 to 2.67 µM.