Saion K. Sinha

Assay-Dependent Phytotoxicity of Nanoparticles to Plants

The effects of five nanomaterials (multiwalled carbon nanotubes [MWCNTs], Ag, Cu, ZnO, Si) and their corresponding bulk counterparts on seed germination, root elongation, and biomass of Cucurbita pepo (zucchini) were investigated. The plants were grown in hydroponic solutions amended with nanoparticles or bulk material suspensions at 1000 mg/L. Seed germination was unaffected by any of the treatments, but Cu nanoparticles reduced emerging root length by 77% and 64% relative to unamended controls and seeds exposed to bulk Cu powder, respectively. During a 15-day hydroponic trial, the biomass of plants exposed to MWCNTs and Ag nanoparticles was reduced by 60% and 75%, respectively, as compared to control plants and corresponding bulk carbon and Ag powder solutions. Although bulk Cu powder reduced biomass by 69%, Cu nanoparticle exposure resulted in 90% reduction relative to control plants. Both Ag and Cu ion controls (1-1000 mg/L) and supernatant from centrifuged nanoparticle solutions (1000 mg/L) indicate that half the observed phytotoxicity is from the elemental nanoparticles themselves. The biomass and transpiration volume of zucchini exposed to Ag nanoparticles or bulk powder at 0-1000 mg/mL for 17 days was measured. Exposure to Ag nanoparticles at 500 and 100 mg/L resulted in 57% and 41% decreases in plant biomass and transpiration, respectively, as compared to controls or to plants exposed to bulk Ag. On average, zucchini shoots exposed to Ag nanoparticles contained 4.7 greater Ag concentration than did the plants from the corresponding bulk solutions. These findings demonstrate that standard phytotoxicity tests such as germination and root elongation may not be sensitive enough or appropriate when evaluating nanoparticle toxicity to terrestrial plant species.

Characterization of Biofilm Formation by Borrelia burgdorferi In Vitro

Borrelia burgdorferi, the causative agent of Lyme disease, has long been known to be capable of forming aggregates and colonies. It was recently demonstrated that Borrelia burgdorferi aggregate formation dramatically changes the in vitro response to hostile environments by this pathogen. In this study, we investigated the hypothesis that these aggregates are indeed biofilms, structures whose resistance to unfavorable conditions are well documented. We studied Borrelia burgdorferi for several known hallmark features of biofilm, including structural rearrangements in the aggregates, variations in development on various substrate matrices and secretion of a protective extracellular polymeric substance (EPS) matrix using several modes of microscopic, cell and molecular biology techniques. The atomic force microscopic results provided evidence that multilevel rearrangements take place at different stages of aggregate development, producing a complex, continuously rearranging structure. Our results also demonstrated that Borrelia burgdorferi is capable of developing aggregates on different abiotic and biotic substrates, and is also capable of forming floating aggregates. Analyzing the extracellular substance of the aggregates for potential exopolysaccharides revealed the existence of both sulfated and non-sulfated/carboxylated substrates, predominately composed of an alginate with calcium and extracellular DNA present. In summary, we have found substantial evidence that Borrelia burgdorferi is capable of forming biofilm in vitro. Biofilm formation by Borrelia species might play an important role in their survival in diverse environmental conditions by providing refuge to individual cells.

Accumulation and phytotoxicity of engineered nanoparticles to Cucurbita pepo.

The effect of bulk and engineered nanoparticle (NP) Ag, Au, Cu, Si, and C at 250 and 750 mg/L on zucchini biomass, transpiration, and element content was determined. The pH of bulk and NP solutions prior to plant growth frequently differed. Nanoparticle Cu solution pH was significantly higher than bulk Cu, whereas for Ag and C, the NPs had significantly lower pH. Plants were unaffected by Au, regardless of particle size or concentration. NP Ag reduced plant biomass and transpiration by 49–91% compared to equivalent bulk Ag. NP Si at 750 mg/L reduced plant growth and transpiration by 30–51% relative to bulk Si. Bulk and NP Cu were phytotoxic but much of the effect was alleviated by humic acid. The shoot Ag and Cu content did not differ based on particle size or concentration. The accumulation of bulk Au was greater than the NP, but humic acid increased the accumulation of NP and bulk Au by 5.6-fold and 80%, respectively. The uptake of NP Si was 5.6–6.5-fold greater than observed with the bulk element. These findings show that the NPs may have unique phytotoxicity or accumulation patterns and that solution properties can significantly impact particle fate and effects.

Introductory Nanotechnology Courses: Experiences of an Educator

The demand for trained professionals in the area of Nanotechnology is increasing as the technology is getting commercialized . Among other regions, the north-eastern United States (the states of New York, New Jersey, Massachusetts and Connecticut) is noticing a quick rise of Nanotechnology and related businesses. Some of these businesses are currently in the process of moving the technology from the lab to the market place and are in need of engineers (Bachelors and Masters level) to achieve this goal. An undergraduate course (Nanoscale Sciences) and a graduate level course (Introduction to Nanotechnology) was offered to Engineering and Science students in the 2004-2005 academic year at the University of New Haven to educate such professionals. A few local Nanotechnology business aided in developing the curriculum and shared resources with the students. The undergraduate course was an overview of Nanotechnology with an emphasis on Nanomaterials. The Graduate course was targeted for Electrical and Computer Engineers with an emphasis on Nanodevices.

Intermediate Frequency AC Signal Analysis for Bionanosensor

Nanobiosensors are devices which incorporate nanomaterials to detect miniscule quantities of biological and chemical agents. The authors have already developed a novel bionanosensor (BNS) for quick, efficient, and precise detection of bacterial pathogens using the principles of CNT-DNA interaction and DNA hybridization. The detection ability of the (BNS) was observed to be independent of the device resistance. Two new methods (low-pass filter (LPF) and curve fitting (CF)) were developed for better analysis of the BNS. These methods successfully model the BNS. Evidence is provided to elucidate the success of the model, which can explain the DNA hybridization on the sensor surface. These models successfully demonstrated the detection of DNA hybridization versus nonhybridization. Thus, the models can not only help in better and efficient design and operation of the BNS, but can also be used to analyze other similar nanoscale devices.

Precise Control of Carbon Nanotube Synthesis of a Single Chirality

This work demonstrates precise control over the synthesis conditions and location during CNT formation, such that single chirality tubes are obtainable. This technique obviates two significant hurdles that prevent the exploitation of CNTs in micro- and nano-devices. Microelectronic applications require precise location and chirality of synthesized CNTs. Conventional CVD synthesis techniques typically yield mixtures of CNTs (semi-conducting and metallic types) that grow at random locations. Dip Pen Nanolithography (DPN) techniques were used to deposit the catalysts at precisely defined locations and to pattern the catalysts on a substrate with specific sizes as well as to control the catalyst composition. After deposition of catalysts, a low temperature Chemical Vapor Deposition (CVD) process was used to synthesize CNT. Various known catalysts were deposited. Characterization studies before and after CVD synthesis of CNT showed that the CNT were of a single chirality as well as uniform diameter (with a very narrow range of variability). The results indicate that the chirality of the synthesized CNT can be controlled by changing the synthesis conditions (e.g., size of the catalyst patterns, composition of the catalysts, temperature of CVD, gas flow rates, etc.).Copyright

A phenomenological electromagnetic theory of CNT-DNA metabiomaterials for applications to biosensing and DNA sequencing

We model DNA-wrapped carbon nanotubes (CNTs) as loaded conducting thin-wire antennas and use MoM to solve for currents induced in hybridized CNT-DNA samples. The coupling between CNT and DNA is phenomenologically treated as a “DNA impedance perturbation” and is inserted into the CNT MoM formulation. The model is valid for arbitrary shaped CNT-DNA geometries and is expected to be accurate for low, RF, and optical frequencies. We utilize the EM model to propose a machine learning framework that can be deployed for electromagnetic DNA sequencing and biosensing.

Nanolithography of metal catalysts by Dip Pen Nanolithography

Nano-patterning of metals on gold film and silicon nitride membrane using Dip Pen Nanolithography (DPNTM) is reported in this study. Using this technique, nano-particles can be delivered or nano-scale features of metals can be deposited precisely at specific locations using the unique registration capabilities of DPN. Monolayers of metal salts (FeCl2, FeCl3, PdCl2, etc.) are deposited with nano-scale precision using DPN. These metal salts can be subsequerntly reduced to pure metals in a reducing environment for various applications (e.g., magnetic memory storage, nano-catalysis, molecular electronics, brand protection, nano-sensors, etc.). Square nano-patterns of Palladium and Iron salts were successfully deposited using this technique with thickness of the deposited materials being less than 1 nm.