Session D24: Bionanotechnology and Nanostructured Sensors

Zirconium tungstate/epoxy resin nanocomposites with negative coefficient of thermal expansion for all-dielectric cryogenic temperature sensors

The $\alpha $-phase of zirconium tungstate (ZrW$_{2}$O$_{8})$ has the remarkable property that its coefficient of thermal expansion (CTE) is negative over its entire range of thermal stability (0-1050K), and through this range it has a nearly constant negative CTE. When ZrW$_{2}$O$_{8}$ nanoparticles are mixed into a polymer resin, the resulting composite has a reduced CTE when compared with that of the pure polymer. However, previous research on such composites has occurred only near room temperature. We show that at cryogenic temperatures, it is possible to make ZrW$_{2}$O$_{8}$/resin nanocomposites with negative CTE. By coating a fiber-optic Bragg grating with such a composite, we were able to create an all-optical temperature sensor without the use of metals, which would be of particular use in superconducting RF cavities. The sensor has sensitivity down to at least 2 K, six times lower than previous fiber-optic temperature sensors.   

Strong two-photon-fluorescence from semiconducting polymer nanoparticles for high contrast imaging of cancerous cells

Strong two-photon-induced fluorescence was observed from a series of novel fluorescent semiconducting polymer nanoparticles using femtosecond laser pulses at 800 nm. The conjugated polymer nanoparticles were fabricated by a simple technique known as the ``mini emulsion'' technique. The quadratic dependence of the two-photon-fluorescence was confirmed by varying the laser intensity. The two-photon-absorption cross- sections of the nanoparticles were determined in aqueous dispersions by comparing with that of Rhodamine 6G. The deep penetration of the near-infrared laser together with large absorption cross-section demonstrated here, renders these fluorescent polymer nanoparticles as ideal candidates for high contrast in vivo fluorescent imaging of certain tumor cells.   

Surface Modified Gadolinium Phosphate Nanoparticles as MRI Contrast Agents

Nanoparticles of GdPO$_{4}$H$_{2}$O were synthesized in a water/oil microemulsion using IGEPAL CO-520 as surfactant resulting in 50 nm to 100 nm particles that are dispersible and stable in water. Using surface modification chemistry previously established for zirconium phosphonate surfaces,\footnote {J. Monot et al., \textit{J. Am. Chem. Soc.} 130 (2008) 6243.} the particles are directly modified with 5'-phosphate terminated oligonucleotides, and the specific interaction of the divalent phosphate with Gd$^{3+}$ sites at the surface is demonstrated. The ability of the modified nanoparticles to act as MRI contrast agents was determined by performing MR relaxivity measurements at 14 T. Solutions of nanopure water, Feridex{\textregistered} and Omniscan{\textregistered} (FDA cleared contrast agents) in 0.25{\%} agarose were used for comparison and control purposes. MRI data confirm that GdPO$_{4}$H$_{2}$O nanoparticles have relaxivities (r$_{1}$,r$_{2})$ comparable to commercially available contrast agents.\footnote {H. Hifumi et al., \textit{J. Am. Chem. Soc. }128 (2006) 15090.} In addition, biofunctionalization of the surface of the nanoparticles does not prevent their function as MRI contrast agents.   

Surface Plasmon Resonance Imaging of the Enzymatic Degradation of Cellulose Microfibrils

As the largest component of biomass on Earth, cellulose represents a significant potential energy reservoir. Enzymatic hydrolysis of cellulose into fermentable sugars, an integral step in the production of biofuel, is a challenging problem on an industrial scale. More efficient conversion processes may be developed by an increased understanding of the action of the cellulolytic enzymes involved in cellulose degradation. We have used our recently developed quantitative, angle-scanning surface plasmon resonance imaging (SPRi) device to study the degradation of cellulose microfibrils upon exposure to cellulosic enzymes. In particular, we have studied the action of individual enzymes, and combinations of enzymes, from the \textit{Hypocrea Jecorina }cellulase system on heterogeneous, industrially-relevant cellulose substrates. This has allowed us to define a characteristic time of action for the enzymes for different degrees of surface coverage of the cellulose microfibrils.   

Non-destructive method for measuring the Ca/P ratio in human bone

Hydroxyapatite (HA) [Ca$_{10}$(PO$_{4})_{6}$(OH)$_{2}$] is the main mineral constituent in human bone. It crystallizes in hexagonal and monoclinic phase, which are very similar in structure and properties. A critical measure for healthy bones is the Ca/P ratio which in turn affects the dielectric constant of the mineral constituent. The dielectric constant of HA varies between 5 and 20 depending on the Ca/P ratio in the sample [J. Mater. Sci.: Mater. Med. \textbf{21}, 399]. We suggest exploiting this large span in the dielectric constant in a non-destructive method to measure the Ca/P ratio in bone by optical spectroscopy. Using density functional theory we calculate the long-range corrected phonon dispersion. We find that only modes around 330 cm$^{-1}$ are strongly affected by the dielectric constant. The shifts in frequency can be up to 20 cm$^{-1}$ as you span the range of the dielectric constant. Thus, by measuring the optical shift and comparing with calibrated samples it is possible to draw conclusions on the Ca/P ratio in the mineral. Importantly, we find the same modes in both the monoclinic and hexagonal phases to be sensitive to changes in the dielectric constant.   

Surface Functionalized Nanocoax Biosensors

We have adapted the nanocoax array architecture for high sensitivity, all-electronic chemical and biological sensing. We previously demonstrated ppb concentration level detection sensitivity to volatile organic compounds in dry air using the nanocoax array with nanoporous coax annuli [1]. Here, we report progress toward modifying/functionalizing the coax metal surfaces to enable specific binding of target molecules (e.g. proteins, toxins, pathogenic organisms), followed by electronic interrogation via capacitance/impedance spectroscopy. As a proxy for target molecules, and in order to confirm the ability to selectively functionalize desired surfaces in our nanopillar / nanocoax geometry, we have selectively attached strepavidin-functionalized core-shell CdSe/ZnS quantum dots to gold nanopillars. Next steps will include substituting antibodies for the quantum dots, and measuring the capacitance and impedance response to the introduction of protein (PSA , CA-125, etc.) in serum. Ref. [1]: H.Z. Zhao, B. Rizal, G. McMahon, H. Wang, P. Dhakal, T. Kirkpatrick, Z.F. Ren, T.C. Chiles, D. Cai and M.J. Naughton (submitted).   

Magnetic wire trap arrays for biomarker-based molecular detection

Submicrometer-scale magnetic devices built on chip-based platforms have recently been shown to present opportunities for new particle trapping and manipulation technologies. Meanwhile, advances in nanoparticle fabrication allow for the building of custom-made particles with precise control of their size, composition, and other properties such as magnetism, fluorescence, and surface biomarker characteristics. In particular, carefully tailored surface biomarkers facilitate precise binding to targeted molecules, self-actuated construction of hybrid structures, and fluorescence-based detection schemes. Based on these progresses, we present an on-chip detection mechanism for molecules with known surface markers. Hybrid nanostructures consisting of micelle nanoparticles, fluorescent quantum dots, and superparamagnetic iron oxide nanoparticles are used to detect proteins or DNA molecules. The target is detected by the magnetic and fluorescent functionalities of the composite nanostructure, whereas in the absence of the target these signals are not present. Underlying this approach is the simultaneous manipulation via ferromagnetic zigzag nanowire arrays and imaging via quantum dot excitation. This chip-based detection technique could provide a powerful, low cost tool for ultrasensitive molecule detection with ramifications in healthcare diagnostics and small-scale chemical synthesis.   

Strategies to enhance the bioavailability of curcumin: a potential antitumor drug

Curcumin is a polyphenol which has elicited considerable interest for its antioxidant and anti tumor properties. Although curcumin may be used as potential therapeutic drug, it is very sparingly soluble in water which makes it less bioavailable under physiological conditions. We report two approaches to make curcumin more bioavailable. The first approach involves fabricating colloidal dispersions of curcumin in the range of tens of nanometers. The second approach involves functionalization of curcumin with polyethylene glycol (PEG) to render it water dispersible or soluble. Since curcumin is a fluorescent molecule as well as a potential drug, its interactions with cells have been investigated using one and two photon confocal fluorescence imaging. We have also observed strong interaction between curcumin and metal ions, which may have physiological implications.   

Comparison anti-bacterial effect of silver/polystyrene nanocomposites on gram negative and positive bacteria

Silver nanoparticles/polystyrene nanocomposites were prepared via casting the solution of polystyrene in a mixture of carbon tetrachloride and acetone containing silver nanoparticles. Colloidal silver nanoparticles in acetone were synthesized by pulsed laser ablation (PLA) of pure bulk silver. Casting the colloidal silver nanoparticles in a solution of polystyrene results in a yellowish transparent polymeric sheet. TEM images show rather spherical nanoparticles with mean diameter of 5 nm. Ag/PS nanocomposites were characterized by UV-VIS spectroscopy. In this study, we also investigated the antimicrobial activity of silver nanocomposites against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) as a model for Gram negative and Gram positive bacteria. Antibacterial tests were performed against E. coli and S.aureus, on LB agar plates containing different amount of nanoparticles. Our results showed at all these concentrations, the nanoparticles caused a growth delay of E. coli, increasing the concentration of nanoparticles increased this growth delay.   

Luminescence of Rare-Earth-Doped Nanoparticles with Aromatic Linker Molecules

Rare-earth-doped vanadate glasses retain their luminescence when formed as shells around magnetic cores [1]. This property has prompted speculation that composite magneto-photoluminescent (CMPL) structures can be used in biological applications. For example, CMPL nanoparticles can be magnetically tuned to separate cells, proteins and nucleic acids [2]. A crucial step in realizing this goal is to attach organic linkers (between the rare-earth-doped shell and bio-probes), which do not affect the luminescence. We demonstrate with IR spectroscopy that Eu:YVO$_{4}$ nanoparticles treated with benzoic acid, 3-nitro 4-chloro-benzoic acid and 3,4-dimethoxy benzoic acid all result in the modification of the surface states, replacing the native metal-hydroxyl bond with a longer chain aromatic linker, which can be later functionalized. Photoluminescence spectra under UV-excitation show that the dominant $^{5}$D$_{0} \quad \to $ $^{7}$F$_{2}$ transition at $\sim $620 nm is unaffected by the chemical treatment. The result provides a platform to facilitate the attachment of bio-probes to Eu:YVO$_{4}$ nanoparticles and related CMPL nanostructures with Fe$_{2}$O$_{4}$ cores. \newline [1] N. B. McDowell et al, J. Appl. Phys. 107, 09B327 (2010). \newline [2] T. R. Sathe et al, Anal. Chem. 78, 5627 (2006).   

Light-powered nanoparticle -- MEMS hybrid

This work presents a light-actuated microelectromechanical (MEMS) structure with bistable elements and its applications in cellular-scale actuation. These devices are built using a metal/oxide bilayer with a stress mismatch. In the hybrid design that uses gold nanoparticles for localized heating, a nanoparticle coating is patterned onto the selected part of the device by Parylene micro-stenciling before releasing the structures from the planar substrate. These gold nanoparticles are attractive for use in $\mu $TAS and biotechnology due to their biocompability and inertness, the ability to conjugate to the surface via thiol chemistry or electrostatic interaction, and especially their strong tunable absorption in the near infrared region. Integration of the near infrared (IR)-resonant gold nanoparticles with bistable MEMS structures creates light-driven hybrid actuators that quickly respond to narrow-band IR light. The movement of the MEMS device is achieved through controlled thermal expansion, with actuation speed in the millisecond range.   

Motion observation and SPR measurements of kinesin motility on microtubules

Motor proteins convert chemical energy directly into mechanical work with high efficiency ($\sim $50{\%}). One of these proteins, kinesin, is used in the cell to transport organelles. It ``walks'' along biopolymer tracks called microtubules and, depending on the type, can reach speeds of a few micrometers per second. Kinesin can carry intracellular cargo over long distances against several piconewtons of loads and is barely limited by the cargo size. Motion of streptavidin-coated quantum dots carried by kinesin on microtubules will be presented. We have expressed biotinylated Kinesin-1 using \textit{Escherichia coli}. Attachment to quantum dots was performed using the strong binding affinity between streptavidin and biotin. Microtubules, labeled with rhodamine, allow visualization by fluorescence microscopy. The measured speed of our kinesin fits well with results found in the literature. Surface Plasmon Resonance (SPR) measurements allow the identification and strength evaluation of bonding. Using this technique, we will present results on the binding between our expressed kinesin and microtubule.   

Construction of Quantum Dot Micro/Nano-track as a Seedbed for Kinesin Motor Proteins

Kinesin is a motor protein engaged in motion on microtubules. It is involved in various subcellular processes such as cell division and transportation of intracellular cargo. The system of (1) kinesin, (2) \textit{in-vitro} polymerized microtubules and (3) specifically functionalized quantum dots has been employed to realize kinesin motility \textit{in-vitro}. Selective attachment of the kinesin motor protein to a surface is an important prerequisite for the development of artificial bio-engineered devices utilizing these dynamic processes in \textit{in-vitro} systems. We will elucidate the feasibility of using a micro/nano-track paved with streptavidin coated quantum dots as fluorescently traceable linkers for biotinylated kinesins. This will be based on results from fluorescence microscopy observations of recent motility assays and quantum dot distributions observed on structured PMMA (polymethyl-methacrylate) surfaces patterned by electron beam lithography.