Parameters affecting intracellular delivery of molecules using laser-activated carbon nanoparticles.

Previous studies showed that carbon nanoparticles exposed to nanosecond laser pulses cause intracellular uptake of molecules. In this study, prostate cancer cells incubated with carbon-black (CB) nanoparticles and fluorescent marker compounds were exposed to 10ns laser pulses at 1064nm wavelength, after which intracellular uptake was measured by flow cytometry. Calcein and dextran (150kDa) were delivered into >50% of cells, whereas larger dextrans (≤2000kDa) were taken up by ~10% of cells. Under all conditions studied, cell viability loss was minimal. Uptake also increased with increasing laser power, increasing CB nanoparticle concentration, increasing CB nanoparticle size and decreasing laser wavelength. CB nanoparticles enabled uptake better than gold nanoparticles or multi-walled carbon nanotubes under the conditions studied. Proof-of-principle experiments showed intracellular uptake by cells in vivo. We conclude that intracellular uptake of molecules using laser-activated CB nanoparticles provides a promising approach to deliver molecules into cells. FROM THE CLINICAL EDITOR: Delivery of drugs using nanoparticles as carriers is promising. The authors in this study investigated the use of laser-activated carbon nanoparticles to increase the cellular uptake of payloads in various parameters. The positive data generated should provide further platform for a new approach for intracellular delivery of molecules.

Magnetic separation of algae genetically modified for increased intracellular iron uptake.

Algae were investigated in the past as a potential source of biofuel and other useful chemical derivatives. Magnetic separation of algae by iron oxide nanoparticle binding to cells has been proposed by others for dewatering of cellular mass prior to lipid extraction. We have investigated feasibility of magnetic separation based on the presence of natural iron stores in the cell, such as the ferritin in Auxenochlorella protothecoides (A. p.) strains. The A. p. cell constructs were tested for inserted genes and for increased intracellular iron concentration by inductively coupled plasma atomic absorption (ICP-AA). They were grown in Sueoka's modified high salt media with added vitamin B1 and increasing concentration of soluble iron compound (FeCl3 EDTA, from 1× to 8× compared to baseline). The cell magnetic separation conditions were tested using a thin rectangular flow channel pressed against interpolar gaps of a permanent magnet forming a separation system of a well-defined fluid flow and magnetic fringing field geometry (up to 2.2 T and 1,000 T/m) dubbed "magnetic deposition microscopy", or MDM. The presence of magnetic cells in suspension was detected by formation of characteristic deposition bands at the edges of the magnet interpolar gaps, amenable to optical scanning and microscopic examination. The results demonstrated increasing cellular Fe uptake with increasing Fe concentration in the culture media in wild type strain and in selected genetically-modified constructs, leading to magnetic separation without magnetic particle binding. The throughput in this study is not sufficient for an economical scale harvest.

High-productivity lipid production using mixed trophic state cultivation of Auxenochlorella (Chlorella) protothecoides.

A mixed trophic state production process for algal lipids for use as feedstock for renewable biofuel production was developed and deployed at subpilot scale using a green microalga, Auxenochlorella (Chlorella) protothecoides. The process is composed of two separate stages: (1) the photoautotrophic stage, focused on biomass production in open ponds, and (2) the heterotrophic stage focused on lipid production and accumulation in aerobic bioreactors using fixed carbon substrates (e.g., sugar). The process achieved biomass and lipid productivities of 0.5 and 0.27 g/L/h that were, respectively, over 250 and 670 times higher than those obtained from the photoautotrophic cultivation stage. The biomass oil content (over 60% w/DCW) following the two-stage process was predominantly monounsaturated fatty acids (~82%) and largely free of contaminating pigments that is more suitable for biodiesel production than photosynthetically generated lipid. Similar process performances were obtained using cassava hydrolysate as an alternative feedstock to glucose.

Low-energy electron-stimulated desorption of cations and neutrals from Si(111)-(7x7):C2D2.

The interactions of low-energy (5-50 eV) electrons with acetylene-d(2) (C(2)D(2)) adsorbed on the Si(111)-(7x7) surface have been examined by monitoring the stimulated desorption products. These include primary cation desorbates, D(+) and C(2)D(2)(+) (C(2)HD(+)), the fragment ion C(2)D(+), smaller amounts of C(2)(+), CDH(+) (CH(3)(+)), and neutral D((2)S). The approximately 23-25 eV threshold energies for D(+) and hydrocarbon fragment ion detection indicate involvement of two-hole or two-hole one electron final states that Coulomb explode. These multihole states can be created via Auger decay of single holes in shallow core levels localized on C or Si surface atoms. The approximately 12 eV appearance threshold for the C(2)D(2)(+) molecular ion can be correlated with direct excitation of an adsorbate-induced surface state, which may initially possess character of the A(3) surface state of Si. The 18 eV threshold for C(2)D(+) correlates with decomposition of C(2)D(2)(+) with excess vibronic energy. C(2)D(+) desorption via direct excitation of the dissociative (2)Sigma(u)(+)-type state of the C(2)D(2)(+) ion is also possible. The approximately 8 eV threshold energy for production and desorption of neutral D((2)S) may correlate with excitation of the perturbed/mixed F (1)Sigma(u)(+)<--X (1)Sigma(g)(+) and E (1)Sigma(u)(+)<--X(1)Sigma(g)(+) dissociative transitions of adsorbed acetylene molecules. Time-of-flight distributions of D((2)S) indicate both nonthermal (557 and 116 meV; 4300 and 900 K) and thermal (17 meV; 130 K) components. The two fast components can be related to the geometry of di-sigma bonded acetylene on the Si(111)-(7x7) surface.

Site-dependent electron-stimulated reactions in water films on TiO2(110).

Electron-stimulated reactions in thin [<3 ML (monolayer)] water films adsorbed on TiO(2)(110) are investigated. Irradiation with 100 eV electrons results in electron-stimulated dissociation and electron-stimulated desorption (ESD) of adsorbed water molecules. The molecular water ESD yield increases linearly with water coverage theta for 0< or =theta< or =1 ML and 11 ML, the water ESD yield per additional water molecule adsorbed (i.e., the slope of the ESD yield versus coverage) is 3.5 times larger than for theta<1 ML. In contrast, the number of water molecules dissociated per incident electron increases linearly for theta< or =2 ML without changing slope at theta=1 ML. The total electron-stimulated sputtering rate, as measured by postirradiation temperature programmed desorption of the remaining water, is larger for theta>1 ML due to the increased water ESD for those coverages. The water ESD yields versus electron energy (for 5-50 eV) are qualitatively similar for 1, 2, and 40 ML water films. In each case, the observed ESD threshold is at approximately 10 eV and the yield increases monotonically with increasing electron energy. The results indicate that excitations in the adsorbed water layer are primarily responsible for the ESD in thin water films on TiO(2)(110). Experiments on "isotopically layered" films with D(2)O adsorbed on the Ti(4+) sites (D(2)O(Ti)) and H(2)O adsorbed on the bridging oxygen atoms (H(2)O(BBO)) demonstrate that increasing the water coverage above 1 ML rapidly suppresses the electron-stimulated desorption of D(2)O(Ti) and D atoms, despite the fact that the total water ESD and atomic hydrogen ESD yields increase with increasing coverage. The coverage dependence of the electron-stimulated reactions is probably related to the different bonding geometries for H(2)O(Ti) and H(2)O(BBO) and its influence on the desorption probability of the reaction products.

Low-energy electron stimulated desorption of neutrals from multilayers of SiCl4 on Si(111).

The interaction of low-energy electrons with multilayers of SiCl(4) adsorbed on Si(111) leads to production and desorption of Cl((2)P(32)), Cl((2)P(12)), Si, and SiCl. Resonant structure in the yield versus incident electron energy (E(i)) between 6 and 12 eV was seen in all neutral channels and assigned to dissociative electron attachment (DEA), unimolecular decay of excited products produced via autodetachment and direct dissociation. These processes yield Cl((2)P(32)) and Cl((2)P(12)) with nonthermal kinetic energies of 425 and 608 meV, respectively. The Cl((2)P(12)) is produced solely at the vacuum surface interface, whereas the formation of Cl((2)P(32)) likely involves subsurface dissociation, off-normal trajectories, and collisions with neighbors. Structure in the Cl((2)P(32)) yield near 14 and 25 eV can originate from excitation of electrons in the 2e, 7t(2) and 6t(2), 6a(1) levels, respectively. Although the 14 eV feature was not present in the Cl((2)P(12)) yield, the broad 25 eV feature, which involves complex Auger filling of holes in the 6t(2) and 6a(1) levels of SiCl(4), is observed. Direct ionization, exciton decay, and DEA from secondary electron scattering all occur at E(i)>14 eV. Si and SiCl were detected via nonresonant ionization of SiCl(x) precursors that are produced via the same states and mechanisms that yield Cl. The Si retains the kinetic energy profile of the desorbed precursors.