Edward Jan

High-content screening as a universal tool for fingerprinting of cytotoxicity of nanoparticles.

Recent advances and progress in nanobiotechnology have demonstrated many nanoparticles (NPs) as potential and novel drug delivery vehicles, therapeutic agents, and contrast agents and luminescent biological labels for bioimaging. The emergence of new biomedical applications based on NPs signifies the need to understand, compare, and manage their cytotoxicity. In this study, we demonstrated the use of high-content screening assay (HCA) as a universal tool to probe the cytotoxicity of NPs and specifically cadmium telluride quantum dots (CdTe QDs) and gold NPs (Au NPs) in NG108-15 murine neuroblastoma cells and HepG2 human hepatocellular carcinoma cells. Neural cells represent special interest for NP-induced cytotoxicity because the optical and electrical functionalities of materials necessary for neural imaging and interfacing are matched well with the properties of many NPs. In addition, the cellular morphology of neurons is particularly suitable for automated high content screening. HepG2 cells represent a good model for high content screening studies since they are commonly used as a surrogate for human hepatocytes in pharmaceutical studies. We found the CdTe QDs to induce primarily apoptotic response in a time- and dosage-dependent manner and produce different toxicological profiles and responses in undifferentiated and differentiated neural cells. Au NPs were found to inhibit the proliferation and intracellular calcium release of HepG2 cells.

Transparent Conductors from Layer-by-Layer Assembled SWNT Films: Importance of Mechanical Properties and a New Figure of Merit

New transparent conductors (TCs) capable of replacing traditional indium tin oxide (ITO) are much needed for displays, sensors, solar cells, smart energy-saving windows, and flexible electronics. Technical requirements of TCs include not only high electrical conductivity and transparency but also environmental stability and mechanical property which are often overlooked in the research environment. Single-walled carbon nanotube (SWNT) coatings have been suggested as alternative TC materials but typically lack sufficient wear resistance compared to ITO. Balancing conductance, transparency, durability, and flexibility is a formidable challenge, which leads us to the introduction of a new TC figure of merit, PiTC, incorporating all these qualities. Maximization of PiTC to that of ITO or better can be suggested as an initial research goal. Fine tuning of SWNT layer-by-layer (LBL) polymeric nanocomposite structures makes possible integration of all the necessary properties. The produced TC demonstrated resistivity of 86 Omega/sq with 80.2% optical transmittance combined with tensile modulus, strength, and toughness of the film of 12.3+/-3.4 GPa, 218+/-13 MPa, and 8+/-1.7 J/g, respectively. A new transparent capping layer to conserve these properties in the hostile environment with matching or better strength, toughness, and transparency parameters was also demonstrated. Due to application demands, bending performance of TC made by LBL was of special interest and exceeded that of ITO by at least 100 times. Cumulative figure of merit PiTC for the produced coatings was 0.15 Omega(-1), whereas the conventional ITO showed PiTC<0.07 Omega(-1). With overall electrical and optical performance comparable to ITO and exceptional mechanical properties, the described coatings can provide an excellent alternative to ITO or other nanowire- and nanotube-based TC specifically in flexible electronics, displays, and sensors.

Multiparameter Structural Optimization of Single-Walled Carbon Nanotube Composites: Toward Record Strength, Stiffness, and Toughness

Efficient coupling of mechanical properties of SWNTs with the matrix leading to the transfer of unique mechanical properties of SWNTs to the macroscopic composites is a tremendous challenge of todays materials science. The typical mechanical properties of known SWNT composites, such as strength, stiffness, and toughness, are assessed in an introductory survey where we focused on concrete numerical parameters characterizing mechanical properties. Obtaining ideal stress transfer will require fine optimization of nanotube-polymer interface. SWNT nanocomposites were made here by layer-by-layer (LBL) assembly with poly(vinyl alcohol) (PVA), and the first example of optimization in respect to key parameters determining the connectivity at the graphene-polymer interface, namely, degree of SWNT oxidation and cross-linking chemistry, was demonstrated. The resulting SWNT-PVA composites demonstrated tensile strength (σ(ult)) = 504.5 ± 67.3 MPa, stiffness (E) = 15.6 ± 3.8 GPa, and toughness (K) = 121.2 ± 19.2 J/g with maximum values recorded at σ(ult) = 600.1 MPa, E = 20.6 GPa, and K = 152.1 J/g. This represents the strongest and stiffest nonfibrous SWNT composites made to date outperforming other bulk composites by 2-10 times. Its high performance is attributed to both high nanotube content and efficient stress transfer. The resulting LBL composite is also one of the toughest in this category of materials and exceeding the toughness of Kevlar by 3-fold. Our observation suggests that the strengthening and toughening mechanism originates from the synergistic combination of high degree of SWNT exfoliation, efficient SWNT-PVA binding, crack surface roughening, and fairly efficient distribution of local stress over the SWNT network. The need for a multiscale approach in designing SWNT composites is advocated.

Layered carbon nanotube-polyelectrolyte electrodes outperform traditional neural interface materials.

The safety, function, and longevity of implantable neuroprosthetic and cardiostimulating electrodes depend heavily on the electrical properties of the electrode-tissue interface, which in many cases requires substantial improvement. While different variations of carbon nanotube materials have been shown to be suitable for neural excitation, it is critical to evaluate them versus other materials used for bioelectrical interfacing, which have not been done in any study performed so far despite strong interest to this area. In this study, we carried out this evaluation and found that composite multiwalled carbon nanotube-polyelectrolyte (MWNT-PE) multilayer electrodes substantially outperform in one way or the other state-of-the-art neural interface materials available today, namely activated electrochemically deposited iridium oxide (IrOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). Our findings provide the concrete experimental proof to the much discussed possibility that carbon nanotube composites can serve as excellent new material for neural interfacing with a strong possibility to lead to a new generation of implantable electrodes.

Chiral luminescent CdS nano-tetrapods

The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS nano-tetrapods, which demonstrated circular dichroism in the band-edge region of the spectrum.

Melanin‐Containing Films: Growth from Dopamine Solutions versus Layer‐by‐Layer Deposition

Films formed by oxidation of dopamine are of interest for functionalisation of solid-liquid interfaces owing to their versatility. However, the ability to modulate the properties of such films, for example, permeability to ionic species and the absorption coefficient, is urgently needed. Indeed, melanin films produced by oxidation of dopamine absorb strongly over the whole UV/Vis part of the electromagnetic spectrum and are impermeable to anions even for a film thickness as low as a few nanometers. Herein we combine oxidation of dopamine to produce a solution containing dopamine-melanin particles and their alternating deposition with poly(diallyldimethylammonium chloride) to produce films which have nearly the same morphology as pure dopamine-melanin films but are less compact, more transparent and more permeable to ferrocyanide anions.

PEDOT coated microelectrode arrays for chronic neural recording and stimulation

The efficacy of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) coatings was tested on microelectrodes for neural recording and stimulation. In vitro tests revealed that PEDOT coated electrodes were capable of injecting 15 times the charge of Platinum Iridium (PtIr) electrodes and Iridium Oxide (IrOx) coated electrodes when using constant current stimulation at zero voltage bias. Furthermore, in vivo chronic testing in rats revealed that PEDOT coated electrodes showed higher signal to noise recordings and superior charge capacity compared to PtIr electrodes.

In situ gene transfection and neuronal programming on electroconductive nanocomposite to reduce inflammatory response

Inflammatory reactions, such as encapsulation of implanted electrodes by scar tissues and gradual degradation of neurons, are the key problems for neural tissue interfacing. These problems must be resolved for treatments of debilitating conditions to be effective. One strategy to mitigate them is to engineer neural electrodes with the ability to control cell response viain situgene transfection. Taking advantage of layer-by-layer (LBL) assembled carbon nanotube (CNT) composites, purposeful engineering of electrostimulating implants with these functionalities becomes realistic. LBL assembled CNT composites are conductive and can incorporate plasmid DNA capable of altering the response/functionality of surrounding cells. Successful expression of Lyn–citrine plasmid DNA was achieved in attached neurons. The transfection efficiency was found to be remarkably higher than conventional solution-mediated techniques. Most importantly, by using plasmid expression vectors for neural basic helix–loop–helix proteins, neurons were generated from multipotent P19 embryonal carcinoma cells adhering to the CNT multilayers. This study illustrates the possibility of fabricating an electrostimulating implant capable of recruiting and programming resident stem cells in the nervous system to provide a substantially improved level of tissue–device integration.

Protease inhibitor-induced cardiotoxicity: direct effects on cell viability and intracellular calcium levels

Purpose of the study Long-term use of protease inhibitors (PIs) is associated with increased cardiovascular risk linked to metabolic imbalance and endothelial dysfunction. The direct effects of PIs on cardiomyocytes have not been studied, but may be critical to our understanding of the cellular mechanisms contributing to ART-associated cardiovascular dysfunction in HIV patients. This study aims to assess the effects of antiviral agents on cell survival and intracellular calcium levels in cardiomyoblasts (H9c2).