Protein spot arrays on graphene oxide coatings for efficient single-cell capture

Biomedical applications such as cell screening or cell–cell interaction studies require placement and adhesion of cells on surfaces with controlled numbers and location. In particular, single-cell arraying and positioning has come into focus as a basis of such applications. An ideal substrate would combine biocompatibility with favorable attributes such as pattern stability and easy processing. Here, we present a simple yet effective approach to single-cell arraying based on a graphene oxide (GO) surface carrying protein (fibronectin) microarrays to define cell adhesion points. These capture NIH-3T3 cells, resulting in cell arrays, which are benchmarked against analogous arrays on silanized glass samples. We reveal significant improvement in cell-capture performance by the GO coating with regards to overall cell adhesion and single-cell feature occupancy. This overall improvement of cell-arraying combined with retained transparency of substrate for microscopy and good biocompatibility makes this graphene-based approach attractive for single-cell experiments.

Adsorption and binding dynamics of graphene-supported phospholipid membranes using the QCM-D technique

We report on the adsorption dynamics of phospholipid membranes on graphene-coated substrates using the quartz crystal microbalance with dissipation monitoring (QCM-D) technique. We compare the lipid vesicle interaction and membrane formation on gold and silicon dioxide QCM crystal surfaces with their graphene oxide (GO) and reduced (r)GO coated counterparts, and report on the different lipid structures obtained. We establish graphene derivative coatings as support surfaces with tuneable hydrophobicity for the formation of controllable lipid structures. One structure of interest formed is lipid monolayer membranes which were formed on rGO, which are otherwise challenging to produce. We also demonstrate and monitor biotin-avidin binding on such a membrane, which will then serve as a platform for a wide range of biosensing applications. The QCM-D technique could be extended to both fundamental studies and applications of other covalent and non-covalent interactions in 2-dimensional materials.

Ultra-thin graphene-polymer heterostructure membranes

The fabrication of arrays of ultra-thin conductive membranes remains a major challenge in realising large-scale micro/nano-electromechanical systems (MEMS/NEMS), since processing-stress and stiction issues limit the precision and yield in assembling suspended structures. We present the fabrication and mechanical characterisation of a suspended graphene-polymer heterostructure membrane that aims to tackle the prevailing challenge of constructing high yield membranes with minimal compromise to the mechanical properties of graphene. The fabrication method enables suspended membrane structures that can be multiplexed over wafer-scales with 100% yield. We apply a micro-blister inflation technique to measure the in-plane elastic modulus of pure graphene and of heterostructure membranes with a thickness of 18 nm to 235 nm, which ranges from the 2-dimensional (2d) modulus of bare graphene at 173 ± 55 N m^-1 to the bulk elastic modulus of the polymer (Parylene-C) as 3.6 ± 0.5 GPa as a function of film thickness. Different ratios of graphene to polymer thickness yield different deflection mechanisms and adhesion and delamination effects which are consistent with the transition from a membrane to a plate model. This system reveals the ability to precisely tune the mechanical properties of ultra-thin conductive membranes according to their applications.

Phonon-assisted electroluminescence from metallic carbon nanotubes and graphene

We report on light emission from biased metallic single-wall carbon nanotube (SWNT), multiwall carbon nanotube (MWNT) and few-layer graphene (FLG) devices. SWNT devices were assembled from tubes with different diameters in the range 0.7-1.5 nm. They emit light in the visible spectrum with peaks at 1.4 and 1.8 eV. Similar peaks are observed for MWNT and FLG devices. We propose that this light emission is due to phonon-assisted radiative decay from populated pi* band states at the M point to the Fermi level at the K point. Since for most carbon nanotubes as well as for graphene the energy of unoccupied states at the M point is close to 1.6 eV, the observation of two emission peaks at approximately 1.6 +/- approximately 0.2 eV could indicate radiative decay under emission or absorption of optical phonons, respectively.

Functionalization of carbon nanotubes using phenosafranin

Spectroscopic analysis and atomic force microscopy (AFM) phase imaging studies show self-assembly of phenosafranin (PSF) to multiwalled carbon nanotubes (MWNTs). The shift in absorption spectra is associated with charge transfer of valence electrons from PSF to electron accepting sites on the MWNTs. The Raman-active disorder modes are used to fingerprint PSF attachment to MWNTs via defect states. AFM phase imaging was used to obtain a molecular topographic visual confirmation of PSF attached to the MWNT.

Multimodality evoked potentials in aortoarteritis

Brainstem auditory evoked potentials (BAEPs) have been used to detect early and even asymptomatic brain ischemia. There is a need to detect subclinical brain and/or spinal cord ischemia in patients with aortoarteritis so that ischemic deficits can be prevented by early intervention. We studied multimodality (Visual evoked potentials--VEPs, Somatosensory evoked potentials--SEPs and BAEPs) evoked potentials (EPs) in 10 neurologically asymptomatic subjects with aortoarteritis. EP latencies were normal in all the patients studied. The possible value of EP latencies in detection of early brain and/or spinal cord ischemia in patients with aortoarteritis is discussed.

Neurological intensive care in India

BACKGROUND

Intensive care units need to be optimally utilized especially in developing countries such as India where they are rare and artificial ventilators are available for a limited number of patients. Data concerning the outcome of diverse neurological emergencies are required to enable physicians to make decisions and to advise families of patients on issues such as the institution of artificial ventilation and the use of pressor agents.

METHODS

We analysed 271 patients admitted over a 24-month period to our 5-bed neurological intensive care unit, and related the outcome to the occurrence of coma (Group I, n=100), respiratory failure without coma (Group II, n=32) and no respiratory failure or coma (Group III, n=139). Patients with pre-terminal coma alone were included in Group III.

RESULTS

Whereas the three groups were similar with regard to age, sex and social class, mortality was entirely different (overall mortality 44%, Group I 86%, Group II 56% , Group III 12%). Only one comatose patient made a good recovery. Among patients requiring ventilatory support, the highest mortality was recorded in comatose patients (62/65; 95%) and the lowest in those with the Guillain-Barré syndrome (6/15; 40%).

CONCLUSIONS

We suggest that artificial ventilation be used only in those comatose patients where the underlying cause is potentially reversible such as status epilepticus and that a multicentre study be conducted in the Third World on the prognosis of coma and the use of intensive care units.