MALDI-TOF mass spectrometry: an emerging technology for microbial identification and diagnosis

Currently microorganisms are best identified using 16S rRNA and 18S rRNA gene sequencing. However, in recent years Matrix Assisted Laser Desorption Ionization-Time of Flight mass spectrometry (MALDI-TOF MS) has emerged as a potential tool for microbial identification and diagnosis. During the MALDI-TOF MS process, microbes are identified using either intact cells or cell extracts. The process is rapid, sensitive and economical in terms of both labor and costs involved. The technology has been readily imbibed by microbiologists who have reported usage of MALDI-TOF MS for a number of purposes like, microbial identification and strain typing, epidemiological studies, detection of biological warfare agents, detection of water- and food-borne pathogens, detection of antibiotic resistance and detection of blood and urinary tract pathogens etc. The limitation of the technology is that identification of new isolates is possible only if the spectral database contains peptide mass fingerprints of the type strains of specific genera/species/subspecies/strains. This review provides an overview of the status and recent applications of mass spectrometry for microbial identification. It also explores the usefulness of this exciting new technology for diagnosis of diseases caused by bacteria, viruses and fungi

In situ intercalation dynamics in inorganic-organic layered perovskite thin films.

The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson-Mehl-Avrami-Kolmogorov model, with results fitting both ideal and nonideal cases.This work is part of High-Impact Research scheme of IIT Delhi, Nano Research Facility (MCIT, Govt. Of India), UK-India Education and Research Initiative (UKIERI) programme, and part funded by EPSRC grant EP/G060649/1, and ERC LINASS 320503.This material is excerpted from a work that was published in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/am501568

Silicon-Based Inorganic–Organic Hybrid Nanocomposites for Optoelectronic Applications

A nanocomposite consisting of a unique combination of optically active materials, that is, an inorganic–organic (IO) layered hybrid and porous silicon (PS), is prepared using a simple but effective three-step electrochemical method. Xray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectral analysis suggest that the IO hybrid (R-MX4-type 2D perovskite, where R represents an organic compound, M a divalent metal ion, and X a halide) is conveniently incorporated into the interstitial spaces of nanoporous silicon. The IO-based 2D perovskite emits a strong and narrow room-temperature exciton line at 520 nm due to effects related to dielectric confinement. Similarly, n-type porous silicon emits in a broad range in the deep-red region at 700 nm, which is attributable to the quantum confinement effects related to the nanoporosity in silicon. Because of the contributions from both entities, the completely space-filled IO–PS nanocomposite shows an orange–yellow emission. The proposed methodology can be easily extended to a large number of such IO–PS functional nanocomposites and is thus expected to be used in optoelectronic applications such as light-emitting diodes (LEDs), solar cells, and other optical elements

Facile growth and re-crystallization of polymer-based inorganic-organic 2D hybrid composites and their applications

The in-situ growth and recrystallization of inorganic-organic (IO) hybrids within the natural free volume of polymer matrices for the realization of significantly stable IO hybrid-polymer composites and its applications have been presented. A general strategy is explored to attain uniform and facile growth of IO hybrid nanocrystals (2–3 nm) within the interstitial spaces of polymer matrix. Annealing further supports the agglomeration and self-assembly of nanocrystals into highly c-oriented hexagonal microplatelets of ∼10–20 μm2 and 50–100 nm thickness within the polymer matrix. The resultant composites endow highly luminescent retaining the typical thermally and mechanically stable polymeric nature. Series of optical, structural, morphological and thermal studies are performed to understand the growth conditions and uniform distribution of IO nanocrystallites within the polymer. To exemplify, LED colour conversion using encapsulation/surface coating and polymeric blocks fabrication for optical waveguide/channel inscription are demonstrated to foresee many new flexible and robust applications. Thus, the present approach offers a new paradigm to achieve light-emitting IO hybrids in the form of polymeric composites for advanced optoelectronic device applications.Authors acknowledge the financial grants of the Department of Science and Technology (DST) Govt. of India, Royal Society (UK) and UK-India Education Research Initiative (UKIERI). This work is part of FIST (DST, Govt. of India) UFO scheme of IIT Delhi. MA and KMD thank INSPIRE research fellowship funded by DST. Authors appreciate the generous free supply of GaN-LED chips from M/s. BridgeLux, USA

<i>Cissampelos pareira</i> Linn: Natural Source of Potent Antiviral Activity against All Four Dengue Virus Serotypes

<div><p>Background</p><p>Dengue, a mosquito-borne viral disease, poses a significant global public health risk. In tropical countries such as India where periodic dengue outbreaks can be correlated to the high prevalence of the mosquito vector, circulation of all four dengue viruses (DENVs) and the high population density, a drug for dengue is being increasingly recognized as an unmet public health need.</p><p>Methodology/Principal findings</p><p>Using the knowledge of traditional Indian medicine, Ayurveda, we developed a systematic bioassay-guided screening approach to explore the indigenous herbal bio-resource to identify plants with pan-DENV inhibitory activity. Our results show that the alcoholic extract of <i>Cissampelos pariera</i> Linn (<i>Cipa</i> extract) was a potent inhibitor of all four DENVs in cell-based assays, assessed in terms of viral NS1 antigen secretion using ELISA, as well as viral replication, based on plaque assays. Virus yield reduction assays showed that <i>Cipa</i> extract could decrease viral titers by an order of magnitude. The extract conferred statistically significant protection against DENV infection using the AG129 mouse model. A preliminary evaluation of the clinical relevance of <i>Cipa</i> extract showed that it had no adverse effects on platelet counts and RBC viability. In addition to inherent antipyretic activity in Wistar rats, it possessed the ability to down-regulate the production of TNF-α, a cytokine implicated in severe dengue disease. Importantly, it showed no evidence of toxicity in Wistar rats, when administered at doses as high as 2g/Kg body weight for up to 1 week.</p><p>Conclusions/Significance</p><p>Our findings above, taken in the context of the human safety of <i>Cipa</i>, based on its use in Indian traditional medicine, warrant further work to explore <i>Cipa</i> as a source for the development of an inexpensive herbal formulation for dengue therapy. This may be of practical relevance to a dengue-endemic resource-poor country such as India.</p></div

Effect of <i>Cipa</i> extract on platelets.

<p>(A) Freshly collected human blood was incubated with saline (white bars) or <i>Cipa</i> extract (at 2 μg/ml: blue bars; or 10 μg/ml: red bars) for up to 4 hours. Aliquots were drawn at the indicated times for determination of platelet counts. (B) Wistar rats were orally administered 0.25% methyl cellulose containing <i>Cipa</i> extract ranging from 0–1000 mg/Kg body weight. Fresh blood collected from these rats at 0 (white bars), 1 (blue bars) and 4 (red bars) hours post-administration, were analysed for platelet counts. For both panels, data shown are mean values (<i>n</i> = 5); the vertical bars represent standard deviation, SD.</p

Inhibition of DENV antigen and virus production by <i>Cipa</i> extract treatment.

<p>Vero cells were used to test the effect of <i>Cipa</i> extract on DENV-3 in a type-3 assay format. The figure depicts the kinetics of NS1 antigen (A) and infectious virus (B) released into the culture supernatant in the absence (empty black circles) and presence of <i>Cipa</i> extract at 22 μg/ml (filled blue circles), 66 μg/ml (empty red squares) and 200 μg/ml (filled green squares) concentrations.</p