Detection of creatinine using surface-driven ordering transitions of liquid crystals

<p>Determining creatinine levels in blood is of great importance in the detection of high risk for renal failure. Here, we report a simple methodology for real-time monitoring of creatinine employing surface-driven ordering transitions in liquid crystals (LCs) by changing pH in presence of creatinine deiminase enzyme. It is found that when 5CB (4-Cyano-4ʹ-pentylbiphenyl) LC doped with 4ʹ-hexyl-biphenyl-4-carboxylic acid, a bright optical appearance was observed (at aqueous–LC interface) which is not disturbed in presence of creatinine, consistent with a planar/tilted orientation of the LC molecules at those interface. Interestingly, in presence of creatinine deiminase, an ordering transition was observed resulting from enzymatic reactions (giving rise to NH₄⁺ ions) that can change the local pH values and lead to dark optical appearance of the LC. Presence of different amounts of creatinine would lead varied ordering transition that can be monitored in real time in presence of creatinine deiminase. Our approach could detect the creatinine levels as low as that of the healthy adult (~50 µM) and can be successfully applied to measure higher concentration of creatinine in real time using dynamic optical response of the LC.</p

Poly(l‑lysine)-Coated Liquid Crystal Droplets for Sensitive Detection of DNA and Their Applications in Controlled Release of Drug Molecules

Interactions between DNA and adsorbed poly­(l-lysine) (PLL) on liquid crystal (LC) droplets were investigated using polarizing optical microcopy and epi-fluorescence microscopy. Earlier, we demonstrated that adsorption of PLL to the LC/aqueous interface resulted in homeotropic orientation of the LC and thus exhibited a radial configuration of the LC confined within the droplets. Subsequent adsorption of DNA (single-stranded DNA/double-stranded DNA) at PLL-coated LC droplets was found to trigger an LC reorientation within the droplets, leading to preradial/bipolar configuration of those droplets. To our surprise, subsequent exposure of complementary ssDNA to ssDNA/adsorbed PLL-modified LC droplets did not cause the LC reorientation. This is likely due to the formation of polyplexes (DNA–PLL complex) as confirmed by fluorescence microscopy and atomic force microscopy. In addition, dsDNA-adsorbed PLL droplets have been found to be effectively useful to displace (controlled release) propidium iodide (a model drug) encapsulated within dsDNA over time. These observations suggest the potential for a label-free droplet-based LC detection system that can respond to DNA and may provide a simple method to develop DNA-based drug nanocarriers

pH-Driven Ordering Transitions in Liquid Crystal Induced by Conformational Changes of Cardiolipin

We report an investigation of interfacial phenomena occurring at aqueous–liquid crystal (LC) interfaces that triggers an orientational ordering transition of the LC in the presence of cardiolipin (CL) by varying pH, salt concentration and valence. In particular, the effects of three different conformational isomeric forms of the CL are observed to cause the response of the LC ordering to vary significantly from one to another at those interfaces. An ordering transition of the LC was observed when the CL is mostly in undissociated (at pH 2) and/or in bicyclic (at pH 4) conformation in which LC shows changes in the optical appearance from bright to dark. By contrast, no change in the optical appearance of the LC was observed when the pH of the system increases to 8 or higher in which the CL mostly exists in the open conformation. Fluorescence microscopy measurements further suggest that pH-dependent conformational forms of the CL have different ability to self-assemble (thus different packing efficiency) at aqueous–LC interfaces leading to dissimilar orientational behavior of the LC. Specifically, we found that change in headgroup–headgroup repulsion of the central phosphatidyl groups of the CL plays a key role in tuning the lipid packing efficiency and thus responses to interfacial phenomena. Orientational ordering transition of the LC was also observed as a function of increasing the ionic strength (buffer capacity) and strongly influenced in the presence of mono and divalent cations. Langmuir–Blodgett (LB) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements provide further insight in modulation of the lipid packing efficiency and alkyl chain conformation of the CL at different pH and ionic conditions. Overall, the results presented in this paper establish that LCs offer a promising approach to differentiate different conformations (label free detection) of the CL through ordering transition of the LC at aqueous–LC interfaces

Transcriptome analysis of mycobacteria in sputum samples of pulmonary tuberculosis patients

<div><p>Pulmonary tuberculosis, the disease caused by <i>Mycobacterium tuberculosis</i>, still retains a top rank among the deadliest communicable diseases. Sputum expectorated during the disease continues to be a primary diagnostic specimen and also serves as a reservoir of bacteria. The expression pattern of mycobacteria in sputum will lead to an insight into bacterial adaptation at the most highly transmissible stage of infection and can also help in identifying newer diagnostic as well as drug targets. Thus, in the present study, a whole genome microarray of <i>Mycobacterium tuberculosis</i> was used to elucidate the transcriptional profile of mycobacteria in the sputum samples of smear positive pulmonary tuberculosis patients. Overall, the mycobacteria in sputum appeared to be in a low energy and low replicative state as compared to <i>in vitro</i> grown log phase <i>M</i>. <i>tb</i> with downregulation of genes involved in ATP synthesis, aerobic respiration and translational machinery. Simultaneously, downregulation was also seen in the genes involved in secretion machinery of mycobacteria along with the downregulation of genes involved in the synthesis of phthiocerol dimycocerosate and phenol glycolipids. In contrast, the majority of the genes which showed an upregulation in sputum mycobacteria were of unknown function. Further identification of these genes may provide new insights into the mycobacterial behavior during this phase of infection and may help in deciphering candidates for development of better diagnostic and drug candidates.</p></div

Virulence-associated cell wall synthesis and transport.

<p>Virulence-associated cell wall synthesis and transport.</p

Validation of microarray data on real time PCR by analyzing the relative expression of 5 genes in smear positive PTB samples as compared to <i>in vitro</i> grown <i>M</i>.<i>tb</i> H37Rv.

<p>16s rRNA was used as reference gene for normalization. Y-axis values (Log2 fold change) of ≥1 indicate upregulation and values ≤ -1 indicate down-regulation. Each bar represents mean ± SD values for each of the genes with three technical replicates. *p<0.05; **p<0.01 by student’s t test.</p

Functional categories of differentially expressed genes.

<p>Functional categories of differentially expressed genes.</p

Venn diagram indicating overlap of <i>M</i>. <i>tb</i> genes detected as upregulated in sputum in TB patients and in sputum from lung cancer patients.

<p>163 genes were upregulated in sputum from PTB patients and 26 genes also showed upregulation in sputum from lung cancer patients out of which 19 genes were common between the two and hence were eliminated from the list of diagnostic candidates</p

Differentially expressed functional categories indicative of <i>M</i>. <i>tb</i> replication.

<p>Differentially expressed functional categories indicative of <i>M</i>. <i>tb</i> replication.</p

Differentially expressed genes located within ESX type VII secretion system loci.

<p>Differentially expressed genes located within ESX type VII secretion system loci.</p