Particle encapsulation in aqueous ferrofluid drops and sorting of particle-encapsulating drops from empty drops using a magnetic field.

Handling and manipulation of particle-encapsulating droplets (PED) have profound applications in biochemical assays. Herein we report encapsulation of microparticles in aqueous ferrofluid droplets in a primary continuous phase (CP) and sorting of PED from empty droplets (ED) at the interface of the CP in coflow with a second continuous phase using a magnetic field. We find that the encapsulation process results in a size contrast between the PED and ED that depends on the flow regime - squeezing, dripping, or jetting - which in turn is governed by the ratio of the discrete phase to the continuous phase capillary number, Car. The difference between the volume fractions of ferrofluid in the PED and ED, ΔαPED, is utilized for sorting, and is found to depend on the ratio of the capillary numbers, Car. The difference ΔαPED is found to be maximum in the jetting regime, suggesting that the jetting regime is most suitable for encapsulation and sorting. The sorting criterion is represented in terms of a parameter ξ, which is a function of the ratios of the magnetic force to the interfacial force experienced by the PED and ED. Our study revealed that sorting is possible for ξ < 0, which corresponds to ΔαPED > 0.25. The maximum sorting efficiency of our system is found to be ∼95% at a throughput of ∼100 drops per s.

Trapping and Coalescence of Diamagnetic Aqueous Droplets Using Negative Magnetophoresis.

The manipulation of aqueous droplets has a profound significance in biochemical assays. Magnetic field-driven droplet manipulation, offering unique advantages, is consequently gaining attention. However, the phenomenon relating to diamagnetic droplets is not well understood. Here, we report the understanding of trapping and coalescence of flowing diamagnetic aqueous droplets in a paramagnetic (oil-based ferrofluid) medium using negative magnetophoresis. Our study revealed that the trapping phenomenon is underpinned by the interplay of magnetic energy (Em) and frictional (viscous) energy (Ef), in terms of magnetophoretic stability number, Sm = (Em/Ef). The trapping and nontrapping regimes are characterized based on the peak value of magnetophoretic stability number, Smp, and droplet size, D*. The study of coalescence of a trapped droplet with a follower droplet (and a train of droplets) revealed that the film-drainage Reynolds number (Refd) representing the coalescence time depends on the magnetic Bond number, Bom. The coalesced droplet continues to remain trapped or gets self-released obeying the Smp and D* criterion. Our study offers an understanding of the magnetic manipulation of diamagnetic aqueous droplets that can potentially be used for biochemical assays in microfluidics.

Transport of a Sessile Aqueous Droplet over Spikes of Oil Based Ferrofluid in the Presence of a Magnetic Field.

Droplets can be used as carrier vehicles for the transportation of biological and chemical reagents. Manipulation of water- and oil-based ferromagnetic droplets in the presence of a magnetic field has been well-studied. Here, we elucidate the transport of a sessile aqueous (diamagnetic) droplet placed over spikes of oil-based ferrofluid (FF) in the presence of a nonuniform magnetic field. An oil-based FF droplet, dispensed over a rigid oleophilic surface, interacts with a magnetic field to get transformed into an array of spikes which then act as a carrier for the transportation of the aqueous droplet. Our study reveals that transportation phenomena is governed by the interplay of three different forces: magnetic force Fm, frictional force Ff, and interfacial tension force Fi, which is expressed in terms of the magnetic Laplace number ( Lam) and magnetic Bond number ( Bom) as Lam?1 = ( Ff1/ Fm, x) and Bom Lam?1 = ( Ff2/ Fi). Based on the values of the dimensionless numbers, three different regimes, steady droplet transport, spike extraction, and magnet disengagement, are identified. It is found that steady droplet transport is observed for Lam?1 ? 1 and Bom Lam?1 ? 1, whereas extraction of spikes is observed for Lam?1 ? 1 and Bom Lam?1 > 1 and magnet disengagement is observed for Lam?1 > 1. In the steady droplet transport regime, velocity of the aqueous droplet Uds was found to be dependent on the volumes of the aqueous droplet Vw and FF droplet VFF following Uds ? Vw?0.19 VFF0.36. A simple model is presented that accurately predicts the aqueous droplet velocity Uds within 5% of the corresponding experimental data. In the spike extraction regime, the spike extraction distance Lse was found to vary with Vw, VFF, and the magnet velocity Ums following Lse ? Vw?1.75 VFF0.75 Ums?1.56.

Results of "Trochanteric Femoral Nailing (TFN)" in comminuted unstable trochanteric fractures.

Unstable trochanteric fractures and fractures with reverse obliquity pose difficulty in fixation. In recent years, intramedullary nails, for the treatment of comminuted and unstable intertrochanteric hip fractures, are becoming more popular relative to conventional, sliding hip screws. The purpose of our study was to evaluate the result of Trochanteric femoral nailing in comminuted, unstable Trochanteric femur fracture in terms of anatomical restoration and functional outcome. It is a prospective and without control study. Trochanteric femoral nailing has been done in comminuted unstable inter-trochanteric fracture femur (AO A2.2 to A3.3) of 25 patients and they are followed up postoperatively for at least 12 months. Pre-operative and post-operative clinical and radio-logical parameters are compared accordingly. Union in all cases. Overall complication rate 12% including some implant related complications. Functional outcome on Harris Hip Score is comparable with standard literature. For treatment of intertrochanteric hip fractures, particularly with comminuted fracture fragments, intramedullary devices offer beneficial features, such as closed insertion, a shorter lever arm, and controlled telescoping of the head-neck fragment. Insertion of the nail through the tip of the greater trochanter requires less dissection and may lead to less blood loss and fewer wound complications, as well as earlier postoperative mobility. Further biomechanical and clinical studies are necessary to validate the efficacy of the trochanteric femoral nail. Level of Evidence : Level III therapeutic study.

Shape evolution and splitting of ferrofluid droplets on a hydrophobic surface in the presence of a magnetic field.

We elucidate the phenomena of dynamic wetting, shape evolution and splitting of ferrofluid (FF) droplets on a hydrophobic surface under the influence of a magnetic field. In the case of a FF droplet interacting with a magnetic field, both surface energy and magnetic energy contribute to the total Gibb's free energy and hence the wetting phenomena. The nanoparticles in the FF droplet migrate and get accumulated at the apex of the droplet which enhances the magnetic interaction causing large deformation of the droplet. The FF droplet deformation and subsequent splitting are governed by the interplay between the magnetic Fm and surface tension Fs forces. The ratio of the forces km = (Fm/Fs) was found to be a function of the magnetic Bond number Bom and non-dimensional gap g* as km ∼ (Bom)0.3(g*)-0.86. Splitting of the FF droplets was observed for km > 1 and for km < 1, an equilibrium droplet shape was observed. The wetting behavior of the FF droplets was found to be strongly dependent on the FF concentration c - concentrated (c = 1.2%) FF droplets exhibit contact line (CL) pinning and decrease in contact angle (CA) θ with time throughout, while diluted (c = 0.6%) FF droplets show a mixed mode (CL pinning followed by constant CA). In splitting of FF droplets, the ratio of the volume of the daughter droplet to that of the parent droplet i.e. (Vd/Vp), was found to decrease with an increase in the parent droplet size Vp.

Correction to: Release of an enantioselective nitrilase from Alcaligenes faecalis MTCC 126: a comparative study.

In the original version of our paper entitled "Release of an enantioselective nitrilase from Alcaligenes faecalis MTCC 126: a comparative study" (2005) 27:415-424, some references to already published articles were inadvertently left out.

Rheological properties and microstructure of xylanase containing whole wheat bread dough.

The present research work was undertaken to investigate the effect of xylanase, produced by Penicillium citrinum, on rheological behavior of whole wheat bread dough at large and small deformation respectively. Dough attributes including textural properties (penetration) and structure related characteristics (oscillatory tests) were evaluated. Change in visco-elastic properties of xylanase containing dough was evaluated by oscillatory and creep measurements. The flow experiments were conducted under steady-state condition with shear rate ranging from 0.01 to 100 s-1. Frequency sweep experiments were performed between 0.01 and 10 Hz. It revealed that in both control and xylanase containing dough formulation, the elastic modulus was higher than viscous modulus in the entire range of frequency. Our results represent the adequacy of fitting of dynamic moduli in Power law model and week gel model. Peleg model as well as six element Kelvin model described well the creep behaviour of control and xylanase-containing dough. Uniaxial extensibility was assessed by Kieffer dough and gluten extensibility rig. Lyophilized powder of untreated and xylanase treated doughs were tested under scanning electron microscope. FTIR spectra of lyophilized powder of untreated and xylanase treated dough were recorded in the range of 600-4000 cm-1.

Dynamics of Aqueous Droplets at the Interface of Coflowing Immiscible Oils in a Microchannel.

We report the dynamics of aqueous droplets of different size and viscosity at the interface of a coflowing stream of immiscible oils (i.e., primary and secondary continuous phases) in a microchannel, at low Re. The lateral migration of droplets introduced into the primary continuous phase toward the interface and subsequent selective migration of droplets across the interface into the secondary continuous phase is investigated. The interplay between the competing noninertial lift and interfacial tension forces, which govern the interfacial migration of the droplets, is presented and discussed. The velocity and strain rate profiles, and interface location, which are critical for calculating the lift force and migration behavior of droplets, are presented. The trajectories of droplets of different size and viscosity in the primary continuous phase are obtained for different interface locations. During interfacial migration, the deformation behavior of droplets of different viscosities is studied. Finally, sorting of droplets based on size contrast is demonstrated and sorting efficiency is found. A new paradigm of migration and sorting of droplets is reported, which could find importance in chemical and biological applications.

Effect of Sub Clinical Hypothyroidism on C-reactive Protein and Ischemia Modified Albumin.

Thyroid disorders are associated with imbalance in redox status throughout the body along with a pro-inflammatory state. Aim of our present study was to evaluate any potential role of ischemia modified albumin (IMA) in both sub clinical and established hypothyroidism and to explore its potential relationship with the hsCRP. Serum TSH, fT4, IMA and hsCRP were measured in 30 cases and 40 age and sex matched controls by ELISA and standard photometric techniques. IMA value was compared between the sub clinical and clinical hypothyroid patients. Strength of association between the IMA and hsCRP was assessed also to analyze the prevalence of pro-inflammatory condition in hypothyroid patients. Serum values (mean ± SD) of hsCRP (07.49 ± 2.73), TSH (22.18 ± 12.9) and IMA (128.31 ± 16.96) were significantly higher in the case group. Bivariate correlation study indicated that TSH and fT4 showed direct and inverse relationship respectively with the hsCRP and IMA. IMA itself exhibited direct correlation with the pro-inflammatory marker hsCRP showing a positive correlation with IMA. Results of the general linear model analysis showed that only TSH had a significant positive predictive value on IMA while fT4 itself as a continuous covariate, or in the fraction of its normal or subnormal range, did not show any significant predictive value on IMA values. We suggest in conclusion that a pro-inflammatory status and derangement of the redox balance towards an overall ischemic state start at an early stage of sub clinical hypothyroidism. Early detection of these parameters may help in provision of necessary preventive measures against complications of hypothyroidism.

Ascorbic acid improves membrane fragility and decreases haemolysis during red blood cell storage.

BACKGROUND: Changes that occur to red blood cells (RBCs) during routine blood bank storage include decreased deformability, increased haemolysis and oxidative damage. Oxidative injury to the RBC membrane and haemoglobin can affect changes in shape and deformability. Ascorbic acid (AA) is an antioxidant that maintains haemoglobin in a reduced state and minimises RBC oxidative injury. We hypothesised that AA would improve membrane fragility and decrease haemolysis during storage. METHODS: Whole blood derived, AS-5 preserved, pre-storage leucoreduced RBC units were exposed to either AA or saline control solutions. Several rheological and biochemical parameters were measured serially during storage, including RBC membrane mechanical fragility, percent haemolysis and methaemoglobin levels. RESULTS: AA exposure significantly reduced mechanical fragility and haemolysis over the entire storage period. The highest two concentrations of AA affected the greatest reductions in mechanical fragility and percent haemolysis. Addition of AA to the RBCs did not significantly alter their biochemical parameters compared to control RBCs incubated with saline. CONCLUSION: AA reduced RBC membrane fragility and decreased haemolysis during storage without adversely affecting other RBC biochemical parameters. The clinical significance of these findings needs to be determined.

Impact of industrial waste effluents on river Damodar adjacent to Durgapur industrial complex, West Bengal, India.

The present study deals with the characterization of industrial effluents released from various industries and distribution of heavy metals in effluent discharge channel and its impact on the river Damodar. The effluent of tamlanala, a natural storm water channel, is extensively used for irrigation for growing vegetables in and around the study area. The heavy metals in water of the study area are in the order of Fe > Mn > Pb > Cd and sediments follow similar trends too. The enrichment of heavy metals in the sediments are in the order of Cd (39.904) > Pb (33.156) > Mn (0.164) > Fe (0.013). The geoaccumulation index values reveal effluent channel is subjected to moderate to high pollution with respect to Cd (4.733) and Pb (4.466). The analyzed data for enrichment factors and the pollution load index (1.305) show that effluent channels have suffered from significant heavy metal contamination following industrialization and urbanization. Compared to baseline values, the surface sediment layers show high enrichment across the channel and at its discharge point. The factor analysis reveals three factors-industrial sources, surface runoff inputs, and background lithogenic factors which clarify the observed variance of the environmental variables. Metal pollution assessment of sediments suggests that pollution from the heavy metals observed is high in the tamlanala which in turn affects the downstream of the river system.

Xanthine oxidoreductase: a journey from purine metabolism to cardiovascular excitation-contraction coupling.

Xanthine oxidoreductase (XOR) is a ubiquitous complex cytosolic molybdoflavoprotein which controls the rate limiting step of purine catabolism by converting xanthine to uric acid. It is known that optimum concentrations of uric acid (UA) and reactive oxygen species (ROS) are necessary for normal functioning of the body. The ability of XOR to perform detoxification reactions, and to synthesize UA and reactive oxygen species (ROS) makes it a versatile intra- and extra-cellular protective "housekeeping enzyme". It is also an important component of the innate immune system. The enzyme is a target of drugs against gout and hyperuricemia and the protein is of major interest as it is associated with ischemia reperfusion (I/R) injury, vascular disorders in diabetes, cardiovascular disorders, adipogenesis, metabolic syndrome, cancer, and many other disease conditions. Xanthine oxidoreductase in conjugation with antibodies has been shown to have an anti-tumor effect due to its ability to produce ROS, which in turn reduces the growth of cancer tissues. Apart from this, XOR in association with nitric oxide synthase also participates in myocardial excitation-contraction coupling. Although XOR was discovered over 100 years ago, its physiological and pathophysiological roles are still not clearly elucidated. In this review, various physiological and pathophysiological functional aspects of XOR and its association with various forms of cancer are discussed in detail.

Effect of agitation and aeration on the production of nitrile hydratase by Rhodococcus erythropolis MTCC 1526 in a stirred tank reactor.

AIMS: To evaluate the effect of different physicochemical parameters such as agitation, aeration and pH on the growth and nitrile hydratase production by Rhodococcus erythropolis MTCC 1526 in a stirred tank reactor. METHODS AND RESULTS: Rhodococcus erythropolis MTCC 1526 was grown in 7-l reactor at different agitation, aeration and controlled pH. The optimum conditions for batch cultivation in the reactor were an agitation rate of 200 rev min(-1) , aeration 0.5 v/v/m at controlled pH 8. In this condition, the increase in nitrile hydratase activity was almost threefold compared to that in the shake flask. CONCLUSION: Agitation and aeration rate affected the dissolved-oxygen concentration in the reactor which in turn affected the growth and enzyme production. SIGNIFICANCE AND IMPACT OF THE STUDY: Cultivation of R. erythropolis MTCC 1526 in the reactor was found to have significant effect on the growth and nitrile hydratase production when compared to the shake flask.

Specification of Drosophila hematopoietic lineage by conserved transcription factors.

Two major classes of cells observed within the Drosophila hematopoietic repertoire are plasmatocytes/macrophages and crystal cells. The transcription factor Lz (Lozenge), which resembles human AML1 (acute myeloid leukemia- 1) protein, is necessary for the development of crystal cells during embryonic and larval hematopoiesis. Another transcription factor, Gcm (glial cells missing), has previously been shown to be required for plasmatocyte development. Misexpression of Gcm causes crystal cells to be transformed into plasmatocytes. The Drosophila GATA protein Srp (Serpent) is required for both Lz and Gcm expression and is necessary for the development of both classes of hemocytes, whereas Lz and Gcm are required in a lineage-specific manner. Given the similarities of Srp and Lz to mammalian GATA and AML1 proteins, observations in Drosophila are likely to have broad implications for understanding mammalian hematopoiesis and leukemias.

The Son of sevenless gene product: a putative activator of Ras.

The Son of sevenless (Sos) gene functions in signaling pathways initiated by the sevenless and epidermal growth factor receptor tyrosine kinases. The Sos gene has now been isolated and sequenced. Its product is a 1595-amino acid protein similar to the CDC25 protein in Saccharomyces cerevisiae, a guanine nucleotide exchange factor that activates Ras. These results imply a role for the ras pathway in Drosophila neuronal development.

In vivo functional analysis of the Ras exchange factor son of sevenless.

The Son of sevenless (Sos) protein functions as a guanine nucleotide transfer factor for Ras and interacts with the receptor tyrosine kinase Sevenless through the protein Drk, a homolog of mammalian Grb2. In vivo structure-function analysis revealed that the amino terminus of Sos was essential for its function in flies. A molecule lacking the amino terminus was a potent dominant negative. In contrast, a Sos fragment lacking the Drk binding sites was functional and its activity was dependent on the presence of the Sevenless receptor. Furthermore, membrane localization of Sos was independent of Drk. A possible role for Drk as an activator of Sos is discussed and a Drk-independent interaction between Sos and Sevenless is proposed that is likely mediated by the pleckstrin homology domain within the amino terminus.

Binding of the Ras activator son of sevenless to insulin receptor substrate-1 signaling complexes.

Signal transmission by insulin involves tyrosine phosphorylation of a major insulin receptor substrate (IRS-1) and exchange of Ras-bound guanosine diphosphate for guanosine triphosphate. Proteins containing Src homology 2 and 3 (SH2 and SH3) domains, such as the p85 regulatory subunit of phosphatidylinositol-3 kinase and growth factor receptor-bound protein 2 (GRB2), bind tyrosine phosphate sites on IRS-1 through their SH2 regions. Such complexes in COS cells were found to contain the heterologously expressed putative guanine nucleotide exchange factor encoded by the Drosophila son of sevenless gene (dSos). Thus, GRB2, p85, or other proteins with SH2-SH3 adapter sequences may link Sos proteins to IRS-1 signaling complexes as part of the mechanism by which insulin activates Ras.

Enantioselective nitrilase from Pseudomonas putida: cloning, heterologous expression, and bioreactor studies.

Nitrilases have attracted tremendous attention for the preparation of optically pure carboxylic acids. This article aims to address the production and utilization of a highly enantioselective nitrilase from Pseudomonas putida MTCC 5110 for the hydrolysis of racemic mandelonitrile to (R)-mandelic acid. The nitrilase gene from P. putida was cloned in pET 21b(+) and over-expressed as histidine-tagged protein in Escherichia coli. The histidine-tagged enzyme was purified from crude cell extracts of IPTG-induced cells of E. coli BL21 (DE3). Inducer replacement studies led to the identification of lactose as a suitable and cheap alternative to the costly IPTG. Effects of medium components, various physico-chemical, and process parameters (pH, temperature, aeration, and agitation) for the production of nitrilase by engineered E. coli were optimized and scaled up to a laboratory scale bioreactor (6.6 l). Finally, the recombinant E. coli whole-cells were utilized for the production of (R)-(-)-mandelic acid.