Crops: a green approach toward self-assembled soft materials

To date, a wide range of industrial materials such as solvents, fuels, synthetic fibers, and chemical products are being manufactured from petroleum resources. However, rapid depletion of fossil and petroleum resources is encouraging current and future chemists to orient their research toward designing safer chemicals, products, and processes from renewable feedstock with an increased awareness of environmental and industrial impact. Advances in genetics, biotechnology, process chemistry, and engineering are leading to a new manufacturing concept for converting renewable biomass to valuable fuels and products, generally known as the biorefinery concept. The swift integration of crop-based materials synthesis and biorefinery manufacturing technologies offers the potential for new advances in sustainable energy alternatives and biomaterials that will lead to a new manufacturing paradigm. This Account presents a novel and emerging concept of generating various forms of soft materials from crops (an alternate feedstock). In future research, developing biobased soft materials will be a fascinating yet demanding practice, which will have direct impact on industrial applications as an economically viable alternative. Here we discuss some remarkable examples of glycolipids generated from industrial byproducts such as cashew nut shell liquid, which upon self-assembly produced soft nanoarchitectures including lipid nanotubes, twisted/helical nanofibers, low-molecular-weight gels, and liquid crystals. Synthetic methods applied to a "chiral pool" of carbohydrates using the selectivity of enzyme catalysis yield amphiphilic products derived from biobased feedstock including amygdalin, trehalose, and vitamin C. This has been achieved with a lipase-mediated regioselective synthetic procedure to obtain such amphiphiles in quantitative yields. Amygdalin amphiphiles showed unique gelation behavior in a broad range of solvents such as nonpolar hexanes to polar aqueous solutions. Importantly, an enzyme triggered drug-delivery model for hydrophobic drugs was demonstrated by using these supramolecularly assembled hydrogels. Following a similar biocatalytic approach, vitamin C amphiphiles were synthesized with different hydrocarbon chain lengths, and their ability to self-assemble into molecular gels and liquid crystals has been studied in detail. Such biobased soft materials were successfully used to develop novel organic-inorganic hybrid materials by in situ synthesis of metal nanoparticles. The self-assembled soft materials were characterized by several spectroscopic techniques, UV-visible, infrared, and fluorescence spectrophotometers, as well as microscopic methods including polarized optical, confocal, scanning, and transmission electron microscopes, and thermal analysis. The molecular packing of the hierarchically assembled bilayer membranes was fully elucidated by X-ray analysis. We envision that the results summarized in this Account will encourage interdisciplinary collaboration between scientists in the fields of organic synthesis, soft materials research, and green chemistry to develop functional materials from underutilized crop-based renewable feedstock, with innovation driven both by material needs and environmentally benign design principles.

Silver-nanoparticle-embedded antimicrobial paints based on vegetable oil

Developing bactericidal coatings using simple green chemical methods could be a promising route to potential environmentally friendly applications. Here, we describe an environmentally friendly chemistry approach to synthesize metal-nanoparticle (MNP)-embedded paint, in a single step, from common household paint. The naturally occurring oxidative drying process in oils, involving free-radical exchange, was used as the fundamental mechanism for reducing metal salts and dispersing MNPs in the oil media, without the use of any external reducing or stabilizing agents. These well-dispersed MNP-in-oil dispersions can be used directly, akin to commercially available paints, on nearly all kinds of surface such as wood, glass, steel and different polymers. The surfaces coated with silver-nanoparticle paint showed excellent antimicrobial properties by killing both Gram-positive human pathogens (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The process we have developed here is quite general and can be applied in the synthesis of a variety of MNP-in-oil systems.

One year trends in the gram-negative bacterial antibiotic susceptibility patterns in a medical intensive care unit in South India

PURPOSE

To describe the changes in antibiotic susceptibility patterns of common intensive care unit pathogens with time from the medical intensive care unit of a tertiary care hospital.

METHODS

A prospective observational study was conducted in the medical intensive care unit (MICU) of a 2100 bed tertiary care hospital in South India. All data regarding patient characteristics, disease characteristics, infective agents, identified along with their antibiotic sensitivity patterns and patient outcomes were prospectively recorded in MICU data base. Various bacterial pathogen antibiotic sensitivity patterns from August 2004 to May 2005 were prospectively documented. During this period 491 patients were admitted to the MICU. Data were analyzed using excel spreadsheets.

RESULTS

Ceftazidime resistance reduced in Klebsiella spp. while cefotaxime resistance increased. In E. coli however, ceftazidime and cefotaxime resistance increased. Klebsiella resistance to cefotaxime and ceftazidime ranged from 25-50% and 14-91%, while E. coli resistance to these antibiotics ranged from 50-70% and 50 to 80% respectively. In Pseudomonas and the non-fermenting gram-negative bacteria (NFGNB) ceftazidime resistance decreased. Third generation cephalosporin resistance seemed to be reducing in the NFGNB, however, carbapenem resistance appeared to be increasing, possibly due to their increasing use.

CONCLUSIONS

This study demonstrates the trend in antibiotic susceptibility pattern (AST) of common gram negative infections seen in intensive care units. It demonstrates the changes seen especially after a change in the protocol antibiotic. Changes in the AST patterns of Klebsiella, E. coli, Pseudomonas and non-fermenting gram negative bacteria were seen. The data on the changing antibiotic susceptibility trends we believe is an important pillar in our efforts at infection control especially in intensive care settings.

An evaluation of the role of noninvasive positive pressure ventilation in the management of acute respiratory failure in a developing country

OBJECTIVE

Noninvasive positive pressure ventilation (NIPPV) has been shown to decrease the need for invasive mechanical ventilation (MV) in patients presenting with acute respiratory failure (ARF). We conducted a prospective study to assess if NIPPV use, in a developing country, was associated with clinical and physiological improvements.

DESIGN

Prospective observational study.

MATERIALS AND METHODS

Forty patients admitted to a medical intensive care unit during a 2-year period who fulfilled criteria for inclusion formed the study cohort to receive NIPPV.

FINDINGS

Baseline (mean +/- SD) pH, PaCO 2 and PaO 2 were 7.25 +/- 0.08, 76.6 +/- 20.9 and 79.18 +/- 40.56 mmHg respectively. The primary indication for NIPPV was hypercapnic respiratory failure (n = 36, 90%). The success rate with NIPPV was 85%, with 34 of 40 patients weaned successfully. Significant improvements were observed at 1 hour following institution of NIPPV in pH (7.31 +/- 0.09, P 2 (65 +/- 17.9, P 2 54.7 +/- 20) and maintained (within 12 h) postweaning from the ventilator (pH 7.39 +/- 0.08, PaCO 2 51.9 +/- 12.4). No significant change in the PaO 2 was observed during NIPPV; PaO 2 after 1 h, prior to weaning and after weaning was 90.53 +/- 42.85, 84.80 +/- 33.76, 78.71 +/- 43.81 respectively.

CONCLUSION

This study has demonstrated benefits of NIPPV in avoiding the need for invasive MV in patients presenting with ARF of diverse etiology, with results comparable to developed nations. Increased use of NIPPV in ARF is likely to impact favorably in nations with limited resources.

Generation of a germ cell-specific mouse transgenic Cre line, Vasa-Cre

Cell type-specific genetic modification using the Cre/loxP system is a powerful tool for genetic analysis of distinct cell lineages. Because of the exquisite specificity of Vasa expression (confined to the germ cell lineage in invertebrate and vertebrate species), we hypothesized that a Vasa promoter-driven transgenic Cre line would prove useful for the germ cell lineage-specific inactivation of genes. Here we describe a transgenic mouse line, Vasa-Cre, where Cre is efficiently and specifically expressed in germ cells. Northern analysis showed that transgene expression was confined to the gonads. Cre-mediated recombination with the Rosa26-lacZ reporter was observed beginning at approximately e15, and was >95% efficient in male and female germ cells by birth. Although there was a potent maternal effect with some animals showing more widespread recombination, there was no ectopic activity in most adults. This Vasa-Cre transgenic line should thus prove useful for genetic analysis of diverse aspects of gametogenesis and as a general deletor line.

Effective use of microarrays in neuroendocrine research

The development of microarray technology makes it possible to simultaneously assay the expression level of hundreds to tens of thousands of mRNA transcripts in one experiment. Genome-wide transcriptional analysis has increasing importance for many areas of neuroendocrinology research. The expense and technical complexity of microarray experiments can make it difficult to navigate the terrain of rival platforms and technologies. In this review, we provide a practical view and comparison of various microarray technologies. Affymetrix arrays, high-density cDNA arrays, membrane arrays and experimental design and data analysis are all discussed by researchers currently using these techniques to study gene regulation in neuroendocrine tissues.

Design and development of soft nanomaterials from biobased amphiphiles

Design and development of different forms of soft matter from renewable (biomass) feedstocks is gaining attention in current research. This highlight summarizes our continuing efforts towards the effective utilization of renewable resources for new chemicals, fuels and soft materials, and selected successful stories in that direction. Cashew nut shell liquid, an industrial by-product, was used as a raw material to synthesize aryl glycolipids which upon self-assembly generated an array of soft materials such as lipid nanotubes, twisted/helical nanofibers, low-molecular-weight hydro/organogels and liquid crystals. These soft architectures were fully characterized by using different techniques. In another example, amygdalin, a by-product of the apricot industry, was used to develop novel amphiphiles, which showed unprecedented gelation properties in a wide range of solvents. To take these soft nanomaterials to a second level, we successfully demonstrated the utility of these hydrogels as drug delivery vehicles. Intriguingly, enzyme catalysis was used as a tool to make and break the hydrogels, which apparently triggered controlled drug delivery. We believe these results and this highlight will motivate us and others in the field of biobased materials research, green chemistry and soft material development through self-assembly processes, to design and develop new functional materials from plant/crop-based renewable resources, otherwise underutilized.

Enzyme Catalysis: Tool to Make and Break Amygdalin Hydrogelators from Renewable Resources: A Delivery Model for Hydrophobic Drugs

We report a novel approach for the controlled delivery of an antiinflammatory, chemopreventive drug by an enzyme-triggered drug release mechanism via the degradation of encapsulated hydrogels. The hydro- and organogelators are synthesized in high yields from renewable resources by using regioselective enzyme catalysis, and a known chemopreventive and antiinflammatory drug, i.e., curcumin, is used for the model study. The release of the drug occurred at physiological temperature, and control of the drug release rate is achieved by manipulating the enzyme concentration and/or temperature. The byproducts formed after the gel degradation were characterized and clearly demonstrated the site specificity of degradation of the gelator by enzyme catalysis. The present approach could have applications in developing cost-effective controlled drug delivery vehicles from renewable resources, with a potential impact on pharmaceutical research and molecular design and delivery strategies.

Predictors of mortality in mechanically ventilated patients

OBJECTIVES

There are scarce data from India validating scoring systems used to predict outcome in patients requiring mechanical ventilation. This study prospectively compared the organ system failure (OSF), the acute physiology and chronic health evaluation (APACHE) II, and the APACHE III, scores on patients requiring mechanical ventilation in the medical intensive care unit, to predict outcome.

METHODS

200 consecutive patients requiring mechanical ventilation in a medical intensive care unit were recruited. OSF, APACHE II, and APCHE III scores were calculated at admission and daily for one week or until discharge in all patients. Other variables recorded include age, sex, diagnosis, oxygen therapy before ventilation, complications on ventilation, duration in hospital before ventilation, duration of ventilation, type of respiratory failure, alveolar arterial oxygen gradient, P/F ratio, use of tracheostomy, time on ventilator before tracheostomy, muscle relaxant used, fluid balance, inotrope support. Logistic regression analysis and area under the curve were computed to determine which variables independently predict outcome.

RESULTS

Of the 200 patients, at discharge 143 patients (71.5%) had died. The factors that independently predicted outcome among these patients on mechanical ventilation were the type of respiratory failure (type I) OR = 2.7 (p = 0.02), the use of inotropes OR 2.4 (p = 0.04), and the APACHE II score OR = 1.8 (p = 0.008) for every five point increase in APACHE II score.

CONCLUSIONS

Type 1 respiratory failure, the use of inotropes, and the APACHE II score measured at admission are significant independent predictors of mortality in the patients on mechanical ventilation.