Groepsgedrag op de nanoschaal

Monodisperse gas microbubbles, encapsulated with a shell of photopolymerizable diacetylene lipids and phospholipids, were produced by microfluidic flow focusing, for use as ultrasound contrast agents. The stability of the polymerized shell microbubbles against both aggregation and gas dissolution under physiological conditions was studied. Polyethylene glycol (PEG) 5000, which was attached to the diacetylene lipids, was predicted by molecular theory to provide more steric hindrance against aggregation than PEG 2000, and this was confirmed experimentally. The polymerized shell microbubbles were found to have higher shell-resistance than nonpolymerizable shell microbubbles and commercially available microbubbles (Vevo MicroMarker). The acoustic stability under 7.5 MHz ultrasound insonation was significantly greater than that for the two comparison microbubbles. The acoustic stability was tunable by varying the amount of diacetylene lipid. Thus, our polymerized shell microbubbles are a promising platform for ultrasound contrast agents

Developing aqueous lipid formulations with low surface tension behavior at physiological conditions and stability against aggregation

The main goal of the thesis is developing aqueous lipid formulations with good stability and with low surface tension behavior at physiological conditions for exogenous lung surfactant therapy. The thesis contains thermodynamic models for pH prediction of phosphate buffer solutions, experimental results for characterization of the lipid dispersions produced with a method developed at Purdue at physiological conditions, a new dimensionless model for interpreting the stabilization mechanism of the dispersion from a fundamental point of view, and finally new results from new lipid formulations which have improved the lipid dispersion properties. The thermodynamic model shows that pH depends primarily on the concentration ratio R of the two monobasic to dibasic sodium phosphate salts, and secondarily on their concentrations and on the concentrations of the supporting electrolytes such as NaCl or KCl. Various ideal and non-ideal solution thermodynamic models are presented. Model predictions using the non-ideal extended Debye-Hückel (D-H) equation agree with the data up to ca.± 0.1 pH units at 298 K and 310 K. When CaCl2 is added to a standard phosphate buffer saline (PBS), up to 3 mM, a phosphate salt often precipitates, affecting the free Ca2+ ion concentration, the phosphate ion concentrations, and the pH. The effect of the buffer composition and the dispersion preparation protocol on the dynamic surface tension (DST) and vesicle sizes of aqueous dipalmitoylphosphatidylcholine (DPPC) dispersions was studied. Two protocols, with a new method and an old method (Bangham method), were used in preparing the DPPC dispersions. The DPPC dispersions prepared with the new method contained mostly vesicles and were quite stable at 25 or 37 °C. The DPPC dispersions of 1000 ppm at 37 °C with the new method produced, at pulsating area conditions at 20 cycles per minute, low dynamic surface tension minima (DSTM, γmin), lower than 10 mN/m. When a 1000 ppm DPPC dispersion was mixed with a stable solution of 1000 ppm BSA (bovine serum albumin), it became colloidally unstable, aggregating within minutes, implying that heterocoagulation between lipid vesicles and albumin takes place. The heterocoagulated dispersion produced high DSTM because the lipid transport rate to the interface became slower. Moreover, the protein may have been transported to the surface faster and adsorb more than the lipid at the surface. The colloidal dispersion stability at 25° C of aqueous dispersions of sonicated DPPC (dipalmitoylphosphatidylcholine) vesicles was quantitatively evaluated from the Fuchs-Smoluchowski stability ratio W. Data of average particle size vs time were obtained with dynamic light scattering measurements. Zeta potentials results imply that there was some contribution of the double-layer electrostatic forces to the dispersion stability. A new dimensionless model of the DLVO theory for spherical particles was formulated, focusing on the conditions for the existence of a positive interaction potential energy maximum, &PHgr;max, which is linked to W. DLVO calculations of &PHgr;max, and W with error analysis show that the charged DPPC vesicles tested are quite more stable than predicted. DPPC lipid vesicles were modified for reducing aggregation with other vesicles or with the protein with the addition of a small weight fraction of a neutral PEGylated lipid, with a covalently bonded PEG (polyethyleneglycol) group. The mixed vesicles were found to be quite more stable than the DPPC vesicles, remaining stable for months, apparently stabilized by steric forces. The colloidal stability at the initial stages of coagulation was evaluated quantitatively from the Fuchs-Smoluchowski stability ratio W. When the modified lipid vesicle dispersion was mixed with the albumin, the vesicles showed no tendency to aggregate with the albumin molecules for days, also probably because of steric repulsion between the PEGylated lipid and the protein. Finally, the mixed lipid dispersions maintained their low DSTM as the DPPC vesicles without the albumin, and also in the presence of albumin. The results have implications on the use of DPPC or DPPC-based lipids in treating alveolar respiratory diseases without albumin inhibition of their surface tension lowering ability

Application of Nanoparticles: Diagnosis, Therapeutics, and Delivery of Insulin/Anti-Diabetic Drugs to Enhance the Therapeutic Efficacy of Diabetes Mellitus

Diabetes mellitus (DM) is a chronic metabolic disorder of carbohydrates, lipids, and proteins due to a deficiency of insulin secretion or failure to respond to insulin secreted from pancreatic cells, which leads to high blood glucose levels. DM is one of the top four noncommunicable diseases and causes of death worldwide. Even though great achievements were made in the management and treatment of DM, there are still certain limitations, mainly related to the early diagnosis, and lack of appropriate delivery of insulin and other anti-diabetic agents. Nanotechnology is an emerging field in the area of nanomedicine and NP based anti-diabetic agent delivery is reported to enhance efficacy by increasing bioavailability and target site accumulation. Moreover, theranostic NPs can be used as diagnostic tools for the early detection and prevention of diseases owing to their unique biological, physiochemical, and magnetic properties. NPs have been synthesized from a variety of organic and inorganic materials including polysaccharides, dendrimers, proteins, lipids, DNA, carbon nanotubes, quantum dots, and mesoporous materials within the nanoscale size. This review focuses on the role of NPs, derived from organic and inorganic materials, in the diagnosis and treatment of DM

Isolation and Genome Characterization of the Virulent Staphylococcus aureus Bacteriophage SA97

A novel bacteriophage that infects S. aureus, SA97, was isolated and characterized. The phage SA97 belongs to the Siphoviridae family, and the cell wall teichoic acid (WTA) was found to be a host receptor of the phage SA97. Genome analysis revealed that SA97 contains 40,592 bp of DNA encoding 54 predicted open reading frames (ORFs), and none of these genes were related to virulence or drug resistance. Although a few genes associated with lysogen formation were detected in the phage SA97 genome, the phage SA97 produced neither lysogen nor transductant in S. aureus. These results suggest that the phage SA97 may be a promising candidate for controlling S. aureus

Combined Analysis of the Chloroplast Genome and Transcriptome of the Antarctic Vascular Plant <i>Deschampsia antarctica</i> Desv

<div><p>Background</p><p>Antarctic hairgrass (<i>Deschampsia antarctica</i> Desv.) is the only natural grass species in the maritime Antarctic. It has been researched as an important ecological marker and as an extremophile plant for studies on stress tolerance. Despite its importance, little genomic information is available for <i>D. antarctica</i>. Here, we report the complete chloroplast genome, transcriptome profiles of the coding/noncoding genes, and the posttranscriptional processing by RNA editing in the chloroplast system.</p><p>Results</p><p>The complete chloroplast genome of <i>D. antarctica</i> is 135,362 bp in length with a typical quadripartite structure, including the large (LSC: 79,881 bp) and small (SSC: 12,519 bp) single-copy regions, separated by a pair of identical inverted repeats (IR: 21,481 bp). It contains 114 unique genes, including 81 unique protein-coding genes, 29 tRNA genes, and 4 rRNA genes. Sequence divergence analysis with other plastomes from the BEP clade of the grass family suggests a sister relationship between <i>D. antarctica</i>, <i>Festuca arundinacea</i> and <i>Lolium perenne</i> of the Poeae tribe, based on the whole plastome. In addition, we conducted high-resolution mapping of the chloroplast-derived transcripts. Thus, we created an expression profile for 81 protein-coding genes and identified <i>ndhC</i>, <i>psbJ</i>, <i>rps19</i>, <i>psaJ</i>, and <i>psbA</i> as the most highly expressed chloroplast genes. Small RNA-seq analysis identified 27 small noncoding RNAs of chloroplast origin that were preferentially located near the 5′- or 3′-ends of genes. We also found >30 RNA-editing sites in the <i>D. antarctica</i> chloroplast genome, with a dominance of C-to-U conversions.</p><p>Conclusions</p><p>We assembled and characterized the complete chloroplast genome sequence of <i>D. antarctica</i> and investigated the features of the plastid transcriptome. These data may contribute to a better understanding of the evolution of <i>D. antarctica</i> within the Poaceae family for use in molecular phylogenetic studies and may also help researchers understand the characteristics of the chloroplast transcriptome.</p></div

Sequence alignment of eight Poaceae chloroplast genomes.

<p>The top line shows genes in order (transcriptional direction indicated by arrows). The sequence similarity of the aligned regions between <i>Deschampsia antarctica</i> and the other seven species is shown as horizontal bars indicating the average percent identity between 50% and 100% (shown on the <i>y</i>-axis of the graph). The <i>x</i>-axis represents the coordinate in the chloroplast genome. Genome regions are color coded as protein-coding (exon), tRNA or rRNA, and conserved noncoding sequences (CNS).</p

Distribution of small RNAs in the chloroplast genome of <i>Deschampsia antarctica</i>.

<p>*F/R: Direction of transcripts (F: forward, R: reverse).</p

Distribution of plastid small RNAs in the <i>Deschampsia antarctica</i> chloroplast genome.

<p>The reads from small RNA-seq were divided into two groups according to the length (20–24 nt and >30 nt) and aligned to the <i>D. antarctica</i> chloroplast genome with 100% identity. The distributions of reads were compared between the two groups. In total, 12,753,636 reads were distributed unevenly in the chloroplast genome with high density in the coding regions of <i>psbA</i> and <i>rbcL</i>, intergenic regions, and inverted repeat regions in which most of the rRNA genes exist. The 27 loci enriched with 20–24 nt RNAs are indicated in red, along with the number of reads. The <i>y</i>-axis shows the number of reads (from 0 to 1000).</p