Studies on Poly(Dialkoxyphosphazenes) for the Medical Applications

Abstract

The presence of trace of chlorine in poly(diorganophosphazenes) [-N=P(OR)2-]., where R = C₂H₅, CH₂CF₃, C₂F₅, C₄H₅, C₆H₁₃, C₈H₁₇, C₁₂H₂₅, CH₂C₆H₅ in many cases leads to the substantial changes of their physicochemical properties and limits application possibilities of this class of polymers especial for the medical materials. Despite the optimization of reaction conditions for each nucleophilic alkoxy substituent, the obtained poly(dia1koxyphosphaenes) exhibited some physicochemical anomalies.     

The effect of carbon nanotubes on epoxy matrix nanocomposites

The paper concerns thermal properties of epoxy/nanotubes composites for aircraft application. In this work, influence of carbon nanotubes on thermal stability, thermal conductivity, and crosslinking density of epoxy matrix was determined. Three kinds of nanotubes were used: non-modified with 1- and 1.5-μm length, and 1-μm length modified with amino groups. Scanning electron microscopy observations were done for examining dispersion of nanotubes in the epoxy matrix. Glass transition temperature (T _g) was readout from differential scanning calorimetry. From dynamic mechanical analysis, crosslinking density was calculated for epoxy and its composites. Also, thermogravimetric analysis was done to determine influence of nanotubes addition on thermal stability and decomposition process of composites. Activation energy was calculated from TGA curves by Flynn–Wall–Ozawa method. Thermal diffusivity was also measured. SEM images proved the uniform dispersion of carbon nanotubes without any agglomerates. It was found that nanotubes modified with amino groups lead to the increase of epoxy matrix crosslinking density. The significant increase in T _g was also observed. On the other hand, addition of carbon nanotubes leads to the decrease of thermal stability of polymer due to the increase of thermal diffusivity.     

EC–SPE–stripline-NMR analysis of reactive products: a feasibility study

Flow-through electrochemical conversion (EC) of drug-like molecules was hyphenated to miniaturized nuclear magnetic resonance spectroscopy (NMR) via on-line solid-phase extraction (SPE). After EC of the prominent p38α mitogen-activated protein kinase inhibitor BIRB796 into its reactive products, the SPE step provided preconcentration of the EC products and solvent exchange for NMR analysis. The acquisition of NMR spectra of the mass-limited samples was achieved in a stripline probe with a detection volume of 150 nL offering superior mass sensitivity. This hyphenated EC–SPE–stripline-NMR setup enabled the detection of the reactive products using only minute amounts of substrate. Furthermore, the integration of conversion and detection into one flow setup counteracts incorrect assessments caused by the degradation of reactive products. However, apparent interferences of the NMR magnetic field with the EC, leading to a low product yield, so far demanded relatively long signal averaging. A critical assessment of what is and what is not (yet) possible with this approach is presented, for example in terms of structure elucidation and the estimation of concentrations. Additionally, promising routes for further improvement of EC–SPE–stripline-NMR are discussed.     

UHPLC: The Greening Face of Liquid Chromatography

Pharmaceutical analysis based on chromatographic separation is an important part of studies aimed at developing routine quality analysis of drugs. High-performance liquid chromatography (HPLC) is one of the main analytical techniques recommended for drug analysis. Although it meets many criteria vital for analysis, it is time-consuming and uses a relatively high amount of organic solvents compared to other analytical techniques. Recently, Ultra-high-performance liquid chromatography (UHPLC) has been frequently proposed as an alternative to HPLC, which means introducing an environment-friendly approach to drug analysis achieved by reducing the consumption of solvents. It also offers greater chromatographic resolution and higher sensitivity as well as requiring less time due to faster analysis. This review focuses on the basics of UHPLC, compares that technique with HPLC and discusses the possibilities of applying UHPLC for the analysis of different pharmaceuticals and biopharmaceuticals.     

Long-Term Cultured Hairy Roots of Chicory—A Rich Source of Hydroxycinnamates and 8-Deoxylactucin Glucoside

Foam fractionation is a promising method for separation and concentration of biochemicals. It is simple, easily scalable, inexpensive, and environment friendly. Foam fractionation thus represents an alternative to the traditional methods used for immunoglobulin enrichment. However, little, if any, literature exists documenting the utilization of foam fractionation in the enrichment of immunoglobulins. Milk were utilized as an immunoglobulin source to serve as examples of a real system in this study. The investigation examined the effects of varying five different process parameters: the initial pH value, the initial concentration of immunoglobulin, the nitrogen flow rate, the column height, and the foaming time. Experimental results demonstrated that immunoglobulin could effectively be enriched from milk by foam fractionation. The maximum enrichment ratio with pretreatment (using pH 4.6 precipitation) was 6.30 along with a more than 92 % recovery for IgG and an enrichment ratio of 5.1 with 85 % recovery for IgM.     

Major and Trace Elements in Spruce Needles from Urban Areas: Some Aspects of Analysis in Environmental Studies

Main and trace elements in samples of spruce needles from urban areas in Poland and Norway were analysed using the ICP-AES method. Concentrations of Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, P, Sr, Ti, V and Zn were measured in needles from conifer trees growing in different locations. Two different procedures of laboratory sample preparation were compared and discussed. Different washing procedures were examined and compared. For quality control of analytical measurements, Standard Reference Material BCR CRM 101 (spruce needles from Europe) was used. Synergistic and antagonistic relationships between elements in spruce needles were investigated. Applicability of spruce needles in biomonitoring of environmental metal pollution was discussed.     

Production of Antibodies and Development of Specific Polarization Fluoroimmunoassay for Acetochlor

Specific polyclonal antibodies towards acetochlor (2-chloro- N -(ethoxymethyl)- N -(2-ethyl-6-methylphenyl)acetamide) were obtained from rabbits immunized against a 3-mercaptopropionic acid derivative of acetochlor, covalently attached to bovine serum albumin. A polarization fluoroimmuoassay (PFIA) based on these antibodies was developed and optimized to detect acetochlor in water samples. The optimized PFIA had a detection limit of 9 µg/L, linear working range from 50 to 5500 µg/L and within-assay coefficient of variation less than 4%. Cross-reactivity studies demonstrated that these antibodies are capable of specific detection of acetochlor amongst structurally related chloroacetanilide herbicides. Assay cross-reactivity values were: alachlor 0%, metolachlor 2.4%, propachlor 0%, butachlor 0.2% and dimethachlor 0.5%. Five organic solvents commonly used in sample extraction were evaluated for their effect on acetochlor PFIA performance, and methanol and ethanol were found to be compatible with the assay up to 10% v/v.     

Synthesis and Properties of Isobicyclo‐DNA

We present the synthesis of the isobicyclo‐DNA building blocks with the nucleobases A, C, G and T, as well as biophysical and biological properties of oligonucleotides derived thereof. The synthesis of the sugar part was achieved in 5 steps starting from a known intermediate of the tricyclo‐DNA synthesis. Dodecamers containing single isobicyclo‐thymidine incorporations, fully modified A‐ and T‐containing sequences, and fully modified oligonucleotides containing all four bases were synthesized and characterized. Isobicyclo‐DNA forms stable duplexes with natural nucleic acids with a pronounced preference for DNA over RNA as complements. The most stable duplexes, however, arise by self‐pairing. Isobicyclo‐DNA forms preferentially B‐DNA‐like duplexes with DNA and A‐like duplexes with complementary RNA as determined by circular dichroism (CD) spectroscopy. Self‐paired duplexes show a yet unknown structure, as judged from CD spectroscopy. Biochemical tests revealed that isobicyclo‐DNA is stable in fetal bovine serum and does not elicit RNaseH activity.     

Cellulose polymorphism study with sum-frequency-generation (SFG) vibration spectroscopy: identification of exocyclic CH2OH conformation and chain orientation

Sum-frequency-generation (SFG) vibration spectroscopy is a technique only sensitive to functional groups arranged without centrosymmetry. For crystalline cellulose, SFG can detect the C6H₂ and intra-chain hydrogen-bonded OH groups in the crystal. The geometries of these groups are sensitive to the hydrogen bonding network that stabilizes each cellulose polymorph. Therefore, SFG can distinguish cellulose polymorphs (I_β, II, III_I and III_II) which have different conformations of the exocyclic hydroxymethylene group or directionalities of glucan chains. The C6H₂ asymmetric stretching peaks at 2,944 cm^?1 for cellulose I_β and 2,960 cm^?1 for cellulose II, III_I and III_II corresponds to the trans-gauche (tg) and gauche-trans (gt) conformation, respectively. The SFG intensity of the stretch peak of intra-chain hydrogen-bonded O–H group implies that the chain arrangement in cellulose crystal is parallel in I_β and III_I, and antiparallel in II and III_II.