Ken J. Rutt

Complement activation by PEGylated single-walled carbon nanotubes is independent of C1q and alternative pathway turnover

We have investigated the interaction between long circulating poly(ethylene glycol)-stabilized single-walled carbon nanotubes (SWNTs) and the complement system. Aminopoly(ethylene glycol)(5000)-distearoylphosphatidylethanolamine (aminoPEG(5000)-DSPE) and methoxyPEG(5000)-DSPE coated as-grown HIPco SWNTs activated complement in undiluted normal human serum as reflected in significant rises in C4d and SC5b-9 levels, but not the alternative pathway split-product Bb, thus indicating activation exclusively through C4 cleavage. Studies in C2-depleted serum confirmed that PEGylated nanotube-mediated elevation of SC5b-9 was C4b2a convertase-dependent. With the aid of monoclonal antibodies against C1s and human serum depleted from C1q, nanotube-mediated complement activation in C1q-depleted serum was also shown to be independent of classical pathway. Nanotube-mediated C4d elevation in C1q-depleted serum, however, was inhibited by N-acetylglucosamine, Futhan (a broad-spectrum serine protease inhibitor capable of preventing complement activation through all three pathways) and anti-MASP-2 antibodies; this strongly suggests a role for activation of MASP-2 in subsequent C4 cleavage and assembly of C4b2a covertases. Intravenous injection of PEGylated nanotubes in some rats was associated with a significant rise in plasma thromboxane B2 levels, indicative of in vivo nanotube-mediated complement activation. The clinical implications of these observations are discussed.

The Transformation of Nesquehonite to Hydromagnesite in the System CaO-MgO-H2O-CO2: An Experimental Spectroscopic Study

This study reports the nature of the nesquehonite-to-hydromagnesite transition at 52°C in an aqueous medium hosting magnesian calcite and nesquehonite. The latter mineral occurs with abundant calcite at the floor of the experimental chamber (substrate) and as a film of needles at the interface between the mother liquor and the atmosphere (surface film). The experimental vessel was held at 52°C for 336 h and at 60°C for a further 192 h. Precipitates were analyzed by Fourier transform (FT)–Raman, augmented by FT-infrared and x-ray diffraction. At 52°C, hydromagnesite and dypingite occur with abundant quantities of a hitherto unreported transitory magnesium hydrate carbonate (TMHC), together with huntite, magnesian calcite, and traces of nesquehonite and monohydrocalcite. The FT-Raman spectra of the first-formed hydromagnesite crystals contain the Raman-forbidden v2 mode, interpreted to indicate a relaxation in selection rules, caused by rapid precipitation. Hydromagnesite growth at the expense of TMHC was more advanced in the substrate than in the coexisting surface film. Additional heating at 60°C resulted in the loss of TMHC and emergence of a dypingite- and hydromagnesite-rich assemblage, with associated strengthening of selection rules. Transitory magnesium hydrate and hydroxyl carbonates and huntite formed during CO2 degassing, fueled by the thermally driven decrease in solubility of CO2 in water and the progressive dissolution of metastable phases. Advancement of the N → HM transition in the substrate most likely reflects greater availability to promote acid generation through calcite precipitation, thereby accelerating transitory-phase dissolution.

A Study of Modified Betaines as Cryoprotective Additives

Abstract— Glycinebetaine and N‐modified betaines have been previously shown to be effective at reducing leakage from liposomes on freeze‐thaw procedures. This study involved the preparation of a series of other modified betaines and the comparison of their abilities to reduce leakage from frozen multilamellar liposomes. All the compounds investigated, with the exception of the octyl ester of betaine, reduced the degree of leakage on freezing and thawing with additive concentrations up to 0·6 m. The betaine esters were less effective than betaine as cryoprotective additives and caused an increase in the leakage from unfrozen liposomes. Taurinebetaine, a sulphobetaine, was also less effective at reducing leakage on freezing than betaine and again increased leakage from unfrozen liposomes. Increasing the number of methylene groups between the carboxylate group and the nitrogen improved the ability to reduce leakage, particularly at lower additive concentrations.

The Effect of the Particle Size on the Fundamental Vibrations of the [CO32–] Anion in Calcite

This study examines the effects of particle sizes between 3 and 121 μm on the fundamental vibrations of the [CO3(2-)] anion in calcite [CaCO3] as analyzed by total attenuated reflectance infrared spectroscopy (ATR-IR) and Raman spectroscopy (RS). The ATR-IR absorbance intensity ratios of the [ν4/ν3] [712 cm(-1)/1393 cm(-1)], [ν4/ν2] [712 cm(-1)/871 cm(-1)], and [ν2/ν3] [871 cm(-1)/1393 cm(-1)] share the same profile for grain size fractions 121 μm through to 42 μm mode. Between 42 and 3 μm mode the three ratios sharply decline in a systematic manner, consistent with a nonuniform decrease in spectral contrast of the [CO3(2-)] internal modes. Raman intensity increased with decreasing particle size from 121 μm until 19 μm mode particle size fraction thereafter decreasing sharply. The [ν4/ν3], [ν1/ν3], and [ν4/ν1] intensity ratios normalized against the corresponding intensity ratio of the 121 μm particle size fraction indicate that the [ν4/ν3] ratio changes by 22%. Both ATR-IR and Raman indicate two critical points in internal mode behavior of the Raman and infrared active ν4 and ν3 internal modes, the first between 42 and 59 μm size range and the second between 19 and 5 μm. Results are interpreted in terms of specular to volume (diffuse) coherent transitions of internal modes and with further grain refinement internal mode specific optically thick to thin transitions.

Quantitative analyses of powdered multi-minerallic carbonate aggregates using a portable Raman spectrometer

Abstract Mg-Ca carbonates are an important group of industrial minerals, which frequently occur intimately intermixed in natural settings and are traditionally assessed for phase purity by X-ray diffraction (XRD). In this study Raman spectroscopy is employed to quantify the modal abundance of hydromagnesite [Mg5(CO3)4(OH)2·4H2O], huntite [CaMg3(CO3)4], dolomite [MgCa(CO3)2], and magnesite [MgCO3], in powdered mixtures constructed from fabricated reference materials. Particle size distributions were assessed by scanning electron microscopy and laser diffraction. Raman analyses performed using a portable instrument were conducted at 25 °C and at atmospheric pressure. XRD was employed to validate the accuracy and precision of Raman measurements. Monovariable and multivariable methods were employed to provide quaternary quantification from the spectroscopic data. For monovariable calibration the amplitude of the peaks was plotted against the measured weight ratios of the four mineral phases. Overlapping bands were resolved using the Gaussian Lorentzian method. Chemometric methods were used to perform the multivariable calibration. The overall lowest error on component values was obtained by principal component regression with application of standard normal variate correction. The quantifications derived by Raman spectroscopy and XRD show close agreement. Hence, evidence suggests that a reliable four-way calibration program to screen the purity of carbonate assemblages can be constructed, providing particle size effects are constrained and spectroscopic operating conditions are uniform.

A comparison of carboxylate salts as liposomal cryoprotectants

The use of liposome suspension for the delivery of water soluble drugs is limited by drug leakage on long term storage. This problem may be overcome by freezing of the liposome suspension if the damage caused by the freeze-thaw process could be overcome. This paper describes an investigation into the use of various carboxylates as cryoprotectants for the frozen storage of liposomes. Although all the compounds investigated reduced the leakage of an entrapped marker from the liposomes, the choice of carboxylate salt was shown to be important in achieving maximal cryoprotection. Acetates were shown to be more effective than formates, propionates and hexanoates and the tetramethylammonium salts were found to be more effective than the sodium, potassium or ammonium salts.

Crystal chemical correlations between the mid and near-infrared in carbonate minerals

Near-infrared (NIR) spectra of carbonates have proved important in many disciplines including planetary exploration. Classically bands in the 4000-6000 cm(-1) (2.5-1.67 μm) region are assigned to [CO3(2-)] internal mode combinations and overtones. However band assignments remain equivocal. This study examines three prominent bands ((ca 4505 cm(-1) (2.219 μm), 4900 cm(-1) (2.041 μm) and 5145 cm(-1) (1.944 μm)) from powdered calcite and aragonite group minerals. Results indicate that the bands originate from anharmonic coupling of degenerate internal mode(s) with external (lattice) modes. On this basis it is suggested that NIR data may provide an untapped source of detailed information on lattice mode frequencies and information on the type(s) of the environmental cation(s) in carbonate minerals.

THE EFFECT OF CRYOPROTECTIVE ADDITIVES ON THE ZETA POTENTIAL OF LIPOSOMES

The ability of polyols and other cryoprotective additives to stabilise phospholipid vesicles during freezing and freeze4ying has been attributed to various interactions between the additive and the phospholipid headgroups (Crowe et a1 1988). A number of postulates have evolved relating these interactions to changes in electrostatic and hydration repulsions between membranes (Rand & Parsegian 1986). Zeta potentials have been widely used as a means of characterising the surface potential of liposomes. The surface potential is an important parameter influencing the distribution of liposomes in vivo and moderating the rate of aggregation and fusion in vitro. This communication describes the novel use of zeta potential determination as a means of investigating the interactions of cryopmtectants with membranes. Multilamellar liposomes were prepared from egg lecithin and egg lecithin with lOmol% dicetylphosphate by hydration of a thin film of lipid with double distilled water at 5OOC. The liposome suspensions were diluted by addition of a few drops to lOmL of cryoprotectant solution. The zeta potentials of the liposomes in the various additive solutions were measured by electrophoretic light scattering using a Coulter Delsa 440 at 25°C.

Structural and adsorption characteristics of porous industrial diamond

Structural and adsorption properties of industrial porous disperse diamond (PDD) were investigated in comparison with such porous materials as graphitized carbon, unmodified and modified silica gels using low-temperature nitrogen adsorptiondesorption, FTIR, EDX, 1H NMR, SEM, and HPLC methods. The PDD compacts possessing both polar and nonpolar surface functionalities and relative broad pore size distribution demonstrate a lower adsorption ability than graphitized carbon (for nonpolar nitrogen) and unmodified silica gel (for polar water) but a stronger one than modified silica gel with octadecylsilyl functionalities.

THE SYNTHESIS AND COMPARISON OF MODIFIED BETAINES AS CRYOPROTECTIVE AGENTS

N-modified betaines have been shown to be more effective than glycinebetaine as cryoprotective additives for the prevention of freeze-thaw damage to liposomes and erythrocytes (Lloyd et al. 1989). Although various carboxylate anions have been shown to behave similarly in preventing leakage from frozen liposomes (Lloyd et al. 1988), the importance of the betaine carboxylate moeity for cryoprotective activity has yet to be established. This communication describes the effects of chemically modifying the carboxylate moeity of glycinebetaine on the cryoprotection afforded to liposomes and erythrocytes on freezing. A series of (carboxymethy1)trimethylammonium chloride esters (gl ycinebetaine esters) were prepared from the appropiate alkylchloroacetates and trimethylamine. Taurine betaine was prepared by refluxkg 2-bromoethyltrimethylammonium bromide with sodium sulphite solution. The 2-bromoethyltrimethylammonium bromide was obtained by treating excess dibromoethane with trimeth ylamine.