Structural characteristics and gel properties of pectin from citrus physiological premature fruit drop

This study is the first to extract and characterize pectin from citrus physiological premature fruit drop. The extraction yield of pectin reached 4.4 % by acid hydrolysis method. The degree of methoxy-esterification (DM) of citrus physiological premature fruit drop pectin (CPDP) was 15.27 %, indicating it was low-methoxylated pectin (LMP). The monosaccharide composition and molar mass test results showed CPDP was a highly branched macromolecular polysaccharide (β: 0.02, Mw: 2.006 × 10⁵ g/mol) with rich rhamnogalacturonan I domain (50.40 %) and long arabinose and galactose side chain (32.02 %). Based on the fact that CPDP is LMP, Ca²⁺ was used to induce CPDP to form gels. Textural and rheological tests showed that the gel strength and storage modulus of CPDP were higher than commercial citrus pectin (CP) used in this paper due to the lower DM and rich neutral sugar side chains of CPDP. Scanning electron microscope (SEM) results showed CPDP had stable gel network structure.

Health Risk Assessment of Heavy Metals (Pb, Cd, Hg) in Hydroalcoholic Gels of Abidjan, Côte d'Ivoire

Despite the high consumption of hydroalcoholic gels worldwide and particularly in Côte d'Ivoire since the outbreak of the COVID-19 pandemic, very few studies have measured the heavy metal content and human exposure in this product. Thus, 30 samples from supermarkets in Abidjan, Côte d'Ivoire, were collected for the study of risk assessment of exposure to heavy metals contained in hydroalcoholic gels. This study consists of the characterization of the danger by calculating the carcinogenic and non-carcinogenic risk by skin contact. Almost all samples analysed contain trace of lead, cadmium and mercury but at concentrations below the Canadian limit in cosmetic products applied to the skin and below the US FDA limit as an impurity in colour additives used in cosmetic products. The mean values of chronic daily intake via dermal absorption (CDIdermal) for adults were found in the order of mercury > lead > cadmium. The health risk estimation indicated that the mean total hazard quotient for dermal adsorption (HIdermal) obtained is 7.10 × 10^-5 ± 5.52 × 10^-5. This value was below 1, the acceptable limit, representing a non-carcinogenic risk for Abidjan residents through dermal adsorption. Moreover, the incremental lifetime cancer risk (ILCR) evaluation for lead and cadmium was insignificant, and the cancer risk can be neglected, but in case of their overusing, they can cause long-term health problems for consumers.

NMR spectral fingerprint patterns as diagnostics for the unambiguous configurational analysis of the classic organo-gelator 1,3:2,4-dibenzylidene-d-sorbitol (DBS) and its derivatives

On the basis of experimental data and density functional theory (DFT) chemical shift and scalar coupling predictions, simple spectral nuclear magnetic resonance (NMR) fingerprint patterns have been established for the determination of the configuration in 1,3:2,4-dibenzylidene-d-sorbitol (DBS), a classic low molecular weight gelator, and its derivatives. The results rigorously prove the orientation of the phenyl rings in DBS that had been previously assumed in the literature on the basis of thermodynamic arguments.

Using inulin-based emulsion gels as fat substitute in salt reduced Bologna sausage

BACKGROUND

A high-fiber emulsion gel (EG) containing inulin, soy protein isolate, and soybean oil was applied as animal fat replacer in reduced salt and fat Bologna sausage containing mechanically deboned chicken meat, pork meat, and pork back fat. Technological and microbiological properties were evaluated for 60 days at 4 °C.

RESULTS

A reduction of 11 to 34% and 35 to 45% of fat and sodium were obtained in reformulated products, respectively. An increase in fiber content and polyunsaturated fatty acid was noticed in the formulations with EG. The addition of EG in Bologna increased L* (lightness) values and reduced a* (redness/greenness) values comparing to control treatment. Microstructural properties of sausages exhibited a denser network with the presence of EG. Softer, more elastic, cohesive and resilient samples with a higher intensity of lipid oxidation (P < 0.05) were observed in EG added sausages. The nuclear magnetic resonance (NMR) data shows that the presence of EG recovers the matrix that has been weakened due to reduction of fat and salt. Sensory evaluation showed that the incorporation of the EGs resulted in acceptable scores.

CONCLUSION

These results suggest that inulin-based EG is a potential fat substitute for developing healthier meat products, with better fatty acids composition and stable to chilled storage. © 2020 Society of Chemical Industry.

Characteristic and shelf life of fish sausage: fortification with fish oil through emulsion and gelled emulsion incorporated with green tea extract

BACKGROUND

Silver carp (Hypophthalmichthys moltrix) fish sausages incorporated with three forms of refined cod liver oil (as a source of polyunsaturated fatty acids: fish oil, oil-in-water emulsion (E), gelled oil-in-water emulsion (G)) and lyophilized aqueous extract of green tea (Camellia sinensis; 700 and 900 mg kg^-1 ) were developed. The composition, technological properties (cooking loss, pH, texture, and color), sensory analysis, and microbial and oxidative stability of fish sausages during storage (4 °C) were evaluated.

RESULTS

Lower value of cooking loss and thiobarbituric acid value were observed by addition of fish oil in emulsions forms. The incorporation of green tea showed no significant differences in preventing oxidation in related samples. Gelled-emulsified fish oil had better textural properties, including hardness and decreased springiness of the sausages. The G and E sausages showed higher values of lightness (L^* ) than the control did. Emulsification had no significant effect on total viable count. Panelists could not distinguish between samples incorporated with fish oil whether in emulsified, gelled-emulsified, or control. Gelled-emulsified treatments were awarded higher scores by panelists for all of the sensory attributes (P < 0.05). Eicosapentaenoic acid and docosahexaenoic acid quantities significantly increased from control (0.48 mg g^-1 and 0.46 mg g^-1 sample respectively) to the enriched batches (>1.50 mg g^-1 sample). The lowest ratio of ω6 to ω3 in batches was observed for gelled-emulsified samples.

CONCLUSION

Overall, the addition of free fish oil affected the properties of the sausages. The gelled-emulsified treatment was a suitable fish oil delivery system in fish sausages, which maintained sensory properties during refrigerated storage.

Development of healthy gummy jellies containing honey and propolis

BACKGROUND

The objective of this work was to develop gummy jellies containing honey and propolis, keeping the natural antioxidant principles of the beehive ingredients and satisfying consumer requirements.

RESULTS

A gummy jelly containing honey and propolis (HPGJ) was developed. A sensory study with consumers (n = 74) performed an intensity level evaluation test analyzing color, hardness, adhesiveness, gumminess, sweet taste and honey taste. A penalty analysis indicated that HPGJ was too hard. However, in the global acceptance study, more than 90% of consumers gave liking categories. Regarding the potential functional properties, the antioxidant capacity (AC) of HPGJ was 8.17 ± 0.55 mmol Trolox equivalent kg^-1 , and up to 40% AC was retained after in vitro digestion. Additionally, AC of HPGJ was up to ten times higher than that of similar commercial products. A storage study at 25 °C showed that color and AC increased significantly over 90 days owing to the development of Maillard reaction. Storage under darkness allowed keeping low values of global color change for up to 45 days. Another positive facet was that the addition of propolis delayed fungal growth during storage.

CONCLUSION

An organoleptically palatable gummy jelly was obtained. Among the positive features, it showed higher AC than similar commercial candies. Additionally, HPGJ offered a high bioaccesible AC input detected upon in vitro digestion. Overall, HPGJ could be considered an interesting, appetizing and healthier alternative to regular gummy jellies available in the market. Adequate packaging should be considered in order to extend HPGJ shelf life, reducing browning reactions. © 2019 Society of Chemical Industry.

Effects of transdermal administration of testosterone gel on the urinary steroid profile in hypogonadal men: Implications in antidoping analysis

Testosterone is one of the most abused pseudo-endogenous anabolic steroids in sport doping. The current method adopted to detect the abuse of testosterone and other pseudo-endogenous steroids (endogenous steroids when administered exogenously) is first based on the longitudinal monitoring of several urinary biomarkers, which constitute the so called "steroidal module" of the Athlete Biological Passport (ABP): atypical samples undergo a confirmation analysis based on the measurement of the ¹³C/¹²C isotopic ratio of selected target compounds, to distinguish their endogenous or exogenous origin. At the same time, testosterone administration can be allowed in athletes diagnosed with hypogonadism, provided they are granted a therapeutic use exemption by the relevant medical authority. In this pilot study we have investigated whether the approach based on the preliminary determination of the urinary steroid profile, in the format considered in the steroidal module of the ABP, also integrated with the inclusion of the sulfo-conjugates and of additional target steroids, can retain its validity also in the case of hypogonadal athletes. We have studied the effects of a single low dose (40 mg) of testosterone gel (T-gel) on the urinary concentration of the markers of steroidal module of the ABP, as well as on some additional steroid markers. The study was based on the analysis of urinary samples from 19 non-hospitalized hypogonadal men, 10 of them with late-onset hypogonadism (LOH), collected before, after 4 h and after 24 h the transdermal self-administration of 40 mg of T-gel. None of the patient had any co-morbidities possibly affecting the urinary excretion of the steroidal markers. The steroidal markers were quantified by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) after the enzymatic hydrolysis of the respective glucuro-conjugates and the chemical hydrolysis of the respective sulfo-conjugates. Targeted GC-MS/MS analysis was carried out operating in electron impact (EI) ionization mode, with acquisition in multiple reaction monitoring (MRM) mode. Our preliminary results show that, as expected, the treatment with T-gel leads, in all hypogonadal men, to an increase of the urinary concentration of the glucuro-conjugate metabolites of testosterone and its main metabolites, with special relevance to those with 5α-reduction. Furthermore, samples collected from non-LOH hypogonadal men showed an increase also in the levels of epitestosterone glucuronide, testosterone sulfate and epitestosterone sulfate. Apart from their biochemical and pharmacological relevance, these outcomes could be leveraged to refine the analytical strategy currently followed in the antidoping field for the analysis of the urinary steroidal markers, with potential implications also in other forensic and/or clinical investigations.

Heat-induced gelation of mixtures of micellar caseins and plant proteins in aqueous solution

The aim of this work was to investigate how the heat-induced gelation of micellar casein (MC)-plant protein mixtures in aqueous solution is affected by protein composition (MC/plant proteins = 100/0 to 0/100) and total protein content (4%, 6% and 8% w/w) at pH 5.8 and 6.0. Two types of plant proteins were used: soy proteins (SP) and pea proteins (PP). Storage moduli (G') were measured during heating ramps from 20 to 90 °C and heat-induced gelation was characterised by a sharp increase in G' at a critical temperature (Tc). The gel stiffness (Gel) was determined after 1 h at 90 °C and the microstructure before and after heating was investigated by confocal laser scanning microscopy (CLSM). Tc was found to increase with increasing the fraction of MC replaced by SP or PP, due to binding of calcium to the plant proteins. The effect was stronger for SP, which bound calcium more efficiently than PP. Tc decreased with decreasing pH, possibly caused by decreased electrostatic repulsion and increased calcium release from MC. Gel increased with increasing total protein content and did not depend significantly on the pH. Interestingly, Gel showed a minimum as a function of the plant protein fraction (40% for SP and 70% for PP) in the mixtures. It is concluded that MC and plant proteins did not co-aggregate in the mixtures during heating, and that each type of protein formed networks independently.

Effects of cornstarch on the gel properties of black bean protein isolate

The effects of common starch (CS) and high amylopectin starch (HAS) from corn on the properties of heat induced black bean protein isolate (BBPI) gels prepared by heating at 95°C for 30 min were investigated by using dynamic oscillatory rheometer, texture analyzer, and scanning electron microscopy (SEM). Compared with BBPI alone, the presence of cornstarch (1-4%, wt/vol) could improve storage modulus (G') and textural properties of BBPI (10%, wt/vol) gels. The mixed system of BBPI and 4% (wt/vol) HAS exhibited the highest G' and formed the gel faster and more easily, which resulted in firmer and more elastic gel than BBPI-CS at all starch concentrations. It was possible that HAS had lower pasting temperature and higher viscosity than CS, which was beneficial to the formation of BBPI gel network and strengthened the stability of network structure. Moreover, it might also be related to the synergistic effect between protein and starch. The CS and HAS existed in the BBPI gel network could bind water, leading to the increase in the water-holding capacity (WHC) of mixed gels, especially 4% (wt/vol) HAS, which was related to homogeneous and compact microstructure with small pores.

Gelation of barramundi (Lates calcarifer) minced muscle as affected by pressure and thermal treatments at low salt concentration

BACKGROUND

Barramundi minced muscle with salt 10 g kg^-1 and 20 g kg^-1 added is gelled by different combinations of pressurisation (300, 400 and 500 MPa at 4 °C for 10 min), cooking (0.1 MPa, 90 °C for 30 min) and setting (0.1 MPa, 50 °C for 2 h) to improve mechanical properties of barramundi gels and reduce salt added to barramundi gels.

RESULTS

At the low salt concentration of 10 g kg^-1 , pressurisation prior to cooking (P-C) treatment induced barramundi gels with comparable mechanical properties and water-holding capacity to those of conventional heat induced (HI) gels with 20 g kg^-1 added salt. At salt concentration of 20 g kg^-1 , pressurisation prior to setting (P-S) and P-C gels exhibited higher mechanical properties and water-holding capacity as compared to HI gels. Scanning electron microscopy images showed a smooth and dense microstructure of P-C and P-S gels whereas the microstructure of HI gels is rough and less compact.

CONCLUSIONS

P-C treatment can reduce salt concentration added to barramundi gels to 10 g kg^-1 . P-S and P-C treatment can result in higher mechanical and functional properties of barramundi gels at conventional salt concentration (20 g kg^-1 ) as compared to HI gels. © 2017 Society of Chemical Industry.

Influence of food intrinsic complexity on Listeria monocytogenes growth in/on vacuum-packed model systems at suboptimal temperatures

Food intrinsic factors e.g., food (micro)structure, compositional and physicochemical aspects, which are mutually dependent, influence microbial growth. While the effect of composition and physicochemical properties on microbial growth has been thoroughly assessed and characterised, the role of food (micro)structure still remains unravelled. Most studies on food (micro)structure focus on comparing planktonic growth in liquid (microbiological) media with colonial growth in/on solid-like systems or on real food surfaces. However, foods are not only liquids or solids; they can also be emulsions or gelled emulsions and have complex compositions. In this study, Listeria monocytogenes growth was studied on the whole spectrum of (micro)structure, in terms of food (model) systems. The model systems varied not only in (micro)structure, which was the target of the study, but also in compositional and physicochemical characteristics, which was an inevitable consequence of the (micro)structural variability. The compositional and physicochemical differences were mainly due to the presence or absence of fat and gelling agents. The targeted (micro)structures were: i) liquids, ii) aqueous gels, iii) emulsions and iv) gelled emulsions. Furthermore, the microbial dynamics were studied and compared in/on all these model systems, as well as on a compositionally predefined canned meat, developed in order to have equal compositional level to the gelled emulsion model system and represent a real food system. Frankfurter sausages were the targeted real foods, selected as a case study, to which the canned meat had similar compositional characteristics. All systems were vacuum packed and incubated at 4, 8 and 12°C. The most appropriate protocol for the preparation of the model systems was developed. The pH, water activity and resistance to penetration of the model systems were characterised. Results indicated that low temperature contributes to growth variations among the model systems. Additionally, the firmer the solid system, the faster L. monocytogenes grew on it. Finally, it was found that L. monocytogenes grows faster on canned meat and real Frankfurters, as found in a previous study, followed by liquids, aqueous gels, emulsions and gelled emulsions. This observation indicates that all model systems, developed in this study, underestimated L. monocytogenes growth. Despite some limitations, model systems are overall advantageous and therefore, their validation is always recommended prior to further use.

Application of melanin-free ink as a new antioxidative gel enhancer in sardine surimi gel

BACKGROUND

The squid ink that is discarded as waste during processing can be effectively utilised as a gel enhancer in surimi gels, especially those prepared from dark-fleshed fish which have poor gel properties. It also acts as an antioxidant, inhibiting lipid oxidation. This investigation aimed to study the effect of melanin-free ink (MFI) from splendid squid (Loligo formosana) on properties and oxidative stability of surimi gel from sardine (Sardinella albella).

RESULTS

MFI (0-0.1 g kg(-1) surimi) increased the breaking force and deformation of sardine surimi gel in a dose-dependent manner (P < 0.05). The addition of MFI had no effect on whiteness of surimi gels (P > 0.05). The expressible moisture content of gels decreased as the levels of MFI increased (P < 0.05). Based on a microstructure study, gel added with MFI at a level of 0.08 g kg(-1) surimi was denser and finer than that of the control (without MFI). Surimi gels with MFI had lower peroxide values, thiobarbituric acid reactive substances, nonanal and 2-decenal.

CONCLUSION

MFI could improve the properties of sardine surimi gel. Additionally, it was able to prevent lipid oxidation in surimi gels during refrigerated storage.

Cleaning painted surfaces: evaluation of leaching phenomenon induced by solvents applied for the removal of gel residues

Cleaning is one of the most important, delicate, and at the same time controversial processes in the conservation treatment of paintings. Although a strict definition of cleaning would be the removal of dirt, grime, or other accretions (surface cleaning), in the conservation field, cleaning is used in the broader meaning to include thinning/removing altered or “unwanted layers” of materials without damaging or altering the physicochemical properties of the surfaces to be preserved. The cleaning of unvarnished paintings is one of the most critical issues that are currently discussed. Several studies exist regarding different cleaning tools, such as gels, soaps, enzymes, ionic liquids, and foams, as well as various dry methods and lasers, but only a few have been performed on the risk associated with the use of water and organic solvents for the cleaning treatments in relation to the original paint binder. The aim of the study is to verify analytically the behavior of water gelling agents during cleaning treatments and the interaction of the following elements: water or organic solvents applied for the removal of gel residues with the original lipid paint binder. For this purpose, the study was conducted on a fragment of canvas painting (sixteenth to seventeenth century) of Soprintendenza per i Beni Storici, Artistici ed Etnoantropologici del Friuli Venezia Giulia (Superintendence for the Historical, Artistic and Ethno-anthropological Heritage of Friuli Venezia Giulia), Udine by means of Fourier transform infrared spectroscopy, gas chromatography/mass spectrometry, and scanning electron microscopy.

Fouling of enhanced biological phosphorus removal-membrane bioreactors by humic-like substances

Fouling by free extracellular polymeric substances was studied in an enhanced biological phosphorus removal-membrane bioreactor. It was demonstrated that the free extracellular polymeric substances, primarily consisting of humic-like substances, were adsorbed to the membrane used in the enhanced biological phosphorus removal-membrane bioreactor plant. Infrared analyses indicated the presence of the humic-like substances on the membrane's active surface after filtration of the free extracellular polymeric substances suspension. Scanning electron microscopy showed the presence of a gel layer on the membrane surface after filtration of the free extracellular polymeric substances suspension. The gel layer caused a significant decline in water flux. This layer was not entirely removed by a backwashing, and the membrane's water flux could not be re-established. The membrane used in the enhanced biological phosphorus removal-membrane bioreactor plant showed infrared spectra similar to that fouled by the free extracellular polymeric substances suspension in the laboratory. Thus, the results of this study show the importance of humic-like substances in irreversible fouling of enhanced biological phosphorus removal-membrane bioreactor systems.

[Causes of gelatinous material on ocular surface of a patient using timolol maleate long-acting eye drops]

PURPOSE

To ascertain the causes of the formation of gelatinous material observed on the ocular surface of a patient using a betamethasone sodium phosphate ophthalmic solution containing fradiomycin sulfate (Rinderon-A) together with a timolol maleate long-acting ophthalmic gel-forming solution (Timoptol-XE).

METHODS

The gellan gum in the Timoptol-XE was suspect as it might have been gelatinized by the fradiomycin sulfate in the Rinderon-A. Mixtures of the chemical compounds such as fradiomycin sulfate with the Timoptol-XE was tested in vitro to find out whether any resulted in gelation.

RESULTS

It was confirmed that Timoptol-XE was gelatinized by the aminoglycoside drugs in vitro. The density of the aminoglycoside drugs needed for the gelation was only about 0.2 mM on average. Gelation was also observed with benzalkonium chloride and vancomycin.

CONCLUSION

The results suggest that the gellan gum in the Timoptol-XE gelatinized by the fradiomycin sulfate in the Rinderon-A and that aminoglycocide compounds act strongly on gellan gum as polycation.

Triazole-modified triphenylene derivative: self-assembly and sensing applications

Triphenylene-based discotic liquid crystal 3 bearing 1,2,3-triazole groups has been synthesized using "click" chemistry. Discotic mesogen 3 has good thermal stability, and incorporation of triazole groups results in stabilization of columnar mesophases down to room temperature and formation of organogels in cyclohexane and mixed solvents such as hexane and dichloromethane (4:1 v/v). Characterization of the organogel of 3 in cyclohexane revealed a porous network. However, presence of Cd(2+) ions in solution obstructed the self-assembly of this derivative due to preferred interactions between Cd(2+) ions and triphenylene units over π-π interactions among triphenylene groups. Further, strong emission of derivative 3 in its nonaggregated form makes it a promising fluorescence sensory material for nitroaromatic compounds.

Solidifying agent and processing of blood used for the larval diet affect screwworm (Diptera: Calliphoridae) life-history parameters

Spray-dried whole bovine blood and a sodium polyacrylate polymer gel as a bulking and solidifying agent are among the constituents of the current larval diet for mass rearing screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae). Locally available, inexpensive dietary materials could reduce rearing cost and address an uncertain commercial supply of spray-dried blood. We compared efficacy of diet prepared from fresh bovine blood after decoagulation with sodium citrate or ethylenediaminetetraacetic acid (EDTA) or after mechanical defibrination, with the diet containing spray-dried blood using either gel or cellulose fiber as the bulking and solidifying agent. Several life-history parameters were compared among insects reared on each of the blood and bulking agent diets combination. Diets containing citrated blood yielded the lightest larval and pupal weights and fewest pupae. EDTA-treated blood with the gel also caused reductions. EDTA-treated blood with fiber yielded screwworms that were heavier and more numerous than those from the diet with citrated blood but lighter than those from the control diet using spray-dried blood. A reduction in percentage of adults emerging from pupae occurred from diets with both bulking agents using citrated blood and the diet using EDTA mixed with the gel bulking agent. As a group, the cellulose-fiber diets performed better than the gel diets. Larval diet did not affect adult longevity, weight of the eggs deposited by the females that emerged or subsequent egg hatch. Parameter measurements of insects from both defibrinated blood diets were similar to those from the spray-dried blood diets, indicating that fresh, defibrinated bovine blood can successfully replace the dry blood in the screwworm rearing medium.

Quantitative determination of dimethylaminoethanol in cosmetic formulations by nuclear magnetic resonance spectroscopy

A nuclear magnetic resonance (NMR) spectroscopic method was validated for the quantitative determination of dimethylaminoethanol (DMAE) in cosmetic formulations. The linearity in the range from 0.5000 to 1.5000 g (DMAE salt/mass maleic acid) presents a correlation coefficient > 0.99 for all DMAE salts. The repeatability (intraday), expressed as relative standard deviation, ranged from 1.08 to 1.44% for samples and 1.31 to 1.88% for raw materials. The detection limit and quantitation limit were 0.0017 and 0.0051 g for DMAE, 0.0018 and 0.0054 g for DMAE bitartrate, and 0.0023 and 0.0071 g for DMAE acetamidobenzoate, respectively. The proposed method is simple, precise, and accurate and can be used in the quality control of raw materials and cosmetic gels containing these compounds as active substances.

Use of Near-Infrared for Quantitative Measurement of Viscosity and Concentration of Active Ingredient in Pharmaceutical Gel

Near infrared (NIR) spectroscopy is gaining worldwide interest as an analytical tool for quality control of raw materials, intermediate products, and final dosage forms. This technique can be used without sample preparation, therefore, avoiding the need for reagents and solvents. Quantitative NIR analyses involve calibration by sophisticated mathematical techniques that have been used extensively since the advent of microcomputing and chemometrics. The main objective of this investigation was to use transmission near-Infrared spectroscopy to measure the potency of an active ingredient in a topical gel preparation. A second objective was to evaluate the effect of gel viscosity on the NIR reflectance spectra. Four gel formulations with different ibuprofen concentrations were used for quantitative determination of the active ingredient, and five gel formulations with different viscosity values were used for the evaluation of the effect of viscosity change on the near-infrared reflectance spectra. The laboratory ibuprofen quantitative determination was compared to near-infrared transmission data using linear, quadratic, cubic and partial least square techniques to determine the relationship between ultraviolet (UV) determination and near-infrared spectra. For viscosity, the laboratory data were compared to near-infrared diffuse reflectance data using the same techniques used to determine the relationship between Brookfield viscometer determination and near-infrared spectra. The results demonstrated that an increase in ibuprofen concentration and viscosity produced an increase in near-infrared absorbance. Series of model equations were developed from the calibration of laboratory vs. the near-infrared data for each formulation. The near-infrared spectroscopy method is an alternative method that does not require sample pretreatment for quantitative measurement of active ingredient and viscosity of pharmaceutical gel.

[Study on extraction and property testing of pastern from mesona blume]

OBJECTIVE

In order to find out the pastem's content and property.

METHODS

The colloid substances-pastem were extracted from the grass with high pressure and high temperature and then were compared.

RESULTS

The pastem's average content was 30. 55 g/100 g. The average intrinsic viscosity of pastem was 85.01 ml/g. Using the cassava starch complex gums as a standard reference, the coefficient of hardness, elastic coefficient and coefficient of cohesion were 23.71, 1.128, 0.431, respectively.

CONCLUSION

This study provides the theory basis of setting quality standard of country, and helps to develop the pastem's prodution.

Robust spatially resolved pressure measurements using MRI with novel buoyant advection-free preparations of stable microbubbles in polysaccharide gels

MRI of fluids containing lipid coated microbubbles has been shown to be an effective tool for measuring the local fluid pressure. However, the intrinsically buoyant nature of these microbubbles precludes lengthy measurements due to their vertical migration under gravity and pressure-induced coalescence. A novel preparation is presented which is shown to minimize both these effects for at least 25 min. By using a 2% polysaccharide gel base with a small concentration of glycerol and 1,2-distearoyl-sn-glycero-3-phosphocholine coated gas microbubbles, MR measurements are made for pressures between 0.95 and 1.44 bar. The signal drifts due to migration and amalgamation are shown to be minimized for such an experiment whilst yielding very high NMR sensitivities up to 38% signal change per bar.

Coupling desorption electrospray ionisation and neutral desorption/extractive electrospray ionisation with a travelling-wave based ion mobility mass spectrometer for the analysis of drugs

Desorption electrospray ionisation (DESI) and neutral desorption/extractive electrospray ionisation (EESI) have been coupled to a hybrid quadrupole travelling-wave (T-Wave)-based ion mobility time-of-flight mass spectrometer for the direct accurate mass analysis of active ingredients formulated into pharmaceutical samples. The collision cross-section measurements of polyethylene glycol (PEG) excipients detected in one formulation were estimated and compared with published data. These estimated collision cross-sections of the PEG species showed good agreement with published data.

Electrochemical monitoring of piroxicam in different pharmaceutical forms with multi-walled carbon nanotubes paste electrode

The electrochemical behavior of piroxicam on a multi-walled carbon nanotubes electrode for the first time was investigated. A highly sensitive and fast responding sensor for determination of piroxicam was simply and conveniently fabricated. The constructed electrode exhibits efficiently catalytic activity for the electrooxidation of piroxicam at a reduced over potential with high sensitivity, stability, and long lifetime in the wide concentration rang of piroxicam. The oxidation process was found to be dependent on the pH of the supporting electrolyte. The behavior is further exploited as a sensitive detection method for piroxicam determination by differential pulse voltammetry. Under the optimized conditions the calibration plots are linear in the concentration range of 0.15-5 microg ml(-1). Application of the method for the determination of the drug in the dosage form (Feledene capsules and tablets and also piroxicam gel), without any interference, from the excipients, resulted in acceptable deviation from the stated concentrations. Recoveries were obtained in the range 96.35-104.16%. The detection limit of 0.1 microg ml(-1) was obtained for piroxicam determination.

Mercury mobilization in estuarine sediment porewaters: a diffusive gel time-series study

To assess the lability of porewater and sediment solid-phase mercury (Hg), mercapto-substituted siloxane gels were deployed within the sediments of the Penobscot estuary in Maine. Gel deployments occurred in time series and at discrete sediment depths. A sediment distribution coefficient (K(D)) was estimated by modeling the resultant gel Hg uptake. For deployments > 1 day, depth-averaged gel Hg uptake was significantly greater at depth (Zone B 6-20 cm) than in the vicinity of the sediment-water interface (Zone A 0-5 cm), with uptake ultimately reaching 16.7 +/- 4.9 ng Hg g(-1) gel versus 35.5 +/- 3.8 ng Hg g(-1) gel for Zone A versus Zone B, respectively. For Zone A, a simple diffusive model adequately describes gel mass flux, suggesting that Hg repartitioning from the solid phase does not generate a net Hg source term within the time frame of gel deployment. For Zone B, model-determined values of K(D) (K(D) = 25-75) were considerably smaller than literature values typically based on total sediment Hg concentration. The magnitude of the modeled K(D) suggests that it is a small fraction of total sediment-sequestered Hg that is likely sensitive, via interaction with porewater ligands, to the presence of an external sink. These observations of low general Hg reactivity suggest that the net porewater Hg pool may be properly defined as a function of porewater ligand production. Such a definition highlights the importance of microbially mediated diagenesis in controlling Hg cycling within estuarine sediments.

Skin penetration behaviour of sesquiterpene lactones from different Arnica preparations using a validated GC-MSD method

Preparations of Arnica montana L. are widely used for the topical treatment of inflammatory diseases. The anti-inflammatory activity is mainly attributed to their sesquiterpene lactones (SLs) from the helenalin and 11alpha,13-dihydrohelenalin type. To study the penetration kinetics of SLs in Arnica preparations, a stripping method with adhesive tape and pig skin as a model was used. For the determination of SLs in the stripped layers of the stratum corneum (SC), a gas chromatography/mass spectrometry method was developed and validated. Thereby the amount of helenalin derivatives was calculated as helenalin isobutyrate, and 11alpha,13-dihydrohelenalin derivatives as 11alpha,13-dihydrohelenalin methacrylate. This GC-MSD method is suitable also to determine low amounts of SLs in Arnica preparations. The penetration behaviour of one gel preparation and two ointment preparations was investigated. The SLs of all preparations show a comparable penetration in and a permeation through the stratum corneum, the uppermost part of the skin. Interestingly, the gel preparation showed a decrease of the penetration rate over 4h, whereas the penetration rate of ointments kept constant over time. Moreover, we could demonstrate that the totally penetrated amount of SLs only depends on the kind of the formulation and of the SLs-content in the formulation but not on the SLs composition or on the used extraction agent.

Hyphenation of Raman spectroscopy with gravimetric analysis to interrogate water–solid interactions in pharmaceutical systems

A moisture sorption gravimetric analyzer has been combined with a Raman spectrometer to better understand the various modes of water-solid interactions relevant to pharmaceutical systems. A commercial automated moisture sorption balance was modified to allow non-contact monitoring of the sample properties by interfacing a Raman probe with the sample holder. This hybrid instrument allows for gravimetric and spectroscopic changes to be monitored simultaneously. The utility of this instrument was demonstrated by investigating different types of water-solid interactions including stoichiometric and non-stoichiometric hydrate formation, deliquescence, amorphous-crystalline transformation, and capillary condensation. In each of the model systems, sulfaguanidine, cromolyn sodium, ranitidine HCl, amorphous sucrose and silica gel, spectroscopic changes were observed during the time course of the moisture sorption profile. Analysis of spectroscopic data provided information about the origin of the observed changes in moisture content as a function of relative humidity. Furthermore, multivariate data analysis techniques were employed as a means of processing the spectroscopic data. Principle components analysis was found to be useful to aid in data processing, handling and interpretation of the spectral changes that occurred during the time course of the moisture sorption profile.

Classification and dating of black gel pen ink by ion-pairing high-performance liquid chromatography

A novel approach for classification and dating of the black gel pen ink entries on document was developed based on ion-pairing high-performance liquid chromatography (IP-HPLC). Ninety-three black gel pens were collected and divided into two groups, dye-based and pigment-based, by preliminary solubility test. The chromatographic conditions for separation of the dye-based black gel pen inks were optimized and the dye components in inks were satisfactorily separated by using 40 mmol/L tetrabutylammonium bromide as ion-pairing reagent. According to the number and the chromatographic retention times of the main dye components, the 50 dye-based inks were categorized into four classes. The inks within a class can be further identified by the percentage of each dye component. The compositional changes of the dye components in the black gel pen ink entries on paper were investigated in light and natural aging conditions and it has been found that the dye components in the ink entries underwent obvious decomposition, and the decomposing extent of the dye components was related to the aging time. The results can provide scientific evidences for dating of the suspicious black gel pen ink entries on documents.

Measurement of the radical scavenging activity of chicken jelly soup, a part of the medicated diet, 'Yakuzen', made from gelatin gel food 'Nikogori', using chemiluminescence and electron spin resonance methods

We reported that gelatin gel 'Nikogori' soup made from the collagen in chicken wing meat, which is a part of the medicated diet 'Yakuzen', has high peroxyl and hydroxyl radical scavenging activities as the antioxidative capacity using chemiluminescence and electron spin resonance methods. The peroxyl radical scavenging activity of the soy sauce and chicken jelly 'Nikogori' soup sample was much higher than that of the chicken-only sample (control) at 100 degrees C heating for 60 min, although the addition of soy sauce only slightly enhanced the hydroxyl radical scavenging activity. Although the addition of garlic slightly enhanced the hydroxyl radical scavenging activity, it strongly inhibited the peroxyl radical scavenging activity. We found that chicken jelly 'Nikogori' soup only and soup with the addition of soy sauce had the highest antioxidative capacity as part of the medicated diet, 'Yakuzen'.

Synergic quenching effects of water and carbon tetrachloride in liquid scintillation gel samples

Although both water and carbon tetrachloride induce chemical quenching when incorporated to Insta Gel, the quenching power of carbon tetrachloride is nearly two orders of magnitude greater than that of water. This huge difference shows how different the chemical quenching mechanisms among quenchers can be. One remarkable fact of all pure beta-ray nuclides is that calibration curves do not depend on the water to scintillator volume ratio or on the nature of the quencher. The fact is clearly surprising, because two tritium samples of different water to scintillator and quencher to scintillator volume ratios may have identical counting efficiencies. As we shall prove, this fact is only possible when the external quench parameter of both samples is the same. We study the synergies in quenching generated when carbon tetrachloride is added to a sample in gel phase.

Label-free measurement of microbicidal gel thickness using low-coherence interferometry

Spectral-domain low-coherence interferometry (LCI) was used to measure the thickness of microbicidal gels applied to a cylindrical calibration test socket. Microbicides are topical formulations containing active ingredients targeted to inhibit specific pathogens that are currently under development for application to the epithelial lining of the lower female reproductive tract to combat sexually transmitted infections such as HIV. Understanding the deployment and drug delivery of these formulations is vital to maximizing their effectiveness. Previously, in vivo measurements of microbicidal formulation thickness were assessed using fluorescence measurements of fluorescein-labeled gels via an optical endoscope-based device. Here we present an LCI-based device that measures the thickness of a formulation without the use of any exogenous agents by analyzing the interference pattern generated between the reflections from the front and back surface of the sample. Results are presented that validate the effectiveness and performance of the LCI measurement in a clinically relevant system as compared to an existing fluorescence-based method. The impact of the new LCI-based design on in vivo measurements is discussed.

Microrheological characterization of anisotropic materials

We describe the measurement of anisotropic viscoelastic moduli in complex soft materials, such as biopolymer gels, via video particle tracking microrheology of colloid tracer particles. The use of a correlation tensor to find the axes of maximum anisotropy without prior knowledge, and hence the mechanical director, is described. The moduli of an aligned DNA gel are reported, as an application of the technique; this may have implications for high DNA concentrations in vivo. We also discuss the errors in microrheological measurement, and describe the use of frequency space filtering to improve displacement resolution, and hence probe these typically high modulus materials.

Discrimination of irradiated starch gels using FT-Raman spectroscopy and chemometrics

The effects of gamma-irradiation on starch gels were characterized at the molecular level by Fourier transform (FT) Raman spectroscopy. Starches from five different sources were gelatinized and irradiated at 3, 5, and 10 kGy using a Co60 gamma-irradiator. Gamma-irradiation effects on starch gels were noted by the C-H stretch (2800-3000 cm(-1)) and O-H stretch (3000-3600 cm(-1)) and bend (1600-1800 cm(-1)) regions of the FT-Raman spectra. FT-Raman molecular fingerprints obtained through spectral analyses were used for discrimination of the gels based on the extent of irradiation by means of two different pattern-recognition techniques: canonical variate analysis (CVA) and soft modeling of class analogy (SIMCA). A complete discrimination of irradiated starches was attained using a hybrid partial least-squares (PLS) and CVA model, using the spectral variations in the C-H stretch and O-H stretch and bend regions of FT-Raman spectra. Using the same spectral regions, SIMCA predicted 84% of samples correctly.

Effectiveness and microbial contamination of an in-house alcohol-based hand rub

OBJECTIVES

To evaluate the effectiveness and contamination of an in-house alcohol-based hand rub in a real clinical setting and to compare its effectiveness in bacterial reduction with that of a commercial product.

MATERIAL AND METHOD

Effectiveness of the hand rub in bacterial reduction was compared to a commercial product using the modified antiseptic/disinfectant testing method of European Standard (EN 1500) in 12 volunteers. In-house alcohol-based hand rub in 50 clinical wards were serially collected and cultured to determine contamination.

RESULTS

The bacterial reduction factor of the hand rub was comparable to that of the commercial product. There was no organisms grown from serial cultures of the in-house alcohol-based hand rub in use for 28 days.

CONCLUSION

The in-house alcohol-based hand rub was effective and there was no contamination up to 28 days in use.

The development of structural and mechanical anisotropy in fibroblast populated collagen gels

An in vitro model system was developed to study structure-function relationships and the development of structural and mechanical anisotropy in collagenous tissues. Fibroblast-populated collagen gels were constrained either biaxially or uniaxially. Gel remodeling, biaxial mechanical properties, and collagen orientation were determined after 72 h of culture. Collagen gels contracted spontaneously in the unconstrained direction, uniaxial mechanical constraints produced structural anisotropy, and this structural anisotropy was associated with mechanical anisotropy. Cardiac and tendon fibroblasts were compared to test the hypothesis that tendon fibroblasts should generate greater anisotropy in vitro. However, no differences were seen in either structure or mechanics of collagen gels populated with these two cell types, or between fibroblast populated gels and acellular gels. This study demonstrates our ability to control and measure the development of structural and mechanical anisotropy due to imposed mechanical constraints in a fibroblast-populated collagen gel model system. While imposed constraints were required for the development of anisotropy in this system, active remodeling of the gel by fibroblasts was not. This model system will provide a basis for investigating structure-function relationships in engineered constructs and for studying mechanisms underlying the development of anisotropy in collagenous tissues.

Characterization of La2Mo2O9 aerogels synthesized by the sol-gel chemistry and high-temperature supercritical drying

A lanthanum molybdate aerogel, La2Mo2O9, with a mean particle size in the range from 100 to 150 nm, was synthesized by the sol-gel method and high-temperature supercritical drying. In this communication it is shown that control over the crystallinity of product aerogels can be exercised by changing the amount of water used for hydrolysis and the temperature for subsequent heat treatment. Methoxy species are formed on the surface during synthesis. The new aerogel may prove useful as a catalyst for the oxidation of hydrocarbons to oxygenated organic compounds.

Structure of a gel phase lipid bilayer prepared by the Langmuir-Blodgett/Langmuir-Schaefer method characterized by sum-frequency vibrational spectroscopy

The structure of a planar supported lipid bilayer (PSLB) prepared by the Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS) method was investigated by sum-frequency vibrational spectroscopy (SFVS). By using asymmetric lipid bilayers composed of selectively deuterated 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) lipids, the orientation of the fatty acid chains and phosphocholine headgroups has been determined independently for both leaflets of the bilayer. The alkyl chains of the lipids were found to be orientated approximately 13 degrees +/- 4 degrees from the surface normal for both leaflets. The lipid chains in both leaflets also contain some gauche content, which is consistent with previous NMR and FTIR studies of similar lipid systems. More importantly, the relative number of gauche defects does not seem to be influenced by the deposition method, LB versus LS. The headgroup orientation for the lipid film in contact with the silica support was determined to be 69 degrees +/- 3 degrees , whereas that in contact with the aqueous phase was 66 degrees +/- 4 degrees from the surface normal. The SFVS results indicate that the structure of the DSPC lipid film in contact with the solid support and the film adjacent to the aqueous phase are nearly identical in structure. These results suggesting the LB/LS deposition method do indeed produce symmetric lipid bilayers. These studies further add to the growing information on the efficacy of PSLBs as suitable models for biological membrane studies.

Inhibition evaluation for a 20-min endotoxin limit test on FDG

OBJECTIVES

In chemical quality control tests for 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG), gel time is inversely related to endotoxin concentration. Solutions for positive product control (PPC) and positive water control (PWC) should contain a highly concentrated endotoxin level. The aims of our study were to derive an endotoxin concentration that causes PPC and PWC to gel and to evaluate inhibitory effects caused by FDG on gel formation in PPC and PWC test solutions.

METHODS

At expiration, the maximum administered total dose (in millilitres) of FDG should contain fewer than 175 endotoxin units (EU). Our average batch volume of FDG is 15 ml; thus, the minimum endotoxin limit should be 12 EU x ml(-1) . Twelve tubes were tested for each of four concentrations. Inhibition was assessed using Limulus amoebocyte lysate reagent, depyrogenated vials, and pyrogen-free sterile micropipette tips. Each study was performed with four groups of solutions: decayed 18F-FDG, negative control, PPC and PWC.

RESULTS

In the study of undiluted FDG, seven of 50 PPC vials at 12 EU x ml(-1) did not gel. The lowest endotoxin concentration that consistently gelled at 20 min was 4 EU x ml(-1) . In the sample tested for inhibition using PPC tubes at 4 EU x ml(-1) , 49 tubes gelled at 20 min, and one did not.

CONCLUSION

The inhibition rate improved between undiluted (i.e., 7/50 (14%)) and diluted (i.e., 1/50 (2%)) FDG PPC trials (P=0.03). However, given that 1 of 50 trials failed for diluted FDG PPC, we conclude that inhibition still occurs and there is a 95% chance that the inhibition rate could be as high as 11% or as low as 0% on repetition of the experiment.

Preliminary dose response study of a gel dosimeter using 2-Hydroxyethyl Methacrylate (HEMA)

In this work we present a gel dosimeter based on 2-Hydroxyethyl Methacrylate (HEMA). The gel dosimeter is manufactured in normal atmospheric oxygen (normoxic) and undergoes a measurable change after irradiation. The gel is shown to provide a signal to noise ratio of up to at least 35 and have a linear change in transverse relaxation rate up to 70 Gy when measured with magnetic resonance imaging.

High-performance thin-layer chromatography determination of some antimycotic imidazole derivatives and preservatives in medicinal creams and a gel

Simple and reliable thin-layer chromatography-densitometry methods for determination of antimycotics (bifonazole, clotrimazole, and miconazole) and preservatives (benzyl alcohol and benzoic acid) were developed. The pairs bifonazole/benzyl alcohol, clotrimazole/benzyl alcohol, and miconazole/benzoic acid were determined simultaneously. The following mobile phases were used: ethyl acetate-n-heptane-methanoldiethylamine (3 + 4.5 + 1 + 0.2, v/v/v/v) for bifonazole and benzyl alcohol; n-butyl acetate-n-heptane-methanol-dietylamine (3 + 4.5 + 1 + 0.2, v/v/v/v) for clotrimazole and benzyl alcohol; and n-butyl acetate-carbon tetrachloride-methanol-diethylamine (3 + 6 + 2.5 + 0.5, v/v/v/v) for miconazole and benzoic acid. The chromatographic zones on silica gel plates were scanned in the reflectance/absorbance mode at 230 nm (bifonazole, benzyl alcohol, miconazole, and benzoic acid) and 210 nm (clotrimazole and benzyl alcohol). The recovery for all substances ranged from 98.7 to 100.7%. The limits of detection and quantitation were 0.03 to 0.2 microg and 0.1 to 0.5 microg/spot, respectively. The proposed methods were applied for determination of antimycotics and preservatives in commercially available pharmaceuticals.

Bubble-based acoustic radiation force elasticity imaging

Acoustic radiation force is applied to bubbles generated by laser-induced optical breakdown (LIOB) to study viscoelastic properties of the surrounding medium. In this investigation, femtosecond laser pulses are focused in the volume of gelatin phantoms of different concentrations to form bubbles. A two-element confocal ultrasonic transducer generates acoustic radiation force on individual bubbles while monitoring their displacement within a viscoelastic medium. Tone burst pushes of varying duration have been applied by the outer element at 1.5 MHz. The inner element receives pulse-echo recordings at 7.44 MHz before, during, and after the excitation bursts, and crosscorrelation processing is performed offline to monitor bubble position. Maximum bubble displacements are inversely related to the Young's moduli for different gel phantoms, with a maximum bubble displacement of over 200 microm in a gel phantom with a Young's modulus of 1.7 kPa. Bubble displacements scale with the applied acoustic radiation force and displacements can be normalized to correct for differences in bubble size. Exponential time constants for bubble displacement curves are independent of bubble radius and follow a decreasing trend with the Young's modulus of the surrounding medium. These results demonstrate the potential for bubble-based acoustic radiation force methods to measure tissue viscoelastic properties.

Dynamical arrest in attractive colloids: the effect of long-range repulsion

We study gelation in suspensions of model colloidal particles with short-ranged attractive and long-ranged repulsive interactions by means of three-dimensional fluorescence confocal microscopy. At low packing fractions, particles form stable equilibrium clusters. Upon increasing the packing fraction the clusters grow in size and become increasingly anisotropic until finally associating into a fully connected network at gelation. We find a surprising order in the gel structure. Analysis of spatial and orientational correlations reveals that the gel is composed of dense chains of particles constructed from face-sharing tetrahedral clusters. Our findings imply that dynamical arrest occurs via cluster growth and association.

A simple, efficient, and economical method for recovering DNA from agarose gel

A simple method of recovering DNA from agarose gel that is fast, inexpensive, and friendly both to operators and environment is described. Two rows of wells are made in an agarose gel, and a DNA sample is loaded into the well nearest to the negative pole for separation by electrophoresis. Recovery is accomplished by pipetting the DNA-containing TAE buffer from the well near the positive pole after target DNA fragments have migrated into the well. A recovery rate of up to 94 +/- 2.3% was observed with this method.

Monitoring the thermal gelation of cellulose ethers in situ using attenuated total reflectance fourier transform infrared spectroscopy

In this work attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to probe the thermal gelation behavior of aqueous solutions of hydroxypropyl methylcellulose (HPMC), specifically thermal gelation and accompanying precipitation. Cloud point measurements are usually evaluated through turbidity in dilute solutions but the method cannot readily be applied to more concentrated or highly viscous solutions. From the ATR-FTIR data, intensity changes of the nu(CO) band marked the onset of gelation and information about the temperature of gelation and the effect of the gel structure on the water hydrogen bonding network was elucidated. Changes in the relative intensities of bands associated with the methoxyl groups and hydrogen-bond-forming secondary alcohol groups indicated that hydrophobic polymer chain interactions were involved in the gelation process. The dominance of inter-molecular H bonding over intra-molecular H bonding within the cellulose ether in solution was also observed. The ATR-FTIR data was in good agreement with measurements of turbidity conducted on the same systems. The work indicates significant potential for the use of ATR-FTIR for the investigation of gelation and cloud point measurements in viscous cellulosic formulations.

Development and validation of HPLC method for determination of indomethacin and its two degradation products in topical gel

Indomethacin forms by decomposition two degradation products: 4-chlorobenzoic acid and 5-methoxy-2-methylindoleacetic acid. They have to be monitored together with an active substance both during manufacturing process and storage of pharmaceuticals. European Pharmacopoeia (Ph. Eur. 4) describes titration method for determination of indomethacin, which is not very convenient in this case for practical use. Therefore, high performance liquid chromatography is the method-of-choice enabling determination of active substance and its degradation products during one-step procedure simultaneously and automatically. We have developed a fast, simple and fully automated analytical method for determination of indomethacin and its two impurities in pharmaceutical preparation using HPLC with UV detection. Various stationary phases were tested, especially new types of Zorbax columns made by Agilent. While the conventional C18 stationary phases were not convenient enough to achieve quick and reliable separation, Zorbax-Phenyl analytical column (75 mm x 4.6 mm, 3.5 microm) enables separation of indomethacin and its two degradation products during 7.5 min. Chromatography was performed using isocratic elution with binary mobile phase composed of acetonitrile and 0.2% phosphoric acid (50:50, v/v) at flow rate 0.6 ml/min. Even faster separation of standards was obtained with analytical column Zorbax SB-CN (150 mm x 4.6 mm, 5 microm). The separation was effected with mobile phase of the same composition, only the flow rate was increased to 1.2 ml/min. The analytical run was shortened to 5 min. Both methods use detection wavelength 237 nm and both can use either ketoprofen or flurbiprofen as internal standard for quantitation. The first method was finally chosen for validation because of the occurrence of placebo interferences in the case of using Zorbax SB-CN. System suitability parameters and validation parameters including method precision, accuracy, linearity, selectivity and robustness were set up. Afterwards, the method was successfully applied for the practical determination of indomethacin and its degradation products in a topical gel and for compound degradation control during stability studies.

Evaluation of the dosimetric performance of BANG3® polymer gel

New radiotherapy techniques call for three-dimensional dosimetric methods with high spatial resolution. Radiation sensitive gels read out using MRI T(2) mapping provide an extremely promising option, and commercially available BANG polymer gels provide a convenient route into gel dosimetry. Gel dosimetry is dependent on the ability to calibrate gel response against radiation dose. This in turn is dependent on the reproducibility of response both between gels irradiated to the same dose and for a single gel sample over time. This study aims to evaluate the performance of a commercially available BANG gel. Our experimental arrangement gave excellent precision of radiation delivery (<0.2%) and reproducibility of T(2) measurement (<0.5%). Seven groups of 10 test tubes containing BANG3 gel were irradiated in 0.5 Gy steps between 0 and 3 Gy. A further four groups of four samples were irradiated in 2 Gy steps between 4 and 10 Gy. The gel samples were identical and derived from the same manufacturing batch. MR imaging was carried out four days after irradiation and then at weekly intervals for four weeks. Short-term variation in gel response can readily be corrected using reference samples. Longer term systematic drift of the gel calibration curve was observed relative to reference samples prepared in-house for quality assurance purposes. This implies that read-out of the calibration gels and dosimetry phantom must be performed at the same time after irradiation, or errors of up to 25% may be incurred. Precision of gel response did not change significantly over time. The observation of significantly different T(2) values both prior to irradiation and following irradiation to the same dose (variation up to 15%) illustrates the current difficulties associated with BANG3 gel calibration and constrains the practical utility of these commercially available gels for clinical radiation dosimetry.

Dynamic mechanical properties of agarose gels modeled by a fractional derivative model

The complex modulus (E*) and elastic modulus (E') of agarose gels (2% to 4%) are measured with a dynamic mechanical analyzer in frequency sweep shear sandwich mode between 0.1 and 20 Hz. The data showed that E* and E' increase with frequency according to a power law which can be described by a fractional derivative model to characterize the dynamic viscoelasticity of the gel. The functions between the model parameters including storage modulus coefficient (H) and the power law exponent (beta) and the agarose concentration are established. A molecular basis for the application of the fractional derivative model to gel polymers is also discussed. Such an approach can be useful in tissue culture studies employing dynamic pressurization or for validation of magnetic resonance elastography.

Direct visualization of asymmetric behavior in supported lipid bilayers at the gel-fluid phase transition

We utilize in situ, temperature-dependent atomic force microscopy to examine the gel-fluid phase transition behavior in supported phospholipid bilayers constructed from 1,2-dimyristoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The primary gel-fluid phase transition at T(m) occurs through development of anisotropic cracks in the gel phase, which develop into the fluid phase. At approximately 5 degrees C above T(m), atomic force microscopy studies reveal the presence of a secondary phase transition in all three bilayers studied. The secondary phase transition occurs as a consequence of decoupling between the two leaflets of the bilayer due to enhanced stabilization of the lower leaflet with either the support or the water entrained between the support and the bilayer. Addition of the transmembrane protein gramicidin A or construction of a highly defected gel phase results in elimination of this decoupling and removal of the secondary phase transition.