Impact of Rapid Molecular Multiplex Gastrointestinal Pathogen Testing in Management of Children during a Shigella Outbreak.

Fecal culture for isolation and identification of Shigella may take days. The BioFire FilmArray Gastrointestinal (GI) panel (bioMérieux, France) is a PCR-based assay that detects enteric pathogens including Shigella/enteroinvasive Escherichia coli (EIEC) in about an hour. The aim of this study was to evaluate the impact of GI panel detection of Shigella in a pediatric emergency department (ED) during an outbreak. Stool samples from children with acute gastroenteritis were tested by the GI panel. Test results were either withheld in preintervention (PRE) or reported to clinicians/families in the postintervention (POST) period. The impact of the GI panel testing on patient management and outcomes was measured. Shigella/EIEC was identified by the GI panel in the PRE (n = 30) and POST (n = 21) phase. The GI panel detected more Shigella infections than did culture; six of 31 (19.4%) Shigella GI panel-positive patients who also had stool cultures were missed by culture. Azithromycin therapy was prescribed for 20% of subjects in the PRE phase and 71.4% of subjects in the POST phase (P < 0.001). Time from the clinical encounter until starting azithromycin therapy was shorter in the POST phase (n = 9), 8.25 h (range, 6.37 to 52.37 h), than in the PRE phase (n = 1), 72 h. Six subjects in the PRE phase visited additional providers compared with one in the POST phase. Prompt diagnosis of shigellosis with the GI panel may provide the opportunity for prompt antimicrobial therapy and avoid additional visits to providers due to early definitive diagnosis. Prompt diagnosis of Shigella at an ED visit may optimize patient management and reduce transmission.

Surgery to relieve nasal obstruction: outcome for 366 patients operated on by one senior surgeon.

BACKGROUND: Studies of patient-rated outcome in septoplasty and turbinoplasty most frequently involve several surgeons with varying surgical skills, techniques and experience. The aim of the present study was to evaluate outcome based on one experienced surgeon. METHODS: Three hundred and sixty-six consecutive patients referred for nasal obstruction were included. All the patients were examined with nasal endoscopy before and after decongestion, they filled out a nose VAS and rated their overall general health before and three to six months after surgery. The patients underwent septoplasty, septoplasty plus turbinoplasty or turbinoplasty. RESULTS: The mean nose VAS for nasal obstruction (0-100) preoperatively was 64.7 for all patients. Patients undergoing septoplasty (n = 159) were younger than patients undergoing septoplasty + turbinoplasty (n = 79) or patients undergoing turbinoplasty alone (n = 128). The nose VAS for nasal obstruction improved significantly in all three groups and 25% had a normal nose VAS after surgery in the septoplasty and septoplasty + turbinoplasty groups compared to only 8% in the turbinoplasty alone group. There was no significant difference in the improvement in nasal obstruction between septoplasty and septoplasty + turbinoplasty, but the septoplasty + turbinoplasty group experienced a significantly greater improvement in general health. CONCLUSIONS: In 366 patients operated on by one experienced surgeon, septoplasty and septoplasty + turbinoplasty were more effective at relieving nasal obstruction than turbinoplasty alone. Septoplasty + turbinoplasty resulted in a greater improvement in general health than septoplasty alone, despite the same improvement in nasal obstruction, indicating a beneficial effect of additional turbinoplasty in septoplasty.

Prognostic factors for outcome after septoplasty in 888 patients from the Swedish National Septoplasty Register.

BACKGROUND: The aim of this study was to identify predictors of outcome after septoplasty in 888 patients from the Swedish National Septoplasty Register. METHODOLOGY: This is an observational register study analysing data from patients undergoing septoplasty in Sweden between 2015 and 2016. The patients reported severity of nasal obstruction (mild, moderate, severe) pre- and again 12 months postoperatively (none, mild, moderate, severe), unplanned visits within 30 days after surgery. The examining doctor reported co-morbidities such as allergic rhinitis and snoring. The primary end-point was one level improvement of the nasal obstruction 12 months after surgery. RESULTS: Nasal obstruction had improved in 63% 12 months after surgery. Twelve months after surgery, 81% with severe nasal obstruction and 31% with mild nasal obstruction before surgery had improved. Only 56% reported that the results of the surgery were as they had expected. Higher patient age at surgery, no unplanned visits within 1 month of surgery and activity limitation before surgery were associated with improvements in nasal breathing in the logistic regression model. CONCLUSION: Septoplasty should be offered to patients with severe nasal obstruction and surgery should be avoided in mild nasal obstruction confirmed by both an improvement in nasal obstruction and patient expectations in this study.

Increase in pollen sensitization in Swedish adults and protective effect of keeping animals in childhood.

BACKGROUND: To date, most studies of the 'allergy epidemic' have been based on self-reported data. There is still limited knowledge on time trends in allergic sensitization, especially among adults. OBJECTIVE: To study allergic sensitization, its risk factors and time trends in prevalence. METHODS: Within West Sweden Asthma Study (WSAS), a population-based sample of 788 adults (17-60 years) underwent skin prick tests (SPTs) for 11 aeroallergens 2009-2012. Specific IgE was analysed in 750 of the participants. Those aged 20-46 years (n = 379) were compared with the European Community Respiratory Health Survey sample aged 20-46 year from the same area (n = 591) in 1991-1992. RESULTS: Among those aged 20-46 years, the prevalence of positive SPT to pollen increased, timothy from 17.1% to 29.0% (P < 0.001) and birch from 15.6% to 23.7% (P = 0.002) between 1991-1992 and 2009-2012. Measurements of specific IgE confirmed these increases. Prevalence of sensitization to all other tested allergens was unchanged. In the full WSAS sample aged 17-60 years, any positive SPT was seen in 41.9%, and the dominating sensitizers were pollen (34.3%), animals (22.8%) and mites (12.6%). Pollen sensitization was strongly associated with rhinitis, whereas indoor allergens were more associated with asthma. Growing up with livestock or furred pets decreased the risk of sensitization, adjusted odds ratio 0.53 (0.28-0.995) and 0.68 (0.47-0.98), respectively. CONCLUSION: Pollen sensitization has increased in Swedish adults since the early 1990s, while the prevalence of sensitization to other allergens has remained unchanged. This is one plausible explanation for the increase in rhinitis 1990-2008 in Swedish adults, during which time the prevalence of asthma, which is more associated with perennial allergens, was stable. Contact with animals in childhood seems to reduce the risk of sensitization well into adulthood. One major factor contributing to the rise in pollen allergy is a significant increase in levels of birch and grass pollen over the past three decades.

Impact of asthma medication and familial factors on the association between childhood asthma and attention-deficit/hyperactivity disorder: a combined twin- and register-based study: Epidemiology of Allergic Disease.

BACKGROUND: Asthma and attention-deficit/hyperactivity disorder (ADHD) are prevalent in childhood and may cause functional impairment and stress in families. Previous research supports an association between asthma and ADHD in children, but several aspects of this relationship are unclear. OBJECTIVE: Our aim was to study whether the association between asthma and ADHD is restricted to either the inattentive or the hyperactive/impulsive symptoms of ADHD, to explore the impact of asthma severity and asthma medication and the contribution of shared genetic and environmental risk factors on the asthma-ADHD relationship. METHODS: Data on asthma, ADHD, zygosity and possible confounders were collected from parental questionnaires at 9 or 12 years on 20 072 twins through the Swedish Twin Register, linked to the Swedish Medical Birth Register, the National Patient Register and the Prescribed Drug Register. The association between asthma and ADHD, the impact of asthma severity and medication, was assessed by generalized estimating equations. Cross-twin-cross-trait correlations (CTCT) were estimated to explore the relative importance of genes and environment for the association. RESULTS: Asthmatic children had a higher risk of also having ADHD [odds ratio (OR) 1.53, 95% confidence interval (CI): 1.16-2.02]. The association was not restricted to either of the two dimensions of ADHD. The magnitude of the association increased with asthma severity (OR 2.84, 95% CI: 1.86-4.35) for ≥ 4 asthma attacks in the last 12 months and was not affected by asthma treatment. The CTCTs possibly indicate that the genetic component in overlap of the disorders is weak. CONCLUSIONS AND CLINICAL RELEVANCE: Childhood asthma, especially severe asthma, is associated with ADHD. Asthma medication seems not to increase the risk of ADHD. Clinicians should be aware of the potential of ADHD in asthma. Optimal asthma care needs to be integrated with effective evaluation and treatment of ADHD in children with co-existing disorders.

Cationic gemini surfactants with cleavable spacer: chemical hydrolysis, biodegradation, and toxicity.

The paper describes synthesis and characterization of a new type of cationic gemini surfactant, which has dodecyl tails and a spacer that contains an ester bond. The nomenclature used to describe the structure is 12Q2OCO1Q12, with Q being a quaternary ammonium group and the numbers indicating the number of methylene or methyl groups. Due to the close proximity to the two quaternary ammonium groups, the ester bond is very stable on the acid side and very labile already at slightly alkaline conditions. The hydrolysis products are two single chain surfactants (i.e. 12Q2OH and 12Q1COOH) which are less surface active than the intact gemini surfactant. 12Q2OCO1Q12 was found to be readily biodegradable, i.e. it gave more than 60% biodegradation after 28 days. This is interesting because similar gemini surfactants but with ester bonds in the tails instead of the spacer, have previously been found not to be readily biodegradable. The gemini surfactant was found to be toxic to aquatic organisms (ErC50 value of 0.27 mg/l), although less toxic than the two hydrolysis products.

Nanostructured fluids from degradable nonionic surfactants for the cleaning of works of art from polymer contaminants.

Nanostructured fluids containing anionic surfactants are among the best performing systems for the cleaning of works of art. Though efficient, their application may result in the formation of a precipitate, due to the combination with divalent cations that might leach out from the artifact. We propose here two new aqueous formulations based on nonionic surfactants, which are non-toxic, readily biodegradable and insensitive to the presence of divalent ions. The cleaning properties of water-nonionic surfactant-2-butanone (MEK) were assessed both on model surfaces and on a XIII century fresco that could not be cleaned using conventional methods. Structural information on nanofluids has been gathered by means of small-angle neutron scattering, dynamic light scattering and nuclear magnetic resonance with diffusion monitoring. Beside the above-mentioned advantages, these formulations turned out to be considerably more efficient in the removal of polymer coatings than those based on anionic surfactants. Our results indicate that the cleaning process most likely consists of two steps: initially, the polymer film is swollen by the MEK dissolved in the continuous domain of the nanofluid; in the second stage, surfactant aggregates come into play by promoting the removal of the polymer film with a detergency-like mechanism. The efficiency can be tuned by the composition and nature of amphiphiles and is promoted by working as close as possible to the cloud point of the formulation, where the second step proceeds at maximum rate.

Screening for attention-deficit/hyperactivity disorder (ADHD): can high-risk children be identified in first grade?

AIM: Recent studies have demonstrated the beneficial long-term effects of an indicated parent support programme for acting out behaviour in pre-school children with attention-deficit/hyperactivity disorder (ADHD) traits. In this study we wanted to assess different thresholds for screening with the Conners scale for hyperactive-inattentive behaviours in first grade for ADHD in grade four. METHOD: The study population consisted of 422 first graders (6- to 7-year-olds) in one municipality in Stockholm County who were screened with Conners 10-item scale and followed up by ADHD assessment in grade four. Sensitivity, specificity, likelihood ratios, and positive predictive value (PPV) of the screening by parents and teachers in first grade for being diagnosed with ADHD in fourth grade were calculated. RESULTS: The prevalence of pervasive and situational ADHD was 5.7% and 5.9% respectively. A score ≥ 10 on the Conners scale in first grade in teachers' reports identified 63% [95% confidence interval (CI): 43-79] of children diagnosed with pervasive ADHD in grade four (P < 0.001) with a PPV of 29% and a positive likelihood ratio (LR+) of 6.72. Parental reports of a score ≥ 10 yielded a lower sensitivity (29%; 95% CI: 15-49), PPV of 20% and LR+ of 4.24 for pervasive ADHD. The best predictor was a combination of parent and teacher scores ≥ 10 with a PPV of 50% and LR+ of 16.63. Associations with situational ADHD were weak with LR+ of 1.81 and 2.49, respectively, for teachers' and parental scores ≥ 10. CONCLUSIONS: This study indicates a strong association between a teacher's report of a score ≥ 10 on the Conners scale in first grade and pervasive ADHD in grade four, while parental reports were less predictive.

Cationic ester-containing gemini surfactants: determination of aggregation numbers by time-resolved fluorescence quenching.

The micellar aggregation number of a series of ester-containing gemini surfactants has been determined with steady state and with time-resolved fluorescence quenching. The latter method gave values of aggregation number about twice those obtained with the former method. It was found that the length of the spacer was the most important factor affecting the aggregation number. The length and the nature of the surfactant alkyl chains were of less importance in spite of the fact that the length of the alkyl chains strongly affects the solution properties of the unimers.

Solubilization of two organic dyes by cationic ester-containing gemini surfactants.

Solubilization of two different types of organic dyes, Quinizarin with an anthraquinone structure and Sudan I with an azo structure, has been studied in aqueous solutions of a series of cationic gemini surfactants and of a conventional monomeric cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Surfactant concentrations both above and below the critical micelle concentration were used. The concentration of solubilized dye at equilibrium was determined from the absorbance of the solution at λ(max) with the aid of a calibration curve. The solubilization power of the gemini surfactants was higher than that of DTAB and increased with increasing alkyl chain length. An increase in length of the spacer unit resulted in increased solubilization power while a hydroxyl group in the spacer did not have much effect. Ester bonds in the alkyl chains reduced the solubilization power with respect to both dyes. A comparison between the absorbance spectra of the dyes in micellar solution with spectra in a range of solvents of different polarity indicated that the dye is situated in a relatively polar environment. One may therefore assume that the dye is located just below the head group region of the micelle. Attractive π-cation interactions may play a role for orienting the dye to the outer region of the micelle.

Academic performance of adolescents with ADHD and other behavioural and learning problems -a population-based longitudinal study.

AIM: To study academic performance (final grades at the age of 16 years) in individuals with i) attention-deficit/hyperactivity disorder (ADHD) and ii) other learning and/or behavioural problems. METHODS: Of a total population of 591 children, originally assessed at the age of 10-11 years, it was possible to obtain final grades for 536 16-year-olds (in grade 9). Those fulfilling the criteria for ADHD/sub-threshold ADHD (n = 39) and those with 'Behaviour and Learning Problems' (BLP group), (n = 80) and a comparison group (n = 417) were contrasted. RESULTS: The ADHD and BLP groups had a significantly lower total mean grade at the age of 16 years than the comparison group. In addition, the ADHD and BLP groups also qualified for further studies in the upper secondary school to a significantly lesser extent than the controls (72%, 68% and 92%, respectively). All IQ measures (at the age of 10-11 years) were positively correlated with the overall grade after grade 9, with especially strong correlations for verbal capacity. CONCLUSION: ADHD and similar problems entail a risk of underachievement at school. The results indicate that pupils with ADHD underachieve in the school situation in relation to their optimal cognitive capacity. The contextual situation and the particular requirements should be considered in order for adequate educational measures to be undertaken.

Cationic ester-containing gemini surfactants: physical-chemical properties.

Three ester-containing cationic gemini surfactants, two with decanoyl chains and either a three-carbon or a six-carbon spacer unit and one with dodecanoyl chains and a three-carbon spacer, were synthesized and evaluated. A corresponding monomeric cationic ester surfactant was used for comparison. This type of amphiphile, a so-called esterquat, is known to undergo rapid hydrolysis above the critical micelle concentration because of micellar catalysis. The esterquat geminis of this work were found to be much more susceptible to hydrolysis than the esterquat monomer. This difference is believed to be caused by anchimeric assistance by the second cationic headgroup in the gemini amphiphiles. However, there is no correlation between the rate of chemical hydrolysis and the rate of biodegradation. The monomeric esterquat, which is the most stable in the chemical hydrolysis experiments, was the only surfactant that passed the test for "readily biodegradable". We also observed a considerable difference in the hydrolysis rate within the small series of gemini surfactants. The amphiphile with two decanoyl chains and a three-carbon spacer, N,N'-bis(2-(decanoyloxy)ethyl)-N,N,N',N'-tetramethyl-1,3-propanediammonium dibromide, had the fastest rate of hydrolysis. This surfactant also exhibited a considerably lower degree of micelle ionization than the other surfactants, which is believed to be due to the closer proximity of the charged groups on the micelle surface. A small distance between headgroups will give more pronounced neighboring group participation, accounting for the increased rate of hydrolysis. An interesting property of the surfactant that is the most susceptible to hydrolysis is that it gives rise to an extremly stable foam. We propose that the foam stability is a result of the partial hydrolysis of the surfactant generating sodium decanoate, an anionic surfactant, that forms a mixed film with the starting cationic gemini surfactant. It is known that mixed monolayers in which there is a strong attractive interaction between surfactant headgroups can lead to stable foams.

Interfacial mechanism of lipolysis as self-regulated process.

Obesity is a serious public health concern with an increasing prevalence worldwide. The diet contributes strongly to this problem and high-fat food leads to unhealthy conditions. Fat digestion is an energy intensive process as it requires hydrolysis to allow the body to profit from this nutrient. This additional energy expenditure is also present in a highly redundant hormonal regulation system for fat storage which is converted in not a readily accessible form (therefore, an upstream is required in order to tackle fat-related diseases). Due to the low water solubility of oils and fats, the lipase catalyzed reactions take place at a specific locus, the oil-water interface. Despite considerable efforts in the past the effects of the interfacial composition on lipase activity have been only qualitatively understood until recently. It has recently been undertaken a detailed study of the interfacial behavior of lipases, their substrates and products which have contributed to shed light into the mechanism of lipolysis [1-4]. In addition, there are strong evidences that lipase activity is a function of interfacial composition and changes concurrently with lipolytic conversion [1]. In these cases lipase "inhibition" should be attributed to substrate depletion and not to lipase desorption or denaturation as previously hypothesized [5]. This self-limiting effect through the feedback of interfacial composition to the reaction conditions of the enzyme opens a new avenue to control lipase catalysis through the interface. A set of experiments are proposed which can be performed to further characterize and gain a deeper insight into interfacial enzymology.

Desloratadine relieves nasal congestion and improves quality-of-life in persistent allergic rhinitis.

BACKGROUND: Symptoms of allergic rhinitis (AR), particularly nasal congestion, can impair quality-of-life (QoL). However, only a modest correlation exists between these symptoms and Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) scores, suggesting that both be evaluated for a complete assessment of health. METHODS: Subjects with a > or =2-year history of moderate-to-severe AR to dust mite or cat dander were randomized to desloratadine 5 mg/day (n = 293) or placebo/day (n = 291) for 28 days. Primary endpoint was change from baseline in a.m./p.m. nasal congestion score. Secondary outcomes included change from baseline in total nasal symptom score, individual symptom scores and RQLQ scores (completed on days 1, 7, and 28). RESULTS: The Allergic Rhinitis and its Impact on Asthma criteria for persistent allergic rhinitis (PER) were fulfilled by 99% of subjects in the placebo arm. Between-treatment difference in a.m./p.m. nasal congestion score, observed from day 8 onward, significantly favored desloratadine (P = 0.0003). Desloratadine significantly improved a.m./p.m. nasal congestion and RQLQ scores after 1 week and at treatment end (P < 0.05). Improvements in 5 of 7 RQLQ domain scores exceeded the minimal important difference. On days 7 and 28, desloratadine was also significantly superior to placebo in mean change from baseline in a.m./p.m. total nasal symptom score and rhinorrhea score (both P < or = 0.01). Symptomatic benefit was primarily driven by improvement in nasal congestion and rhinorrhea. CONCLUSIONS: Desloratadine 5 mg/day significantly improved symptoms associated with PER, including nasal congestion, and provided significant improvement in QoL after 1 week of treatment.

Lipases at interfaces: a review.

Lipases are acyl hydrolases that play a key role in fat digestion by cleaving long-chain triglycerides into polar lipids. Due to an opposite polarity between the enzyme (hydrophilic) and their substrates (lipophilic), lipase reaction occurs at the interface between the aqueous and the oil phases. Hence, interfaces are the key spots for lipase biocatalysis and an appropriate site for modulating lipolysis. Surprisingly enough, knowledge about the effects of the interfacial composition on lipase catalysis is still limited and only described by the term "interfacial quality". Recent systematic studies based on a biophysical approach allowed for the first time to show the effects of the interfacial microenvironment on lipase catalysis. These studies demonstrate that lipase activity as a function of interfacial composition is more attributed to substrate inaccessibility rather than to enzyme denaturation or inactivation, as it is often hypothesized. A detailed analysis of the interfacial properties of all compounds involved in triglyceride digestion revealed that lipolysis is a self-regulated reaction. This feedback mechanism can be explored as a new avenue to control lipase catalysis. To substantiate this hypothesis, oil hydrolysis in a model gastro-intestinal system was performed, which can be seen as an interfacial engineering approach to enzyme reactivity control. The presented characterization of the interfacial composition and its consequences provide a new approach for the understanding of lipase reactions at interfaces with direct impact on biotechnological and health care applications.

A follow-up study of immunotherapy-treated birch-allergic patients: effect on the expression of chemokines in the nasal mucosa.

BACKGROUND: Specific immunotherapy (SIT) is the only treatment producing lasting clinical improvement in patients with allergy. We investigated the long-term effect of SIT treatment on the expression of chemokines: eotaxin, RANTES (regulated upon activation, normal T cell expressed and secreted) and thymus and activation-regulated chemokine (TARC), and their receptors CCR3 and CCR4 in biopsies of nasal mucosa from birch-allergic individuals. METHODS: Sixteen patients who completed a 3-year treatment programme 3-5 years ago, and 12 untreated, matched controls were included in the study. Patients recorded symptoms and use of rescue medication before and during the pollen season. Nasal mucosa samples obtained before and during the season were stained for eosinophil and mast cell markers and for eotaxin, RANTES, TARC, CCR3 and CCR4. RESULTS: During the pollen season, rhinoconjunctivitis symptoms increased in both SIT and control groups (P=0.001 and 0.002, respectively). However, SIT patients had 37% fewer symptoms than controls. Medication use increased in both groups (P=0.002) during the season but the SIT group used 28% less than the controls (P=0.02). The number of eosinophils in the nasal mucosa increased in the control group (P=0.01) and the difference between the groups was significant during the season (P=0.01). No seasonal increase in the numbers of mast cells was seen, but during the pollen season, more (P=0.02) AA(+) cells were found in the controls than in the SIT group. The number of eotaxin(+) and RANTES(+) cells increased in the control group (P=0.01 and 0.03, respectively) and the difference between groups during the season was significant (P=0.01 and 0.01, respectively). The TARC(+) cell numbers were lower in the SIT group during the season (P=0.003). The CCR3(+) cells increased only in the control group during the pollen season and remained unchanged in SIT patients, while CCR4(+) cell numbers increased in both the control (P=0.03) and SIT (P=0.02) groups. CONCLUSION: This study confirmed that decreased numbers of eosinophils in the nasal mucosa is a long-lasting effect of birch SIT. SIT also prevented seasonal rises in the number of cells expressing the chemokines eotaxin and RANTES.

Lipases at interfaces: unique interfacial properties as globular proteins.

The adsorption behavior of two globular proteins, lipase from Rhizomucor miehei and beta-lactoglobulin, at inert oil/water and air/water interfaces was studied by the pendant drop technique. The kinetics and adsorption isotherms were interpreted for both proteins in different environments. It was found that the adopted mathematical models well describe the adsorption behavior of the proteins at the studied interfaces. One of the main findings is that unique interfacial properties were observed for lipase as compared to the reference beta-lactoglobulin. A folded drop with a "skinlike" film was formed for the two proteins after aging followed by compression. This behavior is normally associated with protein unfolding and covalent cross-linking at the interface. Despite this, the lipase activity was not suppressed. By highlighting the unique interfacial properties of lipases, we believe that the presented work contributes to a better understanding of lipase interfacial activation and the mechanisms regulating lipolysis. The results indicate that the understanding of the physical properties of lipases can lead to novel approaches to regulate their activity.

Cationic ester-containing gemini surfactants: adsorption at tailor-made surfaces monitored by SPR and QCM.

Adsorption of a series of ester-containing cationic surfactants at a surface containing 90% methyl groups and 10% carboxyl groups was studied by two surface analysis techniques, surface plasmon resonance (SPR) and quartz crystal microbalance (QCM). Such a surface, which is at the same time hydrophobic and negatively charged, is of interest as a model for many polymeric surfaces. Two different types of ester gemini surfactants and their monomeric counterparts were included together with nonester containing surfactants of similar structure. The results show that the gemini surfactants give the same adsorbed amount at the surface as the monomeric surfactants when compared at the same bulk concentration normalized to the critical micelle concentration (cmc) in bulk. Since the cmc of the geminis is around 20 times lower than the cmc of the corresponding monomeric surfactants, the gemini surfactants are much more effective in covering the surface. The two techniques gave similar relative values but the QCM values were always higher than those from SPR, which is due to the former method taking also adsorbed water into account. The adsorption, as measured by both methods, was found to follow closely the Langmuir adsorption model.

Adsorption of polar lipids at the water-oil interface.

Dietary fat has long been recognized as an essential component in nutrition. However, most of the lipids present in food need to be converted into more bioavailable compounds. Lipases have a crucial role in converting triglycerides into more polar lipids with increased water solubility and a tendency to form micelles. However, the surface active molecules generated by lipolysis may have a detrimental effect on the interfacial biocatalysis. In the present work we evaluate the interfacial properties of lipase-generated molecules during fat digestion. By using the pendant drop technique we assessed the amphiphilic character of fatty acid salts, monoglycerides, and diglycerides as individual surfactants and mixtures. The experimental results are fitted with a mathematical model, which assists in the determination of the interfacial properties of the surfactants. Our results show that monoglycerides have considerably higher interfacial activity than fatty acid salts and diglycerides. Therefore, the interface will soon be dominated by monoglycerides. The pH dependency of the interfacial activity of fatty acids is also explored in the current work. We believe that our results can contribute to a better understanding of the complex interfacial phenomena occurring during fat digestion.

Cationic ester-containing gemini surfactants: chemical hydrolysis and biodegradation.

Two cationic gemini surfactants having ester bonds between the hydrophobic tail and the cationic moiety have been synthesized. The ester bonds were either with the ester carbonyl group away from the positive charge (esterquat type arrangement) or facing the positive charge (betaine ester type arrangement). The chemical hydrolysis of the surfactants was investigated and compared with the hydrolysis of the corresponding monomeric surfactants. The betaine ester type of surfactants was found to hydrolyze much faster than the esterquat surfactants. It was also seen that above the critical micelle concentration the gemini surfactants were much more susceptible to alkaline hydrolysis than the corresponding monomeric surfactants. The biodegradation of the geminis and the monomeric surfactants were also studied. It was found that whereas the monomeric surfactants were rapidly degraded, the two gemini surfactants were more resistant to biodegradation and could not be classified as readily biodegradable. The 60% biodegradation was reached after 35-40 days. Thus, there was no correlation between rate of chemical hydrolysis and rate of biodegradation.