| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Alpeeva, IS, et al.
(författare)
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Palm tree peroxidase-based biosensor with unique characteristics for hydrogen peroxide monitoring
- 2005
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 21:5, s. 742-748
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Tidskriftsartikel (refereegranskat)abstract
- Three amperometric enzyme electrodes have been constructed by adsorbing anionic royal palm tree peroxidase (RPTP), anionic sweet potato peroxidase (SPP), or cationic horseradish peroxidase (HRP-C) on spectroscopic graphite electrodes. The resulting H2O2-sensitive biosensors were characterized both in a flow injection system and in batch mode to evaluate their main bioelectrochemical parameters, such as pH dependency,I-max, K-M(app), detection limit, linear range, operational and storage stability. The obtained results showed a distinctly different behavior for the plant peroxidase electrodes, demonstrating uniquely superior characteristics of the RPTP-based sensors. The broader linear range observed for the RPTP-based biosensor is explained by a high stability of this enzyme in presence of H2O2. The higher storage and operational stability of RPTP-based biosensor as well as its capability to measure hydrogen peroxide under acidic conditions connect with an extremely high thermal and pH-stability of RPTP.
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| 3. |
- Andersen, Karsten Brandt, et al.
(författare)
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Stability of diphenylalanine peptide nanotubes in solution
- 2011
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3372 .- 2040-3364. ; 3:3, s. 994-998
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Tidskriftsartikel (refereegranskat)abstract
- Over the last couple of years, self-organizing nanotubes based on the dipeptide diphenylalanine have received much attention, mainly as possible building blocks for the next generation of biosensors and as drug delivery systems. One of the main reasons for this large interest is that these peptide nanotubes are believed to be very stable both thermally and chemically. Previously, the chemical and thermal stability of self-organizing structures has been investigated after the evaporation of the solvent. However, it was recently discovered that the stability of the structures differed significantly when the tubes were in solution. It has been shown that, in solution, the peptide nanotubes can easily be dissolved in several solvents including water. It is therefore of critical importance that the stability of the nanotubes in solution and not after solvent evaporation be investigated prior to applications in which the nanotube will be submerged in liquid. The present article reports results demonstrating the instability and suggests a possible approach to a stabilization procedure, which drastically improves the stability of the formed structures. The results presented herein provide new information regarding the stability of self-organizing diphenylalanine nanotubes in solution.
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| 4. |
- Bruno, Viguier, et al.
(författare)
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Development of an Electrochemical Meta-Ion Biosensor Using Self-Assembled Peptide Nanofibrils
- 2011
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 3:5, s. 1594-1600
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the combination of self-assembled peptide nanofibrils with metal electrodes for the development of an electrochemical metal-ion biosensor. The biological nanofibrils were immobilized on gold electrodes and used as biorecognition elements for the complexation with copper ions. These nanofibrils were obtained under aqueous conditions, at room temperature and outside the clean room. The functionalized gold electrode was evaluated by cyclic voltammetry, impedance spectroscopy, energy dispersive X-ray and atomic force microscopy. The obtained results displayed a layer of nanofibrils able to complex with copper ions in solution. The response of the obtained biosensor was linear up to 50 mu M copper and presented a sensitivity of 0.68 mu A cm(-2) mu M-1. Moreover, the fabricated sensor could be regenerated to a copper-free state allowing its reutilization.
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| 5. |
- Castillo Leon, Jaime
(författare)
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Amperometric Biosensors for Detection of Analytes in Cellular Models
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Various biological problems such as disease mechanisms, drug development and toxicological studies motivated the introduction of cellular models that today also represent an alternative for reducing the use of animals in controversial medical and pharmaceutical experiments. Cells are complex matrices where several processes occur simultaneously. Because of this, analytical methods with specific paramenters (high sensitivity, response time, good selectivity) are required to efficiently monitor the behaviour and interaction of cells after stimulation with different kinds of compounds: drugs, toxic chemicals, etc. This thesis presents the currently used techniques for monitoring analytes of biomedical importance in cells and cell lines. Special attention is given to amperometric biosensors for the analysis of analytes released by cells. Different biosensor designs are presented, namely; enzyme-modified planar array, and dual needle type ones. The importance of key parameters, such as; recognition elements, immobilisation techniques, miniaturisation, and interference elimination is also discussed in detail and their application possibilities are presented for the case of some neurotransmitters. The design and the application possibilities of the developed biosensors are characterised by an increasing degree of complexity, ranging from simple graphite electrodes to needle type, micro-dual barrel Pt microelectrodes for the simultaneous detection of neurotransmitters released from cells. The thesis demonstrates that amperometric biosensors can be used in complex experiments to analyse the response of cells to different drugs and stress-induced mechanisms in cell cultures. Further application possibilities include the integration of biosensors with advanced imaging techniques, such as e.g. with scaning electrochemical microscopy (SECM).
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| 6. |
- Castillo Leon, Jaime, et al.
(författare)
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Bienzyme biosensors for glucose, ethanol and putrescine built on oxidase and sweet potato peroxidase
- 2003
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Ingår i: Biosensors & Bioelectronics. - 1873-4235. ; 18:5-6, s. 705-714
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Tidskriftsartikel (refereegranskat)abstract
- Amperometric biosensors for glucose, ethanol, and biogenic amines (putrescine) were constructed using oxidase/peroxidase bienzyme systems. The H2O2 produced by the oxidase in reaction with its substrate is converted into a measurable signal via a novel peroxidase purified from sweet potato peels. All developed biosensors are based on redox hydrogels formed of oxidases (glucose oxidase, alcohol oxidase, or amine oxidase) and the newly purified sweet potato peroxidase (SPP) cross-linked to a redox polymer. The developed electrodes were characterized (sensitivity, stability, and performances in organic medium) and compared with similarly built ones using the 'classical' horseradish peroxidase (HRP). The SPP-based electrodes displayed higher sensitivity and better detection limit for putrescine than those using HRP and were also shown to retain their activity in organic phase much better than the HPR based ones. The importance of attractive or repulsive electrostatic interactions between the peroxidases and oxidases (determined by their isoelectric points) were found to play an important role in the sensitivity of the obtained sensors
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| 7. |
- Castillo Leon, Jaime, et al.
(författare)
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Biosensors for life quality - Design, development and applications
- 2004
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Ingår i: Sensors and Actuators B: Chemical. - : Elsevier BV. - 0925-4005. ; 102:2, s. 179-194
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Tidskriftsartikel (refereegranskat)abstract
- Biosensors, combining a selective biological recognition element and a sensitive transducer, are versatile analytical tools applied more and more in different fields, such as medicine, food quality and safety control, and environment pollution monitoring. They are expected to play an increasingly important role in the improvement of life quality. In this context, the present work covers recent approaches in design and development of biosensors applied for analysis of real samples of medical, environmental or industrial relevance. The described sensors meet the sensitivity, selectivity, and response time required by their applications. Moreover, they are designed to avoid contamination of the monitored systems with undesirable components and to minimise the damage of living organisms (when it comes to in vivo monitoring). (C) 2004 Elsevier B.V. All rights reserved.
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| 8. |
- Castillo Leon, Jaime, et al.
(författare)
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Glutamate detection from nerve cells using a planar electrodes array integrated in a microtiter plate
- 2005
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:10, s. 2116-2119
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in new strategies for replacing animal tests in research. The use of cell cultures and integrated electrodes is seen as a promising alternative that could potentially solve this problem. In this work, we present a L-glutamate sensor based on a bienzyme redox hydrogel, capable of detecting the release of this excitatory neurotransmitter from adherently growing cells upon stimulation. The low working potential required for the operation of the sensor decreases the possibility of interference by easily oxidizable compounds always present in complex biological samples. A low detection limit of 0.5 mu M L-glutamate, a response time of about 35 s, and a linear range of up to 60 mu M are the main characteristics of the sensor. The system has been successfully employed to monitor the release of L-glutamate from HN10 and C6 cells upon stimulation with K+-ions. The developed integrated electrochemical platform will be used in future for drug screening and potentially for replacing animal models in neurological experiments.
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| 9. |
- Castillo Leon, Jaime, et al.
(författare)
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Purification and substrate specificity of peroxidase from sweet potato tubers
- 2002
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Ingår i: Plant Science. - 0168-9452. ; 163:5, s. 1011-1019
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Tidskriftsartikel (refereegranskat)abstract
- Previously the screening of tropical plants demonstrated a high peroxidase activity in sweet potato (Ipomoea batatas) tubers. The major peroxidase pool is localized in peel. Using peel of sweet potato as a source, the sweet potato peroxidase (SPP) has been isolated and purified to homogeneity. The enzyme purification included homogenization, extraction of colored compounds and consecutive chromatographies on Phenyl-Sepharose and DEAE-Toyopearl. The purified SPP had specific activity of 4900 U mg(-1) protein, RZ (ratio of absorbances at 403 and 280 nm, respectively) 3.4, molecular mass of 37 kDa and isoelectric point of 3.5. The spectrum of peroxidase from sweet potato is typical for plant peroxidases with a Soret maximum at 401 nm and the maxima in the visible region at 497 and 638 nm, respectively. The substrate specificity of SPP is distinct from the specificity of other plant peroxidases, ferulic acid being the best substrate for SPP.
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| 10. |
- Castillo Leon, Jaime, et al.
(författare)
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Simultaneous detection of the release of glutamate and nitric oxide from adherently growing cells using an array of glutamate and nitric oxide selective electrodes
- 2005
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Ingår i: Biosensors & Bioelectronics. - : Elsevier BV. - 1873-4235 .- 0956-5663. ; 20:8, s. 1559-1565
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Tidskriftsartikel (refereegranskat)abstract
- The simultaneous detection of nitric oxide and glutamate using an array of individually addressable electrodes, in which the individual electrodes in the array were suitably modified with a highly sensitive nitric oxide sensing chemistry or a glutamate oxidase/redox hydrogel-based glutamate biosensor is presented. In a sequence of modification steps one of the electrodes was covered first with a positively charged Ni porphyrin entrapped into a negatively charged electrodeposition paint followed by the manual modification of the second working electrode by a bienzyme sensor architecture based on crosslinked redox hydrogels with entrapped peroxidase and glutamate oxidase. Adherently growing C6-glioma cells were grown on membrane inserts and placed in close distance to the modified sensor surfaces. The current responses recorded at each electrode after stimulation of glutamate and NO release by means of K+ and bradykinin clearly demonstrate the ability of the individual electrode in the array to detect the analyte towards which its sensitivity and selectivity was targeted without interference from the neighbouring electrode or other analytes present in the test mixture.
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