scholarly journals Towards a quantum cascade laser-based implant for the continuous monitoring of glucose

The Analyst ◽  
2018 ◽  
Vol 143 (24) ◽  
pp. 6025-6036 ◽  
Author(s):  
Katharina Isensee ◽  
Niklas Müller ◽  
Annemarie Pucci ◽  
Wolfgang Petrich
Keyword(s):  
Sensitivity And Specificity ◽  
Quantum Cascade Laser ◽  
Continuous Monitoring ◽  
Glucose Monitoring ◽  
Temperature Variations ◽  
Quantum Cascade ◽  
Long Term Stability ◽  
Glucose Sensitivity

Anin vitroinvestigation of a quantum cascade laser-based transflection optofluidic interface for the continuous glucose monitoring in biofluids is presented with respect to its glucose sensitivity and specificity, its glucose exchange time, its resistance against temperature variations and its long-term stability.

THE ROLE OF POLYETHYLENIMINE IN ENHANCING PERFORMANCE OF GLUTAMATE BIOSENSORS

2018 ◽  
Vol 8 (3) ◽  
pp. 36-41
Author(s):  
Diep Do Thi Hong ◽  
Duong Le Phuoc ◽  
Hoai Nguyen Thi ◽  
Serra Pier Andrea ◽  
Rocchitta Gaia
Keyword(s):  
First Generation ◽  
Good Reproducibility ◽  
Complex Matrices ◽  
Long Term Stability ◽  
In Vitro Characterization ◽  
Glutamate Oxidase

Background: The first biosensor was constructed more than fifty years ago. It was composed of the biorecognition element and transducer. The first-generation enzyme biosensors play important role in monitoring neurotransmitter and determine small quantities of substances in complex matrices of the samples Glutamate is important biochemicals involved in energetic metabolism and neurotransmission. Therefore, biosensors requires the development a new approach exhibiting high sensibility, good reproducibility and longterm stability. The first-generation enzyme biosensors play important role in monitoring neurotransmitter and determine small quantities of substances in complex matrices of the samples. The aims of this work: To find out which concentration of polyethylenimine (PEI) exhibiting the most high sensibility, good reproducibility and long-term stability. Methods: We designed and developed glutamate biosensor using different concentration of PEI ranging from 0% to 5% at Day 1 and Day 8. Results: After Glutamate biosensors in-vitro characterization, several PEI concentrations, ranging from 0.5% to 1% seem to be the best in terms of VMAX, the KM; while PEI content ranging from 0.5% to 1% resulted stable, PEI 1% displayed an excellent stability. Conclusions: In the result, PEI 1% perfomed high sensibility, good stability and blocking interference. Furthermore, we expect to develop and characterize an implantable biosensor capable of detecting glutamate, glucose in vivo. Key words: Glutamate biosensors, PEi (Polyethylenimine) enhances glutamate oxidase, glutamate oxidase biosensors

scholarly journals An updated protocol based on CLSI document C37 for preparation of off-the-clot serum from individual units for use alone or to prepare commutable pooled serum reference materials

2020 ◽  
Vol 58 (3) ◽  
pp. 368-374 ◽  
Author(s):  
Uliana Danilenko ◽  
Hubert W. Vesper ◽  
Gary L. Myers ◽  
Patric A. Clapshaw ◽  
Johanna E. Camara ◽  
...  
Keyword(s):  
Human Serum ◽  
Reference Materials ◽  
Frozen Storage ◽  
Metrological Traceability ◽  
Medical Laboratory ◽  
Serum Samples ◽  
Long Term Stability ◽  
Individual Human

AbstractManufacturers of in vitro diagnostic medical devices, clinical laboratories, research laboratories and calibration laboratories require commutable reference materials that can be used in the calibration hierarchies of medical laboratory measurement procedures used for human specimens to establish metrological traceability to higher order reference systems. Commutable materials are also useful in external quality assessment surveys. In order to achieve these goals, matrix-based reference materials with long-term stability, appropriate measurand concentrations and commutability with individual human specimens are required. The Clinical and Laboratory Standards Institute (CLSI) guideline C37-A (now archived) provided guidance to prepare commutable pooled serum reference materials for use in the calibration hierarchies of cholesterol measurement procedures. Experience using the C37-A guideline has identified a number of technical enhancements as well as applications to measurands other than cholesterol. This experience is incorporated into this updated protocol to ensure the procedure will continue to meet the needs of the medical laboratory. The updated protocol describes a procedure for preparing frozen human serum units or pools with minimal matrix alterations that are likely to be commutable with individual human serum samples. The protocol provides step-by-step guidance for the planning phase, collection of individual serum units, processing the units, qualifying the units for use in a pool and frozen storage of aliquots of pooled sera to manufacture frozen serum pools. Guidance on how to perform quality control of the final product and suggestions on documentation are also provided.

scholarly journals Long-Term Stability of a RAFT-Modified Bulk-Fill Resin-Composite under Clinically Relevant versus ISO-Curing Conditions

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5350
Author(s):  
Niklas Graf ◽  
Nicoleta Ilie
Keyword(s):  
Fracture Mechanism ◽  
Resin Composite ◽  
Bending Test ◽  
Depth Sensing ◽  
Matrix Formulation ◽  
Curing Conditions ◽  
Term Stability ◽  
Long Term Stability

The addition of RAFT (reversible addition-fragmentation chain transfer) agents to the matrix formulation of a bulk-fill resin composite can significantly decrease the required curing time down to a minimum of 3 s. Evaluating the long term-stability of this resin composite in relation to varied curing conditions in an in-vitro environment was this study’s goal. Specimens were produced according to either an ISO or one of two clinical curing protocols and underwent a maximum of three successive aging procedures. After each one of the aging procedures, 30 specimens for each curing condition were extracted for a three-point bending test. Fragments were then stereo-microscopically characterized according to their fracture mechanism. Weibull analysis was used to quantify the reliability of each aging and curing combination. Selected fragments (n = 12) underwent further testing via depth-sensing indentation. Mechanical values for either standardized or clinical curing were mostly comparable. However, changes in fracture mechanism and Weibull modulus were observed after each aging procedure. The final procedure exposed significant differences in the mechanical values due to curing conditions. Curing conditions with increased radiant exposure seemingly result in a higher crosslink in the polymer-matrix, thus increasing resistance to aging. Yet, the clinical curing conditions still resulted in acceptable mechanical values, proving the effectiveness of RAFT-polymerization.

Characterization of a near-room-temperature, continuous-wave quantum cascade laser for long-term, unattended monitoring of nitric oxide in the atmosphere

2006 ◽  
Vol 31 (13) ◽  
pp. 2012 ◽  
Author(s):  
David D. Nelson ◽  
J. Barry McManus ◽  
Scott C. Herndon ◽  
Joanne H. Shorter ◽  
Mark S. Zahniser ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Quantum Cascade Laser ◽  
Room Temperature ◽  
Continuous Wave ◽  
Quantum Cascade

scholarly journals Development and test for long-term stability of a synthetic standard for a quantitative Cryptosporidium parvum LightCycler™ PCR assay

2005 ◽  
Vol 3 (1) ◽  
pp. 15-25 ◽  
Author(s):  
Renata Filkorn-Kaiser ◽  
Konrad Botzenhart ◽  
Albrecht Wiedenmann
Keyword(s):  
Cryptosporidium Parvum ◽  
Surrogate Marker ◽  
Target Sequence ◽  
Positive Trend ◽  
Long Term Stability ◽  
Synthetic Standard ◽  
One Year

A recently described quantitative rapid cycle real time PCR (LightCycler™) assay detects Cryptosporidium parvum after in vitro excystation, which is a surrogate marker for the viability of the organisms. In the original assay the quantification standard is a dilution series of C. parvum oocysts with a microscopically determined excystation rate. The need to keep suspensions of viable oocysts in stock and to continuously monitor their excystation rate, however, renders the assay impracticable for routine application. A synthetic standard was developed to replace the in vivo standard and was calibrated using oocysts with known excystation rates. The standard consists of a 486 bp DNA segment ranging from 229 bp upstream to 79 bp downstream of the actual PCR target site. Aliquots of the standard were frozen and stored at −20 °C and at −70 °C or lyophilised and stored at room temperature in the dark. For a period of one year samples preserved with each of the three methods were restored every four or five weeks. They were amplified in the LightCycler™ and the crossing points (CP) were monitored. No significant trend in the raw CP values could be observed for any of the three storage methods. However, when the methods were compared to each other by calculating the CP ratios (−20 °C/−70 °C; −20 °C/lyophilised; −70 °C/lyophilised) at the 10 monitoring dates, the CP ratios −20 °C/−70 °C and −20 °C/lyophilised showed a highly significant positive trend (p<0.0001) while the CP ratio −70 °C/lyophilised did not differ from the null hypothesis (p=0.53). It can be concluded that the latter two preservation methods are both appropriate, while storage at −20 °C is less advisable. Calculations based on the molecular weight of the standard and on the assumption of an average yield of three sporozoites per oocyst led to the conclusion that the target sequence is probably located on a double copy gene

scholarly journals Requirement of the C-terminal proline residue for stability of the Ca2+-activated photoprotein aequorin

1993 ◽  
Vol 293 (1) ◽  
pp. 181-185 ◽  
Author(s):  
N J Watkins ◽  
A K Campbell
Keyword(s):  
Light Emission ◽  
Specific Activity ◽  
In Vitro Transcription ◽  
Wild Type ◽  
Proline Residue ◽  
Long Term Stability ◽  
Recombinant Aequorin

cDNA coding for the Ca(2+)-activated photoprotein aequorin from the jellyfish Aequorea victoria has been engineered to investigate the role of the C-terminal proline residue in bioluminescence. Recombinant aequorin proteins were synthesized by PCR followed by in vitro transcription/translation, and characterized by specific activity, stability, and affinity for coelenterazine. The C-terminal proline residue of aequorin was shown to be essential for the long-term stability of the bound coelenterazine. Aequorin minus proline had only 1% of the specific activity of the wild-type after 2 h, and was virtually inactive after 18 h. The instability of this variant was further demonstrated by re-activating with a coelenterazine analogue (epsilon-coelenterazine), where maximum reactivation was reached in 15 min, and the luminescent activity was almost completely abolished within 3 h. Replacement of the C-terminal proline residue with histidine or glutamic acid decreased the specific activity to 10 and 19% of that of the wild-type respectively. However these variants were also unstable, having t1/2 values of 2.4 h and 2.3 h respectively. Enhancement of the Ca(2+)-independent light emission when proline was replaced by histidine confirmed the stabilizing role of the C-terminal proline. No significant effect of removal of the C-terminal proline was detected on the affinity for coelenterazine.

Thermoelectrically cooled quantum-cascade-laser-based sensor for the continuous monitoring of ambient atmospheric carbon monoxide

2002 ◽  
Vol 41 (6) ◽  
pp. 1169 ◽  
Author(s):  
Anatoliy A. Kosterev ◽  
Frank K. Tittel ◽  
Rüdeger Köhler ◽  
Claire Gmachl ◽  
Federico Capasso ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Quantum Cascade Laser ◽  
Continuous Monitoring ◽  
Quantum Cascade ◽  
Atmospheric Carbon ◽  
Atmospheric Carbon Monoxide

Continuous monitoring of CH4 on a suburban site in Dunkirk using an 8-µm quantum cascade laser sensor

2016 ◽  
Author(s):  
Rabih Maamary ◽  
Eric Fertein ◽  
Patrick Augustin ◽  
Marc Fourmentin ◽  
Dorothée Dewaele ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Continuous Monitoring ◽  
Laser Sensor ◽  
Quantum Cascade ◽  
Suburban Site

Long- and short-term in vitro D-dimer stability measured with INNOVANCE D-Dimer

2010 ◽  
Vol 103 (02) ◽  
pp. 461-465 ◽  
Author(s):  
Martina Böhm-Weigert ◽  
Thomas Wissel ◽  
Heidrun Muth ◽  
Bettina Kemkes-Matthes ◽  
Dirk Peetz
Keyword(s):  
Frozen Storage ◽  
Percentage Change ◽  
Short Term ◽  
Term Stability ◽  
Long Term Stability ◽  
Repeated Freezing ◽  
The Mean ◽  
D Dimer

Summary In vitro D-dimer stability in plasma is widely assumed, but has not yet been documented by systematic studies using samples covering a wide range of D-dimer. We investigated the short- and long-term stability of D-dimer in clinical citrated plasma samples with normal and pathological levels. The short-term stability was analysed by measuring D-dimer fresh, after storage of plasma for 4 hours at room temperature (RT) and after an additional 24 h storage at +2 to +8°C (n=40). Long-term stability samples (n=40) were measured fresh and after storage for 19, 25 and 36 months at ≤-60°C. The effect of repeated freezing was analysed by measuring samples (n=50) fresh and after four consecutive freeze-thaw cycles. D-dimer was measured on the BCS System using the INNOVANCE D-Dimer assay (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). D-dimer values at baseline ranged from 0.23–22.2 mg/l FEU. The mean percentage change after storage for 4 hours at RT and additional 24 hours at +2 to +8°C was +3.8% and +2.7%, respectively. The mean percentage change after frozen storage for 19, 25 and 36 months at ≤-60°C was –11.7%, –4.8% and –9.3%, respectively. The small decrease of D-dimer values after frozen storage was not time-dependent. Repeated freezing did not significantly alter D-dimer values (mean change ≤5%). The data demonstrate stability of D-dimer in plasma prior to freezing for up to 4 hours at RT and for up to 24 hours at +2 to +8°C as well as in plasma stored for up to three years at ≤-60°C.

Nontoxic Silicon Nanocrystals and Nanodiamonds as Substitution for Harmful Quantum Dots

2009 ◽  
Vol 1241 ◽  
Author(s):  
Anna Fucikova ◽  
Jan Valenta ◽  
Ivan Pelant ◽  
Vitezslav Brezina
Keyword(s):  
Quantum Dots ◽  
Chemical Composition ◽  
Silicon Nanocrystals ◽  
Nanocrystalline Silicon ◽  
Semiconductor Quantum Dots ◽  
In Vivo Studies ◽  
Long Term Stability

AbstractThe commercially available semiconductor quantum dots have been proven to be slightly to significantly toxic by recent publications depending on the chemical composition. We are developing new non-toxic fluorescent labels based on (i) nanocrystalline silicon, suitable for in vivo studies due to their biodegrability, and on (ii) nanodiamonds, intended mainly for in vitro use due to their long-term stability and nondegradilibity.

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