scholarly journals A home and rescue gene drive efficiently spreads and persists in populations

2020 ◽  
Author(s):  
Nikolay P. Kandul ◽  
Junru Liu ◽  
Jared B. Bennett ◽  
John M. Marshall ◽  
Omar S. Akbari
Keyword(s):  
Creative Design ◽  
Gene Drive ◽  
Transmission Rates ◽  
Long Term Stability ◽  
Target Populations ◽  
Wide Range ◽  
Population Cage ◽  
Significant Obstacle ◽  
Gene Drives

AbstractHoming based gene drives, engineered using CRISPR/Cas9, have been proposed to spread desirable genes into target populations. However, spread of such drives can be hindered by the accumulation of resistance alleles. To overcome this significant obstacle, we engineer an inherently confinable population modification Home-and-Rescue (HomeR) drive in Drosophila melanogaster that, by creative design, limits the accumulation of such alleles. We demonstrate that HomeR can achieve nearly ∼100% transmission enabling it to spread and persist at genotypic fixation in several multi-generational population cage experiments, underscoring its long term stability and drive potential. Finally, we conduct mathematical modeling determining HomeR can outperform contemporary gene drive architectures for population modification over wide ranges of fitness and transmission rates. Given its straightforward design, HomeR could be universally adapted to a wide range of species.

scholarly journals A confinable home and rescue gene drive for population modification

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Nikolay P Kandul ◽  
Junru Liu ◽  
Jared B Bennett ◽  
John M Marshall ◽  
Omar S Akbari
Keyword(s):  
Mathematical Modeling ◽  
Target Gene ◽  
Essential Gene ◽  
Gene Drive ◽  
Wild Populations ◽  
Fitness Costs ◽  
Recessive Lethal ◽  
Transmission Rates ◽  
Population Cage ◽  
Gene Drives

Homing based gene drives, engineered using CRISPR/Cas9, have been proposed to spread desirable genes throughout populations. However, invasion of such drives can be hindered by the accumulation of resistant alleles. To limit this obstacle, we engineer a confinable population modification Home-and-Rescue (HomeR) drive in Drosophila targeting an essential gene. In our experiments, resistant alleles that disrupt the target gene function were recessive lethal, and therefore disadvantaged. We demonstrate that HomeR can achieve an increase in frequency in population cage experiments, but that fitness costs due to the Cas9 insertion limit drive efficacy. Finally, we conduct mathematical modeling comparing HomeR to contemporary gene drive architectures for population modification over wide ranges of fitness costs, transmission rates, and release regimens. HomeR could potentially be adapted to other species, as a means for safe, confinable, modification of wild populations.

scholarly journals NO2 and NH3 Sensing Characteristics of Inkjet Printing Graphene Gas Sensors

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3379 ◽  
Author(s):  
Caterina Travan ◽  
Alexander Bergmann
Keyword(s):  
Gas Sensors ◽  
Inkjet Printing ◽  
High Mobility ◽  
High Sensitivity ◽  
Low Noise ◽  
Manufacturing Method ◽  
Long Term Stability ◽  
Wide Range ◽  
Ideal Technique

Graphene is a good candidate for filling the market requirements for cheap, high sensitivity, robust towards contamination, low noise, and low power consumption gas sensors, thanks to its unique properties, i.e., large surface, high mobility, and long-term stability. Inkjet printing is a cheap additive manufacturing method allowing fast, relatively precise and contactless deposition of a wide range of materials; it can be considered therefore the ideal technique for fast deposition of graphene films on thin substrates. In this paper, the sensitivity of graphene-based chemiresistor gas sensors, fabricated through inkjet printing, is investigated using different concentrations of graphene in the inks. Samples have been produced and characterized in terms of response towards humidity, nitrogen dioxide, and ammonia. The presented results highlight the importance of tuning the layer thickness and achieving good film homogeneity in order to maximize the sensitivity of the sensor.

Immunohistochemical Detection of Canine Adenovirus in Paraffin Sections of Liver

1986 ◽  
Vol 23 (4) ◽  
pp. 478-484 ◽  
Author(s):  
P. M. Rakich ◽  
K. W. Prasse ◽  
P. D. Lukert ◽  
L. M. Cornelius
Keyword(s):  
Immunohistochemical Detection ◽  
Hepatic Inflammation ◽  
Paraffin Sections ◽  
Inflammatory Lesions ◽  
Long Term Stability ◽  
Formalin Fixed Paraffin ◽  
Wide Range ◽  
Formalin Fixed Paraffin Embedded ◽  
Formalin Fixed

An avidin-biotin immunoperoxidase procedure was optimized for detection of canine adenoviral antigens in formalin-fixed, paraffin-embedded liver. Long-term stability of viral antigen was shown by successful demonstration of virus in liver tissue preserved up to six years from dogs with infectious canine hepatitis. This immunohistochemical stain was applied to sections from livers with a wide range of inflammatory lesions. Examination of sections from 53 dogs yielded five livers with small amounts of adenovirus. An additional virus-positive liver was identified from a dog with no hepatic inflammation. Although a cause and effect relationship remains to be determined, these findings suggest a possible connection between canine adenovirus and spontaneous chronic hepatitis.

scholarly journals Targeting conserved sequences circumvents the evolution of resistance in a viral gene drive against human cytomegalovirus

2021 ◽  
Author(s):  
Marius Walter ◽  
Rosalba Perrone ◽  
Eric Verdin
Keyword(s):  
Cell Culture ◽  
Human Cytomegalovirus ◽  
Viral Population ◽  
Viral Gene ◽  
Gene Drive ◽  
Conserved Sequences ◽  
Evolution Of Resistance ◽  
Gene Drives ◽  
Over Time

Gene drives are genetic systems designed to efficiently spread a modification through a population. They have been designed almost exclusively in eukaryotic species, and especially in insects. We recently developed a CRISPR-based gene drive system in herpesviruses that relies on similar mechanisms and could efficiently spread into a population of wildtype viruses. A common consequence of gene drives in insects is the appearance and selection of drive-resistant sequences that are no longer recognized by CRISPR-Cas9. Here, we analyze in cell culture experiments the evolution of resistance in a viral gene drive against human cytomegalovirus. We report that, after an initial invasion of the wildtype population, a drive-resistant population is positively selected over time and outcompetes gene drive viruses. However, we show that targeting evolutionary conserved sequences ensures that drive-resistant viruses acquire long-lasting mutations and are durably attenuated. As a consequence, and even though engineered viruses do not stably persist in the viral population, remaining viruses have a replication defect, leading to a long-term reduction of viral levels. This marks an important step toward developing effective gene drives in herpesviruses, especially for therapeutic applications. Importance The use of defective viruses that interfere with the replication of their infectious parent after co-infecting the same cells – a therapeutic strategy known as viral interference – has recently generated a lot of interest. The CRISPR-based system that we recently reported in herpesviruses represents a novel interfering strategy that causes the conversion of wildtype viruses into new recombinant viruses and drives the native viral population to extinction. In this report, we analyzed how targeted viruses evolved resistance against the technology. Through numerical simulations and cell culture experiments with human cytomegalovirus, we show that, after the initial propagation, a resistant viral population is positively selected and outcompetes engineered viruses over time. We show however that targeting evolutionary conserved sequences ensures that resistant viruses are mutated and attenuated, which leads to a long-term reduction of viral levels. This marks an important step toward the development of novel therapeutic strategies against herpesviruses.

scholarly journals Experimental Devices to Investigate the Long-Term Stability of Phase Change Materials under Application Conditions

2020 ◽  
Vol 10 (22) ◽  
pp. 7968
Author(s):  
Christoph Rathgeber ◽  
Stefan Hiebler ◽  
Rocío Bayón ◽  
Luisa F. Cabeza ◽  
Gabriel Zsembinszki ◽  
...  
Keyword(s):  
Phase Change ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
Term Stability ◽  
Long Term Stability ◽  
Wide Range ◽  
Solidification Processes ◽  
The Stability ◽  
Solid Liquid

An important prerequisite to select a reliable phase change material (PCM) for thermal energy storage applications is to test it under application conditions. In the case of solid–liquid PCM, a large amount of thermal energy can be stored and released in a small temperature range around the solid–liquid phase transition. Therefore, to test the long-term stability of solid–liquid PCM, they are subjected to melting and solidification processes taking into account the conditions of the intended application. In this work, 18 experimental devices to investigate the long-term stability of PCM are presented. The experiments can be divided into thermal cycling stability tests, tests on PCM with stable supercooling, and tests on the stability of phase change slurries (PCS). In addition to these experiments, appropriate methods to investigate a possible degradation of the PCM are introduced. Considering the diversity of the investigated devices and the wide range of experimental parameters, further work toward a standardization of PCM stability testing is recommended.

scholarly journals Curcumin Containing PEGylated Solid Lipid Nanoparticles for Systemic Administration: A Preliminary Study

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 2991 ◽  
Author(s):  
Debora Santonocito ◽  
Maria Grazia Sarpietro ◽  
Claudia Carbone ◽  
Annamaria Panico ◽  
Agata Campisi ◽  
...  
Keyword(s):  
Zeta Potential ◽  
Solid Lipid Nanoparticles ◽  
Antioxidant Activities ◽  
Lipid Nanoparticles ◽  
Systemic Administration ◽  
Term Stability ◽  
Long Term Stability ◽  
Solid Lipid ◽  
Wide Range

Curcumin (CUR) has a wide range of pharmacological properties, including anti-inflammatory and antioxidant activities, and it can be considered a good candidate for the potential treatment of central nervous system (CNS) pathologies, although its use in clinical practice is compromised due to its high lipophilicity. Solid lipid nanoparticles (SLNs) are well-known nanocarriers representing a consolidated approach for the delivery of lipophilic compounds, but their systemic use is limited due their short half-life. The formulation of stealth SLNs (pSLNs) could be a valid strategy to overcome this limit. Curcumin-loaded-pSLNs were prepared by the solvent evaporation method. Formulation was characterized for their mean size, zeta potential, size distribution, and morphology. Drug antioxidant activity was evaluated by Oxygen Radical Absorbance Capacity (ORAC) assay. Finally, the obtained formulations were analyzed in terms of long-term stability. Curcumin-loaded-pSLNs showed good technological parameters with a mean particle size below 200 nm, as confirmed by TEM images, and a zeta potential value around −30 mV, predicting good long-term stability. Differential Scanning Calorimetry (DSC) analysis confirmed that PEG micelles interacted with the SLN surface; this suggests the location of the PEG on the pSLN surface. Therefore, these preliminary studies suggest that the produced formulation could be regarded as a promising carrier for the systemic administration.

scholarly journals Targeting evolutionary conserved sequences circumvents the evolution of resistance in a viral gene drive against human cytomegalovirus

2021 ◽  
Author(s):  
Marius Walter ◽  
Rosalba Perrone ◽  
Eric Verdin
Keyword(s):  
Human Cytomegalovirus ◽  
Viral Gene ◽  
Gene Drive ◽  
Eukaryotic Species ◽  
Resistant Population ◽  
Evolution Of Resistance ◽  
Gene Drives ◽  
Over Time ◽  
Selection Of

Gene drives are genetic systems designed to efficiently spread a modification through a population. Most engineered gene drives rely on CRISPR-Cas9 and were designed in insects or other eukaryotic species. We recently developed a viral gene drive in herpesviruses that efficiently spread into a population of wildtype viruses. A common consequence of gene drives is the appearance and selection of drive-resistant sequences that are no longer recognized by CRISPR-Cas9. Here, we analyze in cell culture experiments the evolution of resistance in a gene drive against human cytomegalovirus. We report that after an initial invasion of the wildtype population, a drive-resistant population is positively selected over time and outcompetes gene drive viruses. However, we show that targeting evolutionary conserved regions ensures that drive-resistant viruses have a replication defect, leading to a long-term reduction of viral levels. This marks an important step toward developing effective gene drives in viruses, especially for therapeutic applications.

scholarly journals Designing gene drives to limit spillover to non-target populations

2019 ◽  
Author(s):  
Gili Greenbaum ◽  
Marcus W. Feldman ◽  
Noah A. Rosenberg ◽  
Jaehee Kim
Keyword(s):  
Target Population ◽  
Unintended Effects ◽  
Gene Drive ◽  
Migration Rates ◽  
Target Populations ◽  
Disease Vector ◽  
Narrow Region ◽  
Natural Settings ◽  
Gene Drives ◽  
High Migration

AbstractThe prospect of utilizing CRISPR-based gene-drive technology for controlling populations, such as invasive and disease-vector species, has generated much excitement. However, the potential for spillovers of gene drive alleles from the target population to non-target populations — events that may be ecologically catastrophic — has raised concerns. Here, using two-population mathematical models, we investigate the possibility of limiting spillovers and impact on non-target populations by designing differential-targeting gene drives, in which the expected equilibrium gene drive allele frequencies are high in the target population but low in the non-target population. We find that achieving differential targeting is possible with certain configurations of gene drive parameters. Most of these configurations ensure differential targeting only under relatively low migration rates between target and non-target populations. Under high migration, differential targeting is possible only in a narrow region of the parameter space. When migration is increased, differential-targeting states can sharply transition to states of global fixation or global loss of the gene drive. Because fixation of the gene drive in the non-target population could severely disrupt ecosystems, we outline possible ways to avoid this outcome. Our results emphasize that, although gene drive technology is promising, understanding the potential consequences for populations other than the targets requires detailed analysis of gene-drive spillovers, and that ways to limit the unintended effects of gene drives to non-target populations should be explored prior to the application of gene drives in natural settings.

scholarly journals Origin of High Efficiency and Long-Term Stability in Ionic Liquid Perovskite Photovoltaic

Research ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Lingfeng Chao ◽  
Tingting Niu ◽  
Hao Gu ◽  
Yingguo Yang ◽  
Qi Wei ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
High Efficiency ◽  
Perovskite Solar Cells ◽  
Environment Friendly ◽  
Long Term Stability ◽  
Wide Range ◽  
One Step ◽  
Amine Groups ◽  
Perovskite Photovoltaic

Environment-friendly protic amine carboxylic acid ionic liquids (ILs) as solvents is a significant breakthrough with respect to traditional highly coordinating and toxic solvents in achieving efficient and stable perovskite solar cells (PSCs) with a simple one-step air processing and without an antisolvent treatment approach. However, it remains mysterious for the improved efficiency and stability of PSCs without any passivation strategy. Here, we unambiguously demonstrate that the three functions of solvents, additive, and passivation are present for protic amine carboxylic acid ILs. We found that the ILs have the capability to dissolve a series of perovskite precursors, induce oriented crystallization, and chemically passivate the grain boundaries. This is attributed to the unique molecular structure of ILs with carbonyl and amine groups, allowing for strong interaction with perovskite precursors by forming C=O…Pb chelate bonds and N-H…I hydrogen bonds in both solution and film. This finding is generic in nature with extension to a wide range of IL-based perovskite optoelectronics.

scholarly journals Characterization of high-precision resistive voltage divider and buffer amplifier for ac voltage metrology

2019 ◽  
Vol 10 ◽  
pp. 8
Author(s):  
Bjørnar Karlsen ◽  
Kåre Lind ◽  
Helge Malmbekk ◽  
Per Ohlckers
Keyword(s):  
High Precision ◽  
Electrical Power ◽  
Voltage Divider ◽  
Long Term Stability ◽  
Wide Range ◽  
Precision Voltage ◽  
Best Fit ◽  
Better Than

A high-precision voltage buffer and a 10:1 resistive voltage divider have been constructed for use in ac voltage and electrical power metrology. Long-term stability of the buffer's dc response has been demonstrated by two dc sweeps performed 20 days apart, with best-fit linearized gain varying less than 1 μV/V. The absolute ac gain has been measured using a high-precision digital multimeter for 10 Hz and 1 kHz with results consistent with dc within 5 μV/V. This value agrees with the characterization of ac–dc difference using thermal converters from different producers with a variety of resistance for various voltages from 1 V to 5 V. The ac–dc difference was further characterized better than 40 μV/V for the same voltages up to 100 kHz and better than 100 μV/V for 3 V at 1 MHz. Absolute ac gain and ac–dc difference has also been measured for the voltage divider and buffer combination from 10 V to 50 V, with similar agreement up to 1 kHz. The ac–dc difference from 10 Hz to 100 kHz of this combination shows an agreement well within 30 μV/V in this entire voltage span with a total response not exceeding 125 μV/V. This make the voltage divider and buffer combination suitable for sampling electrical powers for a wide range of voltages.

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