Using nanoparticles to deliver drugs to cells has the potential to revolutionize the treatment of many diseases, including HIV, cancer, and diabetes. One of the major challenges facing this field is ...controlling where the drug is trafficked once the nanoparticle is taken up into the cell. In particular, if drugs remain localized in an endosomal or lysosomal compartment, the therapeutic can be rendered completely ineffective. To ensure the design of more effective delivery systems we must first develop a better understanding of how nanoparticles and their cargo are trafficked inside cells. This needs to be combined with an understanding of what characteristics are required for nanoparticles to achieve endosomal escape, along with methods to detect endosomal escape effectively. This review is focused into three sections: first, an introduction to the mechanisms governing internalization and trafficking in cells, second, a discussion of methods to detect endosomal escape, and finally, recent advances in controlling endosomal escape from polymer‐ and lipid‐based nanoparticles, with a focus on engineering materials to promote endosomal escape. WIREs Nanomed Nanobiotechnol 2017, 9:e1452. doi: 10.1002/wnan.1452
This article is categorized under:
Nanotechnology Approaches to Biology > Nanoscale Systems in Biology
Nanoparticles have the potential to drastically improve the delivery of therapeutics, but their use is limited by their ability to escape endosomes after being internalized into cells. As new materials are engineered it is essential we understand how they behave in cells to overcome this substantial barrier.
APOBEC cytidine deaminases are the second-most prominent source of mutagenesis in sequenced tumors. Previous studies have proposed that APOBEC3B (A3B) is the major source of mutagenesis in breast ...cancer (BRCA). We show that APOBEC3A (A3A) is the only APOBEC whose expression correlates with APOBEC-induced mutation load and that A3A expression is responsible for cytidine deamination in multiple BRCA cell lines. Comparative analysis of A3A and A3B expression by qRT-PCR, RSEM-normalized RNA-seq, and unambiguous RNA-seq validated the use of RNA-seq to measure APOBEC expression, which indicates that A3A is the primary correlate with APOBEC-mutation load in primary BRCA tumors. We also demonstrate that A3A has >100-fold more cytidine deamination activity than A3B in the presence of cellular RNA, likely explaining why higher levels of A3B expression contributes less to mutagenesis in BRCA. Our findings identify A3A as a major source of cytidine deaminase activity in breast cancer cells and possibly a prominent contributor to the APOBEC mutation signature.
Molecular design of biosensors based on enzymatic processes taking place in nanofluidic elements is receiving increasing attention by the scientific community. In this work, we describe the ...construction of novel ultrasensitive enzymatic nanopore biosensors employing “reactive signal amplifiers” as key elements coupled to the transduction mechanism. The proposed framework offers innovative design concepts not only to amplify the detected ionic signal and develop ultrasensitive nanopore-based sensors but also to construct nanofluidic diodes displaying specific chemo-reversible rectification properties. The integrated approach is demonstrated by electrostatically assembling poly(allylamine) on the anionic pore walls followed by the assembly of urease. We show that the cationic weak polyelectrolyte acts as a “reactive signal amplifier” in the presence of local pH changes induced by the enzymatic reaction. These bioinduced variations in proton concentration ultimately alter the protonation degree of the polyamine resulting in amplifiable, controlled, and reproducible changes in the surface charge of the pore walls, and consequently on the generated ionic signals. The “iontronic” response of the as-obtained devices is fully reversible, and nanopores are reused and assayed with different urea concentrations, thus ensuring reliable design. The limit of detection (LOD) was 1 nM. To the best of our knowledge, this value is the lowest LOD reported to date for enzymatic urea detection. In this context, we envision that this approach based on the use of “reactive signal amplifiers” into solid-state nanochannels will provide new alternatives for the molecular design of highly sensitive nanopore biosensors as well as (bio)chemically addressable nanofluidic elements.
APOBEC family cytidine deaminases have recently been implicated as powerful mutators of cancer genomes. How APOBECs, which are ssDNA-specific enzymes, gain access to chromosomal DNA is unclear. To ...ascertain the chromosomal ssDNA substrates of the APOBECs, we expressed APOBEC3A and APOBEC3B, the two most probable APOBECs mediating cancer mutagenesis, in a yeast model system. We demonstrate, using mutation reporters and whole genome sequencing, that APOBEC3A- and APOBEC3B-induced mutagenesis primarily results from the deamination of the lagging strand template during DNA replication. Moreover, our results indicate that both genetic deficiencies in replication fork-stabilizing proteins and chemical induction of replication stress greatly augment the mutagenesis of APOBEC3A and APOBEC3B. Taken together, these results strongly indicate that ssDNA formed during DNA lagging strand synthesis is a major substrate for APOBECs and may be the principal substrate in human cancers experiencing replication stress.
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•APOBEC3A and APOBEC3B deaminate ssDNA formed during DNA lagging strand synthesis in yeast•A3A and A3B deaminate lagging strand ssDNA more commonly than transcription bubbles•Replication stress and loss of replisome integrity increase APOBEC mutagenesis•Extensive DNA synthesis may produce substrates for APOBEC editing of cancer genomes
Human cancers commonly contain mutations induced by APOBEC cytidine deaminases. Hoopes et al. find that APOBEC3A and APOBEC3B damage ssDNA formed during DNA replication, especially when DNA synthesis is stressed. Therefore, extensive replication and replication stress, which occur in cancers, may provide an ideal substrate enabling widespread APOBEC mutagenesis.
Single nanochannels show unique transport properties due to nanoconfinement. It has been demonstrated that at submillimolar concentrations of divalent cations, a nanoprecipitation reaction can occur ...in nanochannels. Although several reports have shown, described, and modeled the nanoprecipitation process, no further advantages have been taken from this phenomenon. Here, we show that the nanoprecipitation reaction can be incorporated into enzyme-modified nanochannels to enhance the performance of small-molecule biosensors via in situ amplification reactions. Contrary to the working principle of previous enzymatic nanofluidic biosensors, the nanofluidic biosensor described in this work operates on the basis of concerted functions: pH-shifting enzymatic activity and nanoprecipitation. We show that the simple addition of Ca2+ and Mg2+ ions in the working analyte solution containing urea can lower the detection limit from the nanometer to the subnanometer regime and modulate the dynamic linear range. This approach enables the implementation of more sensitive real-time nanofluidic detection methods without increasing the complexity of the nanofluidic platform or the sensing approach. We envision that the integration of concerted functions in nanofluidic architectures will play a key role in expanding the use of these nanoscale devices for analytical purposes.
The Absolute Limit of Latinx Writing Cortez, José M; García, Romeo
College composition and communication,
06/2020, Letnik:
71, Številka:
4
Journal Article
Recenzirano
This article analyzes contemporary theories of decoloniality at work in Latinx Writing Studies scholarship. We argue that the intellectual articulation of Latinx writing as a signifier of resistance ...to Western epistemologies of writing on the grounds of its mixed identity not only reproduces the very problems associated with purity that have been associated with the "West" but also, and more importantly, reproduces the very conditions of epistemological expropriation that decoloniality aims to unwork. Instead of thinking Latinx writing as a topos of resistance to Western epistemologies of writing we propose to think Latinx writing as the site of a crisis internal to the possibility of knowing in general, as the absolute limit to all epistemologies of writing.
Based on colony spreading, chitosan from shrimp waste in agar media inhibited the growth of
Aspergillus niger by 47.26%; there were not differences (
P
>
0.05) with respect to commercial chitosan ...(Fluka, BioChemika) (56.16%). All chitosan films showed similar glass transition temperatures (
P
>
0.05) with respect to cellophane control; however, chemically, all chitosan films showed an increase in the
T
g values that could be related with the decrease (
P
≤
0.05) in elongation percentage with respect to the control film. According to FT-IR spectroscopic analysis of chitosan films, the fungistatic activity can be related to the hydrogen bonds’ formation between the amino groups of chitosan with the hydroxyl groups from polymer or sorbitol. The plasticizer addition increased (
P
≤
0.05) the elongation of chitosan films. The Young's module,
E, was lower (
P
≤
0.05) for all chitosan films comparing with cellophane. When incorporated into the composite films elaborated by casting, chitosan retained its fungistatic activity. Even though the activity against fungi growth was lower (15.66% for non-plasticized silage chitosan films, pC
S), a reduction (
P
≤
0.05) in the hyphae diameter of
A. niger was observed. Results suggest that it is feasible to elaborate antifungal chitosan films, with good thermal stability and acceptable mechanical properties for food packaging.
Prion diseases are transmissible neurodegenerative disorders that affect mammals, including humans. The central molecular event is the conversion of cellular prion glycoprotein, PrPC, into a plethora ...of assemblies, PrPSc, associated with disease. Distinct phenotypes of disease led to the concept of prion strains, which are associated with distinct PrPSc structures. However, the degree to which intra- and inter-strain PrPSc heterogeneity contributes to disease pathogenesis remains unclear. Addressing this question requires the precise isolation and characterization of all PrPSc subpopulations from the prion-infected brains. Until now, this has been challenging. We used asymmetric-flow field-flow fractionation (AF4) to isolate all PrPSc subpopulations from brains of hamsters infected with three prion strains: Hyper (HY) and 263K, which produce almost identical phenotypes, and Drowsy (DY), a strain with a distinct presentation. In-line dynamic and multi-angle light scattering (DLS/MALS) data provided accurate measurements of particle sizes and estimation of the shape and number of PrPSc particles. We found that each strain had a continuum of PrPSc assemblies, with strong correlation between PrPSc quaternary structure and phenotype. HY and 263K were enriched with large, protease-resistant PrPSc aggregates, whereas DY consisted primarily of smaller, more protease-sensitive aggregates. For all strains, a transition from protease-sensitive to protease-resistant PrPSc took place at a hydrodynamic radius (Rh) of 15 nm and was accompanied by a change in glycosylation and seeding activity. Our results show that the combination of AF4 with in-line MALS/DLS is a powerful tool for analyzing PrPSc subpopulations and demonstrate that while PrPSc quaternary structure is a major contributor to PrPSc structural heterogeneity, a fundamental change, likely in secondary/tertiary structure, prevents PrPSc particles from maintaining proteinase K resistance below an Rh of 15 nm, regardless of strain. This results in two biochemically distinctive subpopulations, the proportion, seeding activity, and stability of which correlate with prion strain phenotype.
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