Sc Formation Research Articles

A Comparative Study on the Influence of N‐Doped Primary and Secondary Hydrochars on the Electrochemical Performance of Biobased Carbon Electrodes for Energy Storage Application

AbstractThe hydrothermal carbonization (HTC) technique and subsequent pyrolysis were applied. Herein, two different types of biobased feedstocks, sucrose (Suc) and Miscanthus (Mis), were chosen. Urea served as N precursor for the in situ doping. HTC of Suc and Mis with urea leads to N‐doped hydrochars (N‐HCs). Suc and Mis decompose in different, complex degradation pathways, which leads to the emergence of N‐HCs consisting of distinct ratios of N‐containing primary chars (N‐PCs) and secondary chars (N‐SCs). After pyrolysis, maximum N contents of 5.6 wt % and 4.8 wt % of the N‐doped pyrolyzed hydrochar (N‐PHC) electrodes from Suc and Mis, respectively were reached. The role of PC and SC formation on the impact of N‐doping in the context of physicochemical properties of the N‐PHCs was compared with each other. In this study, they were tested with respect to the influence of N‐PCs and N‐SCs on their electrochemical performance in energy storage application. It turned out that the electrical conductivity (EC) and specific capacitances increased. Highest EC value of 129.1 S ⋅ cm−1 was obtained with N‐PHC based on Suc. Simultaneously, enhanced average specific capacitances of 47.0 F ⋅ g−1 at 5 mV ⋅ s−1 and 3.5 F ⋅ g−1 at 100 mV ⋅ s−1 are ascertained with N‐PHCs from Suc and Mis, respectively.

Tricarboxylic Acid Cycle Intermediates and Individual Ageing.

Anti-ageing biology and medicine programmes are a focus of genetics, molecular biology, immunology, endocrinology, nutrition, and therapy. This paper discusses metabolic therapies aimed at prolonging longevity and/or health. Individual components of these effects are postulated to be related to the energy supply by tricarboxylic acid (TCA) cycle intermediates and free radical production processes. This article presents several theories of ageing and clinical descriptions of the top markers of ageing, which define ageing in different categories; additionally, their interactions with age-related changes and diseases related to α-ketoglutarate (AKG) and succinate SC formation and metabolism in pathological states are explained. This review describes convincingly the differences in the mitochondrial characteristics of energy metabolism in animals, with different levels (high and low) of physiological reactivity of functional systems related to the state of different regulatory systems providing oxygen-dependent processes. Much attention is given to the crucial role of AKG and SC in the energy metabolism in cells related to amino acid synthesis, epigenetic regulation, cell stemness, and differentiation, as well as metabolism associated with the development of pathological conditions and, in particular, cancer cells. Another goal was to address the issue of ageing in terms of individual characteristics related to physiological reactivity. This review also demonstrated the role of the Krebs cycle as a key component of cellular energy and ageing, which is closely associated with the development of various age-related pathologies, such as cancer, type 2 diabetes, and cardiovascular or neurodegenerative diseases where the mTOR pathway plays a key role. This article provides postulates of postischaemic phenomena in an ageing organism and demonstrates the dependence of accelerated ageing and age-related pathology on the levels of AKG and SC in studies on different species (roundworm Caenorhabditis elegans, Drosophila, mice, and humans used as models). The findings suggest that this approach may also be useful to show that Krebs cycle metabolites may be involved in age-related abnormalities of the mitochondrial metabolism and may thus induce epigenetic reprogramming that contributes to the senile phenotype and degenerative diseases. The metabolism of these compounds is particularly important when considering ageing mechanisms connected with different levels of initial physiological reactivity and able to initiate individual programmed ageing, depending on the intensity of oxygen consumption, metabolic peculiarities, and behavioural reactions.

Enhanced polylactide stereocomplexes by aluminum oxide particles for reliable thermal conductivity at elevated temperature

Stereocomplex-type polylactide (sc-PLA) with high heat resistance provides great promise for renewable and environmentally friendly PLA as alternative engineering plastics. However, due to the weak melt memory of stereocomplex (sc) crystallites, that is, its poor ability to reform sc crystallites after melting, sc-PLA cannot be processed by conventional melting methods, and its lack of functional properties limits its practical applications. In this work, the interchain interactions between PLLA and PDLA chains are found to be well kept in equimolar PLLA/PDLA blends via the incorporation of Al2O3 particles for the first time, which effectively overcomes these drawbacks. The composites show good melt memory for sc crystallization, and exclusive sc crystallites form during cooling after eliminating the thermal history when the content of Al2O3 is higher than 3 vol%. Moreover, exclusive sc crystallites still can be formed in the composites with high Al2O3 contents of 40 vol%. The interchain interactions between PLLA and PDLA chains are well kept in the melt of the composites, endowing the composites with the capability to overcome the kinetic barrier and form sc crystallites rapidly during cooling. Benefiting from the high thermal conductivity of Al2O3, and enhanced sc crystallites with high heat resistance, the sc-PLA composite with 40 vol% Al2O3 shows a thermal conductivity of 1 Wm−1K−1, and the thermal conductivity can be maintained at elevated temperatures (25–180 °C). The synchronously enhanced sc formation and reliable thermal conductivity at elevated temperatures enabled by Al2O3 provide a new design approach for PLA as an alternative engineering plastic.

Prion receptors, prion internalization, intra- and inter-cellular transport.

Cellular prion protein (PrP C ) is a membrane bound protein that undergoes several post translational modifications. It can exert pleiotropic functions either in physiological and pathological conditions. The disease-causing isoform of the prion protein, called PrP Sc , acts as corruptive seed able to establish a process of misfolding and aggregation of further PrP Sc molecules. Therefore, PrP C acts as substrate for PrP Sc formation and as receptor to convey neurotoxic functions typical of other prion-like proteins involved in several neurodegenerative conditions. PrP C is transported from the outer leaflet of the cellular membrane to the intracellular compartments through several endocytic pathways, including clathrin-dependent and independent mechanisms and interactions with different adaptor proteins. During prion infection, the pathological counterpart PrP Sc , can be uptaken by the cells with mechanisms partially overlapping the ones of the physiological form, PrP C . The intercellular routing of both prion protein isoforms involves the release through vesicles and tunneling nanotubes. From the extracellular milieu, PrP C and PrP Sc can be uptaken by adjacent cells, thus exerting physiological and pathological functions.

Synergistic effect of star‐shaped architecture and poly(ethylene glycol) moieties on poly(lactic acid) stereocomplex crystallization behaviors

AbstractStereocomplex (sc) crystal formation represents an important strategy to improve the physical properties of poly(lactic acid) (PLA), including enhanced thermal resistance, anti‐hydrolysis and mechanical performance. Therefore, understanding and controlling the sc crystallization behaviors is an important and widely studied research topic. Herein, we investigate the cooperative effect of star‐shaped PLA chain topology and poly(ethylene glycol) incorporation on sc formation. We synthesize a series of poly(lactides), including poly(l‐lactic acid) (PLLA), poly(d‐lactic acid), star‐shaped PLLA and poly(d‐lactic acid)‐poly(ethylene glycol)‐poly(d‐lactic acid) (DED) triblock copolymer, via ring‐opening polymerization of lactide, followed by solution blending to form PLA stereocomplexes (scPLAs). The chemical structure of the prepared scPLAs is characterized by Fourier transform infrared and nuclear magnetic resonance, whereas the crystallization behavior and spherulite morphology are investigated by wide‐angle X‐ray diffraction, DSC and polarized optical microscopy. Linear PLLA/star‐shaped poly(d‐lactic acid) presents rapid crystallization behaviors and high crystallinity due to the excellent nucleation ability of star‐shaped chain topology. For isothermal crystallization, star‐shaped PLLA/DED exhibits the fastest crystallization kinetics, the highest crystallinity and the lowest crystallization half‐time of all samples. It is found that addition of poly(ethylene glycol) segments can increase chain mobility and backbone flexibility, further facilitating the crystallization of scPLA containing star‐shaped chain architecture. These results demonstrate an effective approach to cooperatively promote scPLA formation, with potential use for practical applications. © 2022 Society of Industrial Chemistry.

Synthesis and mechanochemical properties of biobased ABCBA‐type pentablock copolymers comprising poly‐d‐lactide (A), poly‐l‐lactide (B) and poly(1,2‐propylene succinate) (C)

AbstractThe ABCBA pentablock copolymers (p‐d‐l‐PPS) comprising poly(d‐lactide) (PDLA: A), poly(l‐lactide) (PLLA: B) and poly(propylene succinate) (PPS: C) were successfully synthesized by two‐step ring‐opening polymerization (ROP) of d‐ and l‐lactide using a dihydroxy‐terminated PPS as a macro‐initiator. The pentablock copolymers revealed the high stereocomplex (sc) crystallinity, thermal stability and elastomeric property in their solution‐cast films. It was found that the Tg was found to be proportional to the PPS content, whereas the Tm was proportional to their average block length. The thermal resistivity of the copolymer films was found to be as high as 202°C owing to their sc formation. The copolymers also showed improved stereocomplexibility compared to the enantiomeric mixtures of triblock copolymers (PLLA‐PPS‐PLLA and PDLA‐PPS‐PDLA) having similar PLLA and PDLA chain lengths. These pentablock copolymers can afford thermoplastic elastomers or flexible plastic materials having a 100% bio‐based content, showing high heat‐resistive property.

Substantially Enhanced Stereocomplex Crystallization of Poly(L-lactide)/Poly(D-lactide) Blends by the Formation of Multi-Arm Stereo-Block Copolymers

Stereocomplex-type polylactide (SC-PLA) created by alternate packing of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains in a crystalline state has emerged as a growingly popular engineering bioplastic that possesses excellent hydrolytic stability and thermomechanical properties. However, it is extremely difficult to acquire high-performance SC-PLA products via melt-processing of high-molecular-weight PLLA/PDLA blends because both SC crystallites and homocrystallites (HCs) are competitively formed in the melt-crystallization. Herein, a facile yet powerful way was employed to boost SC formation by introducing trace amounts of some epoxy-functionalized small-molecule modifiers into the enantiomeric blends during reactive melt-blending. The results show that the SC formation is considerably enhanced with the in situ generation of multi-arm stereo-block PLA copolymers, based on the reaction between epoxy groups of the modifiers and hydroxyl end groups of PLAs. More impressively, it is intriguing to find that the introduction of only 0.5 wt% modifiers can induce exclusive SC formation in the blends upon isothermal and non-isothermal melt-crystallizations. The outstanding SC crystallizability might be attributed to the suppressing effect of such unique copolymers on the separation of the alternately arranged PLLA/PDLA chain segments in molten state as a compatibilizer. Furthermore, the generation of these copolymers does not result in a significant increase in melt viscosity of the blends. These findings suggest new opportunities for the high-throughput processing of SC-PLA materials into useful products.

Modulation of environmental conditions on the significant difference in the super cyclone formation rate during the pre- and post-monsoon seasons over the Bay of Bengal

Unlike other tropical ocean basins, the Bay of Bengal (BoB) has two tropical cyclone (TC) seasons: a pre-monsoon season (Pre-MS) and a post-monsoon season (Post-MS). More interestingly, during the period from 1981 to 2016, the global maximum and minimum formation rates of super cyclones (SCs, categories 4 and 5) occurred in the Pre-MS and Post-MS, respectively, in the BoB. Methods including Butterworth filter, box difference index analysis and quantitative diagnosis were utilized herein to detect what and how background environmental factors cause significantly different SC formation rates between the Pre- and Post-MS. Diagnosis results revealed that the vertical temperature difference (VTD) mainly determines whether TCs can develop into SCs during the Post-MS, similar to Pre-MS. It’s in agreement with previous studies demonstrating that the VTD is controlled by the low-level temperature during the Post-MS but is determined by the upper-level temperature during the Pre-MS. The results also revealed that the background sea surface temperature is much higher in the Pre-MS than in the Post-MS and forces higher 1000 hPa-level air temperature. Additionally, there is higher saturated specific humidity (qs) due to the higher temperature in the Pre-MS. The differences in the bottom-level temperature and qs cooperate to predominantly contribute to the significant difference in Vpot2, which could denote the maximum potential intensity of TC, eventually leading to the remarkably different SC formation rates between the Pre- and Post-MS in the BoB.

Recent Progress in Enhancing Poly(Lactic Acid) Stereocomplex Formation for Material Property Improvement.

The production and utilization of polymers have been widely implemented into diverse applications that benefit modern human society, but one of the most valuable properties of polymers, durability, has posed a long-standing environmental challenge from its inception since plastic waste can lead to significant contamination and remains in landfills and oceans for at least hundreds of years. Poly(lactic acid) (PLA) derived from renewable resources provides a sustainable alternative to traditional polymers due to its advantages of comparable mechanical properties with common plastics and biodegradability. However, the poor thermal and hydrolytic stability of PLA-based materials limit their potential for durable applications. Stereocomplex crystallization of enantiomeric poly (l-lactide) (PLLA) and poly (d-lactide) (PDLA) provides a robust approach to significantly enhance material properties such as stability and biocompatibility through strong intermolecular interactions between L-lactyl and D-lactyl units, which has been the key strategy to further PLA applications. This review focuses on discussing recent progress in the development of processing strategies for enhancing the formation of stereocomplexes within PLA materials, including thermal processing, additive manufacturing, and solution casting. The mechanism for enhancing SC formation and resulting material property improvement enabled by each method are also discussed. Finally, we also provide the perspectives on current challenges and opportunities for improving the understanding of processing-structure-property relationship in PLA materials that could be beneficial to their wide practical applications for a sustainable society.

Stereocomplex-type polylactide with remarkably enhanced melt-processability and electrical performance via incorporating multifunctional carbon black

As a popular “green” engineering plastic, stereocomplex-type polylactide (SC-PLA) exhibits great application potential in various fields owing to its outstanding physicochemical performance and durability. However, the applications of SC-PLA still face formidable challenges mostly associated with its inferior melt-processability (i.e., the weak melt memory effect to motivate exclusive SC crystallization and extremely low melt viscosity) and the lack of necessary functional features (e.g., electrical conductivity) in some cases. Herein, we devise a facile and robust strategy to overcome these obstacles by incorporating carbon black (CB) into equimolar poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) blend. It is interesting to find that the CB particles can adsorb many PLLA/PDLA chain segments on their surface and such strongly adsorbed PLA segments could interact with PLA chains outside the surface to form physical junctions capable of stabilizing the PLLA/PDLA chain assemblies in the melt, finally inducing the exclusive SC formation during subsequent crystallization. Meanwhile, the CB particles can substantially enhance the melt viscosity of the blend (from 3.9 Pa s to 844.1 Pa s when measuring at 250 °C and 50 Hz). Because of the greatly improved melt-processability, the PLLA/PDLA/CB composites have been successfully processed into highly crystalline products with exclusive SC crystallites and excellent thermomechanical performance by injection molding. Additionally, the CB particles can endow the composite products with fascinating electrical conductivity (19.0 S/m) and electromagnetic interference shielding effectiveness (26.6 dB). This work could open up a promising avenue towards high-performance and multifunctional PLA engineering Bioplastic.

Seed coat formation: its evolution and regulation

AbstractIn higher plants, the seed precursor (ovule primordia) is composed of three parts: funiculus, nucellus and chalaza, generating the latter one (II) or two (OI and II) protective maternal integuments (seed coat, SC). The appearance of a viable seed requires the coordinate growth and development of the preceding three compartments. Integuments are essentials for seed life as they nourish, protect and facilitate seed dispersion. Endosperm and integument growth and development are tightly coupled. Gymnosperm and angiosperm ovules are commonly unitegmic and bitegmic, respectively. Unusually, ategmy and threetegmy (OI, II and aril) also exist. The expression of theINO,ATSandETTgenes, involved in integument development, seems to have demonstrated that the fusion of OI and II leads to the appearance of unitegmy in higher plants. Likewise,INOexpression also manifests the conservation of OI during evolution. The molecular control of SC development is constituted by a signalling network with still a multitude of gaps. The fertilization-independent development of the ovule is repressed by the FERTILIZATION INDEPENDENT SEED (FIS), a Polycomb-Repressive-Complex-2 (PRC2). Both endosperm and SC development are tightly linked to PRC2 function. As in many other developmental processes, auxin plays an essential role during ovule and SC development. Auxin transport from the endosperm to the integuments is regulated by AGL62 (AGAMOUS-LIKE 62), the encoding gene of which is specifically expressed in the endosperm to suppress its cellularization. In the absence of AGL62 (i.e.agl62mutants), auxin remains trapped in the endosperm and the SC fails to develop (i.e. seed abortion). This update shows that auxin biosynthesis, transport and signalling play a predominant role and seem to be absolutely required in the pathway(s) that lead to SC formation, most likely not as a unique hormonal component.

NVP-BKM120 in combination with letrozole inhibit human breast cancer stem cells via PI3K/mTOR pathway

Objective: Breast cancer stem cells (BCSC) have been suggested to have clinical implications for cancer therapeutics because of their proposed role in chemo-resistance. The aim of this study was to investigate effects of BCSC on endocrine therapy response by regulating PI3K/Akt/mTOR signaling pathway. Methods: We evaluated the susceptibility of BCSC to NVP-BKM120 (BKM120), a new generation of PI3K-specific inhibitor, when used individually or in combination with letrozole in vivo. For this, a stem-like cell population (SC) was enriched from breast cancer cell line MCF-7 after mammosphere cultures. We have constructed high aromatase expression BCSC (BCSC-CYP19) and non-stem cells (MCF-7-CYP19) subcloning. We demonstrate BKM120 inhibits growth, generation of drug-resistant derivatives and SC formation in BCSC-CYP19 and MCF-7-CYP19. Result: BKM120 could inhibit BCSC-CYP19 growth by dose-dependence, reduce migration and colony formation of BCSC-CYP19, and also significantly reduced expression of PI3K, Akt1 and S6. Combined BKM120 and letrozolecaninhibit BCSC-CYP19 growth and proliferation, make BCSC-CYP19 stayed in G0-G1 phase increasing significantly to induce early apoptosis, and down-regulate expression of PI3K, Akt1 and S6. Conclusion: PI3K/Akt/mTOR pathway effects on letrozole resistance by regulating BCBSs characteristics. Combination of PI3K inhibitor BKM120 and letrozole could reduce letrozole resistance.

Understanding Fe3O4 Nanocube Assembly with Reconstruction of a Consistent Superlattice Phase Diagram.

Nanocube (NC) assemblies display complex superlattice behaviors, which require a systematic understanding of their nucleation and growth as well transformation toward construction of a consistent superlattice phase diagram. This work made use of Fe3O4 NCs with controlled environments, and assembled NCs into three-dimensional (3D) superlattices of simple cubic (sc), body-centered cubic (bcc), and face-centered cubic (fcc), acute and obtuse rhombohedral (rh) polymorphs, and 2D superlattices of square and hexagon. Controlled experiments and computations of in situ and static small-angle X-ray scattering (SAXS) as well as electron microscopic imaging revealed that the fcc and bcc polymorphs preferred a primary nucleation at the early stage of NC assembly, which started from the high packing planes of fcc(111) and bcc(110), respectively, in both 3D and 2D cases. Upon continuous growth of superlattice grain (or domain), a confinement stress appeared and distorted fcc and bcc into acute and obtuse rh polymorphs, respectively. The variable magnitudes of competitive interactions between configurational and directional entropy determine the primary superlattice polymorph of either fcc or bcc, while emergent enhancement of confinement effect on enlarged grains attributes to late developed superlattice transformations. Differently, the formation of a sc polymorph requires a strong driving force that either emerges simultaneously or is applied externally so that one easy case of the sc formation can be achieved in 2D thin films. Unlike the traditional Bath deformation pathway that involves an intermediate body-centered tetragonal lattice, the observed superlattice transformations in NC assembly underwent a simple rhombohedral distortion, which was driven by a growth-induced in-plane compressive stress. Establishment of a consistent phase diagram of NC-based superlattices and reconstruction of their assembly pathways provide critical insight and a solid base for controlled design and scalable fabrication of nanocube-based functional materials with desired superlattices and collective properties for real-world applications.

Effects of Solvents on Stereocomplex Crystallization of High‐Molecular‐Weight Polylactic Acid Racemic Blends in the Presence of Carbon Nanotubes

AbstractStereocomplex (SC) crystallization of solution‐casted high‐molecular‐weight polylactic acid/carbon nanotube (CNT) composites is investigated under the effects of solvents, including dichloromethane (CH2Cl2), chloroform (CHCl3),N,N‐dimethylformamide (DMF), and 1,4‐dioxane (DIOX). It is found that addition of 0.1 wt% CNTs can promote the SC formation in the equimolar poly(l‐lactic acid) (PLLA)/poly(d‐lactic acid) (PDLA) blends. More interestingly, the final content of SC crystallites is mediated by solvent species to a large extent. Results of wide‐angle X‐ray diffraction and differential scanning calorimetry reveal that the capability of solvents for enhancing the SC content in PLLA/PDLA/CNT composites follows the sequence: DMF > DIOX > CHCl3> CH2Cl2. Especially, exclusive SC crystallites are formed in the DMF. Such a disparity is explained in terms of solubility parameter and vapor pressure of the solvents. The above results also provide the possible solution to regulate the crystalline composition of the PLLA/PDLA/CNT blends, by which the expected performance may be obtained.

Estimation of critical supersaturation solubility ratio for predicting diameters of dry particles prepared by air-jet atomization of solutions

Air-jet atomization of solution into droplets followed by controlled drying is increasingly being used for producing nanoparticles for drug delivery applications. Nanoparticle size is an important parameter that influences the stability, bioavailability and efficacy of the drug. In air-jet atomization technique, dry particle diameters are generally predicted by using solute diffusion models involving the key concept of critical supersaturation solubility ratio (Sc) that dictates the point of crust formation within the droplet. As no reliable method exists to determine this quantity, the present study proposes an aerosol based method to determine Sc for a given solute-solvent system and process conditions. The feasibility has been demonstrated by conducting experiments for stearic acid in ethanol and chloroform as well as for anti-tubercular drug isoniazid in ethanol. Sc values were estimated by combining the experimentally observed particle and droplet diameters with simulations from a solute diffusion model. Important findings of the study were: (i) the measured droplet diameters systematically decreased with increasing precursor concentration (ii) estimated Sc values were 9.3±0.7, 13.3±2.4 and 18±0.8 for stearic acid in chloroform, stearic acid and isoniazid in ethanol respectively (iii) experimental results pointed at the correct interfacial tension pre-factor to be used in theoretical estimates of Sc and (iv) results showed a consistent evidence for the existence of induction time delay between the attainment of theoretical Sc and crust formation. The proposed approach has been validated by testing its predictive power for a challenge concentration against experimental data. The study not only advances spray-drying technique by establishing an aerosol based approach to determine Sc, but also throws considerable light on the interfacial processes responsible for solid-phase formation in a rapidly supersaturating system. Until satisfactory theoretical formulae for predicting CSS are developed, the present approach appears to offer the best option for engineering nanoparticle size through solute diffusion models.

Preferential formation of stereocomplex in high-molecular-weight polylactic acid racemic blend induced by carbon nanotubes

Abstract Stereocomplex (sc) crystallization is appealing to endow the poly( l -lactic acid)/poly( d -lactic acid) (PLLA/PDLA) blends with superior heat resistance. However, sc formation is dampened in the high-molecular-weight (HMW) racemic blends. Here, we disclosed a simple but effective approach to facilitate sc formation by introducing carbon nanotubes (CNTs) during the solution casting. As revealed by wide-angle X-ray diffraction and differential scanning calorimetry, the HMW equimolar PLLA/PDLA blends were overwhelmingly crystallized into sc modification in presence of a small amount of CNT, and the relative content of homocrystallites was notably decreased. Especially, exclusive formation of sc crystallites was found with only incorporation of 0.2 wt% CNTs. Such an intriguing phenomenon was probably attributed to the fact that CNTs acted as the anchor to promote intermolecular nexus and triggered the headmost crystallization between PLLA and PDLA.

The combination of NVP-BKM120 with trastuzumab or RAD001 synergistically inhibits the growth of breast cancer stem cells in vivo.

Deregulation of the phosphatidylinositol-3-kinase (PI3K)/Akt signalling pathway is common in breast cancer and is frequently associated with resistance to both traditional chemotherapy and targeted drugs. There is a growing body of evidence indicating that a small subpopulation of self-renewing cells, the so called cancer stem cells (CSC), are responsible for the growth of drug resistant secondary tumors. As many CSCs have upregulated the PI3K/Akt signalling pathway, preclinical and clinical studies are addressing the inhibition of this axis to target drug resistance. We evaluated the susceptibility of breast CSCs to NVP-BKM120 (BKM120), a new generation of PI3K-specific inhibitor, when used individually or in combination with trastuzumab or RAD001 both invitro and invivo. For this, a stem-like cell population (SC) was enriched from breast cancer cell lines after mammosphere cultures. We demonstrated that BKM120 inhibits growth, generation of drug-resistant derivatives and SC formation in a panel of four breast cancer cell lines: MCF-7, MDA-MB-231, SK-BR-3 and CAL51. Importantly, BKM120 inhibits the PI3K/Akt signalling pathway in SCs from these cell lines. When BKM120 was used in combination with trastuzumab, a targeted therapy to treat HER2-positive breast cancer, we found synergistic cell growth inhibition, generation of drug resistant cells as well as SC formation from SK-BR-3 cells. Importantly, SK-BR-3 xenograft-derived tumors showed marginal growth when the drug combination was used. We also found a similar synergistic anticancer effect of BKM120 in combination with RAD001, an mTOR inhibitor, when treating triple-negative breast cancer cells invitro and in both MDA-MB-231 and CAL51- mouse xenografts. Moreover, mouse data indicate that these drug combinations are well tolerated and provide the proof-of-concept and rationale to initiate clinical trials in both HER2-positive and triple-negative breast cancer.

Incongruity between Prion Conversion and Incubation Period following Coinfection.

When multiple prion strains are inoculated into the same host, they can interfere with each other. Strains with long incubation periods can suppress conversion of strains with short incubation periods; however, nothing is known about the conversion of the long-incubation-period strain during strain interference. To investigate this, we inoculated hamsters in the sciatic nerve with long-incubation-period strain 139H prior to superinfection with the short-incubation-period hyper (HY) strain of transmissible mink encephalopathy (TME). First, we found that 139H is transported along the same neuroanatomical tracks as HY TME, adding to the growing body of evidence indicating that PrP(Sc) favors retrograde transneuronal transport. In contrast to a previous report, we found that 139H interferes with HY TME infection, which is likely due to both strains targeting the same population of neurons following sciatic nerve inoculation. Under conditions where 139H blocked HY TME from causing disease, the strain-specific properties of PrP(Sc) corresponded with the strain that caused disease, consistent with our previous findings. In the groups of animals where incubation periods were not altered, we found that the animals contained a mixture of 139H and HY TME PrP(Sc) This finding expands the definition of strain interference to include conditions where PrP(Sc) formation is altered yet disease outcome is unaltered. Overall, these results contradict the premise that prion strains are static entities and instead suggest that strain mixtures are dynamic regardless of incubation period or clinical outcome of disease. Prions can exist as a mixture of strains in naturally infected animals, where they are able to interfere with the conversion of each other and to extend incubation periods. Little is known, however, about the dynamics of strain conversion under conditions where incubation periods are not affected. We found that inoculation of the same animal with two strains can result in the alteration of conversion of both strains under conditions where the resulting disease was consistent with infection with only a single strain. These data challenge the idea that prion strains are static and suggests that strain mixtures are more dynamic than previously appreciated. This observation has significant implications for prion adaptation.

Cytotoxicity of Prion Protein-Derived Cell Penetrating Peptides is Independent of Amyloid Formation

Prion diseases are associated with the conversion of the benign cellular form of the prion protein (PrP(C)) into an abnormally folded and aggregated scrapie isoform (PrP(Sc)), which is also responsible for prion infectivity. We previously showed that peptides derived from the unprocessed N-termini of mouse and bovine prion proteins, mPrP(1-28) and bPrP(1-30), function as cell-penetrating peptides (CPPs) that can efficiently deliver a whole host of cargos. mPrP(1-28) and bPrP(1-30) also exhibited membrane-perturbation effects in model membrane systems. Taken together, the behavior of mPrP(1-28) and bPrP(1-30) provides a potential mechanism for the infectivity and toxicity associated with prion diseases. However, in subsequent studies treatment with mPrP(1-28) or bPrP(1-30) significantly reduced PrPSc levels in prion-infected cells and substantially prolonged the time before infection was manifested after infecting healthy cells with scrapie. To explain these seemingly contradictory results, we correlated the aggregation and toxicity of mPrP(1-28) and bPrP(1-30) with their cellular uptake and intracellular localization. Although the two peptides have a similar primary sequence, mPrP(1-28) was highly prone to aggregation and formed amyloid fibers, whereas bPrP(1-30) aggregated much less and was non-amyloidogenic. Surprisingly, the non-amyloidogenic bPrP(1-30) induced much higher cytotoxicity than the amyloidogenic mPrP(1-28), suggesting that amyloid formation and toxicity are independent. The toxicity of these peptides was due to membrane perturbation. Interestingly, aggregation and toxicity of the peptides were inhibited by low pH. Following internalization by lipid-raft dependent macropinocytosis, a receptor-independent form of endocytosis, the peptides localized to lysosomes, where aggregation and toxicity were inhibited. Our results shed light on the antiprion mechanism of the peptides and provide a potential site for PrP(Sc) formation.

Sialic Acid on the Glycosylphosphatidylinositol Anchor Regulates PrP-mediated Cell Signaling and Prion Formation

The prion diseases occur following the conversion of the cellular prion protein (PrP(C)) into disease-related isoforms (PrP(Sc)). In this study, the role of the glycosylphosphatidylinositol (GPI) anchor attached to PrP(C) in prion formation was examined using a cell painting technique. PrP(Sc) formation in two prion-infected neuronal cell lines (ScGT1 and ScN2a cells) and in scrapie-infected primary cortical neurons was increased following the introduction of PrP(C). In contrast, PrP(C) containing a GPI anchor from which the sialic acid had been removed (desialylated PrP(C)) was not converted to PrP(Sc). Furthermore, the presence of desialylated PrP(C) inhibited the production of PrP(Sc) within prion-infected cortical neurons and ScGT1 and ScN2a cells. The membrane rafts surrounding desialylated PrP(C) contained greater amounts of sialylated gangliosides and cholesterol than membrane rafts surrounding PrP(C). Desialylated PrP(C) was less sensitive to cholesterol depletion than PrP(C) and was not released from cells by treatment with glimepiride. The presence of desialylated PrP(C) in neurons caused the dissociation of cytoplasmic phospholipase A2 from PrP-containing membrane rafts and reduced the activation of cytoplasmic phospholipase A2. These findings show that the sialic acid moiety of the GPI attached to PrP(C) modifies local membrane microenvironments that are important in PrP-mediated cell signaling and PrP(Sc) formation. These results suggest that pharmacological modification of GPI glycosylation might constitute a novel therapeutic approach to prion diseases.