Understanding the influence of cation and anion migration on perovskite light-emitting diodes via transient response.

Despite the rapid progress demonstrated in the efficiency of Perovskite light-emitting diodes (PeLEDs) in the past few years, ion migration has challenged the practical applications of these devices with undesirable hysteresis and degradation effect. Mobile ions in PeLEDs induced many unique and fast transient phenomena occurring on the time scale of microseconds to seconds and it is still far from clear how the underlying physical mechanism of ion motion-induced variation relates to the device performance. Therefore, in this work, we employ an ionic Drift-Diffusion Model (DDM) to evaluate measuring transient current response in a time scale of sub-seconds. The results show that spatial redistribution of ions within the perovskite results in dynamic electric field variation, which in turn, affects charge carrier injection and distribution. Moreover, the time delay between anion and cation migration leads to an unequal rate of charge carrier injection, hence the multi-stage behavior of the current-time response. It is also realized that the potential barrier of charge injection due to cation and anion accumulation at perovskite interfaces with electron and hole transporting layers reduces. Therefore, the facilitation of charge injection favors radiative recombination, and improved IQEs are expected at higher ion densities. It is found that the current-time response of the device gives beneficial information on cation and anion migration time scales. Choosing an appropriate scan rate in accordance with cation-related slow migration time is the first step to achieving reliable measurement procedures and hysteresis-free PeLED.

The effect of perovskite interface contacts on hysteresis behavior in perovskite solar cells.

The ionic-electronic drift-diffusion model is employed to simulate the hysteresis behavior in perovskite solar cells (PSCs) under low-to-moderate conditions; the migrating ions stop at the HTL/ETL interfaces. However, for high-applied bias voltage, illumination, air exposure for weeks, and special cell configuration, these ions can also reach the external contact interfaces, presenting anomalous hysteresis behavior. This has already been confirmed experimentally but has not been modeled yet. The ion flux toward contacts has been considered in our model by introducing new parameters, such as boundary absorption velocity for anions and cations (Qa,c). The results comprise low hysteresis in the J-V characteristic by an increase in the boundary absorption velocity. Moreover, by increasing the scanning time (low scan rate), ions have enough time to reach the ETL/contact and HTL/contact interfaces, which leads to enhanced and inverted hysteresis and decreased efficiency. Finally, a unique and optimized set of material parameters, mainly related to ion migration parameters, has been achieved. Therefore, the cell efficiency is enhanced from 16.47 to 26.38% by using the optimized parameters. Our results show that ion migration prevention has an essential role in producing highly efficient, hysteresis-free, and stable solar cells that are ready for real-world applications.

Tumor-derived exosomal non-coding RNAs as diagnostic biomarkers in cancer.

Almost all clinical oncologists agree that the discovery of reliable, accessible, and non-invasive biomarkers is necessary to decrease cancer mortality. It is possible to employ reliable biomarkers to diagnose cancer in the early stages, predict the patient prognosis, follow up the response to treatment, and estimate the risk of disease recurrence with high sensitivity and specificity. Extracellular vesicles (EVs), especially exosomes, have been the focus of translational research to develop such biomarkers over the past decade. The abundance and distribution of exosomes in bodily fluids, including serum, saliva, and urine, as well as their ability to transport various biomolecules (nucleic acids, proteins, and lipids) derived from their parent cells, make exosomes reliable, accessible, and potent biomarkers for diagnosis and follow-up of solid and hematopoietic tumors. In addition, exosomes play a vital role in various cellular processes, including tumor progression, by participating in intercellular communication. Although these advantages underline the high potential of tumor-derived exosomes as diagnostic biomarkers, the lack of standardized effective methods for their isolation, identification, and precise characterization makes their application challenging in clinical settings. We discuss the importance of non-coding RNAs (ncRNAs) in cellular processes, and the role of tumor-derived exosomes containing ncRNAs as potential biomarkers in several types of cancer. In addition, the advantages and challenges of these studies for translation into clinical applications are covered.

Comprehensive study of anomalous hysteresis behavior in perovskite-based solar cells.

Perovskite solar cells (PSCs) have shown remarkable progress with the rapid increase in power conversion efficiency to reach 25.7% over the last few years. However, it is difficult to precisely determine the energy conversion efficiency for PSC, because of anomalous current density-voltage (J-V) hysteresis. Normal J-V hysteresis has been reported in many papers, where the backward scan performance is higher than the forward scan one. In this work, using Drift-Diffusion Modeling, normal hysteretic behavior associated with ion migration with different scanning rates, pre-bias voltages, and charge-carrier mobility is studied. In addition, the inverted J-V hysteresis by modification of the simulation model, where anions and cations flux towards the transport layers and are accumulated simultaneously on both sides, is achieved. It is also found that the flux parameter values (gae and gch) play a critical role in the reduction of inverted hysteresis and the efficiency enhancement. It is suggested from the current studies that perovskite interfaces encapsulation, which prevents ions migration, could be of great importance for achieving hysteresis-free PSCs and reliable device characteristics.

Role of the Wnt and GTPase pathways in breast cancer tumorigenesis and treatment.

Breast cancer (BC) is the most frequently diagnosed cancer among women in all the populations of the world. Although the BC mortality rate has declined, resistance to treatment is still a significant challenge for patient survival. Various cellular signaling pathways, such as Wnt and Rho/GTPase have been linked to the development, migration, and metastasis of BC, and also in treatment resistance mechanisms. Some studies have shown an association between two important cellular pathways, Wnt and Rho/GTPase, in cytoskeleton activation and cancer invasion. However, their involvement in BC has received little attention. This review summarizes the Wnt and Rho/GTPases signaling pathway functions, and also the crosstalk between these pathways in the progression, metastasis, and drug resistance mechanisms in BC. Considering the signaling pathways involved in BC tumorigenesis, future studies will need to investigate possible molecular interventions and new opportunities for the development of personalized strategies for BC treatment in order to improve overall outcomes.

The role of endoplasmic reticulum stress in the regulation of long noncoding RNAs in cancer.

Cancer cells must overcome a variety of external and internal stresses to survive and proliferate. These unfavorable conditions include the accumulation of mutations, nutrient deficiency, oxidative stress, and hypoxia. These stresses can cause aggregation of misfolded proteins inside the endoplasmic reticulum. Under these conditions, the cell undergoes endoplasmic reticulum stress (ER-stress), and consequently initiates the unfolded protein response (UPR). Activation of the UPR triggers transcription factors and regulatory factors, including long noncoding RNAs (lncRNAs), which control the gene expression profile to maintain cellular stability and hemostasis. Recent investigations have shown that cancer cells can ensure their survival under adverse conditions by the UPR affecting the expression of lncRNAs. Therefore, understanding the relationship between lncRNA expression and ER stress could open new avenues, and suggest potential therapies to treat various types of cancer.

A recombinant affitoxin derived from a HER3 affibody and diphteria-toxin has potent and selective antitumor activity.

High expression of receptor tyrosine-protein kinase erbB-3 (HER3) has been found in several malignancies such as breast cancer. In this study, we designed, produced and evaluated a new affitoxin consisting of a truncated form of diphtheria toxin and a HER3-binding affibody domains. The new affitoxin was expressed in Escherichia coli and purified by affinity chromatography. We evaluated the suitability of affitoxin to kill HER3 positive breast cancer cells with MTT and apoptosis assays. The protein synthesis inhibition was also evaluated. The IC50 value in HER3 negative cells is about 10 times more than HER3 positive cells in new design of affitoxin. The specificity of affitoxin for binding to HER3 positive cells was also investigated with binding assay with flow cytometry. The results show that, the new affitoxin is an anti-cancer molecule with specific binding to HER3 positive cells and may open a new window for the treatment of HER3-positive cancers.

Crosstalk between lncRNAs in the apoptotic pathway and therapeutic targets in cancer.

The assertion that a significant portion of the mammalian genome has not been translated and that non-coding RNA accounts for over half of polyadenylate RNA have received much attention. In recent years, increasing evidence proposes non-coding RNAs (ncRNAs) as new regulators of various cellular processes, including cancer progression and nerve damage. Apoptosis is a type of programmed cell death critical for homeostasis and tissue development. Cancer cells often have inhibited apoptotic pathways. It has recently been demonstrated that up/down-regulation of various lncRNAs in certain types of tumors shapes cancer cells' response to apoptotic stimuli. This review discusses the most recent studies on lncRNAs and apoptosis in healthy and cancer cells. In addition, the role of lncRNAs as novel targets for cancer therapy is reviewed here. Finally, since it has been shown that lncRNA expression is associated with specific types of cancer, the potential for using lncRNAs as biomarkers is also discussed.

Development of neoantigens: from identification in cancer cells to application in cancer vaccines.

INTRODUCTION: The discovery of neoantigens as mutated proteins specifically expressed in tumor cells but not in normal cells has led to improved cancer vaccines. Targeting neoantigens can induce anti-tumor T-cell responses to destroy tumors without damaging healthy cells. Extensive advances in genome sequencing technology and bioinformatics analysis have made it possible to discover and design effective neoantigens for use in therapeutic cancer vaccines. Neoantigens-based therapeutic personalized vaccines have shown promising results in cancer immunotherapy. AREAS COVERED: We discuss the types of cancer neoantigens that can be recognized by the immune system in this review. We also summarize the detection, identification, and design of neoantigens and their appliction in developing cancer vaccines. Finally, clinical trials of neoantigen-based vaccines, their advantages, and their limitations are reviewed. From 2015 to 2020, the authors conducted a literature search of controlled randomized trials and laboratory investigations that that focused on neoantigens, their use in the design of various types of cancer vaccines. EXPERT OPINION: Neoantigens are cancer cell-specific antigens, which their expression leads to the immune stimulation against tumor cells. The identification and delivery of specific neoantigens to antigen-presenting cells (APCs) with the help of anti-cancer vaccines promise novel and more effective cancer treatments.

Narrow-band random Raman lasing from Rhodamine 6G assisted by cascaded stimulated Raman scattering effect.

This study reports the first experimental observation of cascaded stimulated Raman scattering (SRS) generation in a colloidal disordered medium. Generation of the cascaded effect requires both a high Raman gain and pump power in the disordered medium. Here, to extend effective path lengths of photons into the Raman gain medium for producing additional SRS processes, ZnO microspheres with abundant nano-protrusions as suitable scattering centers are proposed. It is explained that nano-protrusions on the surface of the spheres can act as nano reflectors and significantly provide potent feedback in the disordered system. This provided feedback via nano-protrusions boosts cascaded SRS generation to allow the appearance of higher Raman signals of Rhodamine 6G dye solution at a low scatterer concentration of 5 mg/ml. The threshold for the formation of the first Raman signal is measured at about 60 mJ/pulse. Also, the evolution of Raman signals under several fixed pump pulses is examined to investigate the stability from pulse to pulse. Our findings provide promising perspectives for achieving the single-frequency laser sources and generate desirable wavelengths for specific applications.

Third-Order Nonlinear Optical Behavior of an Amide-Tricarboxylate Zinc(II) Metal-Organic Framework with Two-Fold 3D+3D Interpenetration.

A new metal-organic framework (MOF), [Zn4(µ4-O)(µ6-L)2(H2O)2]n·nDMF (ZSTU-10), was assembled from zinc(II) nitrate and N,N',N″-bis(4-carboxylate)trimesicamide linkers and fully characterized. Its crystal structure discloses an intricate two-fold 3D+3D interpenetrated MOF driven by the [Zn4(µ4-O)]-based tetragonal secondary building units and the C3-symmetric tris-amide-tricarboxylate linkers (µ6-L3-). Topological analysis of ZSTU-10 reveals two interpenetrated 3,6-connected nets with an rtl (rutile) topology. Z-Scan analysis at 532 nm was conducted to study a nonlinear optical (NLO) behavior of ZSTU-10. The nonlinear responses of ZSTU-10 were explored under various laser intensities, revealing notable third-order NLO properties in the visible region. A large two-photon absorption at lower incident intensities highlights the fact that ZSTU-10 can be applied in optical limiting devices as well as optical modulators. Moreover, a nonlinear refractive index (n2) is indicative of a self-defocusing behavior. This work thus expands a family of novel MOF materials with remarkable optical properties.

Efficiency enhancement of CZTSSe solar cells via screening the absorber layer by examining of different possible defects.

This study represents the investigation of earth-abundant and non-toxic CZTSSe absorber materials in kesterite solar cell by using the Finite Element Method (FEM) with (1) electrical, and (2) optical approaches. The simulated results have been validated with the experimental results to define guidelines for boosting the cell performance. For improving the cell efficiency, potential barrier variations in the front contact, and the effect of different lattice defects in the CZTSSe absorber layer have been examined. Controlling the defects and the secondary phases of absorber layer have significant influence on the cell performance improvement. Previous studies have demonstrated that, synthesis of CZTSSe:Na nanocrystals and controlling the S/(S + Se), Cu/(Zn + Sn), and Zn/Sn ratios (stoichiometry) have significant effects on the reduction of trap-assisted recombination (Shockley-Read-Hall recombination model). In this work, a screening-based approach has been employed to study the cell efficiency over a wide range of defect densities. Two categorized defect types including benign defects ([Formula: see text] cm-3 , Nt defines trap density) and harmful defects [Formula: see text] cm-3) in the absorber bandgap in the CZTSSe solar cell, by analyzing their position changes with respect to the electron Fermi level (Efn) and the Valence Band Maximum positions have been identified. It is realized that, the harmful defects are the dominant reason for the low efficiency of the kesterite solar cells, therefore, reducing the number of harmful defects and also total defect densities lead to the power conversion efficiency record of 19.06%. This increment makes the CZTSSe solar cells as a promising candidate for industrial and commercial applications.