Reformulating lipid nanoparticles for organ-targeted mRNA accumulation and translation.

Fully targeted mRNA therapeutics necessitate simultaneous organ-specific accumulation and effective translation. Despite some progress, delivery systems are still unable to fully achieve this. Here, we reformulate lipid nanoparticles (LNPs) through adjustments in lipid material structures and compositions to systematically achieve the pulmonary and hepatic (respectively) targeted mRNA distribution and expression. A combinatorial library of degradable-core based ionizable cationic lipids is designed, following by optimisation of LNP compositions. Contrary to current LNP paradigms, our findings demonstrate that cholesterol and phospholipid are dispensable for LNP functionality. Specifically, cholesterol-removal addresses the persistent challenge of preventing nanoparticle accumulation in hepatic tissues. By modulating and simplifying intrinsic LNP components, concurrent mRNA accumulation and translation is achieved in the lung and liver, respectively. This targeting strategy is applicable to existing LNP systems with potential to expand the progress of precise mRNA therapy for diverse diseases.

Nitric Oxide-Activated Bioorthogonal Codelivery Nanoassembly for In Situ Synthesis of Photothermal Agent for Precise and Safe Anticancer Treatment.

The development of bioorthogonal activation in drug release represents a promising avenue for precise and safe anticancer treatment. However, two significant limitations currently hinder their clinical application: i) the necessity for separate administration of the drug precursor and its corresponding activator, leading to poor drug accumulation and potential side effects; ii) the reliance on exogenous metal or organic activators for triggering bioorthogonal activation, which often exhibit low efficiency and systemic toxicity when extending to living animals. To overcome these limitations, a nitric oxide (NO)-mediated bioorthogonal codelivery nanoassembly, termed TTB-NH2@PArg, which comprises a precursor molecular (TTB-NH2) and amphipathic polyarginine (PArg) is developed. In TTB-NH2@PArg, PArg serves as both self-assembled nanocarrier for TTB-NH2 and a NO generator. In tumor microenvironment (TME), the TME-specific generation of NO acts as a gas activator, triggering in situ bioorthogonal bond formation that transforms TTB-NH2 into TTB-AZO. This tumor-specific generation of TTB-AZO not only serves as a potential photothermal agent for effective tumor inhibition but also induces fluorescence change that enables real-time monitoring of bioorthogonal activation. This study presents a drug codelivery approach that enables precise and safe control of bioorthogonal activation for anticancer treatment, improving cancer therapy efficacy while minimizing side effects.

Glomerulus-Targeted ROS-Responsive Polymeric Nanoparticles for Effective Membranous Nephropathy Therapy.

Membranous nephropathy (MN) is a common immune-mediated glomerular disease that requires the development of safe and highly effective therapies. Celastrol (CLT) has shown promise as a therapeutic molecule candidate, but its clinical use is currently limited due to off-target toxicity. Given that excess levels of reactive oxygen species (ROS) contributing to podocyte damage is a key driver of MN progression to end-stage renal disease, we rationally designed ROS-responsive cationic polymeric nanoparticles (PPS-CPNs) with a well-defined particle size and surface charge by employing poly(propylene sulfide)-polyethylene glycol (PPS-PEG) and poly(propylene sulfide)-polyethylenimine (PPS-PEI) to selectively deliver CLT to the damaged glomerulus for MN therapy. Experimental results show that PPS-CPNs successfully crossed the fenestrated endothelium, accumulated in the glomerular basement membrane (GBM), and were internalized by podocytes where rapid drug release was triggered by the overproduction of ROS, thereby outperforming nonresponsive CLT nanotherapy to alleviate subepithelial immune deposits, podocyte foot process effacement, and GBM expansion in a rat MN model. Moreover, the ROS-responsive CLT nanotherapy was associated with significantly lower toxicity to major organs than free CLT. These results suggest that encapsulating CLT into PPS-CPNs can improve efficacy and reduce toxicity as a promising treatment option for MN.

Programmable Singlet Oxygen Battery for Automated Photodynamic Therapy Enabled by Pyridone-Pyridine Tautomer Engineering.

The efficacy of photodynamic therapy is hindered by the hypoxic environment in tumors and limited light penetration depth. The singlet oxygen battery (SOB) has emerged as a promising solution, enabling oxygen- and light-independent 1O2 release. However, conventional SOB systems typically exhibit an "always-ON" 1O2 release, leading to potential 1O2 leakage before and after treatment. This not only compromises therapeutic outcomes but also raises substantial biosafety concerns. In this work, we introduce a programmable singlet oxygen battery, engineered to address all the issues discussed above. The concept is illustrated through the development of a tumor-microenvironment-responsive pyridone-pyridine switch, PyAce, which exists in two tautomeric forms: PyAce-0 (pyridine) and PyAce (pyridone) with different 1O2 storage half-lives. In its native state, PyAce remains in the pyridone form, capable of storing 1O2 (t1/2 = 18.5 h). Upon reaching the tumor microenvironment, PyAce is switched to the pyridine form, facilitating rapid and thorough 1O2 release (t1/2 = 16 min), followed by quenched 1O2 release post-therapy. This mechanism ensures suppressed 1O2 production pre- and post-therapy with selective and rapid 1O2 release at the tumor site, maximizing therapeutic efficacy while minimizing side effects. The achieved "OFF-ON-OFF" 1O2 therapy showed high spatiotemporal selectivity and was independent of the oxygen supply and light illumination.

Glycyrrhizic acid inhibits DNA damage repair and enhances cisplatin-induced apoptosis of melanoma cells.

This research was designed to prospect the mechanism and impact of glycyrrhizic acid (GA) on DNA damage repair and cisplatin (CP)-induced apoptosis of melanoma cells. First, human melanoma cell SK-MEL-28 was stimulated using GA for 24, 48, and 72 h. Then, the optimal treatment time and dosage were selected. After that, cell counting kit-8 (CCK-8) was employed for testing the cell viability, flow cytometry for the apoptosis, comet assay for the DNA damage of cells, and western blot for the cleaved-Caspase3, Caspase3, Bcl-2, and γH2AX protein expression levels. The experimental outcomes exhibited that as the GA concentration climbed up, the SK-MEL-28 cell viability dropped largely, while the apoptosis level raised significantly, especially at the concentration of 100 µm. In addition, compared with GA or CPtreatment only, CP combined with GA notably suppressed the viability of melanoma cells and promoted cell apoptosis at the cytological level. At the protein level, the combined treatment notably downregulated the Bcl-2 and Caspase3 expression levels, while significantly upregulated the cleaved-Caspase3 and γH2AX expression levels. Besides, CP + GA treatment promoted DNA damage at the DNA molecular level. Collectively, both GA and CP can inhibit DNA damage repair and enhance the apoptosis of SK-MEL-28 cells, and the synergistic treatment of both exhibits better efficacy.

Seroprevalence and Risk Factors of Toxoplasma gondii Infection of Cattle and Goats in Farms of Hunan Province, China.

Background: Toxoplasmosis is one of the most widespread foodborne parasitic zoonoses caused by the obligate intracellular protozoan Toxoplasma gondii. Although a number of studies have reported on the seroprevalence and risk factors of T. gondii infection in ruminants in China, information about T. gondii infection in cattle in Hunan province of China is not available. Material and Methods: Sera of 985 cattle and 1147 goats were examined for the presence of specific antibodies against T. gondii using the indirect hemagglutination test. Some risk factors related to the presence of cats, herd size, gender, age, and geographical origin were determined using a binary logistic regression. Results: Specific IgG against T. gondii were detected in 8.3% (82/985) and 13.3% (153/1147) of the cattle and goats, respectively. Based on statistical analysis, the presence of cats and gender were considered important risk factors for T. gondii infection in cattle and goats in the farms in this study (P < 0.05). Conclusion: Our results provide a baseline for future prevention and control of T. gondii infection in cattle and goats in Hunan province, subtropical China. This is the first report of T. gondii seroprevalence in cattle in Hunan province, China.

Smart Nanoassembly Enabling Activatable NIR Fluorescence and ROS Generation with Enhanced Tumor Penetration for Imaging-Guided Photodynamic Therapy.

Fluorescence imaging-guided photodynamic therapy (FIG-PDT) holds promise for cancer treatment, yet challenges persist in poor imaging quality, phototoxicity, and insufficient anti-tumor effect. Herein, a novel nanoplatform, LipoHPM, designed to address these challenges, is reported. This approach employs an acid-sensitive amine linker to connect a biotin-modified hydrophilic polymer (BiotinPEG) with a new hydrophobic photosensitizer (MBA), forming OFF-state BiotinPEG-MBA (PM) micelles via an aggregation-caused quenching (ACQ) effect. These micelles are then co-loaded with the tumor penetration enhancer hydralazine (HDZ) into pH-sensitive liposomes (LipoHPM). Leveraging the ACQ effect, LipoHPM is silent in both fluorescence and reactive oxygen species (ROS) generation during blood circulation but restores both properties upon disassembly. Following intravenous injection in tumor-bearing mice, LipoHPM actively targets tumor cells overexpressing biotin-receptors, contributing to enhanced tumor accumulation. Upon cellular internalization, LipoHPM disassembles within lysosomes, releasing HDZ to enhance tumor penetration and inhibit tumor metastasis. Concurrently, the micelles activate fluorescence for tumor imaging and boost the production of both type-I and type-II ROS for tumor eradication. Therefore, the smart LipoHPM synergistically integrates near-infrared emission, activatable tumor imaging, robust ROS generation, efficient anti-tumor and anti-metastasis activity, successfully overcoming limitations of conventional photosensitizers and establishing itself as a promising nanoplatform for potent FIG-PDT applications.

Dual-responsive nanocarriers for efficient cytosolic protein delivery and CRISPR-Cas9 gene therapy of inflammatory skin disorders.

Developing protein drugs that can target intracellular sites remains a challenge due to their inadequate membrane permeability. Efficient carriers for cytosolic protein delivery are required for protein-based drugs, cancer vaccines, and CRISPR-Cas9 gene therapies. Here, we report a screening process to identify highly efficient materials for cytosolic protein delivery from a library of dual-functionalized polymers bearing both boronate and lipoic acid moieties. Both ligands were found to be crucial for protein binding, endosomal escape, and intracellular protein release. Polymers with higher grafting ratios exhibit remarkable efficacies in cytosolic protein delivery including enzymes, monoclonal antibodies, and Cas9 ribonucleoprotein while preserving their activity. Optimal polymer successfully delivered Cas9 ribonucleoprotein targeting NLRP3 to disrupt NLRP3 inflammasomes in vivo and ameliorate inflammation in a mouse model of psoriasis. Our study presents a promising option for the discovery of highly efficient materials tailored for cytosolic delivery of specific proteins and complexes such as Cas9 ribonucleoprotein.

Virtual reality-based cognitive-behavioural therapy for the treatment of anxiety in patients with acute myocardial infarction: a randomised clinical trial.

Background: The presence of mental health conditions is pervasive in patients who experienced acute myocardial infarction (AMI), significantly disrupting their recovery. Providing timely and easily accessible psychological interventions using virtual reality-based cognitive-behavioural therapy (VR-CBT) could potentially improve both acute and long-term symptoms affecting their mental health. Aims: We aim to examine the effectiveness of VR-CBT on anxiety symptoms in patients with AMI who were admitted to the intensive care unit (ICU) during the acute stage of their illness. Methods: In this single-blind randomised clinical trial, participants with anxiety symptoms who were admitted to the ICU due to AMI were continuously recruited from December 2022 to February 2023. Patients who were Han Chinese aged 18-75 years were randomly assigned (1:1) via block randomisation to either the VR-CBT group to receive VR-CBT in addition to standard mental health support, or the control group to receive standard mental health support only. VR-CBT consisted of four modules and was delivered at the bedside over a 1-week period. Assessments were done at baseline, immediately after treatment and at 3-month follow-up. The intention-to-treat analysis began in June 2023. The primary outcome measure was the changes in anxiety symptoms as assessed by the Hamilton Anxiety Rating Scale (HAM-A). Results: Among 148 randomised participants, 70 were assigned to the VR-CBT group and 78 to the control group. The 1-week VR-CBT intervention plus standard mental health support significantly reduced the anxiety symptoms compared with standard mental health support alone in terms of HAM-A scores at both post intervention (Cohen's d=-1.27 (95% confidence interval (CI): -1.64 to -0.90, p<0.001) and 3-month follow-up (Cohen's d=-0.37 (95% CI: -0.72 to -0.01, p=0.024). Of the 70 participants who received VR-CBT, 62 (88.6%) completed the entire intervention. Cybersickness was the main reported adverse event (n=5). Conclusions: Our results indicate that VR-CBT can significantly reduce post-AMI anxiety at the acute stage of the illness; the improvement was maintained at the 3-month follow-up. Trial registration number: The trial was registered at www.chictr.org.cn with the identifier: ChiCTR2200066435.

Proinflammatory polarization of engineered heat-inducible macrophages reprogram the tumor immune microenvironment during cancer immunotherapy.

The success of macrophage-based adoptive cell therapy is largely constrained by poor polarization from alternatively activated (M2-like) to classically activated (M1-like) phenotype in the immunosuppressive tumor microenvironment (TME). Here, we show that the engineered macrophage (eMac) with a heat-inducible genetic switch can induce both self-polarization of adoptively transferred eMac and re-polarization of tumour-associated macrophages in response to mild temperature elevation in a mouse model. The locoregional production of proinflammatory cytokines by eMac in the TME dose not only induces the strong polarization of macrophages into a classically activated phenotype, but also ensures that the side effects typical for systemically administrate proinflammatory cytokines are avoided. We also present a wearable warming device which is adaptable for human patients and can be remotely controlled by a smartphone. In summary, our work represents a safe and efficient adoptive transfer immunotherapy method with potential for human translation.

Salinity-Driven Interface Self-Assembly of a Biological Amphiphilic Emulsifier to Form Stable Janus Core-Shell Emulsion for Enhancing Agrichemical Delivery.

Agrichemical losses are a severe threat to the ecological environment. Additionally, some agrichemical compounds contain abundant salt, which increases the instability of formulations, leading to a lower agrichemical utilization and soil hardening. Fortunately, the biological amphiphilic emulsifier sodium deoxycholate alleviates these problems by forming stable Janus core-shell emulsions through salinity-driven interfacial self-assembly. According to the interfacial behavior, dilational rheology, and molecular dynamics simulations, Janus-emulsion molecules are more closely arranged than traditional-emulsion molecules and generate an oil-water interfacial film that transforms into a gel film. In addition, at the same spray volume, the deposition area of the Janus emulsion increased by 37.70% compared with that of the traditional emulsion. Owing to the topology effect and deformation, the Janus emulsion adheres to rice micropapillae, achieving better flush resistance. Meanwhile, based on response of the Janus emulsion to stimulation by carbon dioxide (CO2), the emulsion lost to the soil can form a rigid shell for inhibiting the release of pesticides and metal ions from harming the soil. The pyraclostrobin release rate decreased by 50.89% at 4 h after the Janus emulsion was exposed to CO2. The Chao1 index of the Janus emulsion was increased by 12.49% as compared to coconut oil delivery in soil microbial community. The Janus emulsion ingested by harmful organisms can be effectively absorbed in the intestine to achieve better control effects. This study provides a simple and effective strategy, which turns waste into treasure, by combining metal ions in agrichemicals with natural amphiphilic molecules to prepare stable emulsions for enhancing agrichemical rainfastness and weakening environmental risk.

Supramolecular Genome Editing: Targeted Delivery and Endogenous Activation of CRISPR/Cas9 by Dynamic Host-Guest Recognition.

We synthesize supramolecular poly(disulfide) (CPS) containing covalently attached cucurbit[7]uril (CB[7]), which is exploited not only as a carrier to deliver plasmid DNA encoding destabilized Cas9 (dsCas9), but also as a host to include trimethoprim (TMP) by CB[7] moieties through the supramolecular complexation to form TMP@CPS/dsCas9. Once the plasmid is transfected into tumor cells by CPS, the presence of polyamines can competitively trigger the decomplexation of TMP@CPS, thereby displacing and releasing TMP from CB[7] to stabilize dsCas9 that can target and edit the genomic locus of PLK1 to inhibit the growth of tumor cells. Following the systemic administration of TMP@CPS/dsCas9 decorated with hyaluronic acid (HA), tumor-specific editing of PLK1 is detected due to the elevated polyamines in tumor microenvironment, greatly minimizing off-target editing in healthy tissues and non-targeted organs. As the metabolism of polyamines is dysregulated in a wide range of disorders, this study offers a supramolecular approach to precisely control CRISPR/Cas9 functions under particular pathological contexts.

An oncolytic virus-T cell chimera for cancer immunotherapy.

The efficacy of oncolytic adenoviruses (OAs) for cancer therapy has been limited by insufficient delivery to tumors after systemic injection and the propensity of OAs to induce the expression of immune checkpoints. To address these limitations, we use T cells to deliver OAs into tumors and engineer the OA to express a Cas9 system targeting the PDL1 gene encoding the immune checkpoint protein PD-L1. By cloaking OAs with cell membranes presenting T cell-specific antigens, we physically conjugated OAs onto T cell surfaces by antigen-receptor interaction. We tested the oncolytic virus-T cell chimera (ONCOTECH) via intravenous delivery in mouse cancer models, including models of melanoma, pancreatic adenocarcinoma, lung cancer and glioblastoma. In the melanoma model, the in vivo delivery of ONCOTECH resulted in a strong accumulation of OAs in tumor cells, where PD-L1 expression was reduced by 50% and the single administration of ONCOTECH enabled 80% survival over 70 days. Collectively, ONCOTECH represents a promising translational technology to combine virotherapy and cell therapy.

Coinoculation of arbuscular mycorrhizal fungi and rhizobia stimulates atrazine dissipation by changing the atrazine-degrading bacterial community at the soil aggregate scale.

As a potential low-cost and environmentally friendly strategy, bioremediation of herbicide polluted soil has attracted increasing attention. However, there is a lack of knowledge regarding the response of the atrazine-degrading bacterial community to coinoculation of arbuscular mycorrhizal (AM) fungi and rhizobia for atrazine dissipation. In this study, a pot experiment was conducted with AM fungi Glomus mosseae (AM), rhizobia Rhizobium trifolii TA-1 (R) and their coinoculation (AMR) with atrazine. In each treatment, the atrazine-degrading bacterial community of four soil size aggregates, namely large macroaggregates (LMa), small macroaggregates (SMa), microaggregates (Mia) and primary particles (P) were investigated. The results showed that the atrazine residue concentration was lowest in AMR, and that in LMa was also significantly lower than that in the other smaller aggregate sizes. Overall, inoculation, the aggregate fraction and their interaction had significant effects on soil TN, SOC, AP and pH. For the atrazine-degrading bacterial community, the Chao1 index increased with decreasing particle size, but the Shannon index decreased. Moreover, the abundances of the dominant atrazine-degrading bacterial genera Arthrobacter, Bacillus, Marmoricola and Nocardioides in the Mia and P particle size groups were greater than those in the LMa and SMa groups in each treatment. The bacterial communities in the Mia and P particle sizes in each treatment group were more complex. Therefore, coinoculation of AM fungi and rhizobia stimulated atrazine dissipation by changing the atrazine-degrading bacterial community, and the response of the atrazine-degrading bacterial community to each aggregate size varied depending on its distinct soil physicochemical properties.

How spin relaxes and dephases in bulk halide perovskites.

Spintronics in halide perovskites has drawn significant attention in recent years, due to their highly tunable spin-orbit fields and intriguing interplay with lattice symmetry. Here, we perform first-principles calculations to determine the spin relaxation time (T1) and ensemble spin dephasing time ([Formula: see text]) in a prototype halide perovskite, CsPbBr3. To accurately capture spin dephasing in external magnetic fields we determine the Landé g-factor from first principles and take it into account in our calculations. These allow us to predict intrinsic spin lifetimes as an upper bound for experiments, identify the dominant spin relaxation pathways, and evaluate the dependence on temperature, external fields, carrier density, and impurities. We find that the Fröhlich interaction that dominates carrier relaxation contributes negligibly to spin relaxation, consistent with the spin-conserving nature of this interaction. Our theoretical approach may lead to new strategies to optimize spin and carrier transport properties.

Correction: Intracellular regulation of zinc by metal-organic framework-mediated genome editing for prostate cancer therapy.

Correction for 'Intracellular regulation of zinc by metal-organic framework-mediated genome editing for prostate cancer therapy' by Yanan Xue et al., Biomater. Sci., 2023, https://doi.org/10.1039/d3bm00002h.

Improvement of lipopeptide production in Bacillus subtilis HNDF2-3 by overexpression of the sfp and comA genes.

Bacillus subtilis HNDF2-3 can produce a variety of lipopeptide antibiotics with lower production. To improve its lipopeptide production, three genetically engineered strains were constructed. The results of real-time PCR showed that the highest transcriptional levels of the sfp gene in F2-3sfp, F2-3comA and F2-3sfp-comA were 29.01, 6.65 and 17.50 times of the original strain, respectively, while the highest transcriptional levels of the comA gene in F2-3comA and F2-3sfp-comA were 10.44 and 4.13 times of the original strain, respectively. The results of ELISA showed that the malonyl-CoA transacylase activity of F2-3comA was the highest, reaching 18.53 IU/L at 24 h, the data was 32.74% higher than that of the original strain. The highest total lipopeptide production of F2-3sfp, F2-3comA and F2-3sfp-comA induced by IPTG at optimal concentration were 33.51, 46.05 and 38.96% higher than that of the original strain, respectively. The results of HPLC showed that iturin A production of F2-3sfp-comA was the highest, which was 63.16% higher than that of the original strain. This study laid the foundation for further construction of genetically engineered strains with high lipopeptide production.

Injectable Supramolecular Hydrogels for In Situ Programming of Car-T Cells toward Solid Tumor Immunotherapy.

Chimeric antigen receptor (CAR)-T cell immunotherapy is approved in the treatment of hematological malignancies, but remains far from satisfactory in solid tumor treatment due to inadequate intra-tumor CAR-T cell infiltration. Herein, an injectable supramolecular hydrogel system, based on self-assembly between cationic polymer mPEG-PCL-PEI (PPP) conjugated with T cell targeting anti-CD3e f(ab')2 fragment and α-cyclodextrin (α-CD), is designed to load plasmid CAR (pCAR) with a T cell specific CD2 promoter, which successfully achieves in situ fabrication and effective accumulation of CAR-T cells at the tumor site in humanized mice models. More importantly, due to this tumor microenvironment reprogramming, secretion of cellular inflammatory cytokines (interleukin-2 (IL-2), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ)) or tumor killer protein granzyme B is significantly promoted, which reverses the immunosuppressive microenvironment and significantly enhances the intra-tumor CAR-T cells and cytotoxic T cells infiltration. To the best of the current knowledge, this is a pioneer report of using injectable supramolecular hydrogel for in situ reprogramming CAR-T cells, which might be beneficial for solid tumor CAR-T immunotherapy.

Comprehensive Genomic and Transcriptomic Analysis of Sclerosing Pneumocytoma.

Sclerosing pneumocytoma is a rare and distinct lung neoplasm whose histogenesis and molecular alterations are the subject of ongoing research. Our recent study revealed that AKT1 internal tandem duplications (ITD), point mutations, and short indels were present in almost all tested sclerosing pneumocytomas, suggesting that AKT1 mutations are a major driving oncogenic event in this tumor. Although the pathogenic role of AKT1 point mutations is well established, the significance of AKT1 ITD in oncogenesis remains largely unexplored. We conducted comprehensive genomic and transcriptomic analyses of sclerosing pneumocytoma to address this knowledge gap. RNA-sequencing data from 23 tumors and whole-exome sequencing data from 44 tumors were used to obtain insights into their genetic and transcriptomic profiles. Our analysis revealed a high degree of genetic and transcriptomic similarity between tumors carrying AKT1 ITD and those with AKT1 point mutations. Mutational signature analysis revealed COSMIC signatures 1 and 5 as the prevailing signatures of sclerosing pneumocytoma, associated with the spontaneous deamination of 5-methylcytosine and an unknown etiology, respectively. RNA-sequencing data analysis revealed that the sclerosing pneumocytoma gene expression profile is characterized by activation of the PI3K/AKT/mTOR pathway, which exhibits significant similarity between tumors harboring AKT1 ITD and those with AKT1 point mutations. Notably, an upregulation of SOX9, a transcription factor known for its involvement in fetal lung development, was observed in sclerosing pneumocytoma. Specifically, SOX9 expression was prominent in the round cell component, whereas it was relatively lower in the surface cell component of the tumor. To the best of our knowledge, this is the first comprehensive investigation of the genomic and transcriptomic characteristics of sclerosing pneumocytoma. Results of the present study provide insights into the molecular attributes of sclerosing pneumocytoma and a basis for future studies of this enigmatic tumor.

Ab Initio Predictions of Spin Relaxation, Dephasing, and Diffusion in Solids.

Spin relaxation, dephasing, and diffusion are at the heart of spin-based information technology. Accurate theoretical approaches to simulate spin lifetimes (τs), determining how fast the spin polarization and phase information will be lost, are important to the understanding of the underlying mechanism of these spin processes, and invaluable in searching for promising candidates of spintronic materials. Recently, we develop a first-principles real-time density-matrix (FPDM) approach to simulate spin dynamics for general solid-state systems. Through the complete first-principles descriptions of light-matter interaction and scattering processes including electron-phonon, electron-impurity, and electron-electron scatterings with self-consistent spin-orbit coupling, as well as ab initio Landé g-factor, our method can predict τs at various conditions as a function of carrier density and temperature, under electric and magnetic fields. By employing this method, we successfully reproduce experimental results of disparate materials and identify the key factors affecting spin relaxation, dephasing, and diffusion in different materials. Specifically, we predict that germanene has long τs (∼100 ns at 50 K), a giant spin lifetime anisotropy, and spin-valley locking effect under electric fields, making it advantageous for spin-valleytronic applications. Based on our theoretical derivations and ab initio simulations, we propose a new useful electronic quantity, named spin-flip angle θ↑↓, for the understanding of spin relaxation through intervalley spin-flip scattering processes. Our method can be further applied to other emerging materials and extended to simulate exciton spin dynamics and steady-state photocurrents due to photogalvanic effect.