Single-cell transcriptomics reveals activation of endothelial cell and identifies LHPP as a potential target in ulcerative colitis.

This study delves into Ulcerative colitis (UC), a persistent gastrointestinal disorder marked by inflammation and ulcers, significantly elevating colorectal cancer risk. The emergence of single-cell RNA sequencing (scRNA-seq) technology has opened new avenues for dissecting the intricate cellular dynamics and molecular mechanisms at play in UC pathology. By analyzing scRNA-seq data from individuals with UC, our study has revealed a consistent enhancement of inflammatory response pathways throughout the course of the disease, alongside detailing the characteristics of endothelial cell damage within colitis environments. A noteworthy finding is the downregulation of Phospholysine Phosphohistidine Inorganic Pyrophosphate Phosphatase (LHPP), which exhibited a inversely correlate with STAT3 expression levels. The markedly reduced expression of LHPP in both the tissues and plasma of UC patients positions LHPP as a compelling target for therapeutic intervention. Our findings highlight the pivotal role LHPP could play in moderating inflammation, spotlighting its potential as a crucial molecular target in the quest to understand and treat UC.

DeLIVR: a deep learning approach to IV regression for testing nonlinear causal effects in transcriptome-wide association studies.

Transcriptome-wide association studies (TWAS) have been increasingly applied to identify (putative) causal genes for complex traits and diseases. TWAS can be regarded as a two-sample two-stage least squares method for instrumental variable (IV) regression for causal inference. The standard TWAS (called TWAS-L) only considers a linear relationship between a gene's expression and a trait in stage 2, which may lose statistical power when not true. Recently, an extension of TWAS (called TWAS-LQ) considers both the linear and quadratic effects of a gene on a trait, which however is not flexible enough due to its parametric nature and may be low powered for nonquadratic nonlinear effects. On the other hand, a deep learning (DL) approach, called DeepIV, has been proposed to nonparametrically model a nonlinear effect in IV regression. However, it is both slow and unstable due to the ill-posed inverse problem of solving an integral equation with Monte Carlo approximations. Furthermore, in the original DeepIV approach, statistical inference, that is, hypothesis testing, was not studied. Here, we propose a novel DL approach, called DeLIVR, to overcome the major drawbacks of DeepIV, by estimating a related but different target function and including a hypothesis testing framework. We show through simulations that DeLIVR was both faster and more stable than DeepIV. We applied both parametric and DL approaches to the GTEx and UK Biobank data, showcasing that DeLIVR detected additional 8 and 7 genes nonlinearly associated with high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol, respectively, all of which would be missed by TWAS-L, TWAS-LQ, and DeepIV; these genes include BUD13 associated with HDL, SLC44A2 and GMIP with LDL, all supported by previous studies.

Evaluation of the liver targeting and anti­liver cancer activity of artesunate­loaded and glycyrrhetinic acid­coated nanoparticles.

Globally, liver cancer ranks among the most lethal cancers, with chemotherapy being one of its primary treatments. However, poor selectivity, systemic toxicity, a narrow treatment window, low response rate and multidrug resistance limit its clinical application. Liver-targeted nanoparticles (NPs) exhibit excellent targeted delivery ability and promising effectivity in treating liver cancer. The present study aimed to investigate the liver-targeting and anti-liver cancer effect of artesunate (ART)-loaded and glycyrrhetinic acid (GA)-decorated polyethylene glycol (PEG)-poly (lactic-co-glycolic acid) (PLGA) (ART/GA-PEG-PLGA) NPs. GA-coated NPs significantly increased hepatoma-targeted cellular uptake, with micropinocytosis and caveolae-mediated endocytosis as its chief internalization pathways. Moreover, ART/GA-PEG-PLGA NPs exhibited pro-apoptotic effects on HepG2 cells, mainly via the induction of a high level of reactive oxygen species, decline in mitochondrial membrane potential and induction of cell cycle arrest. Additionally, ART/GA-PEG-PLGA NPs induced internal apoptosis pathways by upregulating the activity of cleaved caspase-3/7 and expression of cleaved poly (ADP-Ribose)-polymerase and Phos-p38 mitogen-activated protein kinase in HepG2 cells. Furthermore, ART/GA-PEG-PLGA NPs exhibited higher liver accumulation and longer mean retention time, resulting in increased bioavailability. Finally, ART/GA-PEG-PLGA NPs promoted the liver-targeting distribution of ART, increased the retention time and promoted its antitumour effects in vivo. Therefore, ART/GA-PEG-PLGA NPs afforded excellent hepatoma-targeted delivery and anti-liver cancer efficacy, and thus, they may be a promising strategy for treating liver cancer.

Design, Synthesis and Biological Evaluation of Glycosylated Derivatives of Silibinin as Potential Anti-Tumor Agents.

Objective: Silibinin, a natural product extracted from the seeds of the Silybum marianum, is versatile with various pharmacological effects. However, its clinical application was strongly hampered by its low bioavailability and poor water solubility. Herein, a series of glycosylated silibinin derivatives were identified as novel anti-tumor agents. Materials and Methods: The cell viability was evaluated by CCK8 assay. Furthermore, cell apoptosis and cell cycle progression were tested by flow cytometry. In addition, the pharmacokinetic assessment of compound 15 and silibinin through intravenous administration (i.v., 2 mg/kg) to ICR mice were performed. Results: The synthesized compounds showed better water solubilities than silibinin. Among them, compound 15 exhibited inhibitory activity against DU145 cells with IC50 value of 1.37 ± 0.140 µM. Moreover, it arrested cell cycle at G2/M phase and induced apoptosis in DU145 cells. Additionally, compound 15 also displayed longer half-life (T1/2 = 128.3 min) in liver microsomes than that of silibinin (T1/2 = 82.5 min) and appropriate pharmacokinetic parameters in mice. Conclusion: Overall, glycosylation of silibinin would be a valid strategy for the development of silibinin derivatives as anti-tumor agents.

pH-Responsive and liver-targeting drug delivery system for combination delivery of artesunate with arsenic trioxide prodrug against hepatocellular carcinoma.

OBJECTIVE: Arsenic trioxide (ATO) exerts therapeutic effects on various solid tumors, and artesunate (ART) synergizes with antitumor drugs. We herein combined ART and an ATO prodrug (ATOP) in pH-responsive and liver-targeting liposomes to improve targeted hepatocellular carcinoma (HCC) treatment. METHODS: 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-hydrazone (HYD)-polyethylene glycol (PEG)-glycyrrhetinic acid (GA) (DSPE-HYD-PEG-GA) was synthesized and characterized. The optimal ratio of ART and ATOP was selected. Calcium arsenate nanoparticles (CaAs NPs) and DSPE-HYD-PEG-GA@ART/CaAs NPs liposomes were prepared and their physicochemical properties were characterized. Their intracellular uptake, intracellular localization, uptake pathway identification, cytotoxicity, proapoptotic effects, and relevant mechanisms were studied. RESULTS: The DSPE-HYD-PEG-GA was successfully synthesized. The best ratio of ART and ATOP was 7:1. The particle size of CaAs NPs under transmission electron microscopy was 142.39 ± 21.50 nm. Arsenic (As), calcium, and oxygen elements were uniformly distributed in CaAs NPs, and the drug loading and encapsulation efficiency of As are 37.28% and 51.40%, respectively. The liposomes were elliptical, and the particle size was 100.91 ± 39.31 nm. The liposome cell intake was significantly increased in Huh-7 cells. The liposomes entered the cell through macropinocytosis and caveolin-mediated endocytosis and were predominantly distributed in the cytoplasm. They exerted an excellent inhibitory effect on Huh-7 cells and promoted tumor cell apoptosis through lipid peroxidation, mitochondrial membrane potential reduction, and cell-cycle blockage. CONCLUSIONS: The pH-responsive and liver-targeting drug delivery system for the combination delivery of ART with ATOP showed promising effects on hepatocellular carcinoma (HCC).

Using GWAS summary data to impute traits for genotyped individuals.

Genome-wide association study (GWAS) summary data have become extremely useful in daily routine data analysis, largely facilitating new methods development and new applications. However, a severe limitation with the current use of GWAS summary data is its exclusive restriction to only linear single nucleotide polymorphism (SNP)-trait association analyses. To further expand the use of GWAS summary data, along with a large sample of individual-level genotypes, we propose a nonparametric method for large-scale imputation of the genetic component of the trait for the given genotypes. The imputed individual-level trait values, along with the individual-level genotypes, make it possible to conduct any analysis as with individual-level GWAS data, including nonlinear SNP-trait associations and predictions. We use the UK Biobank data to highlight the usefulness and effectiveness of the proposed method in three applications that currently cannot be done with only GWAS summary data (for SNP-trait associations): marginal SNP-trait association analysis under non-additive genetic models, detection of SNP-SNP interactions, and genetic prediction of a trait using a nonlinear model of SNPs.

Single-cell analysis identifies phospholysine phosphohistidine inorganic pyrophosphate phosphatase as a target in ulcerative colitis.

BACKGROUND: Ulcerative colitis (UC) is a chronic gastrointestinal disorder characterized by inflammation and ulceration, representing a significant predisposition to colorectal cancer. Recent advances in single-cell RNA sequencing (scRNA-seq) technology offer a promising avenue for dissecting the complex cellular inter-actions and molecular signatures driving UC pathology. AIM: To utilize scRNA-seq technology to dissect the complex cellular interactions and molecular signatures that underlie UC pathology. METHODS: In this research, we integrated and analyzed the scRNA-seq data from UC patients. Moreover, we conducted mRNA and protein level assays as well as pathology-related staining tests on clinical patient samples. RESULTS: In this study, we identified the sustained upregulation of inflammatory response pathways during UC progression, characterized the features of damaged endo-thelial cells in colitis. Furthermore, we uncovered the downregulation of phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP) has a negative correlation with signal transducer and activator of transcription 3. Significant downregulation of LHPP in UC patient tissues and plasma suggests that LHPP may serve as a potential therapeutic target for UC. This paper highlights the importance of LHPP as a potential key target in UC and unveils its potential role in inflammation regulation. CONCLUSION: The findings suggest that LHPP may serve as a potential therapeutic target for UC, emphasizing its importance as a potential key target in UC and unveiling its role in inflammation regulation.

Statistical power of transcriptome-wide association studies.

Transcriptome-Wide Association Studies (TWASs) have become increasingly popular in identifying genes (or other endophenotypes or exposures) associated with complex traits. In TWAS, one first builds a predictive model for gene expressions using an expression quantitative trait loci (eQTL) data set in stage 1, then tests the association between the predicted gene expression and a trait based on a large, independent genome-wide association study (GWAS) data set in stage 2. However, since the sample size of the eQTL data set is usually small and the coefficient of multiple determination (i.e., R 2 ${R}^{2}$ ) of the model for many genes is also small, a question of interest is to what extent these factors affect the statistical power of TWAS. In addition, in contrast to a standard (univariate) TWAS (UV-TWAS) considering only a single gene at a time, multivariate TWAS (MV-TWAS) methods have recently emerged to account for the effects of multiple genes, or a gene's nonlinear effects, simultaneously. With the absence of the power analysis for these MV-TWAS methods, it would be of interest to investigate whether one can gain or lose power by using the newly proposed MV-TWAS instead of UV-TWAS. In this paper, we first outline a general method for sample size/power calculations for two-sample TWAS, then use real data-the Alzheimer's Disease Neuroimaging Initiative (ADNI) expression quantitative trait loci (eQTL) data and the Genotype-Tissue Expression (GTEx) eQTL data for stage 1, the International Genomics of Alzheimer's Project Alzheimer's disease (AD) GWAS summary data and UK Biobank (UKB) individual-level data for stage 2-to empirically address these questions. Our most important conclusions are the following. First, a sample size of a few thousands (~8000) would suffice in stage 1, where the power of TWAS would be more determined by cis-heritability of gene expression. Second, as in the general case of simple regression versus multiple regression, the power of MV-TWAS may be higher or lower than that of UV-TWAS, depending on the specific relationships among the GWAS trait and multiple genes (or linear and nonlinear terms of the same gene's expression levels), such as their correlations and effect sizes. Interestingly, several top genes with large power gains in MV-TWAS (over that in UV-TWAS) were known to be (and in our data more significantly) associated with AD. We also reached similar conclusions in an application to the GTEx whole blood gene expression data and UKB GWAS data of high-density lipoprotein cholesterol. The proposed method and the conclusions are expected to be useful in planning and designing future TWAS and other related studies (e.g., Proteome- or Metabolome-Wide Association Studies) when determining the sample sizes for the two stages.

Regulation of Mitochondrial Function by Natural Products for the Treatment of Metabolic Associated Fatty Liver Disease.

Metabolic associated fatty liver disease (MAFLD) is a multifactorial systemic disorder that occurs in the absence of excessive alcohol consumption. The disease is characterized by fatty degeneration and fat accumulation in liver parenchymal cells, the incidence of which is increasing annually, particularly in younger adults. MAFLD is caused by genetic and metabolism related disorders, of which mitochondrial dysfunction is the major contributor. Natural products can relieve MAFLD through restoring mitochondrial function. In this article, we describe the relationship between mitochondria and MAFLD and discuss the beneficial effects of natural products as a future anti-MAFLD strategy. Significance Statement. We herein propose that the development of mitochondrial regulators/nutrients from natural products can remedy mitochondrial dysfunction which represents an attractive strategy for the treatment of MAFLD. Furthermore, the mitochondrial regulation of natural products can provide new insight into the underlying mechanisms of action of natural products used for future MAFLD therapeutics.

Structural optimization towards promising ß-methyl-4-acrylamido quinoline derivatives as PI3K/mTOR dual inhibitors for anti-cancer therapy: The in vitro and in vivo biological evaluation.

Built upon the 4-acrylamido quinoline derivative 4, a previously discovered PI3K/mTOR dual inhibitor, structural modification was undertaken in this study with the attempt to improve its oral exposure via introducing steric hindrance to the 4-acrylamido functionality. Consequently, 14d, as the representative among the synthesized compounds, exhibited IC50 values of 0.80, 0.67, 1.30, 1.30 and 5.0 nM against PI3Kα, PI3Kß, PI3Kγ, PI3Kδ and mTOR, respectively. Besides, 14d displayed comparable anti-proliferative activity against both PC3 and U87MG cell lines to that of the positive reference GSK2126458 with respective GI50 value of 0.36 and 0.14 µM. Kinase selectivity assay showed that 14d was selective to PI3K family. In U87MG cells, 14d can strongly down-regulate PI3K/Akt/mTOR pathway via blocking both PI3K and mTOR signaling at the concentration as low as 25 nM. Importantly, following a PO dose of 5 mg/kg in male SD rats, 14d displayed favorable oral exposure (AUC0-t = 1336.16 h × ng/mL, AUC0-∞ = 1447.63 h × ng/mL) and high maximum plasma concentration (Cmax = 903.00 ng/mL). In a U87MG glioblastoma xenograft model, tumor growth inhibition of 93.5% and tumor regression were observed at PO dose of 30 and 60 mg/kg, respectively. Meanwhile, no overt loss of body weight was observed in the 14d-treated groups. Taken together, 14d, by virtue of its attractive performance, merits further development as a potential anti-tumor candidate.

Optimization of piperidine constructed peptidyl derivatives as proteasome inhibitors.

A series of non-covalent piperidine-containing peptidyl derivatives with various substituents at side chains of different residues were designed, synthesized and evaluated as proteasome inhibitors. After proteasome inhibitory evaluations of all the synthesized target compounds, selected ones were tested for their anti-proliferation activities against three multiple myeloma (MM) cell lines. 8 analogues displayed more potent activities than carfilzomib, and the most promising compound 24 showed IC50 values of 0.8 ± 0.2 nM against 20S proteasome and 8.42 ± 0.74 nM, 7.14 ± 0.52 nM, 14.20 ± 1.08 nM for RPMI 8226, NCI-H929 and MM.1S cell lines, respectively. Additionally, mechanisms of anti-cancer activity of representative compound 24 were further investigated. Apoptosis of RPMI-8226 cells were achieved through accumulating polyubiquitin and inducing the cleavage of caspase and PARP. Besides, half-life in rat plasma of compound 24 was prolonged after optimization, which would be helpful for increasing in vivo activities of this series of derivatives. All the studies confirmed that piperidine-containing non-covalent proteasome inhibitors can be potential leads for anti-MM drug development.

Proteasome, a Promising Therapeutic Target for Multiple Diseases Beyond Cancer.

Proteasome is vital for intracellular protein homeostasis as it eliminates misfolded and damaged protein. Inhibition of proteasome has been validated as a powerful strategy for anti-cancer therapy, and several drugs have been approved for treatment of multiple myeloma. Recent studies indicate that proteasome has potent therapeutic effects on a variety of diseases besides cancer, including parasite infectious diseases, bacterial/fungal infections diseases, neurodegenerative diseases and autoimmune diseases. In this review, recent developments of proteasome inhibitors for various diseases and related structure activity relationships are going to be summarized.

Preparation, evaluation, and in vitro cytotoxicity studies of artesunate-loaded glycyrrhetinic acid decorated PEG-PLGA nanoparticles.

OBJECTIVE: The objective of this study was to prepare the liver targeting drug delivery system (TDDS) of artesunate (ART)-loaded polyethylene glycol (PEG)-poly(d,l-lactic-co-glycolic) acid (PLGA) nanoparticles (NPs) modified by glycyrrhetinic acid (GA), and evaluate its in vitro cytotoxicity. SIGNIFICANCE: The GA-PEG-PLGA-ART NPs enhanced the in vitro cytotoxicity on HCC cell lines. The development of GA-PEG-PLGA NPs will greatly push the clinical applications of ART as a novel anticancer drug. METHODS: The NPs were prepared using solvent evaporation method, and the formulation was optimized through an orthogonal design. In addition, physical properties were determined, including particle size, polydispersity index (PDI), zeta potential (ZP), morphology, drug loading capacity (LC) and encapsulation efficiency (EE), and in vitro drug release. Moreover, the in vitro cytotoxicity of NPs with three human cancer cell lines viz. HepG2, Hep3B, and SMCC-7721 was conducted using the SRB assay. Additionally, lyophilization was conducted to improve the long-term physical stability. RESULTS: The GA-PEG-PLGA-ART NPs have spherical shape, small particle size (around 88 nm) with a narrow size distribution (PDI < 0.3), high drug LC (up to 59.3 ± 1.65%), and high EE (up to 73.13 ± 5.17%). In vitro drug release behavior showed that drugs were released from NPs in a sustained and controlled release pattern. Cytotoxicity study indicated the NPs achieved lower cancer cell survival fraction. The GA-PEG-PLGA NPs freeze-dried with 3% (w/v) of mannitol showed better effect on long-term physical stability. CONCLUSION: The GA-PEG-PLGA-ART NPs appear as a potential liver targeted intracellular delivery platform for ART.

Protective effect of apigenin magnesium complex on H2O2-induced oxidative stress and inflammatory responses in rat hepatic stellate cells.

Context: Apigenin displays antioxidant and anti-inflammatory effects. However, effects of apigenin magnesium (AM) complex on these aspects remain unknown.Objective: This study investigated the effects of AM complex on oxidative stress and inflammatory responses in hydrogen peroxide (H2O2)-induced rat hepatic stellate cells (HSCs).Materials and methods: The antioxidant and anti-inflammatory effects of AM complex at concentrations of 0.625, 1.25, and 2.5 mg/mL were evaluated, comparing to HSCs treated by H2O2 alone. Cell viability, reactive oxygen species (ROS), the activity of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), nitric oxide (NO), interleukin 6 (IL-6), and nuclear factor-kappa B (NF-κB) levels were measured. Moreover, cell apoptosis, mRNA expression levels of transforming growth factor-ß (TGF-ß), NF-κB, and inducible nitric oxide synthase (iNOS) were assessed.Results: AM complex significantly inhibited oxidative stress and inflammatory response at concentrations of 0.625, 1.25, and 2.5 mg/mL (IC50 = 1.679 mg/mL). AM complex elevated the survival rate of H2O2-treated HSCs and had no toxic effects on HSCs. AM complex also promoted SOD activity and GSH levels but suppressed ROS, MDA, and NO levels. Additionally, AM complex decreased IL-6 and NF-κB levels, gene expression of TGF-ß, NF-κB, and iNOS, as well as induced apoptosis of HSCs.Discussion and conclusions: Data indicated that AM complex mitigated oxidative stress and inflammatory responses on H2O2-treated HSCs, suggesting that AM complex is a possible candidate for anti-hepatic diseases. Additional efforts, both in vivo and in humans, are required to assess of AM complex as a potential therapeutic drug in liver diseases.

Immunoproteasome-selective inhibitors: An overview of recent developments as potential drugs for hematologic malignancies and autoimmune diseases.

The immunoproteasome, a specialized form of proteasome, is mainly expressed in lymphocytes and monocytes of jawed vertebrates and responsible for the generation of antigenic peptides for cell-mediated immunity. Overexpression of immunoproteasome have been detected in a wide range of diseases including malignancies, autoimmune and inflammatory diseases. Following the successful approval of constitutive proteasome inhibitors bortezomib, carfilzomib and Ixazomib, and with the clarification of immunoproteasome crystal structure and functions, a variety of immunoproteasome inhibitors were discovered or rationally developed. Not only the inhibitory activities, the selectivities for immunoproteasome over constitutive proteasome are essential for the clinical potential of these analogues, which has been validated by the clinical evaluation of immunoproteasome-selective inhibitor KZR-616 for the treatment of systemic lupus erythematosus. In this review, structure, function as well as the current developments of various inhibitors against immunoproteasome are going to be summarized, which help to fully understand the target for drug discovery.

Design, synthesis, and biological evaluation of novel 3-(thiophen-2-ylthio)pyridine derivatives as potential multitarget anticancer agents.

A series of novel 3-(thiophen-2-ylthio)pyridine derivatives as insulin-like growth factor 1 receptor (IGF-1R) inhibitors was designed and synthesized. IGF-1R kinase inhibitory activities and cytotoxicities against HepG2 and WSU-DLCL2 cell lines were tested. For all of these compounds, potent cancer cell proliferation inhibitory activities were observed, but not through the inhibition of IGR-1R. Selected compounds were further screened against various kinases. Typical compound 22 (50% inhibitory concentration [IC50 ] values, HepG2: 2.98 ± 1.11 µM and WSU-DLCL2: 4.34 ± 0.84 µM) exhibited good inhibitory activities against fibroblast growth factor receptor-2 (FGFR2), FGFR3, epidermal growth factor receptor, Janus kinase, and RON (receptor originated from Nantes), with IC50 values ranging from 2.14 to 12.20 µM. Additionally, the cell-cycle analysis showed that compound 22 could arrest HepG2 cells in the G1/G0 phase. Taken together, all the experiments confirmed that the compounds in this series were multitarget anticancer agents worth further optimizing.

Canonical Wnt Signaling Remodels Lipid Metabolism in Zebrafish Hepatocytes following Ras Oncogenic Insult.

There is limited understanding of the effects of major oncogenic pathways and their combinatorial actions on lipid composition and transformation during hepatic tumorigenesis. Here, we report a negative correlation of Wnt/Myc activity with steatosis in human hepatocellular carcinoma (HCC) and perform in vivo functional studies using three conditional transgenic zebrafish models. Double-transgenic zebrafish larvae conditionally expressing human CTNNB1mt and zebrafish tcf7l2 or murine Myc together with krasv12 in hepatocytes led to severe hepatomegaly and significantly attenuated accumulation of lipid droplets and cell senescence triggered by krasv12 expression alone. UPLC-MS-based, nontargeted lipidomic profiling and transcriptome analyses revealed that Wnt/Myc activity promotes triacylglycerol to phospholipid transformation and increases unsaturated fatty acyl groups in phospholipids in a Ras-dependent manner. Small-scale screenings suggested that supplementation of certain free fatty acids (FA) or inhibition of FA desaturation significantly represses hepatic hyperplasia of double-transgenic larvae and proliferation of three human HCC cells with and without sorafenib. Together, our studies reveal novel Ras-dependent functions of Wnt signaling in remodeling the lipid metabolism of cancerous hepatocytes in zebrafish and identify the SCD inhibitor MK8245 as a candidate drug for therapeutic intervention.Significance: These findings identify FA desaturation as a significant downstream therapeutic target for antagonizing the combinatorial effects of Wnt and Ras signaling pathways in hepatocellular carcinoma.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/19/5548/F1.large.jpg Cancer Res; 78(19); 5548-60. ©2018 AACR.

Microsphere Assisted Super-resolution Optical Imaging of Plasmonic Interaction between Gold Nanoparticles.

Conventional far-field microscopy cannot directly resolve the sub-diffraction spatial distribution of localized surface plasmons in metal nanostructures. Using BaTiO3 microspheres as far-field superlenses by collecting the near-field signal, we can map the origin of enhanced two-photon photoluminescence signal from the gap region of gold nanosphere dimers and gold nanorod dimers beyond the diffraction limit, on a conventional far-field microscope. As the angle θ between dimer's structural axis and laser polarisation changes, photoluminescence intensity varies with a cos4θ function, which agrees quantitatively with numerical simulations. An optical resolution of about λ/7 (λ: two-photon luminescence central wavelength) is demonstrated at dimer's gap region.

Imaging Laser-Triggered Drug Release from Gold Nanocages with Transient Absorption Lifetime Microscopy.

Nanoparticles have shown promise in loading and delivering drugs for targeted therapy. Many progresses have been made in the design, synthesis, and modification of nanoparticles to fulfill such goals. However, realizing targeted intracellular delivery and controlled release of drugs remains challenging, partly because of the lack of reliable tools to detect the drug-releasing process. In this paper, we applied femtosecond laser pulses to trigger the explosion of gold nanocages (AuNCs) and control the intracellular release of loaded aluminum phthalocyanine (AlPcS) molecules for photodynamic therapy (PDT). AuNCs were found to enhance the encapsulation efficiency and suppress the PDT effect of AlPcS molecules until they were released. More importantly, we discovered that the excited-state lifetimes of the AlPcS-AuNC conjugate (∼3 ps) and free AlPcS (∼11 ps) differ significantly, which was utilized to image the released drug molecules using transient absorption lifetime microscopy with the same laser source. This technique extracts information similar to fluorescence lifetime imaging microscopy but is superior in imaging the molecules that hardly fluoresce or are prone to photobleaching. We further combined a dual-phase lock-in detection technique to show the potential of real-time imaging based on the change in transient optical behaviors. Our method may provide a new tool for investigating nanoparticle-assisted drug delivery and release.