Fluorescent Protein Research Articles

Imaging Neural Activity in Intact, Semirestrained Drosophila Larvae.

The Drosophila larval nerve cord, which is the equivalent of the vertebrate spinal cord, houses the circuits required to process somatosensory stimuli (e.g., tactile, temperature, vibration, and self-movement) and generate the patterned muscle contractions underlying movement and behavior. Within this complex structure reside many cell types and cellular processes, making it difficult to experimentally access, when compared to peripheral parts of the nervous system (i.e., primary sensory neuron dendrites, motor neuron axons and synapses, and muscles). Additionally, the neurons in the larval nerve cord have small cell bodies, precluding traditional electrophysiological approaches. As such, the function of neurons in the nerve cord is less well studied than other parts of the nervous system, severely limiting our understanding of how larvae process sensory information and generate movement. Ca2+-sensitive fluorescent proteins enable the study of neuronal activity in live, genetically tractable animals, even those with small neuronal cell bodies. In addition, live imaging of neurons within the nerve cord in whole, intact animals is possible because larvae are translucent, and the use of intact animals allows for the peripheral sensory neuron circuits to remain intact. Ca2+-sensitive fluorescent proteins increase their fluorescence when voltage-gated Ca2+ channels are opened in depolarized neurons. Here, we describe an assay where a Ca2+-sensitive fluorescent protein (GCaMP6m) is expressed under the control of a GAL4 driver in a subset of neurons that reside in a circuit for vibration sensation. External vibration (sound) stimulates sensory neurons that activate the cells expressing the Ca2+-sensitive fluorescent protein. Visualization of the calcium-induced fluorescent signal with microscopy allows for quantification of neuronal activity.

Light-triggered protease-mediated release of actin-bound cargo from synthetic cells.

Synthetic cells offer a versatile platform for addressing biomedical and environmental challenges, due to their modular design and capability to mimic cellular processes such as biosensing, intercellular communication, and metabolism. Constructing synthetic cells capable of stimuli-responsive secretion is vital for applications in targeted drug delivery and biosensor development. Previous attempts at engineering secretion for synthetic cells have been confined to non-specific cargo release via membrane pores, limiting the spatiotemporal precision and specificity necessary for selective secretion. Here, we designed and constructed a protein-based platform termed TEV Protease-mediated Releasable Actin-binding protein (TRAP) for selective, rapid, and triggerable secretion in synthetic cells. TRAP is designed to bind tightly to reconstituted actin networks and is proteolytically released from bound actin, followed by secretion via cell-penetrating peptide membrane translocation. We demonstrated TRAP's efficacy in facilitating light-activated secretion of both fluorescent and luminescent proteins. By equipping synthetic cells with a controlled secretion mechanism, TRAP paves the way for the development of stimuli-responsive biomaterials, versatile synthetic cell-based biosensing systems, and therapeutic applications through the integration of synthetic cells with living cells for targeted delivery of protein therapeutics.

Abstract A069: Development of an AAV-mediated GEM model to investigate the impact of age on pancreatic tumorigenesis

Abstract Much of our understanding of PDAC initiation comes from Genetically Engineered Mouse (GEM) models where a pancreas-specific Cre (such as Pdx- or p48-Cre) drives expression of specific mutations. While these GEM models generally recapitulate the key histopathological features of human PDAC, they have limitations when it comes to studying the impact of age on PDAC initiation since the Cre drivers induce recombination at the embryonic stage. This is an important consideration since in humans the disease manifests later in life, with the median age at diagnosis being 70 years old. Here, we describe the development of an intrapancreatic injection model using adeno-associated virus (AAV) to study how age influences PDAC initiation and the dynamics of tumor progression. This new viral transduction-based mouse model employs AAV-Cre to induce expression of an oncogenic KRasG12D allele together with a Trp53R172H tumor suppressor mutation within the pancreata of mice at different ages. Our approach utilizes mice with the genotype LSL-KrasG12D; LSL-Trp53R172H that are injected with different AAV-Cre directly into the parenchyma of the pancreas. In our initial studies, we used rAAV vectors expressing Cre recombinase and EGFP (AAV-Cre-EGFP) into young mice (10-14 weeks old) and older mice (32 weeks old) and analyzed EGFP expression using IVIS imaging and immunohistochemistry (IHC) at various timepoints post-injection. To evaluate tumor initiation, we assessed the extent of PanIN lesion formation using H&E staining. Our preliminary findings indicate that AAV-Cre-EGFP effectively transduces cells in vivo and triggers tumor development in the pancreas. To account for potential immunogenicity of the fluorescent protein, we then used rAAV vectors lacking EGFP expression. As controls, we administered identical rAAV vectors to wild-type cohorts matched for age and sex, along with mock injections. Transduction efficiency within the pancreas was determined by evaluating Cre and p53 expression levels, given that the R172H mutation stabilizes the protein. Notably, we found that EGFP is not necessary for either successful transduction or tumor initiation. We are currently evaluating PDAC initiation using a wide spectrum of ages, but our preliminary data using this model suggest that increased age may impact tumor progression, and that this effect may be sex-specific. Our novel AAV-Cre injection model holds promise for investigating age-related aspects of PDAC initiation, and in the future, such approaches could be leveraged to investigate how age impacts the effectiveness of different therapeutic modalities. Citation Format: Karen XD Duong-Polk, Madelaine Neff, Cosimo Commisso. Development of an AAV-mediated GEM model to investigate the impact of age on pancreatic tumorigenesis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A069.

Gene Therapy in the Light of Lifestyle Diseases: Budesonide, Acetaminophen and Simvastatin Modulates rAAV Transduction Efficiency.

Recombinant AAV (rAAV) vectors are increasingly favored for gene therapy due to their useful features of vectorology, such as transfection of dividing and nondividing cells, the presence of tissue-specific serotypes, and biosafety considerations. This study investigates the impact of commonly used therapeutic drugs-acetaminophen, budesonide, and simvastatin-on rAAV transduction efficiency in HEK-293 cells. Cells were transduced with an AAV mosaic vector under the control of a cytomegalovirus (CMV) promoter encoding green fluorescent protein (GFP). Transduction efficiency was assessed by qPCR and fluorescent microscopy. Analysis of functional interactions between genes potentially involved in rAAV transduction in drug-exposed cells was also performed. This study showed a clear effect of drugs on rAAV transmission. Notably, acetaminophen enhanced transduction efficiency by 9-fold, while budesonide and simvastatin showed 2-fold and 3-fold increases, respectively. The gene analysis illustrates the possible involvement of genes related to cell membranes in the potentiation of rAAV transduction induced by the drugs under investigation. Attention should be paid to S100A8, which is a common drug-modified gene for drugs showing anti-inflammatory effects (budesonide and simvastatin), demonstrating an interaction with the gene encoding the receptor for AAV (HGFR). This study underscores the significance of assessing rAAV pharmacokinetics/pharmacodynamics (PKs/PDs) and drug-gene therapy interactions in optimizing gene therapy protocols.

Venezuelan equine encephalitis virus non-structural protein 3 dictates superinfection exclusion in mammalian cells

Superinfection exclusion (SIE) prevents secondary infections of already infected cells. Arthritogenic alphaviruses induce SIE via early proteolytical cleavage of replicase precursor by non-structural protein 2 (nsP2). Here, we explore the SIE mechanism of the encephalitic Venezuelan equine encephalitis virus (VEEV). Using single-cell imaging techniques and VEEV replicons encoding green or red fluorescent proteins, we observed full SIE capacity in three hours. Transient expression of VEEV nsP3, but not nsP2, reduced alphavirus replication, suggesting a key role for VEEV nsP3 in the SIE mechanism. In particular, the VEEV nsP3 C-terminal hypervariable domain (HVD) was found to be required and sufficient for the SIE of VEEV and the more distantly related Sindbis virus. As the nsP3 HVD is known to bind multiple host proteins to form RNA replication complexes and modulate the cellular stress response, we propose that sequestering essential host protein(s) by VEEV nsP3 interferes with RNA replication of the superinfecting alphavirus.

Tuning the surface charge and colloidal stability of hybrid gold-chitosan derivative nanoparticles for siRNA delivery

In recent years, the therapeutic potential of small interfering RNA (siRNA) has been confirmed by the emergence of commercially available siRNA-based drugs and by advances in the clinical trials phase. However, the many biological barriers faced by siRNA up to its delivery to the intended target make the advances in siRNA therapies highly dependent on the use of efficient gene vectors. In this study, the design of a new nanoparticle structured with a gold core and a diisopropylethylamine-chitosan shell was devised for application as a siRNA carrier. Thiol functionalized diisopropylethylamine-chitosan polymers were grafted onto gold nanoparticles (AuNPs) to obtain pH-responsive hybrid siRNA carriers (AuNP@polymers). The precise control of the diisopropylethylamine (DIPEA) graft and the tuning of the amount of polymer linked to the AuNPs enabled the assembly of hybrid carriers with good colloidal stability in physiological ionic strength (150 mmol L−1), sizes between 50 and 100 nm and positive zeta potentials (up to +17 mV), over a wide range of pH (5.5–7.4). The coated AuNPs were able to bind siRNA at N/P ratios in the range of 5–20, providing protection for the siRNA against RNAse degradation and making the hybrid vectors structurally and colloidally stable even in a protein-supplemented medium. The AuNP@polymers nanocarriers displayed non-cytotoxic effects in both 3T3/NIH fibroblast and HeLa-GFP cells up to an N/P ratio of 20 and the uptake of AuNP@polymers by RAW 264.7 macrophages was similar to Lipofectamine™ RNAiMAX. The zeta potential of the hybrid vectors was accurately adjusted by controlling the DIPEA graft and the pH of the formulation medium, which in turn drove the silencing efficiency of the siRNA nanocarrier as observed by the green fluorescent protein (GFP) knockdowns in HeLa cells. GFP knockdown levels close to that of Lipofectamine (up to 70 %) were achieved for the vectors formulated at pH 5.5. Overall, the results showed that the DIPEA-chitosan/AuNP association is a promising strategy to formulate hybrid nanocarriers for siRNA delivery with potential for in vivo studies.

Differential interference with actin-binding protein function by acute Cytochalasin B.

Dynamic actin filament remodeling is crucial for a plethora of fundamental cell biological processes, ranging from cell division and migration to cell communication, intracellular trafficking or tissue development. Cytochalasin B and -D are fungal secondary metabolites frequently used for interference with such processes. Although generally assumed to block actin filament polymerization at their rapidly growing barbed ends and compete with regulators at these sites, our molecular understanding of their precise effects in dynamic actin structures is scarce. Here we combine live cell imaging and analysis of fluorescent actin-binding protein dynamics with acute treatment of lamellipodia in migrating cells with cytochalasin B. Our results show that in spite of an abrupt halt of lamellipodium protrusion, cytochalasin B affects various actin filament barbed end-binding proteins in a differential fashion. Cytochalasin B enhances instead of diminishes the accumulation of prominent barbed end-binding factors such as Ena/VASP family proteins and heterodimeric capping protein (CP) in the lamellipodium. Similar results were obtained with cytochalasin D. All these effects are highly specific, as cytochalasin-induced VASP accumulation requires the presence of CP, but not vice versa , and coincides with abrogation of both actin and VASP turnover. Cytochalasin B can also increase apparent barbed end interactions with the actin-binding β-tentacle of CP and partially mimic its Arp2/3 complex-promoting activity in the lamellipodium. In conclusion, our results reveal a new spectrum of cytochalasin activities on barbed end-binding factors, with important implications for the interpretation of their effects on dynamic actin structures.

A Novel Method for Separating Full and Empty Adeno-Associated Viral Capsids Using Ultrafiltration.

Adeno-associated viral vectors (AAVs) are the predominant viral vectors used for gene therapy applications. A significant challenge in obtaining effective doses is removing non-therapeutic empty viral capsids lacking DNA cargo. Current methods for separating full (gene-containing) and empty capsids are challenging to scale, produce low product yields, are slow, and are difficult to operationalize for continuous biomanufacturing. This communication demonstrates the feasibility of separating full and empty capsids by ultrafiltration. Separation performance was quantified by measuring the sieving coefficients for full and empty capsids using ELISA, qPCR, and an infectivity assay based on the live cell imaging of green fluorescent protein expression. We demonstrated that polycarbonate track-etched membranes with a pore size of 30 nm selectively permeated empty capsids to full capsids, with a high recovery yield (89%) for full capsids. The average sieving coefficients of full and empty capsids obtained through ELISA/qPCR were calculated as 0.25 and 0.49, indicating that empty capsids were about twice as permeable as full capsids. Establishing ultrafiltration as a viable unit operation for separating full and empty AAV capsids has implications for developing the scale-free continuous purification of AAVs.

A Novel Transgenic Sf9 Cell Line for Quick and Easy Virus Quantification.

The following study was conducted to generate a transgenic Sf9 cell line for rapid and easy virus quantification in the baculovirus expression system (BES). The hr3 (homologous region 3) and 39K and p10 promoters were used as the expression structures to induce rapid and intense expression of the enhanced green fluorescent protein gene in cells in response to viral infection. Of 20 transgenic Sf9 cell lines generated using the piggyBac system, the cell line that showed the highest fluorescence expression in the shortest time in response to viral infection was selected and named Sf9-QE. The average diameter of the Sf9-QE cells was around 16 μm, which is 2 μm smaller than the average diameter of Sf9 cells, whereas the rate of cell proliferation was around 1.6 times higher in the Sf9-QE cells. Virus quantification using the Sf9-QE cell line did not produce significantly different results compared to the other cell lines; however, the time required for complete virus quantification was approximately 5.3 to 6.0 days for the Sf9-QE cells, which is around 4 to 6 days shorter than the time required for the other cell lines, enabling convenient and accurate virus quantification via fluorescence photometry within around 6.0 to 6.3 days. The properties of the Sf9-QE cells were stable for up to at least 100 passages.

Generation of a fluorescent mNeonGreen insulin reporter line in the H1 (WA01) hESC background

Over the past decade, the use of human stem cell-derived β cells (SC-β cells) to model pancreatic β cell development, function and disease has become increasingly common. Though protocols are rapidly improving, current directed differentiation strategies do not yield a pure population of insulin-positive SC-β cells in vitro. Therefore, it is experimentally advantageous to have reporter lines that allow for live sorting of insulin-positive populations. To aid in these studies, we have knocked mNeonGreen fluorescent protein into the endogenous insulin locus of the commonly used H1 (WA01) human embryonic stem cell line.

Remarkable Insensitivity of Protein Diffusion to Protein Charge.

Friction to translational diffusion of ionic particles in polar liquids should scale linearly with the squared ion charge, according to standard theories. Substantial slowing of translational diffusion is expected for proteins in water. In contrast, our simulations of charge mutants of green fluorescent proteins in water show remarkable insensitivity of the translational diffusion constant to protein's charge in the range of charges between -29 and +35. The friction coefficient is given as a product of the force variance and the memory function relaxation time. We find remarkably accurate equality between the variance of the electrostatic force and the negative cross-correlation of the electrostatic and van der Waals forces. The charge invariance of the diffusion constant is a combined effect of the force variance and relaxation time invariances with the protein charge. The temperature dependence of the protein diffusion constant is highly non-Arrhenius, with a fragile-to-strong crossover at the glass transition.

Smooth muscle cells clonally expand in a murine carotid allograft model complicated by immune reactions to reporter transgenes

Background and aimsMost experimental studies of allograft vasculopathy (AV) have relied on transplantation between major histocompatibility complex-mismatched inbred mouse strains, but this leads to the complete eradication of donor smooth muscle cells (SMCs) and lesions formed by recipient cells. This is unlike human AV which is thought to form mainly by donor SMCs. Here, we studied sources of neointimal cells in a minor histocompatibility antigen-mismatched AV model by combining male-to-female orthotopic carotid transplantations and lineage tracing by SMC-specific expression of fluorescent proteins. MethodsTo track SMC-derived cells in allograft vasculopathy, we used male donor mice with SMC-restricted Cre recombination of the mT/mG reporter transgene, which switches expression of membrane-bound red fluorescent protein (RFP) to green fluorescent protein (GFP), or the stochastically recombining Confetti reporter transgene, which yields a mosaic expression of four fluorescent proteins. Donor carotid segments were harvested and orthotopically allografted to female recipients that were wildtype or had non-recombined reporter transgenes. Inhibition of T cell responses by CTLA4Ig was used in some experiments. Sections of lesions harvested after 4 weeks were analyzed by fluorescence microscopy. ResultsDonor-derived SMCs survived and gave rise to part of the neointimal cells in experiments where carotid segments from recombined mT/mG male mice were transplanted into wild-type or non-recombined mT/mG female mice. Sex-mismatched transplants developed significant lesions, increasing the intimal and medial area 4.6-fold (p = 0.038) and 2.0-fold (p = 0.024) compared to sex- and fluorescence-matched controls, respectively. Interestingly, sex-matched fluorescence-positive transplants developed intimal lesions in 50% of fluorescence-naïve recipient controls. To study the clonal structure of the neointimal donor-derived SMC lineage cells, we then transplanted male carotids with heterozygous or homozygous recombined Confetti transgenes into female recipients. These transplants developed lesions with few surviving donor SMCs, indicating that expression of the Confetti reporter increased rejection and donor-specific SMC death. Some of the few remaining donor SMCs underwent clonal expansion. CTLA4Ig administration at the time of surgery did not improve SMC survival in mT/mG or Confetti transplants. ConclusionMale-to-female transplant models feature donor-derived SMCs, some of which undergo clonal expansion, but immune rejection to fluorescence reporters appears to bias results in lineage tracing models. Overcoming these challenges with alternative reporter transgenes or tolerant recipients is necessary to study the mechanisms by which donor SMCs contribute to allograft vasculopathy.

Species-specific ribosomal RNA-FISH identifies interspecies cellular-material exchange, active-cell population dynamics and cellular localization of translation machinery in clostridial cultures and co-cultures.

Though dyes and fluorescent reporter proteins have played an essential role in identifying microbial species in co-cultures, we hypothesized that ribosomal RNA-fluorescence in situ hybridization (rRNA-FISH) could be adapted and applied to quantitatively probe complex interactions between organisms in synthetic consortia. Despite its maturity, several challenges existed before rRNA-FISH could be used to study Clostridium co-cultures of interest. First, species-specific probes for Clostridium acetobutylicum and Clostridium ljungdahlii had not been developed. Second, "state-of-the-art" labeling protocols were tedious and often resulted in sample loss. Third, it was unclear if FISH was compatible with existing fluorescent reporter proteins. We resolved these key challenges and applied the technique to co-cultures of C. acetobutylicum, C. ljungdahlii, and Clostridium kluyveri. We demonstrate that rRNA-FISH is capable of identifying rRNA/ribosome exchange between the three organisms and characterized rRNA localization patterns in each. In combination with flow cytometry, rRNA-FISH can capture sub-population dynamics in co-cultures.

Dynamic Mitotic Localization of the Centrosomal Kinases CDK1, Plk, AurK, and Nek2 in Dictyostelium amoebae.

The centrosome of the amoebozoan model Dictyostelium discoideum provides the best-established model for an acentriolar centrosome outside the Opisthokonta. Dictyostelium exhibits an unusual centrosome cycle, in which duplication is initiated only at the G2/M transition and occurs entirely during the M phase. Little is known about the role of conserved centrosomal kinases in this process. Therefore, we have generated knock-in strains for Aurora (AurK), CDK1, cyclin B, Nek2, and Plk, replacing the endogenous genes with constructs expressing the respective green fluorescent Neon fusion proteins, driven by the endogenous promoters, and studied their behavior in living cells. Our results show that CDK1 and cyclin B arrive at the centrosome first, already during G2, followed by Plk, Nek2, and AurK. Furthermore, CDK1/cyclin B and AurK were dynamically localized at kinetochores, and AurK in addition at nucleoli. The putative roles of all four kinases in centrosome duplication, mitosis, cytokinesis, and nucleolar dynamics are discussed.

Heterogeneity in establishment of polyethylene glycol-mediated plasmid transformations for five forest pathogenic Phytophthora species.

Plasmid-mediated DNA transformation is a foundational molecular technique and the basis for most CRISPR-Cas9 gene editing systems. While plasmid transformations are well established for many agricultural Phytophthora pathogens, development of this technique in forest Phytophthoras is lacking. Given our long-term research objective to develop CRISPR-Cas9 gene editing in a forest pathogenic Phytophthora species, we sought to establish the functionality of polyethylene glycol (PEG)-mediated plasmid transformation in five species: P. cactorum, P. cinnamomi, P. cryptogea, P. ramorum, and P. syringae. We used the agricultural pathogen P. sojae, a species for which PEG-mediated transformations are well-established, as a transformation control. Using a protocol previously optimized for P. sojae, we tested transformations in the five forest Phytophthoras with three different plasmids: two developed for CRISPR-Cas9 gene editing and one developed for fluorescent protein tagging. Out of the five species tested, successful transformation, as indicated by stable growth of transformants on a high concentration of antibiotic selective growth medium and diagnostic PCR, was achieved only with P. cactorum and P. ramorum. However, while transformations in P. cactorum were consistent and stable, transformations in P. ramorum were highly variable and yielded transformants with very weak mycelial growth and abnormal morphology. Our results indicate that P. cactorum is the best candidate to move forward with CRISPR-Cas9 protocol development and provide insight for future optimization of plasmid transformations in forest Phytophthoras.

Sex-Specific ADNP/NAP (Davunetide) Regulation of Cocaine-Induced Plasticity

Cocaine use disorder (CUD) is a chronic neuropsychiatric disorder estimated to effect 1–3% of the population. Activity-dependent neuroprotective protein (ADNP) is essential for brain development and functioning, shown to be protective in fetal alcohol syndrome and to regulate alcohol consumption in adult mice. The goal of this study was to characterize the role of ADNP, and its active peptide NAP (NAPVSIPQ), which is also known as davunetide (investigational drug) in mediating cocaine-induced neuroadaptations. Real time PCR was used to test levels of Adnp and Adnp2 in the nucleus accumbens (NAc), ventral tegmental area (VTA), and dorsal hippocampus (DH) of cocaine-treated mice (15 mg/kg). Adnp heterozygous (Adnp+/−)and wild-type (Adnp+/−) mice were further tagged with excitatory neuronal membrane-expressing green fluorescent protein (GFP) that allowed for in vivo synaptic quantification. The mice were treated with cocaine (5 injections; 15 mg/kg once every other day) with or without NAP daily injections (0.4 µg/0.1 ml) and sacrificed following the last treatment. We analyzed hippocampal CA1 pyramidal cells from 3D confocal images using the Imaris x64.8.1.2 (Oxford Instruments) software to measure changes in dendritic spine density and morphology. In silico ADNP/NAP/cocaine structural modeling was performed as before. Cocaine decreased Adnp and Adnp2 expression 2 h after injection in the NAc and VTA of male mice, with mRNA levels returning to baseline levels after 24 h. Cocaine further reduced hippocampal spine density, particularly synaptically weaker immature thin and stubby spines, in male Adnp+/+) mice while increasing synaptically stronger mature (mushroom) spines in Adnp+/−) male mice and thin and stubby spines in females. Lastly, we showed that cocaine interacts with ADNP on a zinc finger domain identical to ketamine and adjacent to a NAP-zinc finger interaction site. Our results implicate ADNP in cocaine abuse, further placing the ADNP gene as a key regulator in neuropsychiatric disorders. Ketamine/cocaine and NAP treatment may be interchangeable to some degree, implicating an interaction with adjacent zinc finger motifs on ADNP and suggestive of a potential sex-dependent, non-addictive NAP treatment for CUD.

Self-Assembly of Silole-Based Aggregation-Induced Emission Compounds with Green Fluorescent Protein under Physiological Conditions for Traceable and Versatile Drug Delivery.

Biomacromolecules are viewed as promising drugs due to their specific functions in biological processes, biocompatibility, and pharmacological efficacy. Injective administration, chosen to avoid intestinal barriers, may in turn lead to immediate decay in the circulation system, unreliable targeting performance, or the induction of immune responses. For some biomacromolecules, chemically modified proteins have been developed for practical use. Various cargo or carrier systems are under development but have been delayed by technical difficulties. We present self-assembled nanocapsules with diameters ranging from 100 to 500 nm that can be deployed in physiological buffers to enclose various substances present in the buffers at the same time. Our amphiphilic nanocapsule, consisting of silole-core dendrimer products as the hydrophobic part and green fluorescent protein (GFP) derivatives as the hydrophilic part, connects and assembles spontaneously when mixed in solutions while engulfing dissolved or dispersed compounds together in a dose-dependent manner and shows unique optical characteristics because the dendrimer products exhibit aggregation-induced emission. Furthermore, the emission of the dendrimer causes considerable fluorescence resonance energy transfer (FRET) to GFP derivatives upon association. We could easily monitor assemblies by FRET states and particle sizes and have confirmed a stable presence in the buffer for at least a month. Further tracking of nanocapsules by fluorescence confirmed efficient uptake into some cancer cells. Nanocapsules based on GFP variants with or without a cell-surface-specific tag demonstrated that the tag improved the potential for specific targeted delivery. There were also indications that the nanocapsules became unstable after cellular uptake in the intracellular environment. We report here the simple preparation of traceable, stable, and biocompatible self-assembled nanocapsules as the basis for a versatile drug delivery system.

Temperature Sensitive PNIPAm-g-PEI/Gold Nanotriangle for Gene Delivery Promotion.

As a two-dimensional material, gold nanotriangles (GNTs) are rarely studied in the field of gene delivery. In this study, a temperature-responsive GNTs was developed as a novel carrier for gene delivery. The temperature-sensitive copolymer PNIPAm-g-PEI was grafted onto the surface of GNTs to construct a PNIPAm-g-PEI/GNTs composite controllable release platform. The lower critical solution temperature (LCST) of PNIPAm-g-PEI/GNTs was found to be 42°C, and the particle size of PNIPAm-g-PEI/GNTs was 150nm at this temperature. Gel electrophoresis experiments showed that PNIPAm-g-PEI/GNTs completely condensed DNA at 20μg/mL, and PNIPAm-g-PEI/GNTs promoted the release of DNA under laser irradiation. Luciferase and green fluorescent protein reporter gene assays demonstrated that the transfection efficiency of PNIPAm-g-PEI/GNTs was 1.5 and 7.2 times that of PEI, respectively. These results demonstrated the promising potential of temperature-responsive GNTs as effective and safe gene delivery vectors.

Testing the sensitivity of the medaka Transgenic Eleuthero-embryonic THYroid-Specific assay (TETHYS) to different mechanisms of action

There are many concerns about the impacts of Endocrine-Disrupting Chemicals on both wildlife and human populations. A plethora of chemicals have been shown to interfere with the Hypothalamic–Pituitary–Thyroid (HPT) axis in vertebrates. Disruption of the HPT axis is one of main endocrine criteria considered for the regulation of chemicals, along with the estrogen axis, androgen axis and steroidogenesis (EATS). In response to these concerns, the Organization for Economic Cooperation and Development (OECD) initiated the validation of test guidelines (TGs) covering the EATS modalities. Regarding thyroid activity and/or disruption assessment, three OECD TGs are validated, all of them using amphibians. To date, no OECD TGs based on fish are available for the detection of Thyroid Active Chemicals (TACs). To fill this gap, we developed a new test for the detection of TACs, the TETHYS assay (Transgenic Eleuthero-embryonic THYroid-Specific assay). This assay uses a medaka (Oryzias latipes) transgenic line Tg(tg:eGFP) expressing Green Fluorescent Protein in the thyroid follicles, under the control of the thyroglobulin promoter. This assay is performed at eleuthero-embryonic life-stages with an exposure length of 72 h. In the present study, the following reference chemicals with known thyroid hormone system mechanism of action have been tested: methimazole, sodium perchlorate, sodium tetrafluoroborate, diclofenac, iopanoic acid, sobetirome, NH-3 and 1–850. Except for the thyroid receptor antagonists, all chemicals tested were identified as thyroid active, modifying the total fluorescence and the size of the thyroid follicles. To investigate the test specificity, we tested three chemicals presumed to be inert on the HPT axis: cefuroxime, abamectin and 17α-ethinylestradiol. All were found to be inactive in the TETHYS assay. This promising New Approach Methodology can serve as a foundation for the development of a new OECD TG in the frame of regulatory assessment of chemicals for thyroid activity.

The use of thermostable fluorescent proteins for live imaging in Sulfolobus acidocaldarius.

Among hyperthermophilic organisms, in vivo protein localization is challenging due to the high growth temperatures that can disrupt proper folding and function of mostly mesophilic-derived fluorescent proteins. While protein localization in the thermophilic model archaeon S. acidocaldarius has been achieved using antibodies with fluorescent probes in fixed cells, the use of thermostable fluorescent proteins for live imaging in thermophilic archaea has so far been unsuccessful. Given the significance of live protein localization in the field of archaeal cell biology, we aimed to identify fluorescent proteins for use in S. acidocaldarius. We expressed various previously published and optimized thermostable fluorescent proteins along with fusion proteins of interest and analyzed the cells using flow cytometry and (thermo-) fluorescent microscopy. Of the tested proteins, thermal green protein (TGP) exhibited the brightest fluorescence when expressed in Sulfolobus cells. By optimizing the linker between TGP and a protein of interest, we could additionally successfully fuse proteins with minimal loss of fluorescence. TGP-CdvB and TGP-PCNA1 fusions displayed localization patterns consistent with previous immunolocalization experiments. These initial results in live protein localization in S. acidocaldarius at high temperatures, combined with recent advancements in thermomicroscopy, open new avenues in the field of archaeal cell biology. This progress finally enables localization experiments in thermophilic archaea, which have so far been limited to mesophilic organisms.