Smartphone-based multicolor bioluminescent 3D spheroid biosensors for monitoring inflammatory activity

Whole-cell biosensors present many advantages, including being able to monitor the toxicity and bioavailability of chemicals; cells grown in traditional 2D cultures, however, do not reproduce the complexity of in vivo physiology. In the last years, 3D cell-culture models have garnered great attention due to their capability to better mimic in vivo cellular responses to external stimuli, providing excellent model living organisms. In order to obtain a predictive, sensitive, and robust yet low-cost 3D cell biosensor, we developed a smartphone-based bioluminescent 3D cell biosensor platform for effect-based analysis. We exploited the Nuclear Factor-kappa B (NF-kB) signal transduction pathway, which is induced by several types of stressors and is involved in the regulation of cell-cycle/growth, inflammation, apoptosis, and immunity. The smartphone-based biosensor relies on immobilized HEK293 spheroids genetically engineered with powerful red- and green-emitting luciferases utilized as inflammation and viability reporters. It provides a limit of detection for Tumor Necrosis Factor (TNF\u3b1) of 0.15\u202f\ub1\u202f0.05\u202fng/mL and could be a useful tool to initially screen environmental samples or other compounds on-site, especially for additional more accurate chemical analyses

Representative Landscapes in the Forested Area of Canada

Canada is a large nation with forested ecosystems that occupy over 60% of the national land base, and knowledge of the patterns of Canada’s land cover is important to proper environmental management of this vast resource. To this end, a circa 2000 Landsat-derived land cover map of the forested ecosystems of Canada has created a new window into understanding the composition and configuration of land cover patterns in forested Canada. Strategies for summarizing such large expanses of land cover are increasingly important, as land managers work to study and preserve distinctive areas, as well as to identify representative examples of current land-cover and land-use assemblages. Meanwhile, the development of extremely efficient clustering algorithms has become increasingly important in the world of computer science, in which billions of pieces of information on the internet are continually sifted for meaning for a vast variety of applications. One recently developed clustering algorithm quickly groups large numbers of items of any type in a given data set while simultaneously selecting a representative—or “exemplar”—from each cluster. In this context, the availability of both advanced data processing methods and a nationally available set of landscape metrics presents an opportunity to identify sets of representative landscapes to better understand landscape pattern, variation, and distribution across the forested area of Canada. In this research, we first identify and provide context for a small, interpretable set of exemplar landscapes that objectively represent land cover in each of Canada’s ten forested ecozones. Then, we demonstrate how this approach can be used to identify flagship and satellite long-term study areas inside and outside protected areas in the province of Ontario. These applications aid our understanding of Canada’s forest while augmenting its management toolbox, and may signal a broad range of applications for this versatile approach

Bioluminescence Imaging of Spheroids for High‐throughput Longitudinal Studies on 3D Cell Culture Models

Bioluminescent (BL) cell-based assays based on two-dimensional (2D) monolayer cell cultures represent well-established bioanalytical tools for preclinical screening of drugs. However, cells in 2D cultures do not often reflect the morphology and functionality of living organisms, thus limiting the predictive value of 2D cell-based assays. Conversely, 3D cell models have the capability to generate the extracellular matrix and restore cell-to-cell communications; thus, they are the most suitable model to mimic in vivo physiology. In this work, we developed a nondestructive real-time BL imaging assay of spheroids for longitudinal studies on 3D cell models. A high-throughput BL 3D cell-based assay in micropatterned 96-well plate format is reported. The assay performance was assessed using the transcriptional regulation of nuclear factor K beta response element in human embryonic kidney (HEK293) cells. We compared concentration–response curves for tumor necrosis factor-α with those obtained using conventional 2D cell cultures. One of the main advantages of this approach is the nonlysing nature of the assay, which allows for repetitive measurements on the same sample. The assay can be implemented in any laboratory equipped with basic cell culture facilities and paves the way to the development of new 3D bioluminescent cell-based assays

A Firefly Luciferase Dual Color Bioluminescence Reporter Assay Using Two Substrates To Simultaneously Monitor Two Gene Expression Events

Abstract Effective methods for monitoring eukaryotic gene expression and regulation based on bioluminescence - the emission of light by living organisms - are well established. Typically, the expression of a gene of interest is reported on with high sensitivity and over a wide dynamic range by the emission of light from a variety of engineered luciferase genes from beetles and marine organisms. The luciferase reporter genes are expressed downstream of the target gene or promoter and detected after exogenous addition of luciferin substrates. We describe a novel bioluminescence reporter method for the simultaneous monitoring of two genes expressing engineered firefly luciferase variants that emit readily distinguishable green and red light signals. The key feature is the selectivity of the enzymes for two luciferin substrates that determine each emission color. To validate our method, we performed a complex promoter transactivation experiment side-by-side with the Dual-Luciferase Reporter protocol and obtained essentially identical results. Additional comparative experiments demonstrated that our assay system provided improvements in background, cell normalization, and detectability compared to representative available methods. With access to a luminometer equipped with two optical filters, this method is an excellent choice for genetic reporter assays that can be performed with a single reagent solution

Bioluminescence Imaging of Spheroids for High-throughput Longitudinal Studies on 3D Cell Culture Models

none7siBioluminescent (BL) cell-based assays based on two-dimensional (2D) monolayer cell cultures represent well-established bioanalytical tools for preclinical screening of drugs. However, cells in 2D cultures do not often reflect the morphology and functionality of living organisms, thus limiting the predictive value of 2D cell-based assays. Conversely, 3D cell models have the capability to generate the extracellular matrix and restore cell-to-cell communications; thus, they are the most suitable model to mimic in vivo physiology. In this work, we developed a nondestructive real-time BL imaging assay of spheroids for longitudinal studies on 3D cell models. A high-throughput BL 3D cell-based assay in micropatterned 96-well plate format is reported. The assay performance was assessed using the transcriptional regulation of nuclear factor K beta response element in human embryonic kidney (HEK293) cells. We compared concentration–response curves for tumor necrosis factor-α with those obtained using conventional 2D cell cultures. One of the main advantages of this approach is the nonlysing nature of the assay, which allows for repetitive measurements on the same sample. The assay can be implemented in any laboratory equipped with basic cell culture facilities and paves the way to the development of new 3D bioluminescent cell-based assays.mixedCevenini, Luca; Calabretta, Maria M.; Lopreside, Antonia; Branchini, Bruce R.; Southworth, Tara L.; Michelini, Elisa; Roda, AldoCevenini, Luca; Calabretta, Maria M.; Lopreside, Antonia; Branchini, Bruce R.; Southworth, Tara L.; Michelini, Elisa; Roda, Ald

Red-emitting luciferases for bioluminescence reporter and imaging applications

North American firefly Photinus pyralis luciferase, which emits yellow-green light (557 nm), has been adapted for a variety of applications, including gene reporter assays. whole-cell biosensor measurements, and in vivo imaging. Luciferase variants with red-shifted bioluminescence and high specific activity can be paired with green-emitting counterparts for use in dual-color reporter assays or can be used alone for in vivo imaging. Beginning with a previously reported red-emitting thermostable mutant and using mutagenesis techniques, we engineered two luciferases with redder emission maxima while maintaining satisfactory specific activities and thermostability. The novel enzymes were expressed in HEK293 cells, where they performed similarly to Promega's codon-optimized click beetle red luciferase in model reporter assays. When the firefly luciferase variants were codon-optimized and retested using optimized substrate concentrations, they provided 50- to 100-fold greater integrated light intensities than the click beetle enzyme. These results suggest that the novel enzymes should provide superior performance in dual-color reporter and in vivo imaging applications, and they illustrate the importance of codon optimization for assays in mammalian cells. (C) 2009 Elsevier Inc. All rights reserved

An enhanced chimeric firefly luciferase-inspired enzyme for ATP detection and bioluminescence reporter and imaging applications

Firefly luciferases, which emit visible light in a highly specific ATP-dependent process, have been adapted for a variety of applications, including gene reporter assays, whole-cell biosensor measurements, and in vivo imaging. We previously reported the approximately 2-fold enhanced activity and 1.4-fold greater bioluminescence quantum yield properties of a chimeric enzyme that contains the N-domain of Photinus pyralis luciferase joined to the C-domain of Luciola italica luciferase. Subsequently, we identified 5 amino acid changes based on L. italica that are the main determinants of the improved bioluminescence properties. Further engineering to enhance thermal and pH stability produced a novel luciferase called PLG2. We present here a systematic comparison of the spectral and physical properties of the new protein with P. pyralis luciferase and demonstrate the potential of PLG2 for use in assays based on the detection of femtomole levels of ATP. In addition, we compared the performance of a mammalian codon-optimized version of the cDNA for PLG2 with the luc2 gene in HEK293T cells. Using an optimized low-cost assay system, PLG2 activity can be monitored in mammalian cell lysates and living cells with 4.4-fold and approximately 3.0-fold greater sensitivity, respectively. PLG2 could be an improved alternative to Promega's luc2 for reporter and imaging applications

Crystal Structure of Firefly Luciferase in a Second Catalytic Conformation Supports a Domain Alternation Mechanism

Beetle luciferases catalyze a two-step reaction that includes the initial adenylation of the luciferin substrate, followed by an oxidative decarboxylation that ultimately produces light. Evidence for homologous acyl-CoA synthetases supports a domain alternation catalytic mechanism in which these enzymes’ C-terminal domain rotates by ∼140° to adopt two conformations that are used to catalyze the two partial reactions. While many structures exist of acyl-CoA synthetases in both conformations, to date only biochemical evidence supports domain alternation with luciferase. We have determined the structure of a cross-linked luciferase enzyme that is trapped in the second conformation. This new structure supports the role of the second catalytic conformation and provides insights into the biochemical mechanism of the luciferase oxidative step

Pr\ueat-\ue0-porter nanoYES\u3b1 and nanoYES\u3b2 bioluminescent cell biosensors for ultrarapid and sensitive screening of endocrine-disrupting chemicals

Cell-based assays utilizing reporter gene technology have been widely exploited for biosensing, as they provide useful information about the bioavailability and cell toxicity of target analytes. The long assay time due to gene transcription and translation is one of the main drawbacks of cell biosensors. We report the development of two yeast biosensors stably expressing human estrogen receptors \u3b1 and \u3b2 and employing NanoLuc as the reporter protein to upgrade the widely used yeast estrogen screening (YES) assays. A viability control strain was also developed based on a chimeric green-emitting luciferase, PLG2, expressed for the first time in Saccharomycescerevisiae. Thanks to their brightness, NanoLuc and PLG2 provided excellent sensitivity, enabling the implementation of these biosensors into low-cost smartphone-based devices. The developed biosensors had a rapid (1 h) response and reported on (anti)estrogenic activity via human estrogen receptors \u3b1 and \u3b2 as well as general sample toxicity. Under optimized conditions, we obtained LODs of 7.1\u2009\ub1\u20090.4 nM and 0.38\u2009\ub1\u20090.08 nM for E2 with nanoYES\u3b1 and nanoYES\u3b2, respectively. As a proof of concept, we analyzed real samples from plants showing significant estrogenic activity or known to contain significant amounts of phytoestrogens. Graphical abstract