Analysis of Poration-Induced Changes in Cells from Laser-Activated Plasmonic Substrates

Saklayen N, Kalies S, Madrid M, Nuzzo V, Huber M, Shen W, Sinanan-Singh J, Heinemann D, Heisterkamp A, and Mazur E
Laser-exposed plasmonic substrates permeabilize the plasma membrane of cells when in close contact to deliver cell-impermeable cargo. While studies have determined the cargo delivery efficiency and viability of laser-exposed plasmonic substrates, morphological changes in a cell have not been quantified. We porated myoblast C2C12 cells on a plasmonic pyramid array using a 532-nm laser with 850-ps pulse length and time-lapse fluorescence imaging to quantify cellular changes. We obtain a poration efficiency of 80%, viability of 90%, and a pore radius of 20 nm. We quantified area changes in the plasma membrane attached to the substrate (10% decrease), nucleus (5 - 10% decrease), and cytoplasm (5 - 10% decrease) over 1 h after laser treatment. Cytoskeleton fibers show a change of 50% in the alignment, or coherency, of fibers, which stabilizes after 10 mins. We investigate structural and morphological changes due to the poration process to enable the safe development of this technique for therapeutic applications.

Automated Interpretation of Blood Culture Gram Stains Using a Deep Convolutional Neural Network

Smith KP, Kang AD, and Kirby JE
Microscopic interpretation of stained smears is one of the most operator-dependent and time intensive activities in the clinical microbiology laboratory. Here, we investigated application of an automated image acquisition and convolutional neural network (CNN)-based approach for automated Gram stain classification. Using an automated microscopy platform, uncoverslipped slides were scanned with a 40x dry objective, generating images of sufficient resolution for interpretation. We collected 25,488 images from positive blood culture Gram stains prepared during routine clinical workup. These images were used to generate 100,213 crops containing Gram-positive cocci in clusters, Gram-positive cocci in chains/pairs, Gram-negative rods, or background (no cells). These categories were targeted for proof-of-concept development as they are associated with the majority of bloodstream infections. Our CNN model achieved classification accuracy of 94.9% on a test set of image crops. Receiver operating characteristic curve (ROC) analysis indicated a robust ability to differentiate between categories with area under the curve >0.98 for each. After training and validation, we applied the classification algorithm to new images collected from 189 whole slides without human intervention. Sensitivity/specificity was 98.4/75.0% for Gram-positive cocci in chains/pairs; 93.2/97.2% for Gram-positive cocci in clusters; and 96.3/98.1% for Gram-negative rods. Taken together, our data support proof-of-concept for a fully automated classification methodology for blood-culture Gram-stains. Importantly, the algorithm was highly adept at identifying image crops with organisms and could be used to present prescreened, classified crops to technologists to accelerate smear review. This concept could potentially be extended to all Gram stain interpretive activities in the clinical laboratory.

Combined Noninvasive Metabolic and Spindle Imaging as Potential Tools for Embryo and Oocyte Assessment

Tim Sanchez, Marta Venturas, S. Ali Aghvami, Xingbo Yang, Seth Fraden, Denny Sakkas, and Daniel J. Needleman.
Study question: Is the combined use of fluorescence lifetime imaging microscopy (FLIM)-based metabolic imaging and second harmonic generation (SHG) spindle imaging a feasible and safe approach for noninvasive embryo assessment?

Summary answer: Metabolic imaging can sensitively detect meaningful metabolic changes in embryos, SHG produces high-quality images of spindles and the methods do not significantly impair embryo viability.

What is known already: Proper metabolism is essential for embryo viability. Metabolic imaging is a well-tested method for measuring metabolism of cells and tissues, but it is unclear if it is sensitive enough and safe enough for use in embryo assessment.

Study design, size, duration: This study consisted of time-course experiments and control versus treatment experiments. We monitored the metabolism of 25 mouse oocytes with a noninvasive metabolic imaging system while exposing them to oxamate (cytoplasmic lactate dehydrogenase inhibitor) and rotenone (mitochondrial oxidative phosphorylation inhibitor) in series. Mouse embryos (n = 39) were measured every 2 h from the one-cell stage to blastocyst in order to characterize metabolic changes occurring during pre-implantation development. To assess the safety of FLIM illumination, n = 144 illuminated embryos were implanted into n = 12 mice, and n = 108 nonilluminated embryos were implanted into n = 9 mice.

Participants/materials, setting, methods: Experiments were performed in mouse embryos and oocytes. Samples were monitored with noninvasive, FLIM-based metabolic imaging of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) autofluorescence. Between NADH cytoplasm, NADH mitochondria and FAD mitochondria, a single metabolic measurement produces up to 12 quantitative parameters for characterizing the metabolic state of an embryo. For safety experiments, live birth rates and pup weights (mean ± SEM) were used as endpoints. For all test conditions, the level of significance was set at P < 0.05.

Main results and the role of chance: Measured FLIM parameters were highly sensitive to metabolic changes due to both metabolic perturbations and embryo development. For oocytes, metabolic parameter values were compared before and after exposure to oxamate and rotenone. The metabolic measurements provided a basis for complete separation of the data sets. For embryos, metabolic parameter values were compared between the first division and morula stages, morula and blastocyst and first division and blastocyst. The metabolic measurements again completely separated the data sets. Exposure of embryos to excessive illumination dosages (24 measurements) had no significant effect on live birth rate (5.1 ± 0.94 pups/mouse for illuminated group; 5.7 ± 1.74 pups/mouse for control group) or pup weights (1.88 ± 0.10 g for illuminated group; 1.89 ± 0.11 g for control group).

Limitations, reasons for caution: The study was performed using a mouse model, so conclusions concerning sensitivity and safety may not generalize to human embryos. A limitation of the live birth data is also that although cages were routinely monitored, we could not preclude that some runt pups may have been eaten.

Wider implications of the findings: Promising proof-of-concept results demonstrate that FLIM with SHG provide detailed biological information that may be valuable for the assessment of embryo and oocyte quality. Live birth experiments support the method's safety, arguing for further studies of the clinical utility of these techniques.

Development of MAST: A Microscopy-Based Antimicrobial Susceptibility Testing Platform

Smith KP, Richmond DL, Brennan-Krohn T, Elliott HL, and Kirby JE
Antibiotic resistance is compromising our ability to treat bacterial infections. Clinical microbiology laboratories guide appropriate treatment through antimicrobial susceptibility testing (AST) of patient bacterial isolates. However, increasingly, pathogens are developing resistance to a broad range of antimicrobials, requiring AST of alternative agents for which no commercially available testing methods are available. Therefore, there exists a significant AST testing gap in which current methodologies cannot adequately address the need for rapid results in the face of unpredictable susceptibility profiles. To address this gap, we developed a multicomponent, microscopy-based AST (MAST) platform capable of AST determinations after only a 2 h incubation. MAST consists of a solid-phase microwell growth surface in a 384-well plate format, inkjet printing-based application of both antimicrobials and bacteria at any desired concentrations, automated microscopic imaging of bacterial replication, and a deep learning approach for automated image classification and determination of antimicrobial minimal inhibitory concentrations (MICs). In evaluating a susceptible strain set, 95.8% were within ±1 and 99.4% were within ±2, twofold dilutions, respectively, of reference broth microdilution MIC values. Most (98.3%) of the results were in categorical agreement. We conclude that MAST offers promise for rapid, accurate, and flexible AST to help address the antimicrobial testing gap.

EM Fields Comparison Between Planar vs. Solenoidal µMS Coil Designs for Nerve Stimulation

Giorgio Bonmassar and Laleh Golestanirad
Micro-magnetic stimulation (μMS) is an emerging neurostimulation technology that promises to revolutionize the therapeutic stimulation of the human nervous system. μMS uses sub-millimeter sized coils that can be implemented in the central nervous system to elicit neuronal activation using magnetically induced electric currents. By their microscopic size, μMS coils can be acutely implanted in deep brain structures to deliver therapeutic stimulation with effects analogous to those achieved by state-of-the-art deep brain stimulation (DBS). However, μMS technology has inherent advantages that make it particularly appealing for clinical applications. Specifically, μMS induces a focal electric current in the tissue, limiting the extent of activation to a few hundred microns. We recently demonstrated the feasibility of using μMS to elicit neuronal activation in vitro [1], as well as the possibility of activating neuronal circuitry on the system level in rodents [2]. As μMS is a novel technology, its mechanism(s) of nerve activation, induced field characteristics, and optimum topological features are yet to be explored. In this regard, numerical simulations play a crucially important role, because they provide an insight into spatial distribution of induced electric fields, which in turn, dictate the dynamics of nerve stimulation. Here we report results of numerical simulations to predict the nerve-stimulation performance of different μMS geometries.

Engineering a 3D-Bioprinted Model of Human Heart Valve Disease Using Nanoindentation-Based Biomechanics

Dewy C van der Valk, Casper FT van der Vem, Mark C Blaser, Joshua M Grolman, Pin-Jou Wu, Owen S Fenton, Lang H Lee, Mark W Tibbitt, Jason L Andresen, Jennifer R Wen, Anna H Ha, Fabrizio Buffolo, Alain van Mil, Carlijn VC Bouten, Simon C Body, David J Mooney, Joost PG Sluijter, Masanori Aikawa, Jesper Hjortnaes, Robert Langer, and Elena Aikawa
In calcific aortic valve disease (CAVD), microcalcifications originating from nanoscale calcifying vesicles disrupt the aortic valve (AV) leaflets, which consist of three (biomechanically) distinct layers: the fibrosa, spongiosa, and ventricularis. CAVD has no pharmacotherapy and lacks in vitro models as a result of complex valvular biomechanical features surrounding resident mechanosensitive valvular interstitial cells (VICs). We measured layer-specific mechanical properties of the human AV and engineered a three-dimensional (3D)-bioprinted CAVD model that recapitulates leaflet layer biomechanics for the first time. Human AV leaflet layers were separated by microdissection, and nanoindentation determined layer-specific Young’s moduli. Methacrylated gelatin (GelMA)/methacrylated hyaluronic acid (HAMA) hydrogels were tuned to duplicate layer-specific mechanical characteristics, followed by 3D-printing with encapsulated human VICs. Hydrogels were exposed to osteogenic media (OM) to induce microcalcification, and VIC pathogenesis was assessed by near infrared or immunofluorescence microscopy. Median Young’s moduli of the AV layers were 37.1, 15.4, and 26.9 kPa (fibrosa/spongiosa/ventricularis, respectively). The fibrosa and spongiosa Young’s moduli matched the 3D 5% GelMa/1% HAMA UV-crosslinked hydrogels. OM stimulation of VIC-laden bioprinted hydrogels induced microcalcification without apoptosis. We report the first layer-specific measurements of human AV moduli and a novel 3D-bioprinted CAVD model that potentiates microcalcification by mimicking the native AV mechanical environment. This work sheds light on valvular mechanobiology and could facilitate high-throughput drug-screening in CAVD.

In Vitro 3D Model and miRNA Drug Delivery to Target Calcific Aortic Valve Disease

Van der ven CF, Wu PJ, Tibbitt MW, Mil van A, Sluijter JP, Langer R, and Elena Aikawa
Calcific aortic valve disease (CAVD) is the most prevalent valvular heart disease in the Western population, claiming 17000 deaths per year in the United States and affecting 25% of people older than 65 years of age. Contrary to traditional belief, CAVD is not a passive, degenerative disease but rather a dynamic disease, where initial cellular changes in the valve leaflets progress into fibrotic lesions that induce valve thickening and calcification. Advanced thickening and calcification impair valve function and lead to aortic stenosis (AS). Without intervention, progressive ventricular hypertrophy ensues, which ultimately results in heart failure and death. Currently, aortic valve replacement (AVR), surgical or transcatheter, is the only effective therapy to treat CAVD. However, these costly interventions are often delayed until the late stages of the disease. Nonetheless, 275000 are performed per year worldwide, and this is expected to triple by 2050. Given the current landscape, next-generation therapies for CAVD are needed to improve patient outcome and quality of life. Here, we first provide a background on the aortic valve (AV) and the pathobiology of CAVD as well as highlight current directions and future outlook on the development of functional 3D models of CAVD in vitro We then consider an often-overlooked aspect contributing to CAVD: miRNA (mis)regulation. Therapeutics could potentially normalize miRNA levels in the early stages of the disease and may slow its progression or even reverse calcification. We close with a discussion of strategies that would enable the use of miRNA as a therapeutic for CAVD. This focuses on an overview of controlled delivery technologies for nucleic acid therapeutics to the valve or other target tissues.

Intracellular Delivery Using Nanosecond-Laser Excitation of Large-Area Plasmonic Substrates

Saklayen N, Huber M, Madrid M, Nuzzo V, Vulis DI, Shen W, Nelson J, McClelland AA, Heisterkamp A, and Mazur E.
Efficiently delivering functional cargo to millions of cells on the time scale of minutes will revolutionize gene therapy, drug discovery, and high-throughput screening. Recent studies of intracellular delivery with thermoplasmonic structured surfaces show promising results but in most cases require time- or cost-intensive fabrication or lead to unreproducible surfaces. We designed and fabricated large-area (14 × 14 mm), photolithography-based, template-stripped plasmonic substrates that are nanosecond laser-activated to form transient pores in cells for cargo entry. We optimized fabrication to produce plasmonic structures that are ultrasmooth and precisely patterned over large areas. We used flow cytometry to characterize the delivery efficiency of cargos ranging in size from 0.6 to 2000 kDa to cells (up to 95% for the smallest molecule) and viability of cells (up to 98%). This technique offers a throughput of 50000 cells/min, which can be scaled up as necessary. This technique is also cost-effective as each large-area photolithography substrate can be used to deliver cargo to millions of cells, and switching to a nanosecond laser makes the setup cheaper and easier to use. The approach we present offers additional desirable features: spatial selectivity, reproducibility, minimal residual fragments, and cost-effective fabrication. This research supports the development of safer genetic and viral disease therapies as well as research tools for fundamental biological research that rely on effectively delivering molecules to millions of living cells.