We gratefully acknowledge financial support for this project by the Volkswagen Stiftung (grant no. 89 883) and the European Research Council (grant agreement no. 694410 - AEDNA). M.S.-S. acknowledges support by the DFG through GRK 2062.

<ol>
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S., Bar-Ziv, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emergent+properties+of+dense+DNA+phases+toward+artificial+biosystems+on+a+surface.">Emergent properties of dense DNA phases toward artificial biosystems on a surface.</a> Accounts Of Chemical Research. 47 (6), 1912-1921 (2014).</li><li>Bracha, D., Bar-Ziv, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+and+nanowire+assemblies+of+condensed+DNA+polymer+brushes.">Dendritic and nanowire assemblies of condensed DNA polymer brushes.</a> Journal of the American Chemical Society. 136 (13), 4945-4953 (2014).</li><li>Daube, S. S., Bracha, D., Buxboim, A., Bar-Ziv, R. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Propagating+gene+expression+fronts+in+a+one-dimensional+coupled+system+of+artificial+cells.">Propagating gene expression fronts in a one-dimensional coupled system of artificial cells.</a> Nature Physics. 11 (12), 1037-1041 (2015).</li><li>Pardatscher, G., Schwarz-Schilling, M., Daube, S. S., Bar-Ziv, R. H., Simmel, F. 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The authors declare that they have no competing interests.

Bephore lithography is a robust and versatile technique for the patterned immobilization of DNA or RNA. Yet, the procedure includes several steps, which - if changed - may be a source for failure or reduced performance of the system.
A crucial step in the fabrication of Bephore chips is the PEGylation of the substrate, which provides the biocompatibility of the surface. Here, the cleaning step with an RCA procedure is important, since it also activates the surface for the subsequent silanizati...

Cell-free gene expression reactions are of great interest for various applications in biochemistry, biotechnology, and synthetic biology. Cell-free expression of proteins was instrumental for the preparation of pure protein samples, which were the basis for numerous studies in structural biology. For instance, cell-free systems were successfully used for the expression of protein complexes1 or membrane proteins2, which are difficult to produce using cell-based expression. Notably, cell-free gene expression reactions were also used to elucidate the structure of the genetic code, starting with the groundbreaking experiments by Nirenberg and Matthaei in 19613.
Recently, there has been a renewed interest in cell-free methods in biotechnology and synthetic biology4,5,6. Cell-free systems can be augmented with non-biological compounds, and components of diverse biological origin can be combined more easily7. Even though cell-free systems have the apparent disadvantage that they do not &#34;grow and divide&#34;, it is conceivable to prepare open cell-free bioreactors with basic metabolic functions and let them synthesize metabolites when provided with simple carbon and energy inputs8. Within the emerging field of synthetic biology, cell-free systems promise to be a more predictable &#34;chassis&#34; for the implementation of synthetic biological functions.
Currently, cell-free gene expression reactions are carried out either using cell extracts (from different sources such as bacteria, yeast, insects), or transcription/translation systems which were optimized for different applications (e.g., prokaryotic vs. eukaryotic gene expression, production of membrane proteins, etc.). A popular protocol for the preparation of bacterial cell extract (commonly termed TXTL) was provided recently by V. Noireaux and coworkers9. Its biophysical properties have been thoroughly characterized10, and the TXTL system has been already used successfully to perform a series of complex biochemical tasks: e.g., the assembly of functional bacteriophages via cell-free expression of the phage genome11, the synthesis of bacterial protein filaments12, or the implementation of cell-free gene circuits13,14.
Another system popular in cell-free synthetic biology is the PURE system, which is reconstituted from purified components15,16. Compared to the TXTL system, it does not contain nucleases or protein degradation machinery. While degradation of linear DNA, RNA molecules or proteins is less of an issue in the PURE system, decay pathways are actually important for the implementation of dynamical functions. In order to reduce the effect of exonuclease degradation of linear gene templates in the TXTL system (through RecBCD), the end-protecting GamS protein has to be added. Both the TXTL and the PURE system are commercially available.
A topic closely related to cell-free biology concerns the study of the effect of compartmentalization on biochemical reactions, and further the creation of artificial cell-like structures or protocells17,18,19,20. Research on artificial cells typically involves the encapsulation of a biochemical reaction system inside of vesicular compartments made from phospholipids or other amphiphiles. While such systems help to explore fundamental aspects of compartmentalization, or the emergence of cellularity and self-replicating structures, they face the typical problems of closed systems: in the absence of a functioning metabolism and appropriate membrane transport mechanisms, it is difficult to keep compartmentalized reactions running for extended periods of time - fuel molecules are used up and waste products accumulate.
An interesting alternative to compartmentalization inside of such cell-mimicking compartments is the spatial organization of genetic material using photolithographic methods. Immobilization of &#34;genes on a chip&#34; was pioneered by the Bar-Ziv group at the Weizmann Institute more than ten years ago21. Among the major issues that had to be resolved were the non-specific adsorption of DNA and the potential denaturation of proteins on the chip surface. Bar-Ziv et al. developed a dedicated photolithography resist termed &#34;Daisy&#34;, which was composed of a reactive terminal silane for immobilization of the resist molecules on silicon dioxide surfaces, a long polyethylene glycol (PEG) spacer that assured biocompatibility, and a photocleavable headgroup, which was converted into a reactive amine upon irradiation with ultraviolet (UV) light. It has been shown that Daisy can be used to immobilize gene-length DNA molecules (with lengths of several kilo base-pairs (kbp)) on a chip surface. From a polymer physics point of view, the systems represented polymer brushes grafted onto a solid substrate. Due to the polyelectrolyte nature of DNA, the conformation of these brushes is strongly affected by osmotic and other ion-specific effects22,23.
Most importantly, it has been shown that substrate-immobilized genes are still functional and can be transcribed and translated into RNA and protein. Gene brushes are accessible for RNA polymerases from solution24, and the complex macromolecular mixture of the transcription/translation is not denatured at the surface. One of the advantages of immobilization of genetic components on a substrate is that they can be operated in an open microfluidic reactor system that is continuously supplied with small precursor molecules and from which waste products can be removed25,26.
We recently developed a variant of this method termed Bephore (for Biocompatible electron-beam and photoresist)27, which was based exclusively on commercially available components and utilized sequence-specific DNA strand invasion reactions for the realization of a simple-to-implement multistep lithography procedure for the creation of chip-based artificial cells. A schematic overview of the procedure is shown in Figure 1. It is based on DNA hairpin molecules containing a photocleavable group, which are immobilized on a biocompatible PEG&#160;layer. Photocleavage of the hairpin exposes a single-stranded toehold sequence, through which DNA molecules of interest (containing the &#34;displacing&#34; DIS sequence) can be attached via toehold-mediated strand invasion.
While Bephore is potentially simpler to implement, Daisy allows the realization of very dense and clean &#34;gene brushes&#34;, which has advantages in certain applications. In principle, however, Daisy and Bephore lithography could be easily combined. A related lithography method utilizing DNA strand displacement for structuring DNA brushes on gold was previously developed by Huang et al., but was not utilized in the context of cell-free gene expression28,29.
In the following protocol we provide a detailed description of the production of DNA brushes for cell-free gene expression using the Bephore method. We describe how the gene chips are fabricated and demonstrate the use of multi-step photo-lithography for the spatially structured immobilization of genes on a chip. We also discuss the fabrication of reaction chambers and the application of microfluidics for the performance of on-chip gene expression reactions.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Silicon wafer with 50 nm silicon dioxide (Bephore substrate)</td>
			<td>Siegert Wafer</td>
			<td></td>
			<td>Thickness (&#181;m): 525 &#177;25, Diameter (mm): 100</td>
		</tr>
		<tr>
			<td>Silicon wafer (for PDMS master mold)</td>
			<td>Siegert Wafer</td>
			<td></td>
			<td>Thickness (&#181;m): 525 &#177;25, Diameter (mm): 76.2 (3&#8221;)</td>
		</tr>
		<tr>
			<td>Glass slides no. 4</td>
			<td>Menzel</td>
			<td></td>
			<td>22 mm x 50 mm</td>
		</tr>
		<tr>
			<td>Glass slides no. 1.5</td>
			<td>Assistent</td>
			<td></td>
			<td>24 mm x 24 mm</td>
		</tr>
		<tr>
			<td>Biotin-PEG-Silane</td>
			<td>Laysan Bio</td>
			<td></td>
			<td>MW 5,000</td>
		</tr>
		<tr>
			<td>Anhydrous toluene</td>
			<td>Sigma Aldrich (Merck)</td>
			<td>244511</td>
			<td></td>
		</tr>
		<tr>
			<td>Streptavidin</td>
			<td>Thermo-Fisher Scientific</td>
			<td>S888</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA</td>
			<td>Integrated DNA Technologies (IDT)</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phusion High-Fidelity PCR Master Mix with HF Buffer</td>
			<td>New England Biolabs</td>
			<td>M0531S</td>
			<td>PCR kit</td>
		</tr>
		<tr>
			<td>Wizard SV Gel and PCR Clean-Up System&#160;</td>
			<td>Promega</td>
			<td>A9281</td>
			<td>Spin-column PCR clean-up kit</td>
		</tr>
		<tr>
			<td>PURExpress</td>
			<td>New England Biolabs</td>
			<td>E6800S</td>
			<td>Cell-free expression system</td>
		</tr>
		<tr>
			<td>PDMS&#160;</td>
			<td>Dow Corning</td>
			<td>Slygard 184</td>
			<td></td>
		</tr>
		<tr>
			<td>FluoSpheres</td>
			<td>Thermo-Fisher Scientific</td>
			<td>F8771</td>
			<td></td>
		</tr>
		<tr>
			<td>PTFE tubing (ID: 0.8mm, OD: 1.6 mm)</td>
			<td>Bola</td>
			<td>S 1810-10</td>
			<td></td>
		</tr>
		<tr>
			<td>EpoCore 20</td>
			<td>micro resist technology&#160;GmbH</td>
			<td></td>
			<td>Photoresist</td>
		</tr>
		<tr>
			<td>mr-Dev 600</td>
			<td>micro resist technology&#160;GmbH</td>
			<td></td>
			<td>Photoresist developer</td>
		</tr>
		<tr>
			<td>Ti-Prime</td>
			<td>MicroChemicals</td>
			<td></td>
			<td>Adhesion promoter</td>
		</tr>
		<tr>
			<td>Two-component silicon glue</td>
			<td>Picodent</td>
			<td>Twinsil&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-protection yellow foil</td>
			<td>Lithoprotect (via MicroChemicals)</td>
			<td>Y520E212</td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Masks for photolithography</td>
			<td>Zitzmann GmbH</td>
			<td></td>
			<td>64.000 dpi, 180x240 mm</td>
		</tr>
		<tr>
			<td>Upright microscope</td>
			<td>Olympus</td>
			<td>BX51</td>
			<td>Photolithography and fluorescence imaging</td>
		</tr>
		<tr>
			<td>60x water immersion objective</td>
			<td>Olympus</td>
			<td>LumPlanFl</td>
			<td>Used with Olympus BX51, NA 0.9</td>
		</tr>
		<tr>
			<td>20x water immersion objective</td>
			<td>Olympus</td>
			<td>LumPlanFl</td>
			<td>Used with Olympus BX51, NA 0.5</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Photometrics</td>
			<td>Coolsnap HQ</td>
			<td>Used with Olympus BX51</td>
		</tr>
		<tr>
			<td>Ligtht source</td>
			<td>EXFO</td>
			<td>X-Cite 120Q</td>
			<td>Used with Olympus BX51</td>
		</tr>
		<tr>
			<td>Inverted microscope</td>
			<td>Nikon</td>
			<td>Ti2-E</td>
			<td>Fluorescence imaging of gene expression</td>
		</tr>
		<tr>
			<td>4x objective</td>
			<td>Nikon</td>
			<td>CFI P-Apo 4x Lambda</td>
			<td>Used with Nikon Ti2-E</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Andor</td>
			<td>Neo5.5</td>
			<td>Used with Nikon Ti2-E</td>
		</tr>
		<tr>
			<td>Light source</td>
			<td>Lumencor</td>
			<td>SOLA SM II</td>
			<td>Used with Nikon Ti2-E</td>
		</tr>
		<tr>
			<td>Cage incubator</td>
			<td>Okolab</td>
			<td>bold line</td>
			<td>Used with Nikon Ti2-E</td>
		</tr>
		<tr>
			<td>Pressure Controller</td>
			<td>Elveflow</td>
			<td>OB1 MK3</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoPhotometer</td>
			<td>Implen</td>
			<td></td>
			<td>DNA concentration measurement</td>
		</tr>
		<tr>
			<td>Plasma cleaner</td>
			<td>Diener</td>
			<td>Femto</td>
			<td>200 W, operated at 0.8 mbar with the sample in a Faraday cage</td>
		</tr>
	</tbody>
</table>

functional surface-immobilization of genes using multistep strand displacement lithography

Immobilization of genes on lithographically structured surfaces allows the study of compartmentalized gene expression processes in an open microfluidic bioreactor system. In contrast to other approaches towards artificial cellular systems, such a setup allows for a continuous supply with gene expression reagents and simultaneous draining of waste products. This facilitates the implementation of cell-free gene expression processes over extended periods of time, which is important for the realization of dynamic gene regulatory feedback systems. Here we provide a detailed protocol for the fabrication of genetic biochips using a simple-to-use lithographic technique based on DNA strand displacement reactions, which exclusively uses commercially available components. We also provide a protocol on the integration of compartmentalized genes with a polydimethylsiloxane (PDMS)-based microfluidic system. Furthermore, we show that the system is compatible with total internal reflection fluorescence (TIRF) microscopy, which can be used for the direct observation of molecular interactions between DNA and molecules contained in the expression mix.

Two-step lithography: Figure 5 shows the result of a two-step lithographic process on a glass slide with overlapping patterns of fluorescently labeled DIS strands.
Expression of a fluorescent protein from a gene brush: Figure 6 demonstrates the expression of the fluorescent protein YPet from immobilized DNA. At several points in time we assessed the gene expression rate...

Watch this Scientific Journal Video about Functional Surface-immobilization of Genes Using Multistep Strand Displacement Lithography at JoVE.com

Functional Surface-immobilization of Genes Using Multistep Strand Displacement Lithography

We describe a simple lithographic procedure for the immobilization of gene-length DNA molecules on a surface, which can be used to perform cell-free gene expression experiments on biochips.

Immobilization of genes on lithographically structured surfaces allows the study of compartmentalized gene expression processes in an open microfluidic ...

functional-surface-immobilization-genes-using-multistep-strand

Research

JoVE Journal

Bioengineering

7.4K Views.  Technical University of Munich. We describe a simple lithographic procedure for the immobilization of gene-length DNA molecules on a surface, which can be used to perform cell-free gene expression experiments on biochips.

Video: Functional Surface-immobilization of Genes Using Multistep Strand Displacement Lithography

Plasma Lithography Surface Patterning for Creation of Cell Networks

Systematic manipulation of a cell microenvironment with micro- and nanoscale resolution is often required for deciphering various cellular and molecular phenomena. To address this requirement, we have developed a plasma lithography technique to manipulate the cellular microenvironment by creating a patterned surface with feature sizes ranging from 100 nm to millimeters. The goal of this technique is to be able to study, in a controlled way, the behaviors of individual cells as well as groups of cells and their interactions.
This plasma lithography method is based on selective modification of the surface chemistry on a substrate by means of shielding the contact of low-temperature plasma with a physical mold. This selective shielding leaves a chemical pattern which can guide cell attachment and movement. This pattern, or surface template, can then be used to create networks of cells whose structure can mimic that found in nature and produces a controllable environment for experimental investigations. The technique is well suited to studying biological phenomenon as it produces stable surface patterns on transparent polymeric substrates in a biocompatible manner. The surface patterns last for weeks to months and can thus guide interaction with cells for long time periods which facilitates the study of long-term cellular processes, such as differentiation and adaption. The modification to the surface is primarily chemical in nature and thus does not introduce topographical or physical interference for interpretation of results. It also does not involve any harsh or toxic substances to achieve patterning and is compatible for tissue culture. Furthermore, it can be applied to modify various types of polymeric substrates, which due to the ability to tune their properties are ideal for and are widely used in biological applications. The resolution achievable is also beneficial, as isolation of specific processes such as migration, adhesion, or binding allows for discrete, clear observations at the single to multicell level.
This method has been employed to form diverse networks of different cell types for investigations involving migration, signaling, tissue formation, and the behavior and interactions of neurons arraigned in a network.

A versatile plasma lithography technique has been developed to generate stable surface patterns for guiding cellular attachment. This technique can be applied to create cell networks including those that mimic natural tissues and has been used for studying several, distinct cell types.

Systematic manipulation of a cell microenvironment with micro- and nanoscale resolution is often required for deciphering various cellular and molecular ...

Capillary Force Lithography for Cardiac Tissue Engineering

Cardiovascular disease remains the leading cause of death worldwide1. Cardiac tissue engineering holds much promise to deliver groundbreaking medical discoveries with the aims of developing functional tissues for cardiac regeneration as well as in vitro screening assays. However, the ability to create high-fidelity models of heart tissue has proven difficult. The heart&#8217;s extracellular matrix (ECM) is a complex structure consisting of both biochemical and biomechanical signals ranging from the micro- to the nanometer scale2. Local mechanical loading conditions and cell-ECM interactions have recently been recognized as vital components in cardiac tissue engineering3-5.
A large portion of the cardiac ECM is composed of aligned collagen fibers with nano-scale diameters that significantly influences tissue architecture and electromechanical coupling2. Unfortunately, few methods have been able to mimic the organization of ECM fibers down to the nanometer scale. Recent advancements in nanofabrication techniques, however, have enabled the design and fabrication of scalable scaffolds that mimic the in vivo structural and substrate stiffness cues of the ECM in the heart6-9.
Here we present the development of two reproducible, cost-effective, and scalable nanopatterning processes for the functional alignment of cardiac cells using the biocompatible polymer poly(lactide-co-glycolide) (PLGA)8 and a polyurethane (PU) based polymer. These anisotropically nanofabricated substrata (ANFS) mimic the underlying ECM of well-organized, aligned tissues and can be used to investigate the role of nanotopography on cell morphology and function10-14.
Using a nanopatterned (NP) silicon master as a template, a polyurethane acrylate (PUA) mold is fabricated. This PUA mold is then used to pattern the PU or PLGA hydrogel via UV-assisted or solvent-mediated capillary force lithography (CFL), respectively15,16. Briefly, PU or PLGA pre-polymer is drop dispensed onto a glass coverslip and the PUA mold is placed on top. For UV-assisted CFL, the PU is then exposed to UV radiation (&#955; = 250-400 nm) for curing. For solvent-mediated CFL, the PLGA is embossed using heat (120 &#176;C) and pressure (100 kPa). After curing, the PUA mold is peeled off, leaving behind an ANFS for cell culture. Primary cells, such as neonatal rat ventricular myocytes, as well as human pluripotent stem cell-derived cardiomyocytes, can be maintained on the ANFS2.

In this protocol, we demonstrate the fabrication of biomimetic cardiac cell culture substrata made from two distinct polymeric materials using capillary force lithography. The described methods provide a scalable, cost-effective technique to engineer the structure and function of macroscopic cardiac tissues for in vitro and in vivo applications.

Cardiovascular disease remains the leading cause of death worldwide1. Cardiac tissue engineering holds much promise to deliver groundbreaking medical ...

Generation of Aligned Functional Myocardial Tissue Through Microcontact Printing

Advanced heart failure represents a major unmet clinical challenge, arising from the loss of viable and/or fully functional cardiac muscle cells. Despite optimum drug therapy, heart failure represents a leading cause of mortality and morbidity in the developed world. A major challenge in drug development is the identification of cellular assays that accurately recapitulate normal and diseased human myocardial physiology in vitro. Likewise, the major challenges in regenerative cardiac biology revolve around the identification and isolation of patient-specific cardiac progenitors in clinically relevant quantities. These cells have to then be assembled into functional tissue that resembles the native heart tissue architecture. Microcontact printing allows for the creation of precise micropatterned protein shapes that resemble structural organization of the heart, thus providing geometric cues to control cell adhesion spatially. Herein we describe our approach for the isolation of highly purified myocardial cells from pluripotent stem cells differentiating in vitro, the generation of cell growth surfaces micropatterned with extracellular matrix proteins, and the assembly of the stem cell-derived cardiac muscle cells into anisotropic myocardial tissue.

The generation of aligned myocardial tissue is a key requirement for adapting the recent advances in stem cell biology to clinically useful purposes. Herein we describe a microcontact printing approach for the precise control of cell shape and function. Using highly purified populations of embryonic stem cell derived cardiac progenitors, we then generate anisotropic functional myocardial tissue.

Advanced heart failure represents a major unmet clinical challenge,  arising from the loss of viable and/or fully functional cardiac muscle  cells. ...

Robotic Mirror Therapy System for Functional Recovery of Hemiplegic Arms

Mirror therapy has been performed as effective occupational therapy in a clinical setting for functional recovery of a hemiplegic arm after stroke. It is conducted by eliciting an illusion through use of a mirror as if the hemiplegic arm is moving in real-time while moving the healthy arm. It can facilitate brain neuroplasticity through activation of the sensorimotor cortex. However, conventional mirror therapy has a critical limitation in that the hemiplegic arm is not actually moving. Thus, we developed a real-time 2-axis mirror robot system as a simple add-on module for conventional mirror therapy using a closed feedback mechanism, which enables real-time movement of the hemiplegic arm. We used 3 Attitude and Heading Reference System sensors, 2 brushless DC motors for elbow and wrist joints, and exoskeletal frames. In a feasibility study on 6 healthy subjects, robotic mirror therapy was safe and feasible. We further selected tasks useful for activities of daily living training through feedback from rehabilitation doctors. A chronic stroke patient showed improvement in the Fugl-Meyer assessment scale and elbow flexor spasticity after a 2-week application of the mirror robot system. Robotic mirror therapy may enhance proprioceptive input to the sensory cortex, which is considered to be important in neuroplasticity and functional recovery of hemiplegic arms. The mirror robot system presented herein can be easily developed and utilized effectively to advance occupational therapy.

We developed a real-time mirror robot system for functional recovery of hemiplegic arms using automatic control technology, conducted a clinical study on healthy subjects, and determined tasks through feedback from rehabilitation doctors. This simple mirror robot can be applied effectively to occupational therapy in stroke patients with a hemiplegic arm.

Mirror therapy has been performed as effective occupational therapy in a clinical setting for functional recovery of a hemiplegic arm after stroke. It is ...

Synthesis of Cationized Magnetoferritin for Ultra-fast Magnetization of Cells

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide nanoparticles (SPIONs). Achieving sufficient cellular uptake of SPIONs is a challenge that has traditionally been met by exposing cells to elevated concentrations of SPIONs or by prolonging exposure times (up to 72 hr). However, these strategies are likely to mediate toxicity. Here, we present the synthesis of the protein-based SPION magnetoferritin as well as a facile surface functionalization protocol that enables rapid cell magnetization using low exposure concentrations. The SPION core of magnetoferritin consists of cobalt-doped iron oxide with an average particle diameter of 8.2 nm mineralized inside the cavity of horse spleen apo-ferritin. Chemical cationization of magnetoferritin produced a novel, highly membrane-active SPION that magnetized human mesenchymal stem cells (hMSCs) using incubation times as short as one minute and iron concentrations as lows as 0.2 mM.

A protocol for the synthesis and cationization of cobalt-doped magnetoferritin is presented, as well as a method to rapidly magnetize stem cells with cationized magnetoferritin.

Many important biomedical applications, such as cell imaging and remote manipulation, can be achieved by labeling cells with superparamagnetic iron oxide ...

Development of an Electrochemical DNA Biosensor to Detect a Foodborne Pathogen

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, significantly affecting the rate of human mortality and morbidity. Conventional methods for the detection of V. parahaemolyticus such as culture-based methods, immunological assays, and molecular-based methods require complicated sample handling and are time-consuming, tedious, and costly. Recently, biosensors have proven to be a promising and comprehensive detection method with the advantages of fast detection, cost-effectiveness, and practicality. This research focuses on developing a rapid method of detecting V. parahaemolyticus with high selectivity and sensitivity using the principles of DNA hybridization. In the work, characterization of synthesized polylactic acid-stabilized gold nanoparticles (PLA-AuNPs) was achieved using X-ray Diffraction (XRD), Ultraviolet-visible Spectroscopy (UV-Vis), Transmission Electron Microscopy (TEM), Field-emission Scanning Electron Microscopy (FESEM), and Cyclic Voltammetry (CV). We also carried out further testing of stability, sensitivity, and reproducibility of the PLA-AuNPs. We found that the PLA-AuNPs formed a sound structure of stabilized nanoparticles in aqueous solution. We also observed that the sensitivity improved as a result of the smaller charge transfer resistance (Rct) value and an increase of active surface area (0.41 cm2). The development of our DNA biosensor was based on modification of a screen-printed carbon electrode (SPCE) with PLA-AuNPs and using methylene blue (MB) as the redox indicator. We assessed the immobilization and hybridization events by differential pulse voltammetry (DPV). We found that complementary, non-complementary, and mismatched oligonucleotides were specifically distinguished by the fabricated biosensor. It also showed reliably sensitive detection in cross-reactivity studies against various food-borne pathogens and in the identification of V. parahaemolyticus in fresh cockles.

A protocol for the development of an electrochemical DNA biosensor comprising a polylactic acid-stabilized, gold nanoparticles-modified, screen-printed carbon electrode to detect Vibrio parahaemolyticus is presented.

Vibrio parahaemolyticus (V. parahaemolyticus) is a common foodborne pathogen that contributes to a large proportion of public health problems globally, ...

Focused Ion Beam Lithography to Etch Nano-architectures into Microelectrodes

With advances in electronics and fabrication technology, intracortical microelectrodes have undergone substantial improvements enabling the production of sophisticated microelectrodes with greater resolution and expanded capabilities. The progress in fabrication technology has supported the development of biomimetic electrodes, which aim to seamlessly integrate into the brain parenchyma, reduce the neuroinflammatory response observed after electrode insertion and improve the quality and longevity of electrophysiological recordings. Here we describe a protocol to employ a biomimetic approach recently classified as nano-architecture. The use of focused ion beam lithography (FIB) was utilized in this protocol to etch specific nano-architecture features into the surface of non-functional and functional single shank intracortical microelectrodes. Etching nano-architectures into the electrode surface indicated possible improvements of biocompatibility and functionality of the implanted device. One of the benefits of using FIB is the ability to etch on manufactured devices, as opposed to during the fabrication of the device, facilitating boundless possibilities to modify numerous medical devices post-manufacturing. The protocol presented herein can be optimized for various material types, nano-architecture features, and types of devices. Augmenting the surface of implanted medical devices can improve the device performance and integration into the tissue.

We have shown that the etching of nano-architecture into intracortical microelectrode devices may reduce the inflammatory response and has the potential to improve electrophysiological recordings. The methods described herein outline an approach to etch nano-architectures into the surface of non-functional and functional single shank silicon intracortical microelectrodes.

With advances in electronics and fabrication technology, intracortical microelectrodes have undergone substantial improvements enabling the production of ...

Cerebral Blood Flow-Based Resting State Functional Connectivity of the Human Brain using Optical Diffuse Correlation Spectroscopy

To obtain a comprehensive understanding of the human brain, utilization of cerebral blood flow (CBF) as a source of contrast is desired because it is a key hemodynamic parameter related to cerebral oxygen supply. Resting state low frequency fluctuations based on oxygenation contrast have been shown to provide correlations between functionally connected regions. The presented protocol uses optical diffuse correlation spectroscopy (DCS) to assess blood flow-based resting state functional connectivity (RSFC) in the human brain. Results of CBF-based RSFC in human frontal cortex indicate that intra-regional RSFC is significantly higher in the left and right cortices compared to inter-regional RSFC in both cortices. This protocol should be of interest to researchers who employ multi-modal imaging techniques to study human brain function, especially in the pediatric population.

This protocol demonstrates how to measure resting state functional connectivity in the human prefrontal cortex using a custom-made diffuse correlation spectroscopy instrument. The report also discuss practical aspects of the experiment as well as detailed steps for analyzing the data.

To obtain a comprehensive understanding of the human brain, utilization of cerebral blood flow (CBF) as a source of contrast is desired because it is a ...

Generation and Quantitative Characterization of Functional and Polarized Biliary Epithelial Cysts

Cholangiocytes, the epithelial cells that line up the bile ducts in the liver, oversee bile formation and modification. In the last twenty years, in the context of liver diseases, 3-dimensional (3D) models based on cholangiocytes have emerged such as cysts, spheroids, or tube-like structures to mimic tissue topology for organogenesis, disease modeling, and drug screening studies. These structures have been mainly obtained by embedding cholangiocytes in a hydrogel. The main purpose was to study self-organization by addressing epithelial polarity, functional, and morphological properties. However, very few studies focus on cyst formation efficiency. When this is the case, the efficiency is often quantified from images of a single plane. Functional assays and structural analysis are performed without representing the potential heterogeneity of cyst distribution arising from hydrogel polymerization heterogeneities and side effects. Therefore, the quantitative analysis, when done, cannot be used for comparison from one article to another. Moreover, this methodology does not allow comparisons of 3D growth potential of different matrices and cell types. Additionally, there is no mention of the experimental troubleshooting for immunostaining cysts. In this article, we provide a reliable and universal method to show that the initial cell distribution is related to the heterogeneous vertical distribution of cyst formation. Cholangiocyte cells embedded in hydrogel are followed with Z-stacks analysis along the hydrogel depth over the time course of 10 days. With this method, a robust kinetics of cyst formation efficiency and growth is obtained. We also present methods to evaluate cyst polarity and secretory function. Finally, additional tips for optimizing immunostaining protocols are provided in order to limit cyst collapse for imaging. This approach can be applied to other 3D cell culture studies, thus opening the possibilities to compare one system to another.

Three-dimensional (3D) cellular systems are relevant models for investigating organogenesis. A hydrogel-based method for biliary cysts production and their characterization is proposed. This protocol unravels the barriers of 3D characterization, with a straightforward and reliable method to assess cyst formation efficiency, sizes, and to test their functionality.

Cholangiocytes, the epithelial cells that line up the bile ducts in the liver, oversee bile formation and modification. In the last twenty years, in the ...

Biomimetic Replication of Root Surface Microstructure using Alteration of Soft Lithography

Biomimetics is the use of chemistry and material sciences to mimic biological systems, specifically biological structures, to better humankind. Recently, biomimetic surfaces mimicking the microstructure of leaf surface, were used to study the effects of leaf microstructure on leaf-environment interactions. However, no such tool exists for roots. We developed a tool allowing the synthetic mimicry of the root surface microstructure into an artificial surface. We relied on the soft lithography method, known for leaf surface microstructure replication, using a two-step process. The first step is the more challenging one as it involves the biological tissue. Here, we used a different polymer and curing strategy, relying on the strong, rigid, polyurethane, cured by UV for the root molding. This allowed us to achieve a reliable negative image of the root surface microstructure including the delicate, challenging features such as root hairs. We then used this negative image as a template to achieve the root surface microstructure replication using both the well-established polydimethyl siloxane (PDMS) as well as a cellulose derivative, ethyl cellulose, which represents a closer mimic of the root and which can also be degraded by cellulase enzymes secreted by microorganisms. This newly formed platform can be used to study the microstructural effects of the surface in root-microorganism interactions in a similar manner to what has previously been shown in leaves. Additionally, the system enables us to track the microorganism&#8217;s locations, relative to surface features, and in the future its activity, in the form of cellulase secretion.

Biomimetics has been previously used as a tool to study leaf-microorganism interactions. However, no such tool exists for roots. Here, we develop a protocol to form synthetic surfaces mimicking root surface microstructure for the study of root-environment interactions.

Biomimetics is the use of chemistry and material sciences to mimic biological systems, specifically biological structures, to better humankind. Recently, ...