This work was supported by a RO1 from NIH and Merit Reviews from the VA Research Service to C.-M. T., and an individual NRSA to C.W.L.

General design considerations
If the wavelength of photo stimulation is in the visible range, such as for optogenetic experiments, the layout of the system will be considerably simpler than for UV photolysis experiments. One only needs to purchase a dual camera port module that is available from all of the microscope companies. The DMD plane can be positioned at the conjugate image plane of either one of the two camera ports. But in UV photolysis the light originating from the DMD must be brought in through the epi-illumination path (Fig. 3A), because the imaging tube lens leading to the camera is not corrected for UV wavelength in any of the commercially available microscopes. The spherical aberration of the imaging tube lens at 350 nm is severe enough to prevent the ability to focus light to a tight spot and to generate sufficient spatial resolution. This problem is not encountered in confocal microscopy because the tube lens is removed when a collimated laser beam is brought in along the same optical axis. The problem of UV illumination can be solved by bring in the light through the epi-fluorescent path because the tube lenses there are all partially corrected for spherical aberration at UV wavelength. We can expand on the optics of microscopes to any degree the journal wishes. The scientific community is in general quick interested in this topic and there are not many sources that teaches it well.
In order to minimize modifications of the microscope and because of tight space constraints at the epi-fluorescence unit, the DMD is placed at a newly created conjugate image plane created by a relay lens (point out the position of the DMD unit in relation to the microscope). A commercial UV corrected relay lens was purchased (Specialty Optics) (point it out in the diagram and on the microscope).
Illumination of the DMD
Upon receiving its binary input a micromirror can switch between a positive and a negative 12&deg; tilt relative to the plane of the chip. The axis of rotation is along the diagonal corners of each mirror (45&deg; to the sides of the chip). The orientation of the mirror rotation is designated by a gold colored triangle at one corner on the front surface of the chip. The tilt angle of the micromirror dictates the alignment of the pitch and azithmus of the incoming illumination beam. The pitch of the illumination beam needs to be 24&deg; from the perpendicular axis of the DMD chip and azithmus needs to be perpendicular to the axis of mirror rotation. Precise beam alignment is critical for efficient operation. In the prototype system we designed multiple manual tilt adjustments that allowed us to correct for design and machining inadequacies. This resulted in a system that is considerably more bulky than is necessary. Alternate, more compact arrangement for bringing in the light is possible (show alternate design if deemed useful).
For photolysis experiments a laser source is required to generate the high light intensity focused beam necessary for rapid uncaging. For optogenetic experiments where high intensity sharply focused light is not required, a non-coherent light source would be adequate. In the photolysis experiment described here we employed a quasi-continuous diode pumped solid state (DPSS) frequency tripled NdVO4 laser (1 W, 355 nm). (For a detailed discussion of the choices of light sources for photolysis see reference 2). A relatively high power laser is required in the experiments described here because only a small fraction of the laser output is actually delivered to the specimen when using a DMD system. The amount of light delivered to the specimen is proportional to the ratio of the number of ON/OFF mirrors within the region illuminated by the laser beam.
If a laser light source is required, it is best to launch the output of the laser into a multimode fiber so that it can be easily position and oriented along the correct axis for illuminating the DMD. Transmitting the light through the optical fiber solves a second problem, how to eliminate the speckle patterns inherent to coherent illumination. The fiber is wound around a piezoelectric fiber stretcher (model 915, Canadian Instrumentation &amp; Research, Ltd) that oscillates at ~40 kHz. (point these out in the rig) The microscopic stretching of the fiber is sufficient to moves the speckle pattern many times during the milliseconds duration of each photo stimulation pulse, thus effectively eliminating the effect of speckling. The output of the optical fiber is then collimated with a UV microscope objective (Olympus DApo20UV). (point this out) A calibration of the optical resolution of the system is shown in Fig. 3B. The effective physiological resolution as measured by the amplitude of current flow as a function of position of the spot of photostimulation is shown in Fig. 3C. Current responses to photostimulation of different intensities are illustrated in Fig. 3D.
Operation of the system:
Co-registering the CCD pixels with the DMD mirrors
An in-house software was written that determines the correspondence of individual DMD mirrors to specific pixels of the imaging CCD camera. The graphics user interface (GUI) within this software then allows the user to assign the DMD mirrors that corresponds to the region on the CCD image tagged by the mouse. Thus, the location for photo stimulation can be tagged by simply moving the cursor over the image displayed on the computer screen and clicking the tagged region of interest. (A fluorescent image of a dendritic arbor will be displayed on the computer screen. Student will mark a number of locations over the image on the computer screen.)
Programming the patterns for light delivery
The pattern marked on the computer screen by the operator is stored as a series of separate images. The timing of the laser pulses for each spatial pattern is then programmed into the software which is integrated with data acquisition program (pClamp). (demonstrate this).
Coordinating the laser pulses to the DMD patterns
The data acquisition program initiates and coordinates the timing of the DMD electronics, the gating of the laser, and the acquisition of the patch clamped electrical signal from the target neuron. (simulate this sequence on the computer)
Experimental data:
Non-linear summation across distal dendritic branch points
Dendritic integration with electrodes has traditionally been carried out by varying the amplitude of stimulation at discrete locations rather than expanding the area of stimulation while maintaining a constant intensity. Issues relating to saturation of electrogenesis and recruitment of location dependent channels can influence the result and conclusion. Distributed dendritic stimulation can be easily implemented using a DMD based system (Fig. 4A). Input intensity was varied by increasing the number of spots of photostimulation. We can see that spatial summation can be non-linear across branch points becoming increasingly supra-linear with increasing input amplitudes arriving on the two daughter branches. The supra-linearity is largely mediated NMDA receptors and not to voltage gated channels (Fig. 5)
Representative Results
<img src="/files/ftp_upload/2003/2003fig1.jpg" alt="Figure 1" /> Figure 1. Operation of the micromirrors in the DMD. (Side view) Electrostatic forces directed at individual mirrors cause the mirror to be tilted in one of two possible orientations 12&deg; from the horizontal. In the ON position an incident beam is directed along the optical axis perpendicular of the chip. In the OFF position the incident beam is directed 48&deg; off axis. Light that hits the thin gaps between the mirrors is directed 24&deg; off axis. (Top view) the tilt is oriented 45&deg; with respect to the sides of the mirrors and chip.
<img src="/files/ftp_upload/2003/2003fig2.jpg" alt="Figure 2" /> Figure 2. Basic layout of the modern fluorescent microscope. The filter cube is positioned in the "infinity space" between the objective and the tube lens. There is an imaging path that leads to the camera and there is an illumination path that brings the light to the sample. The tube lens for these two light path are typically different in design and in focal length. The illumination, but not the imaging, tube lens is designed for operation in the UV spectrum.
<img src="/files/ftp_upload/2003/2003fig3.jpg" alt="Figure 3" /> Figure 3. Layout for UV based DMD system. If the illumination is in the UV spectrum, then it must be brought through the tube lens that is corrected for UV. The tube lens in the imaging path is not designed for UV. A relay system is needed to create an easily accessible conjugate image plane. The different conjugate image planes in the microscope is marked by dotted red lines. Bright patterns in one image plane are projected in other conjugate planes. During imaging the pattern in the sample plane is projected onto the detector/camera. For illumination the pattern generated by the DMD is projected onto the sample.
<img src="/files/ftp_upload/2003/2003fig4.jpg" alt="Figure 4" /> Figure 4. Layout for visible light DMD projection system. If the illumination light is in the visible range, it is possible to bring the DMD generated light pattern through the imaging light path. This can be easily implemented with commercial dual camera port attachments and the appropriate dichroic mirror.
<img src="/files/ftp_upload/2003/2003fig5.jpg" alt="Figure 5" /> Figure 5. Lateral resolution of system. (A) Optical resolution on fluorescent target is ~2 &mu;m. (B) Effective resolution as measured by photolysis of caged glutamate across a dendrite is ~5 &mu;m. The increased distance is due to a combination of diffusion of glutamate and the finite width of the dendrite. (C) Photolysis can mimic the kinetics of synaptic events. The family of voltage clamped current responses is due to variations in the light energy delivered to the dendrite.
<img src="/files/ftp_upload/2003/2003fig6.jpg" alt="Figure 6" /> Figure 6. Non-linear summation across dendritic branch points. (A) Distributed inputs are applied to two dendritic branches separately. Their respective voltage responses are shown below. (B) The stimuli are then given simultaneously. The measured response (red trace) is different than the arithmetic sum of the two individual responses (grey trace).
<img src="/files/ftp_upload/2003/2003fig7.jpg" alt="Figure 7" /> Figure 7. Supralinear summation is NMDA receptor dependent. (A) APV, a selective NMDA receptor antagonist blocks the supralinear summation. (B) The stimulus intensity relationship and its sensitivity to NMDA receptor antagonist is plotted.

<ol>
	<li>Scanziani, M., Hausser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiology+in+the+age+of+light.">Electrophysiology in the age of light.</a> Nature. 461, 930-939 (2009).</li><li>Tang, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photolysis+of+caged+neurotransmitters:+Theory+and+procedures+for+light+delivery.">Photolysis of caged neurotransmitters: Theory and procedures for light delivery.</a> Curr. Prot. Neurosci. , 6.21.1-6.21.12 (2006).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nature+Technology+Feature,+Cell+imaging:+Light+activated.">Nature Technology Feature, Cell imaging: Light activated.</a> Nature. 456, 826-827 (2008).</li><li>Lutz, C., Otis, T. S., DeSars, V., Charpak, S., DeGregorio, D. A., Emiliani, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Holographic+photolysis+of+caged+neurotransmitters.">Holographic photolysis of caged neurotransmitters.</a> Nature Methods. 5, 821-827 (2008).</li><li>Hornbeck, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Digital Light Processing and MEMs: An overview. , .</li></ol>

No conflicts of interest declared.

The advantage of DMD based photostimulation approach is most apparent for situations where the target occupies a relatively large area. If the target of interest is very small, such as a few dendritic spines, sequential scanning confocal and 2-photon systems are likely to be the better approach. One significant weakness of the DMD approach is its inefficient use of the available light. The bulk of the available light is necessarily directed to the OFF mirrors and not used.
The DMD based syste...

Erratum: Patterned Photostimulation with Digital Micromirror Devices to Investigate Dendritic Integration Across Branch Points

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">	
		
		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Modern upright fluorescent microscope</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>CCD camera and image acquisition software</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Computer and data acquisition/interface system</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>DLP Discovery Developer Kit </td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>ALP3 USB interface</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>S2 + Optics w/LED</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Dual camera port unit</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>355nm frequency tripled NdVO4 laser (~1 W)</td>
<td>&nbsp;</td>
<td>DPSS Laser Inc.</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Laser shutter Model LS6</td>
<td>&nbsp;</td>
<td>Uniblitz</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Multimode optical fiber and fiber stretcher Model# 915</td>
<td>&nbsp;</td>
<td>Canadian Instrument and Research, Ltd </td>
<td>&nbsp;</td>
<td>100 um core multimode fiber</td>
</tr>
<tr>
<td>Multimode Fiber launcher </td>
<td>&nbsp;</td>
<td>Oz Optics</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Signal generator</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>up to 50 kHz</td>
</tr>
<tr>
<td>Beam collimator</td>
<td>&nbsp;</td>
<td>Olympus</td>
<td>DApo20UV340</td>
<td>&nbsp;</td>
<tr>
<td>UV relay lens</td>
<td>&nbsp;</td>
<td>Special Optics</td>
<td>#: 54-25-60-355</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

patterned photostimulation with digital micromirror devices to investigate dendritic integration across branch points

Light is a versatile and precise means to control neuronal excitability. The recent introduction of light sensitive effectors such as channel-rhodopsin and caged neurotransmitters have led to interests in developing better means to control patterns of light in space and time that are useful for experimental neuroscience. One conventional strategy, employed in confocal and 2-photon microscopy, is to focus light to a diffraction limited spot and then scan that single spot sequentially over the region of interest. This approach becomes problematic if large areas have to be stimulated within a brief time window, a problem more applicable to photostimulation than for imaging. An alternate strategy is to project the complete spatial pattern on the target with the aid of a digital micromirror device (DMD). The DMD approach is appealing because the hardware components are relatively inexpensive and is supported by commercial interests. Because such a system is not available for upright microscopes, we will discuss the critical issues in the construction and operations of such a DMD system. Even though we will be primarily describing the construction of the system for UV photolysis, the modifications for building the much simpler visible light system for optogenetic experiments will also be provided. The UV photolysis system was used to carryout experiments to study a fundamental question in neuroscience, how are spatially distributed inputs integrated across distal dendritic branch points. The results suggest that integration can be non-linear across branch points and the supralinearity is largely mediated by NMDA receptors.

Watch this Scientific Journal Video about Patterned Photostimulation with Digital Micromirror Devices to Investigate Dendritic Integration Across Branch Points at JoVE.com

Patterned Photostimulation with Digital Micromirror Devices to Investigate Dendritic Integration Across Branch Points

Digital micromirror devices (DMD) can generate complex patterns in time and space with which to control neuronal excitability. Issues relevant to the design, construction, and operation of DMD systems are discussed. Such a system enabled the demonstration of non-linear integration across distal dendritic branch points.

Light is a versatile and precise means to control neuronal excitability. The recent introduction of light sensitive effectors such as channel-rhodopsin ...

patterned-photostimulation-with-digital-micromirror-devices-to

Research

JoVE Journal

Bioengineering

15.6K vues.  University of Maryland School of Medicine. Appareils numériques à micromiroirs (DMD) peut générer des modèles complexes dans le temps et l'espace avec lequel contrôler l'excitabilité neuronale. Questions pertinentes pour la conception, la construction et l'exploitation des systèmes DMD sont discutées. Un tel système a permis la démonstration de la non-linéaires intégration à travers des points de ramification distale dendritiques.

Vidéo: Patterned Photostimulation with Digital Micromirror Devices to Investigate Dendritic Integration Across Branch Points

Creating Two-Dimensional Patterned Substrates for Protein and Cell Confinement

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1 While microcontact printing can be employed to directly print a large number of molecules, including proteins,2 DNA,3 and silanes,4 the formation of self-assembled monolayers (SAMs) from long chain alkane thiols on gold provides a simple way to confine proteins and cells to specific patterns containing adhesive and resistant regions. This confinement can be used to control cell morphology and is useful for examining a variety of questions in protein and cell biology. Here, we describe a general method for the creation of well-defined protein patterns for cellular studies.5 This process involves three steps: the production of a patterned master using photolithography, the creation of a PDMS stamp, and microcontact printing of a gold-coated substrate. Once patterned, these cell culture substrates are capable of confining proteins and/or cells (primary cells or cell lines) to the pattern.
The use of self-assembled monolayer chemistry allows for precise control over the patterned protein/cell adhesive regions and non-adhesive regions; this cannot be achieved using direct protein stamping. Hexadecanethiol, the long chain alkane thiol used in the microcontact printing step, produces a hydrophobic surface that readily adsorbs protein from solution. The glycol-terminated thiol, used for backfilling the non-printed regions of the substrate, creates a monolayer that is resistant to protein adsorption and therefore cell growth.6 These thiol monomers produce highly structured monolayers that precisely define regions of the substrate that can support protein adsorption and cell growth. As a result, these substrates are useful for a wide variety of applications from the study of intercellular behavior7 to the creation of microelectronics.8
While other types of monolayer chemistry have been used for cell culture studies, including work from our group using trichlorosilanes to create patterns directly on glass substrates,9 patterned monolayers formed from alkane thiols on gold are straight-forward to prepare. Moreover, the monomers used for monolayer preparation are commercially available, stable, and do not require storage or handling under inert atmosphere. Patterned substrates prepared from alkane thiols can also be recycled and reused several times, maintaining cell confinement.10

Self-assembled monolayers (SAMs) formed from long chain alkane thiols on gold provide well-defined substrates for the formation of protein patterns and cell confinement. Microcontact printing of hexadecanethiol using a polydimethylsiloxane (PDMS) stamp followed by backfilling with a glycol-terminated alkane thiol monomer produces a pattern where protein and cells adsorb only to the stamped hexadecanethiol region.

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1  While microcontact printing ...

Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. Additionally, traversing cellular barriers in the body is crucial for both oral delivery of therapeutic NCs into the circulation and transport from the blood into tissues, where intervention is needed. NC transport across cellular barriers is achieved by: (i) the paracellular route, via transient disruption of the junctions that interlock adjacent cells, or (ii) the transcellular route, where materials are internalized by endocytosis, transported across the cell body, and secreted at the opposite cell surface (transyctosis). Delivery across cellular barriers can be facilitated by coupling therapeutics or their carriers with targeting agents that bind specifically to cell-surface markers involved in transport. Here, we provide methods to measure the extent and mechanism of NC transport across a model cell barrier, which consists of a monolayer of gastrointestinal (GI) epithelial cells grown on a porous membrane located in a transwell insert. Formation of a permeability barrier is confirmed by measuring transepithelial electrical resistance (TEER), transepithelial transport of a control substance, and immunostaining of tight junctions. As an example, ~200&#160;nm polymer NCs are used, which carry a therapeutic cargo and are coated with an antibody that targets a cell-surface determinant. The antibody or therapeutic cargo is labeled with 125I for radioisotope tracing and labeled NCs are added to the upper chamber over the cell monolayer for varying periods of time. NCs associated to the cells and/or transported to the underlying chamber can be detected. Measurement of free 125I allows subtraction of the degraded fraction. The paracellular route is assessed by determining potential changes caused by NC transport to the barrier parameters described above. Transcellular transport is determined by addressing the effect of modulating endocytosis and transcytosis pathways.

Many therapeutic applications require safe and efficient transport of drug carriers and their cargoes across cellular barriers in the body. This article describes an adaptation of established methods to evaluate the rate and mechanism of transport of drug nanocarriers (NCs) across cellular barriers, such as the gastrointestinal (GI) epithelium.

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. ...

Helical Organization of Blood Coagulation Factor VIII on Lipid Nanotubes

Cryo-electron microscopy (Cryo-EM)1 is a powerful approach to investigate the functional structure of proteins and complexes in a hydrated state and membrane environment2.
Coagulation Factor VIII (FVIII)3 is a multi-domain blood plasma glycoprotein. Defect or deficiency of FVIII is the cause for Hemophilia type A&#160;-&#160;a severe bleeding disorder. Upon proteolytic activation, FVIII binds to the serine protease Factor IXa on the negatively charged platelet membrane, which is critical for normal blood clotting4. Despite the pivotal role FVIII plays in coagulation, structural information for its membrane-bound state is incomplete5. Recombinant FVIII concentrate is the most effective drug against Hemophilia type A and commercially available FVIII can be expressed as human or porcine, both forming functional complexes with human Factor IXa6,7.
In this study we present a combination of Cryo-electron microscopy (Cryo-EM), lipid nanotechnology and structure analysis applied to resolve the membrane-bound structure of two highly homologous FVIII forms: human and porcine. The methodology developed in our laboratory to helically organize the two functional recombinant FVIII forms on negatively charged lipid nanotubes (LNT) is described.&#160;The representative results demonstrate that our approach is sufficiently sensitive to define the differences in the helical organization between the two highly homologous in sequence (86% sequence identity) proteins. Detailed protocols for the helical organization, Cryo-EM and electron tomography (ET) data acquisition are given. The two-dimensional (2D) and three-dimensional (3D) structure analysis applied to obtain the 3D reconstructions of human and porcine FVIII-LNT is discussed. The presented human and porcine FVIII-LNT structures show the potential of the proposed methodology to calculate the functional, membrane-bound organization of blood coagulation Factor VIII at high resolution.

We present a combination of Cryo-electron microscopy, lipid nanotechnology, and structure analysis applied to resolve the membrane-bound structure of two highly homologous FVIII forms: human and porcine. The methodology developed in our laboratory&#160;to helically organize the two functional recombinant FVIII forms on negatively charged lipid nanotubes (LNT) is described.

Cryo-electron microscopy (Cryo-EM)1 is a powerful approach to investigate the functional structure of proteins and complexes in a hydrated state and ...

Planar Gradient Diffusion System to Investigate Chemotaxis in a 3D Collagen Matrix

The importance of cell migration can be seen through the development of human life. When cells migrate, they generate forces and transfer these forces to their surrounding area, leading to cell movement and migration. In order to understand the mechanisms that can alter and/or affect cell migration, one can study these forces. In theory, understanding the fundamental mechanisms and forces underlying cell migration holds the promise of effective approaches for treating diseases and promoting cellular transplantation. Unfortunately, modern chemotaxis chambers that have been developed are usually restricted to two dimensions (2D) and have complex diffusion gradients that make the experiment difficult to interpret. To this end, we have developed, and describe in this paper, a direct-viewing chamber for chemotaxis studies, which allows one to overcome modern chemotaxis chamber obstacles able to measure cell forces and specific concentration within the chamber in a 3D environment to study cell 3D migration. More compelling, this approach allows one to successfully model diffusion through 3D collagen matrices and calculate the coefficient of diffusion of a chemoattractant through multiple different concentrations of collagen, while keeping the system simple and user friendly for traction force microscopy (TFM) and digital volume correlation (DVC) analysis.

Cell migration is an important part of human development and life. In order to understand the mechanisms that can alter cell migration, we present a planar gradient diffusion system to investigate chemotaxis in a 3D collagen matrix, which allows one to overcome modern diffusion chamber limitations of existing assays.

The importance of cell migration can be seen through the development of human life. When cells migrate, they generate forces and transfer these forces to ...

Fabrication of a Functionalized Magnetic Bacterial Nanocellulose with Iron Oxide Nanoparticles

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide nanoparticles (IONP) (Fe3O4) to yield a magnetic bacterial nanocellulose (MBNC). The synthesis of MBNC is a precise and specifically designed multi-step process. Briefly, bacterial nanocellulose (BNC) pellicles are formed from preserved G. xylinus strain according to our experimental requirements of size and morphology. A solution of iron(III) chloride hexahydrate (FeCl3&#183;6H2O) and iron(II) chloride tetrahydrate (FeCl2&#183;4H2O) with a 2:1 molar ratio is prepared and diluted in deoxygenated high purity water. A BNC pellicle is then introduced in the vessel with the reactants. This mixture is stirred and heated at 80 &#176;C in a silicon oil bath and ammonium hydroxide (14%) is then added by dropping to precipitate the ferrous ions into the BNC mesh. This last step allows forming in situ magnetite nanoparticles (Fe3O4) inside the bacterial nanocellulose mesh to confer magnetic properties to BNC pellicle. A toxicological assay was used to evaluate the biocompatibility of the BNC-IONP pellicle. Polyethylene glycol (PEG) was used to cover the IONPs in order to improve their biocompatibility. Scanning electron microscopy (SEM) images showed that the IONP were located preferentially in the fibril interlacing spaces of the BNC matrix, but some of them were also found along the BNC ribbons. Magnetic force microscope measurements performed on the MBNC detected the presence magnetic domains with high and weak intensity magnetic field, confirming the magnetic nature of the MBNC pellicle. Young&#39;s modulus values obtained in this work are also in a reasonable agreement with those reported for several blood vessels in previous studies.

Here, we present a protocol to make a bacterial nanocellulose (BNC) magnetic for applications in damaged blood vessel reconstruction. The BNC was synthesized by G. xylinus strain. On the other hand, magnetization of the BNC was realized through in situ precipitation of Fe2+ and Fe3+ ferrous ions inside the BNC mesh.

In this study, bacterial nanocellulose (BNC) produced by the bacteria Gluconacetobacter xylinus is synthesized and impregnated in situ with iron oxide ...

Fabricating Cotton Analytical Devices

A robust, low-cost analytical device should be user-friendly, rapid, and affordable. Such devices should also be able to operate with scarce samples and provide information for follow-up treatment. Here, we demonstrate the development of a cotton-based urinalysis (i.e., nitrite, total protein, and urobilinogen assays) analytical device that employs a lateral flow-based format, and is inexpensive, easily fabricated, rapid, and can be used to conduct multiple tests without cross-contamination worries. Cotton is composed of cellulose fibers with natural absorptive properties that can be leveraged for flow-based analysis. The simple but elegant fabrication process of our cotton-based analytical device is described in this study. The arrangement of the cotton structure and test pad takes advantage of the hydrophobicity and absorptive strength of each material. Because of these physical characteristics, colorimetric results can persistently adhere to the test pad. This device enables physicians to receive clinical information in a timely manner and shows great potential as a tool for early intervention.

To investigate simple fabrication approaches for multiple assay needs, we created a fluid-absorbing channel system made of cotton material. This device was used to establish a multiple detection platform, and solve contamination issues that commonly affect lateral flow-based biomedical devices, for clinical urinalysis of nitrite, total protein, and urobilinogen.

A robust, low-cost analytical device should be user-friendly, rapid, and affordable. Such devices should also be able to operate with scarce samples and ...

Using Adhesive Patterning to Construct 3D Paper Microfluidic Devices

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol adhesive through a metal stencil, the overall amount of adhesive used in assembling paper microfluidic devices can be significantly reduced. We show on a simple 4-layer planar paper microfluidic device that the optimal adhesive application technique and device construction style depends heavily on desired performance characteristics. By moderately increasing the overall area of a device, it is possible to dramatically decrease the wicking time and increase device success rates while also reducing the amount of adhesive required to keep the device together. Such adhesive application also causes the adhesive to form semi-permanent bonds instead of permanent bonds between paper layers, enabling single-use devices to be non-destructively disassembled after use. Nonplanar 3D origami devices also benefit from the semi-permanent bonds during folding, as it reduces the likelihood that unrelated faces may accidently stick together. Like planar devices, nonplanar structures see reduced wicking times with patterned adhesive application vs uniformly applied adhesive.

We demonstrate the use of patterned aerosol adhesives to construct 3D paper microfluidic devices. This method of adhesive application forms semi-permanent bonds between layers, enabling single-use devices to be non-destructively disassembled after use and to ease folding complex nonplanar structures.

We demonstrate the use of patterned aerosol adhesives to construct both planar and nonplanar 3D paper microfluidic devices. By spraying an aerosol ...

An Experimental and Finite Element Protocol to Investigate the Transport of Neutral and Charged Solutes across Articular Cartilage

Osteoarthritis (OA) is a debilitating disease that is associated with degeneration of articular cartilage and subchondral bone. Degeneration of articular cartilage impairs its load-bearing function substantially as it experiences tremendous chemical degradation, i.e. proteoglycan loss and collagen fibril disruption. One promising way to investigate chemical damage mechanisms during OA is to expose the cartilage specimens to an external solute and monitor the diffusion of the molecules. The degree of cartilage damage (i.e. concentration and configuration of essential macromolecules) is associated with collisional energy loss of external solutes while moving across articular cartilage creates different diffusion characteristics compared to healthy cartilage. In this study, we introduce a protocol, which consists of several steps and is based on previously developed experimental micro-Computed Tomography (micro-CT) and finite element modeling. The transport of charged and uncharged iodinated molecules is first recorded using micro-CT, which is followed by applying biphasic-solute and multiphasic finite element models to obtain diffusion coefficients and fixed charge densities across cartilage zones.

We propose a protocol to investigate the transport of charged and uncharged molecules across articular cartilage with the aid of recently developed experimental and numerical methods.

Osteoarthritis (OA) is a debilitating disease that is associated with degeneration of articular cartilage and subchondral bone. Degeneration of articular ...

Soft Lithographic Procedure for Producing Plastic Microfluidic Devices with View-ports Transparent to Visible and Infrared Light

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable microfluidic devices. Here, a protocol for the fabrication of plastic microfluidic devices is demonstrated, where soft lithographic techniques are used to embed transparent Calcium Fluoride (CaF2) view-ports in connection with observation chamber(s). The method is based on a replica casting approach, where a polydimethylsiloxane (PDMS) mold is produced through standard lithographic procedures and then used as the template to produce a plastic device. The plastic device features ultraviolet/visible/infrared (UV/Vis/IR) -transparent windows made of CaF2 to allow for direct observation with visible and IR light. The advantages of the proposed method include: a reduced need for accessing a clean room micro-fabrication facility, multiple view-ports, an easy and versatile connection to an external pumping system through the plastic body, flexibility of the design, e.g., open/closed channels configuration, and the possibility to add sophisticated features such as nanoporous membranes.

A protocol for the fabrication of plastic microfluidic devices with transparent view-ports for visible and infrared light imaging is described.

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable ...

Calorespirometry: A Powerful, Noninvasive Approach to Investigate Cellular Energy Metabolism

Many cell lines used in basic biological and biomedical research maintain energy homeostasis through a combination of both aerobic and anaerobic respiration. However, the extent to which both pathways contribute to the landscape of cellular energy production is consistently overlooked. Transformed cells cultured in saturating levels of glucose often show a decreased dependency on oxidative phosphorylation for ATP production, which is compensated by an increase in substrate-level phosphorylation. This shift in metabolic poise allows cells to proliferate despite the presence of mitochondrial toxins. In neglecting the altered metabolic poise of transformed cells, results from a pharmaceutical screening may be misinterpreted since the potentially mitotoxic effects may not be detected using model cell lines cultured in the presence of high glucose concentrations. This protocol describes the pairing of two powerful techniques, respirometry and calorimetry, which allows for the quantitative and noninvasive assessment of both aerobic and anaerobic contributions to cellular ATP production. Both aerobic and anaerobic respirations generate heat, which can be monitored via calorimetry. Meanwhile, measuring the rate of oxygen consumption can assess the extent of aerobic respiration. When both heat dissipation and oxygen consumption are measured simultaneously, the calorespirometric ratio can be determined. The experimentally obtained value can then be compared to the theoretical oxycaloric equivalent and the extent of the anaerobic respiration can be judged. Thus, calorespirometry provides a unique method to analyze a wide range of biological questions, including drug development, microbial growth, and fundamental bioenergetics under both normoxic and hypoxic conditions.

This protocol describes calorespirometry, the direct and simultaneous measurement of both heat dissipation and respiration, which provides a noninvasive approach to assess energy metabolism. This technique is used to assess the contribution of both aerobic and anaerobic pathways to energy utilization by monitoring the total cellular energy flow.