Name: cellular affinity of particle-stabilized emulsion to boost antigen internalization
Uploaded: 2022-09-02T13:00:00
Description: Watch this Scientific Journal Video about Cellular Affinity of Particle-Stabilized Emulsion to Boost Antigen Internalization at JoVE.com

This work was supported by Project supported by the National Key Research and Development Program of China (2021YFE020527, 2021YFC2302605, 2021YFC2300142), From 0 to 1 Original Innovation Project of Basic Frontier Scientific Research Program of Chinese Academy of Sciences (ZDBS-LY-SLH040), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant No. 21821005).

All methods described in this protocol have been approved by the Institute of Process Engineering, Chinese Academy of Sciences. All animal experiments were performed in strict accordance with the Regulations for the Care and Use of Laboratory Animals and Guideline for Ethical Review of Animal (China, GB/T35892-2018).
1. Preparation and characterization of PLGA nanoparticles
<ol>
	<li>Preparation of PLGA nanoparticles (PNPs)
	<ol>
		<li>Add 0.5 g of polyvinyl alcohol (PVA) to...

<ol>
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We developed PLGA nanoparticle-stabilized oil/water emulsion as a delivery system for enhanced antigen internalization. The prepared PNPE possessed a densely packed surface to support the landing spot and unique softness and fluidity for potent cellular contact with the immune cell membrane. Furthermore, the oil/water interface offered high-content antigen loading, and amphiphilic PLGA conferred PNPE with high stability for the transportation of antigens to immune cells. The PNPE could rapidly adhere to the surface of th...

To combat epidemic, chronic, and infectious diseases, it is imperative to develop effective adjuvants for prophylactic and therapeutic vaccinations1,2. Ideally, the adjuvants should possess excellent safety and immune activation3,4,5. Effective uptake and process of antigens by antigen-presenting cells (APCs) are thought to be an essential stage in the downstream signaling cascades and initiation of the immune response6,7,8. Hence, gaining a clear understanding of the mechanism of interaction of immune cells with antigens and designing adjuvants to enhance internalization are efficient strategies to enhance the efficiency of vaccines.
Micro-/nanoparticles with unique properties have been previously investigated as antigen delivery systems to mediate the cellular uptake of antigens and the cellular interaction with pathogen-associated molecular patterns9,10. Upon contacting with cells, delivery systems begin to interact with the extracellular matrix and cell membrane, which led to internalization and subsequent cellular responses11,12. Previous studies have brought to light that the internalization of particles takes place through cell membrane-particle adhesion13, followed by flexible deformation of the cell membrane and diffusion of the receptor to the surface membrane14,15. Under these circumstances, the properties of the delivery system depend on the affinity to APCs, which subsequently affect the uptake quantity16,17.
To gain insights into the design of the delivery system for improved immune response, extensive efforts have been focused on the investigation of the relationship between the properties of particles and cellular uptake. The present study stemmed from the observation that solid micro-/nanoparticles with various charges, sizes, and shapes are often studied in this light, while the role of fluidity in antigen internalization is seldom investigated18,19. In fact, during adhesion, the soft particles demonstrated dynamic curvature changes and lateral diffusions to increase the contact area for multivalent interactions, which can hardly be replicated by the solid particles20,21. In addition, cell membranes are phospholipid bilayers (sphingolipids or cholesterol) at the site of uptake, and hydrophobic substances can alter the conformational entropy of lipids, reducing the amount of energy required for cellular uptake22,23. Thus, amplifying mobility and promoting hydrophobicity of the delivery system may be an effective strategy for strengthening antigen internalization to enhance immune response.
Pickering emulsion, stabilized by solid particles assembled at the interface between two immiscible liquids, have been widely used in the biological field24,25. In fact, the aggregating particles on the oil/water interface determine the formulation of multi-level structures, which promote multi-level delivery system-cellular interactions, and further induce multi-functional physiochemical properties in drug delivery. Because of their deformability and lateral mobility, Pickering emulsions were expected to enter in multi-valent cellular interaction with the immunocytes and be recognized by the membrane proteins26. In addition, as oily micelle cores in Pickering emulsions are not completely covered with solid particles, Pickering emulsions possess gaps of different sizes between particles on the oil/water interface, which cause higher hydrophobicity. Thus, it is crucial to explore the affinity of Pickering emulsions to APCs and elaborate on the subsequent internalization to develop efficient adjuvants.
Based on these considerations, we engineered a PLGA nanoparticle-stabilized Pickering emulsion (PNPE) as a fluidity vaccine delivery system that also helped to gain valuable insights in the affinity of the PNPE to BMDCs and cellular internalization. The real-time adhesion of bio- mimetic extracellular vesicles (bEVs; a replacement of BMDCs) to PNPE was monitored via a label-free method using a quartz crystal microbalance with dissipation monitoring (QCM-D). Following characterization of the affinity of PNPE to BMDCs, confocal laser scanning microscopy (CLSM) was used to determine the antigen uptake. The result indicated the higher affinity of PNPE to BMDCs, and the efficient internalization of the antigen. We anticipated that the PNPE would exhibit higher affinity to APCs, which may better stimulate the internalization of antigens to enhance immune responses.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>AddVax</td>
			<td>InvivoGen</td>
			<td>Vac-adx-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell Strainer</td>
			<td>Biosharp</td>
			<td>BS-70-CS</td>
			<td>70 &#956;m</td>
		</tr>
		<tr>
			<td>Confocal Laser Scanning Microscope (CLSM)</td>
			<td>Nikon</td>
			<td></td>
			<td>A1</td>
		</tr>
		<tr>
			<td>Cy3 NHS Ester</td>
			<td>YEASEN</td>
			<td>40777ES03</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI Staining Solution</td>
			<td>Beyotime</td>
			<td>C1005</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Gibco</td>
			<td>16000-044</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC Phalloidin</td>
			<td>Solarbio</td>
			<td>CA1620</td>
			<td></td>
		</tr>
		<tr>
			<td>Mastersizer 2000 Particle Size Analyzer</td>
			<td>Malvern</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro BCA protein Assay Kit</td>
			<td>Thermo Science</td>
			<td>23235</td>
			<td></td>
		</tr>
		<tr>
			<td>Membrane emulsification equipment</td>
			<td>Zhongke Senhui Microsphere Technology</td>
			<td></td>
			<td>FM0201/500M</td>
		</tr>
		<tr>
			<td>Mini-Extruder</td>
			<td>Avanti Polar Lipids, Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NANO ZS</td>
			<td>Malvern</td>
			<td></td>
			<td>JSM-6700F</td>
		</tr>
		<tr>
			<td>Polycarbonate membranes</td>
			<td>Avanti Polar Lipids, Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Poly (lactic-co-glycolic acid) (PLGA)</td>
			<td>Sigma-Aldrich</td>
			<td>26780-50-7</td>
			<td>Mw 7,000-17,000</td>
		</tr>
		<tr>
			<td>Poly-L-lysine Solution</td>
			<td>Solarbio</td>
			<td>P2100</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly (vinyl alcohol) (PVA)</td>
			<td>Sigma-Aldrich</td>
			<td>9002-89-5</td>
			<td></td>
		</tr>
		<tr>
			<td>QSense Silicon dioxide sensor</td>
			<td>Biolin Scientific</td>
			<td>QSX 303</td>
			<td>Surface roughness &#60; 1 nm RMS</td>
		</tr>
		<tr>
			<td>Quartz Crystal Microbalance</td>
			<td>Biosharp</td>
			<td></td>
			<td>Q-SENSE E4</td>
		</tr>
		<tr>
			<td>RPMI Medium 1640 basic</td>
			<td>Gibco</td>
			<td>C22400500BT</td>
			<td>L-Glutamine, 25 mM HEPES</td>
		</tr>
		<tr>
			<td>Scanning Electron Microscopy (SEM)</td>
			<td>JEOL</td>
			<td></td>
			<td>JSM-6700F</td>
		</tr>
		<tr>
			<td>Squalene</td>
			<td>Sigma-Aldrich</td>
			<td>111-02-4</td>
			<td></td>
		</tr>
	</tbody>
</table>

cellular affinity of particle-stabilized emulsion to boost antigen internalization

The cellular affinity of micro-/nanoparticles is the precondition for cellular recognition, cellular uptake, and activation, which are essential for drug delivery and immune response. The present study stemmed from the observation that the effects of charge, size, and shape of solid particles on cell affinity are usually considered, but we seldom realize the essential role of softness, dynamic restructuring phenomenon, and complex interface interaction in cellular affinity. Here, we developed poly-lactic-co-glycolic acid (PLGA) nanoparticle-stabilized Pickering emulsion (PNPE) that overcame the shortcomings of rigid forms and simulated the flexibility and fluidity of pathogens. A method was set up to test the affinity of PNPE to cell surfaces and elaborate on the subsequent internalization by immune cells. The affinity of PNPE to bio-mimetic extracellular vesicles (bEVs)-the replacement for bone marrow dendritic cells (BMDCs)-was determined using a quartz crystal microbalance with dissipation monitoring (QCM-D), which allowed real-time monitoring of cell-emulsion adhesion. Subsequently, the PNPE was used to deliver the antigen (ovalbumin, OVA) and the uptake of the antigens by BMDCs was observed using confocal laser scanning microscope (CLSM). Representative results showed that the PNPE immediately decreased frequency (&#916;F) when it encountered the bEVs, indicating rapid adhesion and high affinity of the PNPE to the BMDCs. PNPE showed significantly stronger binding to the cell membrane than PLGA microparticles (PMPs) and AddaVax adjuvant (denoted as surfactant-stabilized nano-emulsion [SSE]). Furthermore, owing to the enhanced cellular affinity to the immunocytes through dynamic curvature changes and lateral diffusions, antigen uptake was subsequently boosted compared with PMPs and SSE. This protocol provides insights for designing novel formulations with high cell affinity and efficient antigen internalization, providing a platform for the development of efficient vaccines.

A simple one-step sonification was used to obtain PNPE. First, we prepared uniform PNPs for use as the solid stabilizer (Figure 1A). The morphology of PNPs were observed though SEM, showing that they are mostly uniform and spherical (Figure 1B). The hydrodynamic size and zeta potential of the formulations were detected via DLS. The diameter of the PNPs was 187.7 &#177; 3.5 nm and the zeta potential was -16.4 &#177; 0.4 mV (Figure 1C...

Watch this Scientific Journal Video about Cellular Affinity of Particle-Stabilized Emulsion to Boost Antigen Internalization at JoVE.com

Cellular Affinity of Particle-Stabilized Emulsion to Boost Antigen Internalization

To rationally design efficient adjuvants, we developed poly-lactic-co-glycolic acid nanoparticle-stabilized Pickering emulsion (PNPE). The PNPE possessed unique softness and a hydrophobic interface for potent cellular contact and offered high-content antigen loading, improving the cellular affinity of the delivery system to antigen-presenting cells and inducing efficient internalization of antigens.

The cellular affinity of micro-/nanoparticles is the precondition for cellular recognition, cellular uptake, and activation, which are essential for drug ...

We developed the PLGA nanoparticles stabilized Pickering emulsion. The Pickering emulsion improved the cellular affinity to antigen protein cells, inducing efficient internalization of antigens. The nanoparticle stabilized Pickering emulsions were easy to prepare and deliver antigen efficiently.Additionally, a method was used to monitor the affinity of emulsion to cell and elaborate on the internalization. This protocol provides insights for designing novel formulations with high cell efficiency and efficient antigen internalization, which provide a platform for the development of efficient vaccines. To begin, add 100 milligrams of polylactic-co-glycolic acid to 10 milliliters of acetone and ethanol mixture in a ratio of four to one to serve as the oil phase.Place 20 milliliters of PVA aqueous solution under the fume hood and magnetically stir at 400 rotations per minute. Add five milliliters of the oil phase into the PVA solution drop-by-drop using a syringe pump. Then stir the mixture in the fume hood until the organic solvents completely evaporate.After the volatilization of organic solvents, centrifuge the mixture at 15, 000 G.Wash three or more times until the final washing water is clear and transparent. Re-suspend the washed PLGA nanoparticles in two milliliters of deionized water and freeze the mixture at 80 degrees Celsius for 24 hours. To characterize the size and zeta potential of PLGA nanoparticles, add 10 microliters of PLGA nanoparticles into one milliliter of deionized water to obtain a diluent solution and transfer the diluent solution to a DTS1070 cell.Switch on the computer and dynamic light scattering analyzer. Then place the DTS1070 cell in the DLS system. Click on the Zetasizer software and create a new measurement file to set up the determination procedure.Then start the determination procedure to obtain the particle size and zeta potential distribution. To prepare PLGA nanoparticles stabilized Pickering emulsion, or PNPE, add freeze-dried PLGA nanoparticles to deionized water at a concentration of four milligrams per milliliter and then add squalane as the oil phase. Prepare PNPE via one-step sonication for five minutes at 100 watt in a water bath sonicator.Dilute 20 microliters of PNPE and one milliliter of deionized water. Drop 20 microliters of the emulsion on the slide. Observe the morphology and homogeneity of the emulsion using optical microscopy at 40 times magnification and obtain photographs.Turn on the spin coater by pressing the power button. Press the control button and set the coating time and speed. Connect the nitrogen pipe to the spin coater and adjust the fractionation of the gas cylinder to 0.4 kilopascals.Place the clean chip on the suction cup of the spin coater. Add 100 microliters of poly-l-lysine dropwise to the center of the silicon dioxide sensor and close the top cover of the spin coater. Press the start button to start coating the sample and stop the machine when finished.Turn off the vacuum pump, turn off the power and control buttons, and remove the poly-l-lysine modified silicon dioxide sensor. To determine the adhesion of biomimetic extracellular vesicles to PNPE, turn on the computer, the electronic unit, and the peristaltic pump, and activate the temperature control at the bottom right in the software to ensure that the set temperature is approximately one degree Celsius below room temperature. Place the poly-l-lysine modified silicon dioxide sensors in the flow cell according to the operating instructions and connect the measurement line between the flow cell and the flow pump.Place the flow cell inside the flow module system. Click on the Acquisition toolbar and select Setup Measurement to search for 1, 3, 5, 7, 9, and 11 octaves of the chip in the channel used. To correct the baseline, click on Start Measurement to allow air to enter the flow module until the air baseline is smooth.After flowing deionized water for 10 to 15 minutes to enable the solution baseline equilibrium again, pump the prepared PNPE solution into the flow module at a flow rate of 50 microliters per minute to achieve equilibrium adsorption on the silicon dioxide sensor. Pump the prepared biomimetic extracellular vesicle solution into the flow module at a flow rate of 50 microliters per minute to track the process of bEV adhesion to the PNPE surface. Incubate the bone marrow dendritic cells with 1640 complete media for seven days and then seed them into small confocal laser dishes at 1 times 10 to the 6 per well overnight at 37 degrees Celsius and a 5%carbon dioxide incubator.Mix 0.5 milliliters of cyanine 5 labeled ovalbumin, with 0.5 milliliters of PNPE for one hour and remove the fluidic antigen by centrifugation at 5, 000 G for 20 minutes to develop vaccine formulation. After re-suspension with 200 microliters of deionized water, add 10 microliters of the formulation into the small confocal laser dishes under a super clean bench and co-culture with bone marrow dendritic cells for six hours. After removing the culture fluid from the cells, wash them twice with pre-warmed phosphate buffered saline.Fix the cells with 4%formaldehyde solution and PBS for 10 minutes at room temperature. Wash the cells with PBS two or three times at room temperature for 10 minutes each. Permeabilize the cells with 100 microliters of 0.5%Triton X-100 solution for five minutes at room temperature.After washing the cells again with PBS, cover the cells on the glass bottom dish of the small confocal laser dishes with 200 microliters of fluorescein isothiocyanate conjugated phalloidin working solution and incubate for 30 minutes at room temperature in the dark. After washing the cells with PBS three times for five minutes each, restain the nuclei with 200 microliters of DAPI solution for around 30 seconds. For image analysis, switch on the confocal microscope hardware in sequence including the laser, confocal, microscope and computer.Click the software and select Nikon Confocal to enter the testing system. In the confocal microscope system, turn on the various units in the order noted. First, set up the FITC, DAPI and Cy5 channels and adjust the corresponding HV and offset.Then after selecting the 100 times oil lens and put a drop of cedar oil on the top place the small confocal laser dishes containing stained bone marrow dendritic cells on the microscope stage. Click the scan button. Under fluorescence microscope, locate cells of interest by moving the x-axis, y-axis and z-axis.Tune the laser intensity, image size and other parameters to enable scanning high quality confocal images. Finally, click Capture button and save the images. The adhesion of biomimetic extracellular vesicles to PNPE was tracked using QCM-D.An immediate decrease in frequency, indicated a rapid adhesion of biomimetic extracellular vesicles to PNPE after the encounter. Moreover, delta F decreased with increasing biomimetic extracellular vesicles concentration, reflecting a concentration-dependent effect. PLGA microparticles and surfactant-stabilized nano emulsion were weakly bound to biomimetic extracellular vesicles, even at high concentration of 80 micrograms per milliliter, which probably resulted from a lack of contact sites with the immune cells.The cyanine-5 ovalbumin fluorescent signal indicated that the total amount of antigen internalized into cells is significantly higher in the PNPE treated group compared to that in the PLGA microparticles and surfactant-stabilized nano emulsion treated group. The quantitative analysis of cellular uptake showed a significant higher relative intensity of fluorescence and bone marrow dendritic cells treated with PNPE than in those treated with PLGA microparticles and surfactant-stabilized nano emulsion. The obtained results demonstrated that the PNPE promoted the antigen internalization and effectively delivered the antigen intracellularly.In order to obtain homogeneous emulsion, the mixture must be continuously shaken during sonication.

cellular-affinity-particle-stabilized-emulsion-to-boost-antigen

Research

JoVE Journal

Bioengineering

The Three-Dimensional Human Skin Reconstruct Model: a Tool to Study Normal  Skin and Melanoma Progression

Most in vitro studies in experimental skin biology have been done in 2-dimensional (2D) monocultures, while accumulating evidence suggests that cells behave differently when they are grown within a 3D extra-cellular matrix and also interact with other cells (1-5). Mouse models have been broadly utilized to study tissue morphogenesis in vivo. However mouse and human skin have significant differences in cellular architecture and physiology, which makes it difficult to extrapolate mouse studies to humans. Since melanocytes in mouse skin are mostly localized in hair follicles, they have distinct biological properties from those of humans, which locate primarily at the basal layer of the epidermis. The recent development of 3D human skin reconstruct models has enabled the field to investigate cell-matrix and cell-cell interactions between different cell types. The reconstructs consist of a "dermis" with fibroblasts embedded in a collagen I matrix, an "epidermis", which is comprised of stratified, differentiated keratinocytes and a functional basement membrane, which separates epidermis from dermis. Collagen provides scaffolding, nutrient delivery, and potential for cell-to-cell interaction. The 3D skin models incorporating melanocytic cells recapitulate natural features of melanocyte homeostasis and melanoma progression in human skin. As in vivo, melanocytes in reconstructed skin are localized at the basement membrane interspersed with basal layer keratinocytes. Melanoma cells exhibit the same characteristics reflecting the original tumor stage (RGP, VGP and metastatic melanoma cells) in vivo. Recently, dermal stem cells have been identified in the human dermis (6). These multi-potent stem cells can migrate to the epidermis and differentiate to melanocytes.

In this report, we describe the three-dimensional skin reconstruct model which mimics human skin in architecture and composition. Melanocyte physiology, melanoma progression and the fate of dermal stem cells have been investigated using the skin reconstruct model. The model is also useful as a preclinical tool for drug assessment.

Most in vitro studies in experimental skin biology have been done in 2-dimensional (2D) monocultures, while accumulating evidence suggests that cells ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Analyzing Cellular Internalization of Nanoparticles and Bacteria by Multi-spectral Imaging Flow Cytometry

Nanoparticulate systems have emerged as valuable tools in vaccine delivery through their ability to efficiently deliver cargo, including proteins, to antigen presenting cells1-5. Internalization of nanoparticles (NP) by antigen presenting cells is a critical step in generating an effective immune response to the encapsulated antigen. To determine how changes in nanoparticle formulation impact function, we sought to develop a high throughput, quantitative experimental protocol that was compatible with detecting internalized nanoparticles as well as bacteria. To date, two independent techniques, microscopy and flow cytometry, have been the methods used to study the phagocytosis of nanoparticles. The high throughput nature of flow cytometry generates robust statistical data. However, due to low resolution, it fails to accurately quantify internalized versus cell bound nanoparticles. Microscopy generates images with high spatial resolution; however, it is time consuming and involves small sample sizes6-8. Multi-spectral imaging flow cytometry (MIFC) is a new technology that incorporates aspects of both microscopy and flow cytometry that performs multi-color spectral fluorescence and bright field imaging simultaneously through a laminar core. This capability provides an accurate analysis of fluorescent signal intensities and spatial relationships between different structures and cellular features at high speed.
	Herein, we describe a method utilizing MIFC to characterize the cell populations that have internalized polyanhydride nanoparticles or Salmonella enterica serovar Typhimurium. We also describe the preparation of nanoparticle suspensions, cell labeling, acquisition on an ImageStreamX system and analysis of the data using the IDEAS application. We also demonstrate the application of a technique that can be used to differentiate the internalization pathways for nanoparticles and bacteria by using cytochalasin-D as an inhibitor of actin-mediated phagocytosis.

In this article, we describe a method utilizing multi-spectral imaging flow cytometry to quantify the internalization of polyanhydride nanoparticles or bacteria by RAW 264.7 cells.

Nanoparticulate  systems have emerged as valuable tools in vaccine delivery through their  ability to efficiently deliver cargo, including proteins, to ...

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. ...

PLGA Nanoparticles Formed by Single- or Double-emulsion with Vitamin E-TPGS

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible member of the aliphatic polyester family of biodegradable polymers. PLGA has long been a popular choice for drug delivery applications, particularly since it is already FDA-approved for use in humans in the form of resorbable sutures. Hydrophobic and hydrophilic drugs are encapsulated in PLGA particles via single- or double-emulsion. Briefly, the drug is dissolved with polymer or emulsified with polymer in an organic phase that is then emulsified with the aqueous phase. After the solvent has evaporated, particles are washed and collected via centrifugation for lyophilization and long term storage. PLGA degrades slowly via hydrolysis in aqueous environments, and encapsulated agents are released over a period of weeks to months. Although PLGA is a material that possesses many advantages for drug delivery, reproducible formation of nanoparticles can be challenging; considerable variability is introduced by the use of different equipment, reagents batch, and precise method of emulsification. Here, we describe in great detail the formation and characterization of microparticles and nanoparticles formed by single- or double-emulsion using the emulsifying agent vitamin E-TPGS. Particle morphology and size are determined with scanning electron microscopy (SEM). We provide representative SEM images for nanoparticles produced with varying emulsifier concentration, as well as examples of imaging artifacts and failed emulsifications. This protocol can be readily adapted to use alternative emulsifiers (e.g. poly(vinyl alcohol), PVA) or solvents (e.g.&#160;dichloromethane, DCM).

We describe the production and characterization of nanoparticles and microparticles composed of poly(lactic-co-glycolic acid) using vitamin E-TPGS as an emulsifier. By varying formulation parameters such as the concentration of emulsifier, it is possible to produce nanoparticles with mean diameters ranging from 220 nm to&#160;1.98 &#181;m.

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible member of the aliphatic polyester family of biodegradable polymers. PLGA has long been a popular ...

Utilization of Microscale Silicon Cantilevers to Assess Cellular Contractile Function In Vitro

The development of more predictive and biologically relevant in vitro assays is predicated on the advancement of versatile cell culture systems which facilitate the functional assessment of the seeded cells. To that end, microscale cantilever technology offers a platform with which to measure the contractile functionality of a range of cell types, including skeletal, cardiac, and smooth muscle cells, through assessment of contraction induced substrate bending. Application of multiplexed cantilever arrays provides the means to develop moderate to high-throughput protocols for assessing drug efficacy and toxicity, disease phenotype and progression, as well as neuromuscular and other cell-cell interactions. This manuscript provides the details for fabricating reliable cantilever arrays for this purpose, and the methods required to successfully culture cells on these surfaces. Further description is provided on the steps necessary to perform functional analysis of contractile cell types maintained on such arrays using a novel laser and photo-detector system. The representative data provided highlights the precision and reproducible nature of the analysis of contractile function possible using this system, as well as the wide range of studies to which such technology can be applied. Successful widespread adoption of this system could provide investigators with the means to perform rapid, low cost functional studies in vitro, leading to more accurate predictions of tissue performance, disease development and response to novel therapeutic treatment.

Utilization of Microscale Silicon Cantilevers to Assess Cellular Contractile Function In Vitro

This protocol describes the use of microscale silicon cantilevers as pliable culture surfaces for measuring the contractility of muscle cells in vitro. Cellular contraction causes cantilever bending, which can be measured, recorded, and converted into readouts of force, providing a non-invasive and scalable system for measuring contractile function in vitro.

The development of more predictive and biologically relevant in vitro assays is predicated on the advancement of versatile cell culture systems which ...

Double Emulsion Generation Using a Polydimethylsiloxane (PDMS) Co-axial Flow Focus Device

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 &#181;m to 50 &#181;m in diameter while using large channels that are robust against fouling and clogging.

Double Emulsion Generation Using a Polydimethylsiloxane PDMS Co-axial Flow Focus Device

Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 &#181;m.

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper ...

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.

Many cell lines used in basic biological and biomedical research maintain energy homeostasis through a combination of both aerobic and anaerobic ...

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and chemical complexity of living tissues and mimic in vivo tissue functions. Recent advances in microfabrication technologies have facilitated the development of 3D in vitro environments in which cells can be integrated into a well-defined extracellular matrix (ECM) and a defined set of soluble or matrix associated biomolecules. However, technological barriers have limited their widespread use in research laboratories. Here, we describe a method to construct simple devices for 3D culture and experimentation with cells and multicellular organoids in 3D microenvironments with a defined chemoattractant gradient. We illustrate the use of this platform for analysis of the response of epithelial cells and organoids to gradients of growth factors, such as epidermal growth factor (EGF). EGF gradients were stable in the devices for several days leading to directed branch formation in breast organoids. This analysis allowed us to conclude that collective gradient sensing by groups of cells is more sensitive vs. single cells. We also describe the fabrication method, which does not require photolithography facilities nor advanced soft lithography techniques. This method will be helpful to study 3D cellular behaviors in the context of the analysis of development and pathological states, including cancer.

We describe a method to construct devices for 3D culture and experimentation with cells and multicellular organoids. This device allows analysis of cellular responses to soluble signals in 3D microenvironments with defined chemoattractant gradients. Organoids are better than single cells at detection of weak noisy inputs.

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and ...

Using Magnetometry to Monitor Cellular Incorporation and Subsequent Biodegradation of Chemically Synthetized Iron Oxide Nanoparticles

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized in cells and then left within. One challenge is to assess their fate in the intracellular environment with reliable and precise methodologies. Herein, we introduce the use of the vibrating sample magnetometer (VSM) to precisely quantify the integrity of magnetic nanoparticles within cells by measuring their magnetic moment. Stem cells are first labeled with two types of magnetic nanoparticles; the nanoparticles have the same core produced via a fast and efficient microwave-based nonaqueous sol gel synthesis and differ in their coating: the commonly used citric acid molecule is compared to polyacrylic acid. The formation of 3D cell-spheroids is then achieved via centrifugation and the magnetic moment of these spheroids is measured at different times with the VSM. The obtained moment is a direct fingerprint of the nanoparticles&#8217; integrity, with decreasing values indicative of a nanoparticle degradation. For both nanoparticles, the magnetic moment decreases over culture time revealing their biodegradation. A protective effect of the polyacrylic acid coating is also shown, when compared to citric acid.

Iron oxide nanoparticles are synthesized via a nonaqueous sol gel procedure and coated with anionic short molecules or polymer. The use of magnetometry for monitoring the incorporation and biotransformations of magnetic nanoparticles inside human stem cells is demonstrated using a vibrating sample magnetometer (VSM).

Magnetic nanoparticles, made of iron oxide, present a peculiar interest for a wide range of biomedical applications for which they are often internalized ...