Name: magnetic and thermal-sensitive poly(n-isopropylacrylamide)-based microgels for magnetically triggered controlled release
Uploaded: 2017-07-04T14:00:00
Description: Watch this Scientific Journal Video about Magnetic and Thermal-sensitive PolyN-isopropylacrylamide-based Microgels for Magnetically Triggered Controlled Release at JoVE.com

This work was financially supported by Ministry of Science and Technology of Taiwan (MOST 104-2221-E-131-010, MOST 105-2622-E-131-001-CC2), and partially supported by Institute of Atomic and Molecular Sciences, Academia Sinica.

1. Synthesis of Surface-modified, Water-dispersible, Magnetic Nanoparticles, Fe3O4 and Fe3O4-NH2
<ol>
	<li>Add 14.02 g of FeCl3, 8.6 g of FeCl2&#183;4H2O and 250 mL water to a 500-mL beaker.</li>
	<li>Connect the rotor and controller to set up mechanic stirring. Mix the solution at 300 rpm for 30 min at room temperature (RT).</li>
	<li>Add 25 mL of ammonium hydroxide (33%) into the solution at RT and keep stirring (300 rpm) for 30 min. Keep the beaker op...

<ol>
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Z., Chu, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+the+molecular+weight+of+polyethylene+glycol+(PEG)+on+the+properties+of+chitosan-PEG-poly(N-isopropylacrylamide)+hydrogels.">Effect of the molecular weight of polyethylene glycol (PEG) on the properties of chitosan-PEG-poly(N-isopropylacrylamide) hydrogels.</a> J Mater Sci Mater Med. 19 (8), 2865-2872 (2008).</li><li>Sun, Y. -. M., Yu, C. -. W., Liang, H. -. C., Chen, J. -. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-Sensitive+Latex+Particles+for+Immobilization+of+&#945;-Amylase.">Temperature-Sensitive Latex Particles for Immobilization of &#945;-Amylase.</a> Journal of Dispersion Science and Technology. 20 (3), 907-920 (1999).</li><li>Chiang, P. 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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solution+Properties+of+Poly(N-isopropylacrylamide).">Solution Properties of Poly(N-isopropylacrylamide).</a> J Polym Sci A Polym Chem. 2 (8-9), 1441-1455 (1968).</li><li>Chuang, C. -. Y., Don, T. -. M., Chiu, W. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+properties+of+chitosan-based+thermo-+and+pH-responsive+nanoparticles+and+application+in+drug+release.">Synthesis and properties of chitosan-based thermo- and pH-responsive nanoparticles and application in drug release.</a> J Polym Sci A Polym Chem. 47 (11), 2798-2810 (2009).</li><li>Lee, C. -. F., Lin, C. -. C., Chiu, W. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermosensitive+and+control+release+behavior+of+poly+(N-isopropylacrylamide-co-acrylic+acid)+latex+particles.">Thermosensitive and control release behavior of poly (N-isopropylacrylamide-co-acrylic acid) latex particles.</a> J Polym Sci A Polym Chem. 46 (17), 5734-5741 (2008).</li><li>Lee, C. -. F., Wen, C. -. J., Lin, C. -. L., Chiu, W. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology+and+temperature+responsiveness-swelling+relationship+of+poly(N-isopropylamide-chitosan)+copolymers+and+their+application+to+drug+release.">Morphology and temperature responsiveness-swelling relationship of poly(N-isopropylamide-chitosan) copolymers and their application to drug release.</a> J Polym Sci A Polym Chem. 42 (12), 3029-3037 (2004).</li><li>Lin, C. L., Chiu, W. Y., Lee, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+thermoresponsive+core-shell+copolymer+latex+with+potential+use+in+drug+targeting.">Preparation of thermoresponsive core-shell copolymer latex with potential use in drug targeting.</a> J Colloid Interface Sci. 290 (2), 397-405 (2005).</li><li>Ma, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+method+to+in+situ+synthesis+of+magnetic+poly(N-isopropylacrylamide-co-acrylic+acid)+nanogels.">A novel method to in situ synthesis of magnetic poly(N-isopropylacrylamide-co-acrylic acid) nanogels.</a> Colloid Polym Sci. 294 (8), 1251-1257 (2016).</li><li>Du, G. H., Liu, Z. L., Xia, X., Chu, Q., Zhang, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+and+application+of+Fe3O4/SiO2+nanocomposites.">Characterization and application of Fe3O4/SiO2 nanocomposites.</a> Journal of Sol-Gel Science and Technology. 39 (3), 285-291 (2006).</li><li>Moroz, P., Jones, S. K., Gray, B. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetically+mediated+hyperthermia:+current+status+and+future+directions.">Magnetically mediated hyperthermia: current status and future directions.</a> International Journal of Hyperthermia. 18 (4), 267-284 (2002).</li><li>Silva-Buzanello, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validation+of+an+Ultraviolet-visible+(UV-Vis)+technique+for+the+quantitative+determination+of+curcumin+in+poly(l-lactic+acid)+nanoparticles.">Validation of an Ultraviolet-visible (UV-Vis) technique for the quantitative determination of curcumin in poly(l-lactic acid) nanoparticles.</a> Food Chemistry. 172, 99-104 (2015).</li><li>Kim, H. J., Jang, Y. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+analysis+of+curcumin+in+turmeric+by+DART-MS.">Direct analysis of curcumin in turmeric by DART-MS.</a> Phytochemical Analysis. 20 (5), 372-377 (2009).</li><li>Horowitz, H. H., Metzger, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+analysis+of+thermogravimetric+traces.">A new analysis of thermogravimetric traces.</a> Analytical Chemistry. 35 (10), 1464-1468 (1963).</li><li>Smith, B. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fourier transform infrared spectroscopy. , (1996).</li><li>Williams, D. B., Carter, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Transmission Electron Microscopy: A Textbook for Materials Science. , 3-17 (1996).</li><li>Xie, Y., Sougrat, R., Nunes, S. 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The most important steps of the preparation are in protocol section 2, for the synthesis of the magnetic microgels by thermo-induced emulsion. As shown in Figure 2 (TEM images), the spherical structure of microgels could be maintained at RT (lower than the LCST) due to the physical crosslinking resulting from the strong H-bonding between PNIPAAm (amide groups), PEI (amine groups) and Fe3O4-NH2 (amine groups). Based on the comparison in Fi...

Hydrogels are three-dimensionally (3D) polymeric networks which cannot dissolve but can swell in aqueous solutions1. The polymeric networks have hydrophilic domains (which can be hydrated to provide the hydrogel structure), and a cross-linked conformation (which can prevent the collapse of the network). Various methods have been investigated for preparation of hydrogels, such as emulsion polymerization, anionic copolymerization, crosslinking of neighboring polymer chains, and inverse micro-emulsion polymerization2. Physical and chemical cross-linking are introduced through these methods to obtain structurally stable hydrogels1,3. Chemical crosslinking normally requires the participation of the crosslinking agent, which connects the backbone or the side-chain of the polymers. Compared to chemical crosslinking, physical crosslinking is a better choice to fabricate hydrogels due to the avoidance of a crosslinking agent, since these agents are often toxic for practical applications4. Several approaches have been investigated for synthesizing physically cross-linked hydrogels, like crosslinking with ionic interaction, crystallization, bonding between amphiphilic blocks or grafting on the polymer chains, and hydrogen bonding4,5,6,7.
Stimuli-sensitive polymers, which can undergo conformational, chemical or physical property changes in response to different environmental conditions (i.e., temperature, pH, light, ionic strength, and magnetic field), have recently attracted attention as a potential platform for controlled release systems, drug delivery, and anti-cancer therapy8,9,10,11,12. Researchers are focusing on thermo-sensitive polymers where intrinsic temperature can be easily controlled. PNIPAAm is a thermally sensitive polymer, which contains both hydrophilic amide groups and hydrophobic isopropyl groups, and has a lower critical solution temperature (LCST)13. Hydrogen bonding between amide groups and water molecules provides the dispersity of PNIPAAm in aqueous solution at low temperatures (below the LCST), while the hydrogen-bonding between polymer chains occurs at high temperatures (above the LCST) and excludes water molecules so that the polymer network collapses. Regarding this unique property, many reports have been published for preparing temperature-triggered, self-assembled hydrogels by adjusting the hydrophobic and hydrophilic ratio of the polymer chain length, such as copolymerization, grafting, or side-chain modification for pharmaceutical platforms14,15,16,17.
Magnetic materials such as iron, cobalt, and nickel have also received increased attention during the past decades for biochemical applications18. Among those candidates, iron oxide is the most widely used because of its stability and low toxicity. Nano-sized iron oxides respond instantly to the magnetic field and behave as superparamagnetic atoms. However, such small particles easily aggregate; this reduces the surface energy, and therefore they lose their dispersity. In order to improve the water-dispersity, grafting or coating to protect the layer are commonly applied not only to separate each individual particle for stability but also to further functionalize the reaction site19.
Here, we fabricated magnetic PNIPAAm-based microgels to serve as drug carriers for controlled release systems. The synthesis process is described and shown in Figure 1. Instead of complicated copolymerization and chemical crosslinking, the novel temperature-induced emulsion of PNIPAAm followed by physical crosslinking was employed for obtaining the microgels without additional surfactant or crosslinking agents. This simplified the synthesis and prevented undesired toxicity. Within such a simple preparation protocol, the as-synthesized microgels offered water-dispersity for both the magnetic iron oxide nanoparticles and the hydrophobic, anti-cancer drug, curcumin. FT-IR, TEM, and imaging provided evidence of dispersion and encapsulation. Due to the embedded Fe3O4-NH2, the magnetic microgels showed potential for serving as micro-devices for controlled release under HFMF.

<table border="0" cellpadding="0" cellspacing="0" width="773">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Poly(N-isopropylacrylamide)</td>
			<td style="width:139px;">Polyscience, Inc</td>
			<td style="width:119px;">21458-10</td>
			<td style="width:205px;">Mw~40000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">(3-aminopropyl)trimethoxysilane</td>
			<td>Sigma-Aldrich</td>
			<td>440140</td>
			<td>&#62; 99 %</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iron(II) chloride tetrahydrate</td>
			<td>Sigma-Aldrich</td>
			<td>44939</td>
			<td>99%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iron(III) chloride</td>
			<td>Sigma-Aldrich</td>
			<td>157740</td>
			<td>97%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Curcumin</td>
			<td>Sigma-Aldrich</td>
			<td>00280590</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonia hydroxide</td>
			<td>Fisher Chemical</td>
			<td>A/3240/PB15</td>
			<td>35%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phosphate Buffered Saline</td>
			<td>Sigma-Aldrich</td>
			<td>806552</td>
			<td>pH 7.4, liquid, sterile-filtered</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polyethylenimine (PEI)</td>
			<td>Sigma-Aldrich</td>
			<td>P3143</td>
			<td>50 % (w/v) in water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">High-frequency magnetic field (HFMF)</td>
			<td>Lantech Industrial Co., Ltd.,Taiwan</td>
			<td>LT-15-80</td>
			<td>15 kV, 50&#8211;100 kHz</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultraviolet-Visible Spectrophotometry</td>
			<td>Thermo Scientific Co.</td>
			<td>Genesys</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transmission electron microscopy (TEM)</td>
			<td>JEM-2100</td>
			<td>JEOL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fourier transform infrared spectroscopy (FTIR)</td>
			<td>PerkinElmer</td>
			<td>Spectrum 100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thermogravimetric analyzer</td>
			<td>PerkinElmer</td>
			<td>Pyris 1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic cell disruptor</td>
			<td>Hielscher Ultrasonics</td>
			<td>UP50H</td>
			<td></td>
		</tr>
	</tbody>
</table>

magnetic and thermal-sensitive poly(n-isopropylacrylamide)-based microgels for magnetically triggered controlled release

Magnetically and thermally sensitive poly(N-isopropylacrylamide) (PNIPAAm)/Fe3O4-NH2 microgels with the encapsulated anti-cancer drug curcumin (Cur) were designed and fabricated for magnetically triggered release. PNIPAAm-based magnetic microgels with a spherical structure were produced via a temperature-induced emulsion followed with physical-crosslinking by mixing PNIPAAm, polyethylenimine (PEI), and Fe3O4-NH2 magnetic nanoparticles. Because of their dispersity, the Fe3O4-NH2 nanoparticles were embedded inside the polymer matrix. The amine groups exposed on the Fe3O4-NH2 and PEI surface supported the spherical structure by physically crosslinking with the amide groups of the PNIPAAm. The hydrophobic anti-cancer drug curcumin can be dispersed in water after encapsulation into the microgels. The microgels were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectral analysis. Furthermore, magnetically triggered release was studied under an external high frequency magnetic field (HFMF). A significant &#34;burst release&#34; of curcumin was observed after applying the HFMF to the microgels due to the magnetic inductive heating (hyperthermia) effect. This manuscript describes the magnetically triggered controlled release of Cur-PNIPAAm/Fe3O4-NH2 encapsulated curcumin, which can be potentially applied for tumor therapy.

The schematic for synthesis of PNIPAAm/PEI/Fe3O4-NH2 microgels is shown in Figure 1. TGA was applied to estimate the relative composition of the organic compound against the whole microgel. Since only the organic compound PNIPAAm could be burned, the relative composition of PNIPAAm and Fe3O4 (or Fe3O4-NH2) was determined and is shown in Table 1. Why do PNI...

Watch this Scientific Journal Video about Magnetic and Thermal-sensitive PolyN-isopropylacrylamide-based Microgels for Magnetically Triggered Controlled Release at JoVE.com

Magnetic and Thermal-sensitive PolyN-isopropylacrylamide-based Microgels for Magnetically Triggered Controlled Release

This manuscript describes the preparation of magnetic and thermal-sensitive microgels via a temperature-induced emulsion without chemical reaction. These sensitive microgels were synthesized by mixing poly(N-isopropylacrylamide) (PNIPAAm), polyethylenimine (PEI) and Fe3O4-NH2 nanoparticles for the potential use in magnetically and thermally triggered drug-release.

Magnetic and Thermal-sensitive Poly(N-isopropylacrylamide)-based Microgels for Magnetically Triggered Controlled Release

Magnetically and thermally sensitive poly(N-isopropylacrylamide) (PNIPAAm)/Fe3O4-NH2 microgels with the encapsulated anti-cancer drug curcumin (Cur) were ...

The overall goal of this procedure is to investigate the behaviors of curcumin-loaded magnetically and thermally sensitive hydrogels before and during magnetically triggered curcumin release. This method can help answer key questions in the anti-cancer drug field about the encapsulation of hydrophobic anti-cancer drugs such as curcumin for localized delivery to tumor cells. The main advantage of this technique is hydrophobic anti-cancer drugs are encapsulated by a spherical thermal-induced physical-crosslinking between polyethylenime-PNIPAAm and magnetic nanoparticles enabling targeting delivery with high-frequency magnetic fields.Though this method can provide insight into thermal-induced self-assemblies of PNIPAAm, it can also be applied to other substances such as emulsions, or polymerizations, or nanoparticle preparations. To begin the procedure, place 0.2 grams of PEI, 0.25 grams of polyNIPAM, five milliliters of 9.1 weight percent iron two three oxide nanoparticles dispersed in water, and 20 milliliters of deionized water in a glass vial. Use the same stirring conditions to combine in another vial 0.2 grams of PEI, 0.25 grams of polyNIPAM, five milliliters of 4.76 weight percent aminosilane functionalized iron two three oxide nanoparticles dispersed in water, and 20 milliliters of deionized water.Next, prepare two batches of 0.8 grams of PEI and 18.2 milliliters of deionized water. Heat both solutions at 70 degrees Celsius, in a water bath, for 30 minutes, while stirring. Then, while still stirring in the water bath, begin sonicating one batch, with a 50-watt probe sonicator.Using a three milliliter syringe, add this batch to the polyNIPAM and iron oxide suspension drop-wise, at a rate of one milliliter per minute. The addition should be as slow as possible to keep the physical cross-linking minimal. Otherwise, it will need a large magnetic microgel, that is difficult to disperse in water.Continue sonicating and stirring the suspension at 70 degrees Celsius, for 30 minutes. Then, allow the suspension to cool to room temperature. Turn off the sonicator and remove the suspension from the water bath.Remove the magnetic stir bar from the suspension. Place a magnet next to the vial and wait for the magnetic polyNIPAM iron oxide microgels to collect at the bottom of the vial. Then, remove the supernatant, and add 25 milliliters of deionized water to the microgels.Remove the magnet and vortex the mixture to obtain a dispersion of polyNIPAM iron oxide microgels in water. Repeat this process with the polyNIPAM aminosilane functionalized iron oxide suspension and the second batch of the PEI solution, to produce the corresponding functionalized microgel dispersion. In an aluminum foil-wrapped vial, dissolve 100 milligrams of curcumin, and 20 milliliters of HPLC-grade ethanol.Add two milliliters of the solution to the polyNIPAM aminosilane functionalized iron oxide dispersion. Stir the mixture at 400 RPM, overnight at room temperature. Then, remove the stir bar.Place a magnet next to the vial, and wait for the curcumin-loaded microgels to collect at the bottom of the vial. Replace the supernatant with 25 milliliters of deionized water, and disperse the microgels by vortexing. Next, to test the magnetically triggered curcumin release, first transfer 10 milliliters of the curcumin-loaded microgel dispersion to a 15 milliliter conical centrifuge tube.Add two milliliters of deionized water to the tube and vortex to re-disperse the microgels. Place the tube at the center of the coil of a high frequency magnetic field. Apply the magnetic field at 15 kilohertz for 20 minutes.Every two minutes, transfer 0.5 milliliters of the upper layer of the dispersion to a one milliliter cuvette. Replace each aliquot with 0.5 milliliters of deionized water. Use a thermometer to mix the water into the dispersion and to measure the dispersion temperature.Measure the absorption of each aliquot at 482 nanometers. Calculate the concentration of released curcumin in each aliquot from a standard calibration curve. Organic inorganic microgels were prepared from polyNIPAM and iron two three oxide nanoparticles.Microgels prepared with the 3-aminopropyltriethyloxysilane iron oxide particles were found to have a much lower relative iron oxide composition than non-functionalized particles, suggesting that the functionalized particles had cross-linked a larger amount of polyNIPAM than the non-functionalized particles. Aminosilane functionalized microgels, loaded with curcumin, showed increased isolation compared to their precursor microgels, suggesting that the hydrophobic curcumin was at least partially present in the microgel surfaces. Encapsulation of curcumin was confirmed by the appearance of characteristic absorption peaks in the FTIR spectrum of the loaded microgels.The rate of curcumin release was evaluated with and without exposure to a high frequency magnetic field. The curcumin release rate over a period of 20 minutes was 2.5 times greater in the presence of a high frequency magnetic field. Exposure to the magnetic field increased the bulk solution temperature to approximately 50 degrees Celsius, thus altering the microgel properties to exclude curcumin.Thermostability tests showed that the microgels remain dispersed in water in temperatures up to 70 degrees Celsius, despite aggregation. After watching this video, you should have a good understanding of how to encapsulation, hydrophobic, and high cancer drugs in polyNIPAM-based magnetic microgels by temperature-induced immersion, and how to perform a rapid targeted delivery by the manipulation of high frequency magnetic fields.

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Bioengineering

Magnetically-Assisted Remote Controlled Microcatheter Tip Deflection under Magnetic Resonance Imaging

X-ray fluoroscopy-guided endovascular procedures have several significant limitations, including difficult catheter navigation and use of ionizing radiation, which can potentially be overcome using a magnetically steerable catheter under MR guidance.
	The main goal of this work is to develop a microcatheter whose tip can be remotely controlled using the magnetic field of the MR scanner. This protocol aims to describe the procedures for applying current to the microcoil-tipped microcatheter to produce consistent and controllable deflections.
	A microcoil was fabricated using laser lathe lithography onto a polyimide-tipped endovascular catheter. In vitro testing was performed in a waterbath and vessel phantom under the guidance of a 1.5-T MR system using steady-state free precession (SSFP) sequencing. Various amounts of current were applied to the coils of the microcatheter to produce measureable tip deflections and navigate in vascular phantoms.
	The development of this device provides a platform for future testing and opportunity to revolutionize the endovascular interventional MRI environment.

Current applied to an endovascular microcatheter with microcoil tip made by laser lathe lithography can achieve controllable deflections under magnetic resonance (MR) guidance, which may improve speed and efficacy of navigation of vasculature during various endovascular procedures.

X-ray fluoroscopy-guided  endovascular procedures have several significant limitations, including  difficult catheter navigation and use of ionizing ...

Characteristics of Precipitation-formed Polyethylene Glycol Microgels Are Controlled by Molecular Weight of Reactants

This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Precipitation reactions offer several advantages over traditional microsphere fabrication techniques. Contrary to emulsion, suspension, and dispersion techniques, microgels formed by precipitation are of uniform shape and size, i.e.&#160;low polydispersity index, without the use of organic solvents or stabilizers. The mild conditions of the precipitation reaction, customizable properties of the microgels, and low viscosity for injections make them applicable for in vivo purposes. Unlike other fabrication techniques, microgel characteristics can be modified by changing the starting polymer molecular weight. Increasing the starting PEG molecular weight increased microgel diameter and swelling ratio. Further modifications are suggested such as encapsulating molecules during microgel crosslinking. Simple adaptations to the PEG microgel building blocks are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds.

This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Increasing the PEG molecular weight increased microgel diameter and swelling ratio. Simple adaptations to the PEG microgel precipitation reaction are explored for future applications of microgels as drug delivery vehicles and tissue engineering scaffolds.

This work describes the formation of poly(ethylene glycol) (PEG) microgels via a photopolymerized precipitation reaction. Precipitation reactions offer ...

Imaging Denatured Collagen Strands In vivo and Ex vivo via Photo-triggered Hybridization of Caged Collagen Mimetic Peptides

Collagen is a major structural component of the extracellular matrix that supports tissue formation and maintenance. Although collagen remodeling is an integral part of normal tissue renewal, excessive amount of remodeling activity is involved in tumors, arthritis, and many other pathological conditions. During collagen remodeling, the triple helical structure of collagen molecules is disrupted by proteases in the extracellular environment. In addition, collagens present in many histological tissue samples are partially denatured by the fixation and preservation processes. Therefore, these denatured collagen strands can serve as effective targets for biological imaging. We previously developed a caged collagen mimetic peptide (CMP) that can be photo-triggered to hybridize with denatured collagen strands by forming triple helical structure, which is unique to collagens. The overall goals of this procedure are i)&#160;to image denatured collagen strands resulting from normal remodeling activities in vivo, and ii) to visualize collagens in ex vivo tissue sections using the photo-triggered caged CMPs. To achieve effective hybridization and successful in vivo and ex vivo imaging, fluorescently labeled caged CMPs are either photo-activated immediately before intravenous injection, or are directly activated on tissue sections. Normal skeletal collagen remolding in nude mice and collagens in prefixed mouse cornea tissue sections are imaged in this procedure. The imaging method based on the CMP-collagen hybridization technology presented here could lead to deeper understanding of the tissue remodeling process, as well as allow development of new diagnostics for diseases associated with high collagen remodeling activity.

Imaging Denatured Collagen Strands In vivo and Ex vivo via Photo-triggered Hybridization of Caged Collagen Mimetic Peptides

This procedure demonstrates in vivo near IR fluorescence imaging of collagen remodeling activities in mice as well as ex vivo staining of collagens in tissue sections using caged collagen mimetic peptides that can be photo-triggered to hybridize with denatured collagen strands.

Collagen is a major structural component of the extracellular matrix that supports tissue formation and maintenance. Although collagen remodeling is an ...

Custom-designed Laser-based Heating Apparatus for Triggered Release of Cisplatin from Thermosensitive Liposomes with Magnetic Resonance Image Guidance

Liposomes have been employed as drug delivery systems to target solid tumors through exploitation of the enhanced permeability and retention (EPR) effect resulting in significant reductions in systemic toxicity. Nonetheless, insufficient release of encapsulated drug from liposomes has limited their clinical efficacy. Temperature-sensitive liposomes have been engineered to provide site-specific release of drug in order to overcome the problem of limited tumor drug bioavailability. Our lab has designed and developed a heat-activated thermosensitive liposome formulation of cisplatin (CDDP), known as HTLC, to provide triggered release of CDDP at solid tumors. Heat-activated delivery in vivo was achieved in murine models using a custom-built laser-based heating apparatus that provides a conformal heating pattern at the tumor site as confirmed by MR thermometry (MRT). A fiber optic temperature monitoring device was used to measure the temperature in real-time during the entire heating period with online adjustment of heat delivery by alternating the laser power. Drug delivery was optimized under magnetic resonance (MR) image guidance by co-encapsulation of an MR contrast agent (i.e.,&#160;gadoteridol) along with CDDP into the thermosensitive liposomes as a means to validate the heating protocol and to assess tumor accumulation. The heating protocol consisted of a preheating period of 5 min prior to administration of HTLC and 20 min heating post-injection. This heating protocol resulted in effective release of the encapsulated agents with the highest MR signal change observed in the heated tumor in comparison to the unheated tumor and muscle. This study demonstrated the successful application of the laser-based heating apparatus for preclinical thermosensitive liposome development and the importance of MR-guided validation of the heating protocol for optimization of drug delivery.

AN MRI-compatible&#160;custom-designed laser-based heating apparatus has been developed to provide local heating of subcutaneous tumors in order to activate release of agents from thermosensitive liposomes specifically at the tumor region.

Liposomes have been employed as drug delivery systems to target solid tumors through exploitation of the enhanced permeability and retention (EPR) effect ...

Composite Scaffolds of Interfacial Polyelectrolyte Fibers for Temporally Controlled Release of Biomolecules

Various scaffolds used in tissue engineering require a controlled biochemical environment to mimic the physiological cell niche. Interfacial polyelectrolyte complexation (IPC) fibers can be used for controlled delivery of various biological agents such as small molecule drugs, cells, proteins and growth factors. The simplicity of the methodology in making IPC fibers gives flexibility in its application for controlled biomolecule delivery. Here, we describe a method of incorporating IPC fibers into two different polymeric scaffolds, hydrophilic polysaccharide and hydrophobic polycaprolactone, to create a multi-component composite scaffold. We showed that IPC fibers can be easily embedded into these polymeric structures, enhancing the capability for sustained release and improved preservation of biomolecules. We also created a composite polymeric scaffold with topographical cues and sustained biochemical release that can have synergistic effects on cell behavior. Composite polymeric scaffolds with IPC fibers represent a novel and simple method of recreating the cellular niche.

Scaffolds for tissue engineering need to recapitulate the complex biochemical and biophysical microenvironment of the cellular niche. Here, we show the use of interfacial polyelectrolyte complexation fibers as a platform to create composite, multi-component polymeric scaffolds with sustained biochemical release.

Various scaffolds used in tissue engineering require a controlled biochemical environment to mimic the physiological cell niche. Interfacial ...

Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of smart soft devices for biomedical applications. Although a number of magnetically-responsive drug delivery systems have demonstrated efficacies through either in vitro proof of concept studies or in vivo preclinical applications, their use in clinical settings is still limited by their insufficient biocompatibility or biodegradability. Additionally, many of the existing platforms rely on sophisticated techniques for their fabrications. We recently demonstrated the fabrication of biodegradable, gelatin-based thermo-responsive microgel by physically entrapping poly(N-isopropylacrylamide-co-acrylamide) chains as a minor component within a three-dimensional gelatin network. In this study, we present a facile method to fabricate a biodegradable drug release platform that enables a magneto-thermally triggered drug release. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and thermo-responsive polymers within gelatin-based colloidal microgels, in conjunction with an alternating magnetic field application system.

We present a facile method to fabricate a biodegradable gelatin-based drug release platform that is magneto-thermally responsive. This was achieved by incorporating superparamagnetic iron oxide nanoparticles and poly(N-isopropylacrylamide-co-acrylamide) within a spherical gelatin micro-network crosslinked by genipin, in conjunction with an alternating magnetic field application system.

Magnetically-responsive nano/micro-engineered biomaterials that enable a tightly controlled, on-demand drug delivery have been developed as new types of ...

An Additive Manufacturing Technique for the Facile and Rapid Fabrication of Hydrogel-based Micromachines with Magnetically Responsive Components

Polyethylene glycol (PEG)-based hydrogels are biocompatible hydrogels that have been approved for use in humans by the FDA. Typical PEG-based hydrogels have simple monolithic architectures and often function as scaffolding materials for tissue engineering applications. More sophisticated structures typically take a long time to fabricate and do not contain moving components. This protocol describes a photolithography method that allows for facile and rapid microfabrication of PEG structures and devices. This strategy involves an in-house developed fabrication stage that allows for the rapid fabrication of 3D structures by building upwards in a layer-by-layer fashion. Independent moving components can also be aligned and assembled onto support structures to form integrated devices. These independent components are doped with superparamagnetic iron oxide nanoparticles that are sensitive to magnetic actuation. In this manner, the fabricated devices can be actuated using external magnets to yield movement of the components within. Hence, this technique allows for the fabrication of sophisticated MEMS-like devices (micromachines) that are composed entirely out of a biocompatible hydrogel, able to function without an onboard power source, and respond to a contact-less method of actuation. This manuscript describes the fabrication of both the fabrication set-up as well as the step-by-step method for the microfabrication of these hydrogels-based MEMS-like devices.

An additive manufacturing strategy for processing UV-crosslinkable hydrogels has been developed. This strategy allows for the layer-by-layer assembly of microfabricated hydrogel structures as well as the assembly of independent components, yielding integrated devices containing moving components that are responsive to magnetic actuation.

Polyethylene glycol (PEG)-based hydrogels are biocompatible hydrogels that have been approved for use in humans by the FDA. Typical PEG-based hydrogels ...

Magnetic-, Acoustic-, and Optical-Triple-Responsive Microbubbles for Magnetic Hyperthermia and Pothotothermal Combination Cancer Therapy

The precision delivery of anti-cancer agents which aim for targeted and deep-penetrated delivery as well as a controlled release at the tumor site has been challenged. Here, we fabricate iron oxide nanoparticle shelled microbubbles (NSMs) through self-assembly, synergizing magnetic, acoustic, and optical responsiveness in one nanotherapeutic platform. Iron oxide nanoparticles serve as both magnetic and photothermal agents. Once intravenously injected, NSMs can be magnetically guided to the tumor site. Ultrasound triggers the release of iron oxide nanoparticles, facilitating the penetration of nanoparticles deep into the tumor due to the cavitation effect of microbubbles. Thereafter, magnetic hyperthermia and photothermal therapy can be performed on the tumor for combinational cancer therapy, a solution for cancer resistance due to the tumor heterogeneity. In this protocol, the synthesis and characterization of NSMs including structural, chemical, magnetic and acoustic properties were performed. In addition, the anti-cancer efficacy by thermal therapy was investigated using in vitro cell cultures. The proposed delivery strategy and combination therapy holds great promise in cancer treatment to improve both delivery and anticancer efficacies.

Presented here is a protocol for the fabrication of iron oxide nanoparticle-shelled microbubbles (NSMs) through self-assembly, synergizing magnetic, acoustic, and optical responsiveness in one nanotherapeutic platform for magnetic hyperthermia and photothermal combination cancer therapy.

The precision delivery of anti-cancer agents which aim for targeted and deep-penetrated delivery as well as a controlled release at the tumor site has ...

Low-Cost, Volume-Controlled Dipstick Urinalysis for Home-Testing

Dipstick urinalysis provides quick and affordable estimations of multiple physiological conditions but requires good technique and training to use accurately. Manual performance of dipstick urinalysis relies on good human color vision, proper lighting control, and error-prone, time-sensitive comparisons to chart colors. By automating the key steps in the dipstick urinalysis test, potential sources of error can be eliminated, allowing self-testing at home. We describe the steps necessary to create a customizable device to perform automated urinalysis testing in any environment. The device is cheap to manufacture and simple to assemble. We describe the key steps involved in customizing it for the dipstick of choice and for customizing a mobile phone app to analyze the results. We demonstrate its use to perform urinalysis and discuss the critical measurements and fabrication steps necessary to ensure robust operation. We then compare the proposed method to the dip-and-wipe method, the gold standard technique for dipstick urinalysis.

Dipstick urinalysis is a quick and affordable method of assessing one&#8217;s personal state of health. We present a method to perform accurate, low-cost dipstick urinalysis that removes the primary sources of error associated with traditional dip-and-wipe protocols and is simple enough to be performed by lay users at home.

Dipstick urinalysis provides quick and affordable estimations of multiple physiological conditions but requires good technique and training to use ...

Controlled Strain of 3D Hydrogels under Live Microscopy Imaging

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized in vitro stretching methods. Various available systems use 2D substrate-based stretchers, while the accessibility of 3D techniques to strain soft hydrogels, is more restricted. Here, we describe a method that allows external stretching of soft hydrogels from their circumference, using an elastic silicone strip as the sample carrier. The stretching system utilized in this protocol is constructed from 3D-printed parts and low-cost electronics, making it simple and easy to replicate in other labs. The experimental process begins with polymerizing thick (&#62;100 &#956;m) soft fibrin hydrogels (Elastic Modulus of ~100 Pa) in a cut-out at the center of a silicone strip. Silicone-gel constructs are then attached to the printed-stretching device and placed on the confocal microscope stage. Under live microscopy the stretching device is activated, and the gels are imaged at various stretch magnitudes. Image processing is then used to quantify the resulting gel deformations, demonstrating relatively homogenous strains and fiber alignment throughout the gel&#8217;s 3D thickness (Z-axis). Advantages of this method include the ability to strain extremely soft hydrogels in 3D while executing in situ microscopy, and the freedom to manipulate the geometry and size of the sample according to the user&#8217;s needs. Additionally, with proper adaptation, this method can be used to stretch other types of hydrogels (e.g., collagen, polyacrylamide or polyethylene glycol) and can allow for analysis of cells and tissue response to external forces under more biomimetic 3D conditions.

The presented method involves uniaxial stretching of 3D soft hydrogels embedded in silicone rubber while allowing live confocal microscopy. Characterization of the external and internal hydrogel strains as well as fiber alignment are demonstrated. The device and protocol developed can assess the response of cells to various strain regimes.

External forces are an important factor in tissue formation, development, and maintenance. The effects of these forces are often studied using specialized ...