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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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 ...

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