Name: alternating magnetic field-responsive hybrid gelatin microgels for controlled drug release
Uploaded: 2016-02-13T15:00:00
Description: Watch this Scientific Journal Video about Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release at JoVE.com

This study was supported by Farris Family Innovation Award and NIH 1R01NR015674-01 to MK. The authors thank Josep Nayfach (Qteris, Inc) for providing an electro-magnetic generator system as well as his technical consultation. The authors also thank Huan Yan (LCI &#38; Chemical Physics Interdisciplinary Program, Kent State University) for her technical assistants.

Note: The overall process of fabricating magnetic field-responsive gelatin microgels is illustrated in Figure 1A.
1. Preparing Solutions and Suspensions
<ol>
	<li>Prepare a crosslinker genipin (1% w/v) solution by dissolving 20 mg of genipin in 2 ml of phosphate buffered saline (1x PBS; pH 7.4). Vortex the solution and place in a 50 oC water bath for 2 hr to completely dissolve the solution.</li>
	<li>Prepare a surfactant solution by dissolving 20 mg of poly(ethyl...

<ol>
	<li>Langer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomaterials+in+drug+delivery+and+tissue+engineering:+one+laboratory's+experience.">Biomaterials in drug delivery and tissue engineering: one laboratory's experience.</a> Acc. Chem. Res. 33, 94-101 (2000).</li><li>Rivest, C. M., Morrison, D., Ni, B., Rubib, J., Yadav, V., Mahdavi, A., Karp, J., Khademhosseini, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microscale+hydrogels+for+medicine+and+biology:+synthesis,+characteristics+and+applications.">Microscale hydrogels for medicine and biology: synthesis, characteristics and applications.</a> J Mech Mater Struct. 2, 1103-1119 (2007).</li><li>Kawaguchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoresponsive+microhydrogels:+preparation,+properties+and+applications.">Thermoresponsive microhydrogels: preparation, properties and applications.</a> Polym. Int. 63, 925-932 (2014).</li><li>Vinogradov, S. 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D., 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=Magnetic+field+activated+lipid-polymer+hybrid+nanoparticles+for+stimuli-responsive+drug+release.">Magnetic field activated lipid-polymer hybrid nanoparticles for stimuli-responsive drug release.</a> Acta biomaterialia. 9, 5447-5452 (2013).</li><li>Hayashi, K., 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=Magnetically+responsive+smart+nanoparticles+for+cancer+treatment+with+a+combination+of+magnetic+hyperthermia+and+remote-control+drug+release.">Magnetically responsive smart nanoparticles for cancer treatment with a combination of magnetic hyperthermia and remote-control drug release.</a> Theranostics. 8, 834-844 (2014).</li><li>Suzuki, D., Kawaguchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimuli-sensitive+core/shell+template+particles+for+immobilizing+inorganic+nanoparticles+in+the+core.">Stimuli-sensitive core/shell template particles for immobilizing inorganic nanoparticles in the core.</a> Colloid Polym Sci. 284, 1443-1451 (2006).</li><li>Bhattacharya, S., Eckert, F., Boyko, V., Pich, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-,+pH-,+and+magnetic-field-sensitive+hybrid+microgels.">Temperature-, pH-, and magnetic-field-sensitive hybrid microgels.</a> Small. 3, 650-657 (2007).</li><li>Wong, J. E., Gaharwar, A. K., Muller-Schulte, D., Bahadur, D., Richtering, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual-stimuli+responsive+PNiPAM+microgel+achieved+via+layer-by-layer+assembly:+Magnetic+and+thermoresponsive.">Dual-stimuli responsive PNiPAM microgel achieved via layer-by-layer assembly: Magnetic and thermoresponsive.</a> J Colloid Interf Sci. 324, 47-54 (2008).</li><li>Zhao, X., 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=Active+scaffolds+for+on-demand+drug+and+cell+delivery.">Active scaffolds for on-demand drug and cell delivery.</a> Proc. Natl. Acad. Sci. U.S.A. 108, 67-72 (2011).</li><li>Xu, F., 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=Release+of+magnetic+nanoparticles+from+cell-encapsulating+biodegradable+nanobiomaterials.">Release of magnetic nanoparticles from cell-encapsulating biodegradable nanobiomaterials.</a> ACS nano. 6, 6640-6649 (2012).</li><li>Li, Y. H., 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=Magnetic+Hydrogels+and+Their+Potential+Biomedical+Applications.">Magnetic Hydrogels and Their Potential Biomedical Applications.</a> Adv Funct Mater. 23, 660-672 (2013).</li><li>Cooperstein, M. A., Canavan, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+cytotoxicity+of+(N-isopropyl+acrylamide)+and+poly(N-isopropyl+acrylamide)-coated+surfaces.">Assessment of cytotoxicity of (N-isopropyl acrylamide) and poly(N-isopropyl acrylamide)-coated surfaces.</a> Biointerphases. 8, 19 (2013).</li><li>Jorgensen, L., Moeller, E. H., van de Weert, M., Nielsen, H. M., Frokjaer, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparing+and+evaluating+delivery+systems+for+proteins.">Preparing and evaluating delivery systems for proteins.</a> Eur J Pharm Sci. 29, 174-182 (2006).</li><li>Holland, T. A., Tabata, Y., Mikos, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+release+of+transforming+growth+factor-beta+1+from+gelatin+microparticles+encapsulated+in+biodegradable,+injectable+oligo(poly(ethylene+glycol)+fumarate)+hydrogels.">In vitro release of transforming growth factor-beta 1 from gelatin microparticles encapsulated in biodegradable, injectable oligo(poly(ethylene glycol) fumarate) hydrogels.</a> J Control Release. 91, 299-313 (2003).</li><li>Liang, H. C., Chang, W. H., Lin, K. J., Sung, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genipin-crosslinked+gelatin+microspheres+as+a+drug+carrier+for+intramuscular+administration:+in+vitro+and+in+vivo+studies.">Genipin-crosslinked gelatin microspheres as a drug carrier for intramuscular administration: in vitro and in vivo studies.</a> J Biomed Mater Res. Part A. 65, 271-282 (2003).</li><li>Solorio, L., Zwolinski, C., Lund, A. W., Farrell, M. J., Stegemann, J. 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The technology described here demonstrates a proof of concept on the use of nanoparticle-microgel hybrids for magneto-thermally triggered drug release. This was achieved by physically entrapping MNPs and p(NIPAM-co-AAm) chains within a microscale three-dimensional gelatin network crosslinked by genipin. The magnetic field-responsive platform was sufficient to generate heat within the microgel in response to a remotely applied AMF, which in turn triggered the release of a model drug, BSA.
<p class="jove_conte...

Stimuli-responsive drug delivery systems that enable a tightly controlled drug delivery in response to either endogenous or exogenous stimuli (e.g., temperature or pH) have been extensively investigated as new types of smart soft devices for drug delivery. Microscale hydrogels have been widely employed as a drug delivery platform in that they confer controllable and sustainable drug release profiles as well as tunable chemical and mechanical properties1-3. In particular, the colloidal microgels exhibit many advantages as a vehicle for drug delivery due to their rapid responsiveness to external stimuli and suitable injectability to local tissue in a minimally invasive manner4. The poly(N-isopropylacrylamide) (pNIPAM) or its copolymers have been widely adopted in synthesizing thermo-responsive microgels by grafting pNIPAM with biodegradable/ biocompatible polymers including gelatin, chitosan, alginate acid, or hyaluronic acid5,6, in which a phase transition characteristic of pNIPAM at its lower critical solution temperature (LCST) can be used as a trigger of drug release7. We recently demonstrated a fabrication of biodegradable, gelatin-based thermo-responsive microgel by incorporating poly(N-isopropylacrylamide-co-acrylamide) [p(NIPAM-co-AAm)] chains as a minor component within three-dimensional gelatin networks8. The gelatin/p(NIPAM-co-AAm) microgel exhibited a tunable deswelling to temperature increase, which positively correlated to the release of bovine serum albumin (BSA).
During the last several years, there have been increasing efforts to develop a magnetically responsive drug delivery platform that can trigger the release of drug in an on-demand fashion9,10. The basic principle for the synthesis of magnetically responsive drug delivery platform utilizes the characteristic of superparamagnetic nanoparticles (MNPs) to generate heat when they receive a high frequency alternating magnetic field (AMF), which triggers a temperature-sensitive drug release. This holds promise for future clinical applications in that this system can target deep into the tissue, enables a non-invasive and remotely controlled drug release and can be combined with hyperthermia treatment and magnetic resonance imaging system10-12. Such platforms include: (1) MNPs/pNIPAM hybrid microgel particles 13-15 and (2) macroscopic hydrogel scaffolds incorporating immobilized MNPs16-18. The pNIPAM-based microgel platforms demonstrated a finely-tunable volume phase transition responsiveness to magneto-thermal stimuli. However, they still rely on complex and sophisticated techniques in the fabrication and the use of pNIPAM polymers with a high content can be potentially cytotoxic to cells19, which may limit their in vivo applications. The macroscopic scaffolds exhibit a relatively slow response to external stimuli and require an invasive surgical transplantation compared to colloidal microgels.
The water-in-oil emulsification has been the standard method to produce submillimeter or micrometer-sized gel particles20. At the water-oil interface of the emulsion, microgel particle forms a spherical shape due to the minimization of surface energy of the water droplet under mechanical shear force. This method allows the production of a large amount of aqueous spherical gel droplets in a simple fabrication procedure and has been successfully adopted for fabricating gelatin-based microgels for drug delivery applications21-23.
Here, we present a facile method to synthesize a magnetothermally responsive gelatin-based microgels for drug delivery application by employing the water-in-oil emulsification method. This was achieved by physically incorporating iron oxide MNPs and p(NIPAM-co-AAm) chains as a minor component within a spherical microscale gelatin network that is covalently crosslinked by a naturally-derived crosslinker genipin, in conjunction with a high frequency alternating magnetic field (AMF) application system.

<table border="0" cellpadding="0" cellspacing="0" width="706">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gelatin</td>
			<td style="width:204px;">Sigma-Aldrich, MO, USA</td>
			<td style="width:119px;">G2500</td>
			<td style="width:167px;">Gelatin type A, porcine skin</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">poly(N-isopropylacrylamide-co-acrylamide)&#160;</td>
			<td style="width:204px;">Sigma-Aldrich, MO, USA</td>
			<td>738727</td>
			<td>MW=20,000, LCST=34-38 oC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silicon oil</td>
			<td style="width:204px;">Sigma-Aldrich, MO, USA</td>
			<td>378372</td>
			<td>Viscosity 350 cSt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pluoronic L64</td>
			<td style="width:204px;">Sigma-Aldrich, MO, USA</td>
			<td style="width:119px;">435449</td>
			<td>100 ppm poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">genipin</td>
			<td style="width:204px;">TimTec LLC, DE, USA</td>
			<td>ST080860</td>
			<td>Mw = 226.23;&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Magnetic nanoparticles (MNPs)</td>
			<td style="width:204px;">Micromod Inc, Germany</td>
			<td>79-00-102</td>
			<td>nanomag-D-spio, 100 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TR-BSA</td>
			<td style="width:204px;">Life Technologies, NY USA</td>
			<td>A23017</td>
			<td>Albumin from Bovine Serum (BSA), Texas Red conjugate</td>
		</tr>
	</tbody>
</table>

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.

When the protocol is performed correctly, the fabricated microgels should exhibit a well-characterized spherical morphology and colloidal dispersibility with diameters in the range between 5 &#956;m to 20 &#956;m (Figure 1B and C). Either fluorescent MNPs or fluorescent BSA can be used to confirm whether MNPs or drugs (BSA in this study) are properly encapsulated within the microgel (Figure 1D). The fabricated microgels can be stable and stored at 4 ...

Watch this Scientific Journal Video about Alternating Magnetic Field-Responsive Hybrid Gelatin Microgels for Controlled Drug Release at JoVE.com

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

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 ...

This overall goal of this protocol is to present a facile method for fabrication of magnetothermally responsive nanoparticle microgel hybrids, and to demonstrate a proof of concept on the use of the microgel hybrids for controllable drug release. The main advantages of this protocol are that the process is relatively simple and it confers the microgel to exhibit the magnetothermally responsive characteristic by simply entrapping magnetic nanoparticles and thermoresponsive PNIPAM copolymers within the gelatin matrix. This allows for drug released in response to an alternating magnetic field, which is induced by the swelling of the PNIPAM copolymer associated with the increasing temperature of the nanoparticles as the nanoparticles respond to the magnetic waves.The implications of this technique extend toward developing on-demand drug delivery system because this controllable drug release platform is responsive to multiple on and off cycles induced by non-invasive external stimuli. The process of fabricating magnetic field responsive gelatin microgels begins with preparing the solutions in suspension. Basic solution preparation is described in the text protocol.When preparing the gelatin solution, keep it in a water bath until it reaches the fluidic phase. Then homogenize it with a vortex. With all the solutions prepared mix equal volumes of gelatin solution and the PNIPAM copolymer containing magnetic nonaparticles and vortex the mixture thoroughly.The next step is to emulsify the aqueous mixture in silicon oil and then apply a surfactant coat. Pour 15ml of silicone oil into a sterile beaker and immediately add 0.86ml of the prepared mixture. Then stir the mixture at 900 rpm at 30 degrees Celsius for half an hour.After producing the emulsion, transfer it to a 50ml tube and cool it down at four degrees Celsius for 10 minutes. Microdroplets will now form in the oil. Next, mostly fill the tube with Pluronic L-64 surfactant solution, Cool to four degrees Celsius, and shake the tube vigorously so the L-64 molecules get adsorbed into gel surface and stabilize the microgel suspension.Then centrifuge the tube for 20 mintues at 2300 Gs and at four degrees Celsius. After 20 minutes, examine the tube for a pellet of gel particles. Repeat the centrifugation cycle until one can be seen.Then carefully remove the supernatant and fill the tube to 45 ml with cold L-64 solution. Shake the tube hard to mix the pelleted microgels into the surfactant. And transfer the suspension to a new 50ml tube.Then repeat the centrifugation process and collect the pellet of microgels again. Now, to ensure that no surfactants or oil droplets remain in the sample suspension thoroughly aspirate the supernatant. The next step to preparing the microgels is to crosslink their gelatin matrix.To begin, suspend the pellet in 2ml of the prepared Genipin solution. Use a vortex. Then quickly transfer the suspension to a 23 degrees Celsius water bath to initiate the covalent crosslinking reaction.The reaction can be run for five minutes to two hours. Once completed, removed the excess crosslinkers. Centrifuge the sample for 20 minutes at 2300 Gs and at four degrees Celsius as before.Then, aspirate and discard the supernatant. Repeat the washing step in PBS a total of three times, breaking up the pellet mechanically with a pipette tip if needed. Complete removal of the unreacted excess crosslinkers is critical.After the last wash, bring the microgels up in PBS to the desired density. Measure their density using a hemocytometer. The fabricated microgels are stable for up to four weeks when stored at four degrees Celsius, provided that there is no degrading agent, such as collagenase.To characterize the microgels by microscopy load them on a slide and seal them under a cover slip with epoxy resin. The final step of the procedure is to measure drug release from the microgels. Place the tube with the desired concentration of microgels into the chamber of magnetic coils.Then, insert a fiber optic temperature probe to monitor temperature change during the application of the alternating magnetic field. Now, apply high frequency alternating magnetic field at a defined field strength and for a specified duration. Following the treatment, centrifuge the tube for 20 minutes at 2300 Gs and at four degrees Celsius.Collect the supernatant to quantify the amount of drug released from the microgels. In this case, use spectrophotometry to detect the texas red. The fabricated microgels should exhibit a well-characterized spherical morphology and colloidal dispersability with diameters between five to 20 microns.Either fluorescent superparamagnetic nanoparticles or fluorescently labelled BSA can be used to confirm proper encapsulation within the microgel. The entrapment of PNIPAM copolymer in the gelatin microgel matrix enables it to exhibit a temperature-dependent volume change. Increasing the temperature of the media from 22 to 42 degrees Celsius resulted in deswelling of gelatin microgels by about 40%In contrast, only 10%deswelling was observed in gelatin microgel without PNIPAM copolymer.When superparamagnetic nanoparticles were incorporated into the gelatin PNIPAM copolymer microgel, the microgel increased in temperature when exposed to the appropriate alternating magnetic field. Measured TRBSA release from these microgels was about 35%Without incorporating the copolymer into the microgels, the release of TRBSA was significantly lower. Only around 10%Thus, the release of BSA in response to the alternating magnetic field was likely due to deswelling associated with the shrinkage of PNIPAM copolymer chains within the microgel.After watching this video, you should have a good understanding of how to fabricate biodegradeable magnetic field responsive nanoparticle microgel hybrids that enable controllable drug release using a simple water-in-oil emulsification method. Once mastered, this technique can be done in three hours if it is performed properly. This protocol also can be modified to fabricate microgel hybrids that are responsive to other stimuli, such as near infrared light.By simply incorporating near infrared responsive gold nanoparticle with gelatin matrix.

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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 ...

Hybrid &#181;CT-FMT imaging and image analysis

Fluorescence-mediated tomography (FMT) enables longitudinal and quantitative determination of the fluorescence distribution in vivo and can be used to assess the biodistribution of novel probes and to assess disease progression using established molecular probes or reporter genes. The combination with an anatomical modality, e.g., micro computed tomography (&#181;CT), is beneficial for image analysis and for fluorescence reconstruction. We describe a protocol for multimodal &#181;CT-FMT imaging including the image processing steps necessary to extract quantitative measurements. After preparing the mice and performing the imaging, the multimodal data sets are registered. Subsequently, an improved fluorescence reconstruction is performed, which takes into account the shape of the mouse. For quantitative analysis, organ segmentations are generated based on the anatomical data using our interactive segmentation tool. Finally, the biodistribution curves are generated using a batch-processing feature. We show the applicability of the method by assessing the biodistribution of a well-known probe that binds to bones and joints.

Hybrid  &amp;#181;CT-FMT imaging and image analysis

We describe a protocol for hybrid imaging, combining fluorescence-mediated tomography (FMT) with micro computed tomography (&#181;CT). After fusion and reconstruction, we perform interactive organ segmentation to extract quantitative measurements of the fluorescence distribution.

Fluorescence-mediated tomography (FMT) enables longitudinal and quantitative determination of the fluorescence distribution in vivo and can be used to ...

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 ...

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.

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.

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

Wet-spinning-based Molding Process of Gelatin for Tissue Regeneration

This article presents an inexpensive method to fabricate gelatin, as a natural polymer, into monofilament fibers or other appropriate forms. Through the wet spinning method, gelatin fibers are produced by smooth extrusion in a suitable coagulation medium. To increase the functional surface of these gelatin fibers and their ability to mimic the features of tissues, gelatin can be molded into a tube form by referring to this concept. Examined by in vitro and in vivo tests, the gelatin tubes demonstrate a great potential for application in tissue engineering. Acting as a suitable filling gap material, gelatin tubes can be used to substitute the tissue in the damaged area (e.g., in the nervous or cardiovascular system), as well as to promote regeneration by providing a direct replacement of stem cells and neural circuitry. This protocol provides a detailed procedure for creating a biomaterial based on a natural polymer, and its implementation is expected to greatly benefit the development of correlative natural polymers, which help to realize tissue regeneration strategies.

We developed and describe a protocol based on the wet spinning concept, for the construction of gelatin-based biomaterials used for the application of tissue engineering.

This article presents an inexpensive method to fabricate gelatin, as a natural polymer, into monofilament fibers or other appropriate forms. Through the ...

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 ...

Multi-timescale Microscopy Methods for the Characterization of Fluorescently-labeled Microbubbles for Ultrasound-Triggered Drug Release

Microbubble contrast agents hold great promise for drug delivery applications with ultrasound. Encapsulating drugs in nanoparticles reduces systemic toxicity and increases circulation time of the drugs. In a novel approach to microbubble-assisted drug delivery, nanoparticles are incorporated in or on microbubble shells, enabling local and triggered release of the nanoparticle payload with ultrasound. A thorough understanding of the release mechanisms within the vast ultrasound parameter space is crucial for efficient and controlled release. This set of presented protocols is applicable to microbubbles with a shell containing a fluorescent label. Here, the focus is on microbubbles loaded with poly(2-ethyl-butyl cyanoacrylate) polymeric nanoparticles, doped with a modified Nile Red dye. The particles are fixed within a denatured casein shell. The microbubbles are produced by vigorous stirring, forming a dispersion of perfluoropropane gas in the liquid phase containing casein and nanoparticles, after which the microbubble shell self-assembles. A variety of microscopy techniques are needed to characterize the nanoparticle-stabilized microbubbles at all relevant timescales of the nanoparticle release process. Fluorescence of the nanoparticles enables confocal imaging of single microbubbles, revealing the particle distribution within the shell. In vitro ultra-high-speed imaging using bright-field microscopy at 10 million frames per second provides insight into the bubble dynamics in response to ultrasound insonation. Finally, nanoparticle release from the bubble shell is best visualized by means of fluorescence microscopy, performed at 500,000 frames per second. To characterize drug delivery in vivo, the triggered release of nanoparticles within the vasculature and their extravasation beyond the endothelial layer is studied using intravital microscopy in tumors implanted in dorsal skinfold window chambers, over a timescale of several minutes. The combination of these complementary characterization techniques provides unique insight into the behavior of microbubbles and their payload release at a range of time and length scales, both in vitro and in vivo.

The presented protocols can be used to characterize the response of fluorescently-labeled microbubbles designed for ultrasound-triggered drug delivery applications, including their activation mechanisms as well as their bioeffects. This paper covers a range of in vitro and in vivo microscopy techniques performed to capture the relevant length and timescales.

Microbubble contrast agents hold great promise for drug delivery applications with ultrasound. Encapsulating drugs in nanoparticles reduces systemic ...

3D Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell cultures. Microcarrier culture technology has become one of the main techniques in cytological research and is commonly used in the field of large-scale cell expansion. Microcarriers have also been shown to play an increasingly important role in in vitro tissue engineering construction and clinical drug screening. Current methods for preparing microcarriers include microfluidic chips and inkjet printing, which often rely on complex flow channel design, an incompatible two-phase interface, and a fixed nozzle shape. These methods face the challenges of complex nozzle processing, inconvenient nozzle changes, and excessive extrusion forces when applied to multiple bioink. In this study, a 3D printing technique, called alternating viscous-inertial force jetting, was applied to enable the construction of hydrogel microcarriers with a diameter of 100-300 &#181;m. Cells were subsequently seeded on microcarriers to form tissue engineering modules. Compared to existing methods, this method offers a free nozzle tip diameter, flexible nozzle switching, free control of printing parameters, and mild printing conditions for a wide range of bioactive materials.

3D Printing of In Vitro Hydrogel Microcarriers by Alternating Viscous-Inertial Force Jetting

Presented here is a mild 3D printing technique driven by alternating viscous-inertial forces to enable the construction of hydrogel microcarriers. Homemade nozzles offer flexibility, allowing easy replacement for different materials and diameters. Cell binding microcarriers with a diameter of 50-500 &#181;m can be obtained and collected for further culturing.

Microcarriers are beads with a diameter of 60-250 &#181;m and a large specific surface area, which are commonly used as carriers for large-scale cell ...