Browsing by Author "Liu, Ting-Yu"

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A High-Sensitivity and Low-Power Theranostic Nanosystem for Cell SERS Imaging and Selectively Photothermal Therapy Using Anti-EGFR-Conjugated Reduced Graphene Oxide/Mesoporous Silica/AuNPs Nanosheets
(2016-03-16)
Chen, Yu-Wei
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Liu, Ting-Yu
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Chen, Po-Jung
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Chang, Po-Hsueh
;
Chen, San-Yuan
A high-sensitivity and low-power theranostic nanosystem that combines with synergistic photothermal therapy and surface-enhanced Raman scattering (SERS) mapping is constructed by mesoporous silica self-assembly on the reduced graphene oxide (rGO) nanosheets with nanogap-aligned gold nanoparticles (AuNPs) encapsulated and arranged inside the nanochannels of the mesoporous silica layer. Rhodamine 6G (R6G) as a Raman reporter is then encapsulated into the nanochannels and anti-epidermal growth factor receptor (EGFR) is conjugated on the nanocomposite surface, defined as anti-EGFR-PEG-rGO@CPSS-Au-R6G, where PEG is polyethylene glycol and CPSS is carbon porous silica nanosheets. SERS spectra results show that rGO@CPSS-Au-R6G enhances 5 x 10(6) magnification of the Raman signals and thus can be applied in the noninvasive cell tracking. Furthermore, it displays high sensitivity (detection limits: 10(-8) M R6G solution) due to the "hot spots" effects by the arrangements of AuNPs in the nanochannels of mesoporous silica. The highly selective targeting of overexpressing EGFR lung cancer cells (A549) is observed in the anti-EGFR-PEG-rGO@CPSS-Au-R6G, in contrast to normal cells (MRC-5). High photothermal therapy efficiency with a low power density (0.5 W cm(-2)) of near-infrared laser can be achieved because of the synergistic effect by conjugated AuNPs and rGO nanosheets. These results demonstrate that the anti-EGFR-PEG-rGO@CPSS-Au-R6G is an excellent new theranostic nanosystem with cell targeting, cell tracking, and photothermal therapy capabilities.
An optical biosensing platform for proteinase activity using gold nanoparticles
(2010-08-01)
Chuang, Yao-Chen
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Li, Jung-Chun
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Chen, Sz-Hau
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Liu, Ting-Yu
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Kuo, Ching-Han
The surface plasmon resonance (SPR) wavelength of colloidal gold nanoparticles (AuNPs) can vary when the AuNPs aggregate, have different sizes or shapes, or are modified with chemical molecules. In this study, an optical biosensing platform for a proteinase activity assay was established based on the SPR property of AuNPs. The 13-nm AuNPs were modified with gelatin (AuNPs-gelatin) as a proteinase substrate and subsequently modified with 6-mercaptohexan-1-ol (MCH) (AuNPs/MCH-gelatin). After proteinase (trypsin or gelatinase) digestion, the AuNPs lose shelter, and MCH increases the attractive force between the modified AuNPs. Therefore, the AuNPs gradually move closer to each other, resulting in AuNPs aggregation. The AuNPs aggregation can be monitored by the red shift of surface plasmon absorption and a visible color change of the AuNPs is from red to blue. Such a color change can be observed with the naked eye. For detection, the absorption ratio, A(625)/A(525), of the reacted AuNPs solution can be used to estimate quantitatively the proteinase activity. A linear correlation has been established with trypsin activity at concentrations from 1.25 x 10(-1) to 1.25 x 10(2) U and matrix metalloproteinase-2 activity at concentrations from 50 ng/mL to 600 ng/mL. (C) 2010 Elsevier Ltd. All rights reserved.
Biomedical nanoparticle carriers with combined thermal and magnetic responses
(2009-02-01)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Liu, Dean-Mo
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Chen, San-Yuan
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Chen, I-Wei
Several biocompatible polymers are capable of large responses to small temperature changes around 37 degrees C In water, their responses include shrinkage and swelling as well as transitions in wettability. These properties have been harnessed for biomedical applications such as tissue engineering scaffolds and drug delivery carriers. A soft material/hard material hybrid in which a magnetic: metal or oxide is embedded in a temperature-responsive polymer matrix can combine the thermal sensitivity with magnetic signatures. Importantly, nanosizing such construct brings about new desirable features of extremely fast thermal response time, small magnetic hysteresis and enhanced magnetic susceptibility. Remote magnetic maneuvering and heating of the hybrid nanocolloids makes possible such applications as high-throughput enzyme separation and cell screening. Robust drug release on demand may also be obtained using these colloids and nanoparticle-derived thin film devices of combined thermal magnetic sensitivity. (C) 2008 Elsevier Ltd. All rights reserved.
Cartilage Tissue-Mimetic Pellets with Multifunctional Magnetic Hyaluronic Acid-Graft-Amphiphilic Gelatin Microcapsules for Chondrogenic Stimulation
(2020-04-01)
Hou, Kai-Ting
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Liu, Ting-Yu
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Chiang, Min-Yu
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Chen, Chun-Yu
;
Chang, Shwu-Jen
Articular cartilage defect is a common disorder caused by sustained mechanical stress. Owing to its nature of avascular, cartilage had less reconstruction ability so there is always a need for other repair strategies. In this study, we proposed tissue-mimetic pellets composed of chondrocytes and hyaluronic acid-graft-amphiphilic gelatin microcapsules (HA-AGMCs) to serve as biomimetic chondrocyte extracellular matrix (ECM) environments. The multifunctional HA-AGMC with specific targeting on CD44 receptors provides excellent structural stability and demonstrates high cell viability even in the center of pellets after 14 days culture. Furthermore, with superparamagnetic iron oxide nanoparticles (SPIOs) in the microcapsule shell of HA-AGMCs, it not only showed sound cell guiding ability but also induced two physical stimulations of static magnetic field(S) and magnet-derived shear stress (MF) on chondrogenic regeneration. Cartilage tissue-specific gene expressions of Col II and SOX9 were upregulated in the present of HA-AGMC in the early stage, and HA-AGMC+MF+S held the highest chondrogenic commitments throughout the study. Additionally, cartilage tissue-mimetic pellets with magnetic stimulation can stimulate chondrogenesis and sGAG synthesis.
Controlled pulsatile drug release from a ferrogel by a high-frequency magnetic field
(2007-09-18)
Hu, Shang-Hsiu
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Liu, Ting-Yu
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Liu, Dean-Mo
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Chen, San-Yuan
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材料科學與工程學系
Core-shell magnetic nanoparticles of heparin conjugate as recycling anticoagulants
(2007-12-01)
Liu, Ting-Yu
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Huang, Li-Ying
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Hu, Shang-Hsiu
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Yang, Ming-Chien
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Chen, San-Yuan
Polyvinyl alcohol-shell magnetic nanoparticles (PVA-shell MNPs, PMNPs) were successfully prepared by in-situ co-precipitation process. Heparin (HEP) was then covalently conjugated on the PMNPs by using aminotrimethoxysilane (ATMS) and 4,4-diphenyl methane diisocyanate (HMDI) as molecular coupling agent (spacer). The morphology of the core-shell PMNPs was examined using transmission electron microscope (TEM), X-ray diffraction (XRD), and Raman spectrometry to demonstrate the core-shell structure, as well as X-ray photoelectron spectroscope (X-PS) to provide direct evidence that the heparin molecules were immobilized on the surface of the core-shell PMNPs. Anticoagulant activity was evaluated with several parameters including activated partial thrombin time (APTT), prothrombin time (PT), fibrinogen time (FT), and thrombin time (TT). The results show that longer spacer would give better anticoagulant activity since lower steric hindrance can induce higher heparin grafting density. It might be anticipated that PMNPs of heparin conjugate can be used as anticoagulants instead of traditional free heparin, owing to its recycling characteristics by magnetic fields.
Drug release behavior of chitosan-montmorillonite nanocomposite hydrogels following electro stimulation
(2008-07-01)
Liu, Kun-Ho
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Liu, Ting-Yu
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Chen, San-Yuan
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Liu, Dean-Mo
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材料科學與工程學系
Nanocomposites hydrogel (nanohydrogel) composed of chitosan (CS) and montmorillonite (MMT) were prepared and systematically studied for drug release behavior following electrostimulation. The deterioration of the responsiveness and reversibility of CS upon repeated on-off electrostimulation switching operations are major limitations for clinical applications, as it suffers from too much structural instability for the precise control of the release of drug upon cyclic electrostimulation. To overcome these limitations, an inorganic phase, MMT, was incorporated in the CS matrix to enhance the anti-fatigue property and corresponding long-term stable release kinetics. X-ray diffraction analysis and time-dependent optical absorbance showed that the MMT incorporated into the nanohydrogel exhibited an exfoliated nanostructure. The exfoliated silica nanosheets are able to act as cross-linkers to form a network structure between the CS and MMT, and this difference in the cross-linking density strongly affects the release of vitamin B-12 under electrostimulation. With a lower MMT concentration (1 wt.%), the release kinetics of vitamin B-12 from the nanohydrogel shows a pseudo-zero-order release, and the release mechanism was changed from a diffusion-controlled mode to a swelling-controlled mode under electrostimulation. Further increasing the MMT content reduced both the diffusion exponent n and the responsiveness of the nanohydrogel to electrostimulation. In addition, a consecutively repeated "on" and "off" operation shows that the electroresponsiveness of the nanohydrogel with higher MMT concentrations was reduced, but its anti-fatigue behavior was considerably improved. In this work, the nanohydrogel with 2 wt.% MMT achieved a mechanically reliable and practically desirable pulsatile release profile and excellent anti-fatigue behavior, compared with that of the pure CS. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Effect of clay content on electrostimulus deformation. and volume recovery behavior of a clay-chitosan hybrid composite
(2007-11-01)
Liu, Kun-Ho
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Liu, Ting-Yu
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Chen, San-Yuan
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Liu, Dean-Mo
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材料科學與工程學系
Electrostimulus-responsive hybrid composites composed of chitosan (CS) and clay were successfully developed and systematically characterized. The addition of negatively charged clay as an ionic cross-linker strongly affect the cross-linking density as well as the mechanical property, swelling-deswelling behavior and fatigue property of the hybrids. With lower clay content, the crystallinity of the CS was slightly reduced, resulting in a decrease in the mechanical properties and an increase in the swelling ratio of the hybrid. However, the swelling kinetics were accelerated due to a reduction in CS crystallinity. On the other hand, with increasing clay concentration, the increased cross-linked bonding mechanically reinforced the hybrid beyond the aforementioned adverse effect, to show improved tensile strength and a decrease in the swelling ratio. The voltage-induced deformation of hybrids became more pronounced with increasing applied voltage, but became less pronounced with increasing clay content under an applied electric field. After repeatedly switching the electric field on and off, the higher clay concentration (C-clay > 0.5 wt.%) of the hybrid composites maintained the same capability of deswelling and swelling after more than 10 cycles, compared with both the pure CS film and the hybrid composites with lower clay content (e.g., 0.5 wt.%). Compared with pure CS, a significant improvement in the anti-fatigue property against cyclic electric stimulations of the hybrid was found, which encourages the use of such a new class of hybrid composite in medical and pharmaceutical applications. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Effect of hydroxyapatite nanoparticles on ibuprofen release from carboxymethyl-hexanoyl chitosan/O-hexanoyl chitosan hydrogel
(2006-09-01)
Liu, Tse-Ying
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Liu, Ting-Yu
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Chen, San-Yuan
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Chen, Shian-Chuan
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Liu, Dean-Mo
In order to explore the effect of nanofiller on the regulation of the drug release behavior from micro sphere-embedded hydrogel prepared by carboxymethyl-hexanoyl chitosan (HNOCC) and O-hexanoyl chitosan (OHC), the release kinetics was investigated in terms of various amounts of calcium-deficient hydroxyapatite (CDHA) nanoparticles incorporated. HNOCC is a novel chitosan-based hydrophilic matrix with a burst release profile in a highly swollen state. The drug release kinetics of the HNOCC hydrogel can be regulated by incorporation of well-dispersed CDHA nanoparticles. It was found that the release duration of ibuprofen (IBU) from HNOCC was prolonged with increasing amounts of CDHA which acts as a crosslink agent and diffusion barrier. On the contrary, the release duration of the IBU from OHC (hydrophobic phase) was shortened through increasing the CDHA amount over 5%, which is due to the hydrophilic nature of the CDHA nanoparticles destroying the intermolecular hydrophobic interaction and accelerating OHC degradation. Thus, water accessibility and molecular relaxation were enhanced, resulting in a higher release rate. In addition, sustained and sequential release behavior was achieved by embedding the OHC microspheres (hydrophobic phase) into the HNOCC (hydrophilic phase) matrix, which could significantly prolong the release duration of the HNOCC drug-loaded implant.
Electrical-Sensitive Nanoparticle Composed of Chitosan and Tetraethyl Orthosilicate for Controlled Drug Release
(2009-02-01)
Liu, Kun-Ho
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Liu, Ting-Yu
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Liu, Dean-Mo
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Chen, San-Yuan
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材料科學與工程學系
In the present study, the nanoparticles with size of 50-130 nm composed of chitosan (CS) and tetraethyl orthosilicate (TEOS), which showed electrically-control led release profile, were prepared. Myoglobin was encapsulated into the nanoparticles with an encapsulation efficiency as high as 91.5% and a maximum loading capacity of 70.2% that can be achieved. Here, TEOS was hydrolyzed and condensed to form interpenetration network with CS. Increase of TEOS content results in a shift of the release profile from swelling-controlled towards diffusion-controlled mechanism. The "slow-to-burst" and "near-zero" release of the myoglobin can be effectively controlled by applying DC electric field between "on" and "off."
Gold nanoparticles conjugates-amplified aptamer immunosensing screen-printed carbon electrode strips for thrombin detection
(2014-11-15)
Yeh, Fang-Yuan
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Liu, Ting-Yu
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Tseng, I-Hua
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Yang, Chung-Wei
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Lu, Li-Che
Thrombin plays the role in cardiovascular diseases and regulates many processes in inflammation and could be a feature of many pathological conditions, including the thromboembolic disease, cancer and neurodegenerative diseases. An ultrasensitive and amplified electrochemical sandwich assay using screen-printed carbon electrode (SPCE) strips for thrombin detection was established in this study. The conductivity and sensing performance of the carbon electrodes were enhanced by using gold nanoparticles (AuNPs). The aptamer addressed on the strips was used as a primary probe to capture thrombin in the detected samples. An amplifier was invented for recognizing thrombin captured on the SPCE, which is the multiple molecules of anti-thrombin antibody (Ab) and horseradish peroxidase (HRP) co-modified AuNPs (AuNPs/Ab-HRP). Hydrogen peroxide was used as the substrate for HRP and then the response current (RC) could be detected. The optimization of these AuNPs conjugates-amplified aptamer immunosensing SPCE strips was conducted for thrombin detection. The detection sensitivity showed a linear relation between RC and thrombin concentration in the range of 10 pM-100 nM, and limit of detection (LOD) was 1.5 pM. The fabricated AuNPs/Ab-HRP-amplified aptamer immunosensing SPCE strips were further used to detect thrombin in human serum with a linear range of 100 pM-100 nM. This study provided the promising SPCE strips with highly sensitive and rapid detection for thrombin by the electrochemical aptasensor combined with AuNPs conjugates for amplifying the detection signal. (C) 2014 Elsevier B.V. All rights reserved.
Instantaneous Drug Delivery of Magnetic/Thermally Sensitive Nanospheres by a High-Frequency Magnetic Field
(2008-12-02)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Liu, Kun-Ho
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Shaiu, Ren-Shiuan
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Liu, Dean-Mo
Novel dual-functional nanospheres composed of magnetic iron oxide nanoparticles embedded in a thermo-sensitive Pluronic F127 (17127) matrix were successfully synthesized by an in situ coprecipitation process. The nanospheres were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Experimental observations indicated that the F127 was subjected to a rapid structural change when the magnetic phase caused rapid heating after a short exposure to a high-frequency magnetic field. During the field duration, considerable volume shrinkage of the nanospheres (2.3-fold diameter reduction) was detected. This has been translated to an instantaneous release of a drug, Doxorubicin (DOX), when the DOX was encapsulated within the nanospheres. Such a rapidly responsive release of the DOX from the nanospheres was due to an intimate contact between the nanomagnet and F127, where an effective thermal and mechanical transfer between core and shell phases efficiently took place in the presence of the magnetic field.
Magnetic-sensitive behavior of intelligent ferrogels for controlled release of drug
(2006-07-04)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Liu, Tse-Ying
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Liu, Dean-Mo
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Chen, San-Yuan
An intelligent magnetic hydrogel (ferrogel) was fabricated by mixing poly(vinyl alcohol) (PVA) hydrogels and Fe3O4 magnetic particles through freezing-thawing cycles. Although the external direct current magnetic field was applied to the ferrogel, the drug was accumulated around the ferrogel, but the accumulated drug was spurt to the environment instantly when the magnetic fields instantly switched "off". Furthermore, rapid to slow drug release can be tunable while the magnetic field was switched from "off" to "on" mode. The drug release behavior from the ferrogel is strongly dominated by the particle size of Fe3O4 under a given magnetic field. The best "magnetic-sensitive effects" are observed for the ferrogels with larger Fe3O4 particles due to its stronger saturation magnetization and smaller coercive force. Furthermore, the amount of drug release can be controlled by fine-tuning of the switching duration time (SDT) through an externally controllable on-off operation in a given magnetic field. It was demonstrated that the highest burst drug amounts and best "close" configuration of the ferrogel were observed for the SDT of 10 and 5 min, respectively. By taking these peculiar magnetic-sensitive characteristics of the novel ferrogels currently synthesized, it is highly expected to have a controllable or programmable drug release profile that can be designed for practical clinical needs.
Magnetic-sensitive silica nanospheres for controlled drug release
(2008-01-01)
Hu, Shang-Hsiu
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Liu, Ting-Yu
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Huang, Hsin-Yang
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Liu, Dean-Mo
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Chen, San-Yuan
Recently, magnetic silica-based nanospheres have received great attention and displayed magnificent potential for bioimaging and therapeutic purposes. This study provided a way to accelerate drug release from magnetic-sensitive silica nanospheres by controlled bursting to a therapeutically effective concentration by a high-frequency magnetic field (HFMF). The magnetic-sensitive silica nanospheres were synthesized by an in situ process, with particle sizes about 50 nm and able to release specific amounts of drug in a burst manner via short exposure to a HFMF. The HFMF accelerates the rotation of magnetic nanoparticles deposited in the silica matrix with generated heat energy and subsequently enlarges the nanostructure of the silica matrix to produce porous channels that cause the drug to be released easily. By taking these magnetic-responsive controllable drug release behaviors, the magnetic silica nanospheres can be designed for controlled burst release of therapeutic agents for especially urgent physiological needs.
Nano-ferrosponges for controlled drug release
(2007-08-28)
Hu, Shang-Hsiu
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Liu, Ting-Yu
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Liu, Dean-Mo
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Chen, San-Yuan
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材料科學與工程學系
Magnetic sponge-like hydrogels (ferrosponges) were fabricated by using an in-situ synthesis of magnetic nanoparticles (MNPs) in the presence of various concentrations of gelatin. The resulting ferrosponges show an interconnected nanopore structure which serves as a reservoir to accommodate therapeutic drugs and the nanoporous networks demonstrate magnetic sensitive behavior under the application of magnetic field. The ferrosponges showed high swelling ratios, together with excellent elasticity and hydrophilicity, allow them to response rapidly to an external magnetic stimulation for fast and repeatable swelling-deswelling (or expansion-contractile) operations. The ferrosponges with lower gelatin concentration exhibited good performance on magnetification. Furthermore, drug release from the ferrosponges is relatively magnetic-sensitive and is dominated by its magnetism and associated interaction between the magnetic nanoparticle and the gelatin matrix under an external magnetic field. Higher MNPs concentration in the ferrosponges exhibited higher degree of magnetic sensitive which is due to stronger interparticle forces. By taking these peculiar magnetic sensitive behaviors of the ferrosponges, a novel drug delivery system can be designed for medical uses. (C) 2007 Elsevier B.V. All rights reserved.
Preparation and characterization of magnetic ferroscaffolds for tissue engineering
(2007-03-01)
Hu, Shang-Hsiu
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Liu, Ting-Yu
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Tsai, Chia-Hui
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Chen, San-Yuan
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材料科學與工程學系
Magnetic-based scaffolds (ferroscaffolds) were fabricated using an in-situ synthesis of iron oxide nanoparticles in the presence of various concentration of biodegradable gelatin. The resulting ferroscaffolds show an interconnected pore structure with pore sizes ranging from 50 to 200 mm depending on gelatin concentrations. However, the yield of the iron oxide nanoparticles decreases with the increase of gelatin contents, which is due to the presence of polymeric chains that hindered the growth of iron oxide upon coprecipitation. The content of deposited magnetic nanoparticles could reach up to 9.41% and its saturation magnetization (Ms) was 23.5 emu/g. In addition, while applying a magnetic field (MF), the magnetic interparticles forces immediately formed to reduce the drug release rates in the ferroscaffolds. The ferroscaffolds which possess an excellently magnetic-sensitive behaviors can be potentially used as stimuli-responsive drug carriers and scaffolding materials for tissue engineering. (C) 2006 Elsevier B.V. All rights reserved.
Preparation and characterization of smart magnetic hydrogels and its use for drug release
(2006-09-01)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Liu, Kun-Ho
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Liu, Dean-Mo
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Chen, San-Yuan
The magnetic hydrogels were successfully fabricated by chemically cross-linking of gelatin hydrogels and Fe(3)O(4) nanoparticles (ca. 40-60 nm) through genipin (GP) as cross-linking agent. The cross-sectional SEM observation demonstrates that the Fe(3)O(4) nanoparticles were fairly uniformly distributed in the gelatin matrix. Moreover, in vitro release data reveal that drug release profile of the resulting hydrogels is controllable by switching on or off mode of a given magnetic field. While applying magnetic fields to the magnetic hydrogels, the release rate of vitamin B(12) of the hydrogels was considerably decreased as compared with those when the field was turned off, suggesting a close configuration of the hydrogels as a result of the aggregation of Fe(3)O(4) nanoparticles. Based on this on-&-off mechanism, the smart magnetic hydrogels based on the gelatin-ferrite hybrid composites can be potentially developed for application in novel drug delivery systems. (C) 2006 Elsevier B. V. All rights reserved.
Preparation and characterization of thermal-sensitive ferrofluids for drug delivery application
(2007-03-01)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Hu, Sheng-Hsiang
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Tsai, Szu-Ping
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Chen, San-Yuan
Novel thermal-sensitive ferro fluids (F127-ferro fluids) consisting of core-shell-type magnetic nanoparticles dispersed in Pluronic F127-containing aqueous solution were prepared. The core (magnet)-shell (Pluronic F127) nanoparticles were synthesized by in situ coprecipitation process, which were characterized using transmission electron microscope, X-ray diffraction and vibrating sample magnetometer. The F127-ferro fluids gelled above the lower critical solution temperatures (LCST) of approximately 23-28 degrees C, which were higher than that of pure Pluronic F127-. fluids ( 21-25 degrees C). The increase in the LCST of the F127 ferro. fluids may be attributed to a result of a physical interaction between the F127 molecules and the core-shell magnetic nanoparticles. (C) 2006 Elsevier B. V. All rights reserved.
Stimuli-Responsive Controlled Drug Release from Magnetic-Sensitive Silica Nanospheres
(2009-02-01)
Hu, Shang-Hsiu
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Liu, Ting-Yu
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Huang, Hsin-Yang
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Liu, Dean-Mo
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Chen, San-Yuan
A novel method for control burst releasing of drug via a high frequency magnetic field (HFMF) from magnetic-sensitive silica nanospheres was developed. The nanospheres were synthesized by a combination of emulsion and sol-gel process with the particles controlled at about 80 nm in diameter. Under repeated exposures to the high frequency magnetic stimulus, the drug release behaviors showed reproducible slow-to-burst profiles while consecutively applying the magnetic stimulus at 10-min switching time and the release profile restored immediately when the stimulus was removed. By taking this non-contact control-burst method, the magnetic silica nanospheres can be designed to treat the cancer therapy and urgent physiological needs.
Study on controlled drug permeation of magnetic-sensitive ferrogels: Effect of Fe3O4 and PVA
(2008-03-20)
Liu, Ting-Yu
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Hu, Shang-Hsiu
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Liu, Kun-Ho
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Liu, Dean-Mo
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Chen, San-Yuan
A PVA-based magnetic-sensitive hydrogel (ferrogel) was fabricated by physical cross-linking through a freezing-thawing method. The influence of the constituting components, i.e., Fe3O4 and PVA, on the magnetic-sensitive behavior of the ferrogels was systematically investigated in terms of permeability coefficient (P), partition coefficient (H), space restriction and magnetization. The results show that, the P value in these ferrogels decreases and displays a magnetic sensitivity when it is subjected to magnetic field (MF), which is correlated with the change of H value. In addition, it was found that although the factor of space restriction or magnetization exerts opposite effect on resulting magnetic-sensitive behavior, the superior magnetic-sensitive behavior was observed for the ferrogels with an optimal composition of 17-34% Fe3O4 and 10-12.5% PVA, and can be well correlated with theoretical calculation from the critical parameters of available free volume per nanoparticle (V-free) and magnetization. A map of magnetic-sensitive behavior was constructed, where a region with relatively stable and highly stimuli-responsive behavior in terms of the concentration of FC3O4 was observed, however, below or above the "saturation" region (17-34% Fe3O4), a reduction in the magnetic-sensitive behavior was detected. The resulting ferrogels can be engineered with a precise control of the opening and closure of pore configuration, which allows a burst release or no-release action of therapeutically active agent to be controlled externally and magnetically. This suggests that this type of ferrogel can be considered as a class of novel magnetically-tunable drug delivery system. (c) 2007 Elsevier B.V. All rights reserved.