• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.1
• /
• pp.49-54
• /
• 2014

Background: Hydrogels are a class of polymers that can absorb water or biological fluids and swell to several times their dry volume, dependent on changes in the external environment. In recent years, hydrogels and hydrogel nanocomposites have found a variety of biomedical applications, including drug delivery and cancer treatment. The incorporation of nanoparticulates into a hydrogel matrix can result in unique material characteristics such as enhanced mechanical properties, swelling response, and capability of remote controlled actuation. Materials and Methods: In this work, synthesis of hydrogel nanocomposites containing magnetic nanoparticles are studied. At first, magnetic nanoparticles ($Fe_3O_4$) with an average size 10 nm were prepared. At second approach, thermo and pH-sensitive poly (N-isopropylacrylamide -co-methacrylic acid-co-vinyl pyrrolidone) (NIPAAm-MAA-VP) were prepared. Swelling behavior of co-polymer was studied in buffer solutions with different pH values (pH=5.8, pH=7.4) at $37^{\circ}C$. Magnetic iron oxide nanoparticles ($Fe_3O_4$) and doxorubicin were incorporated into copolymer and drug loading was studied. The release of drug, carried out at different pH and temperatures. Finally, chemical composition, magnetic properties and morphology of doxorubicin-loaded magnetic hydrogel nanocomposites were analyzed by FT- IR, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM). Results: The results indicated that drug loading efficiency was increased by increasing the drug ratio to polymer. Doxorubicin was released more at $40^{\circ}C$ and in acidic pH compared to that $37^{\circ}C$ and basic pH. Conclusions: This study suggested that the poly (NIPAAm-MAA-VP) magnetic hydrogel nanocomposite could be an effective carrier for targeting drug delivery systems of anti-cancer drugs due to its temperature sensitive properties.

• Polymer(Korea)
• /
• v.35 no.3
• /
• pp.223-227
• /
• 2011

Stimuli-responsive polymers have been investigated as the materials playing the critical roles in various applications. Thermoresponsive graft copolymers, poly (N-isopropylacrylamide)-g-hyaluronic acid (PNIPAAm-g-HA) and elastin-like peptide-g-hyaluronic acid (ELP-g-HA), were synthesized by coupling carboxylic polymers (PNIPAAm-COOH or ELP) to biocompatible HA through amide linkages. Thermoresponsive behavior was observed in both the copolymers, and the results of turbidity measurement were consistent with the results of rheological examination. Among the two copolymers, the ELP graft copolymer shows less cooperative LCST transition than the PNIPAAm case. As the content of graft chains of PNIPAAm and ELP increases, viscosity increases, and the increase was larger in PNIPAAm case at a graft content. These results shows us that the introduction of grafts provides thermosensitivity to biocompatible HA, whose characteristics can be engineered.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.21 no.1
• /
• pp.11-20
• /
• 2003

Equilibrium swelling curves of N-isopropyl acrylamide(NIPA) gel and its ionized copolymer gels were obtained as a function of temperature. Discontinuous volume changes of the gels were observed. Phase transition temperature was increased with the ionized counter parts of the gels. Equilibrium swelling of ionized copolymer gel cylinder was found to depend strongly on their diameters. Crosslinking density of NIPA gel was adjusted by increasing N,N'-methylenebisacrylamide(BIS). Phase transition temperature was increased with the crosslinking density.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.101-101
• /
• 2006

We have studied the micellisation of poly(n-butyl acrylate)-block-poly(acrylic acid) and poly(n-butyl acrylate)-graft-poly(acrylic acid) in aqueous solution. The size and structure of the formed micelles was elucidated by scattering and imaging techniques. The micelle structure depends on pH, composition, and topology: graft copolymers form much smaller micelles that block copolymers of similar composition. We have also synthesized block copolymers of acrylic acid and N-isopropylacrylamide (NIPAAm) or N,N-diethylacrylamide (DEAAm). Due to the LCST of polyNIPAAm and polyDEAAm, these block copolymers spontaneously form micelles upon heating and they form inverse micelles upon decreasing pH below 4. If the LCST block is much longer than the PAA one, this presents a very convenient way to prepare crew-cut micelles. The polymers have been successfully used as stabilizers in emulsion polymerization. They also have been conjugated to streptavidin. The conjugates reversibly form mesoscopic particles on heating.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.33-34
• /
• 2006

The graft copolymer consisting of poly(N-isopropylacrylamide) (PNIPAAm) and single-stranded DNA was prepared. Interestingly, the copolymer was found to form nanoparticles above physiological temperature. We found that non-crosslinking aggregation of the nanoparticles was induced by the hybridization of the surface-bound DNA with the full-match complementary DNA, but not with one-base mismatch. The core material is not restricted to PNIPAAm; DNA-functionalized gold nanoparticle was found to show a similar aggregation induced only by the fully-complementary DNA, resulting in rapid color change within 3 min at ambient temperature. This methodology is general in principle and applicable for wide variety of clinical gene diagnosis.

• KSBB Journal
• /
• v.14 no.1
• /
• pp.58-65
• /
• 1999

A hydrogel, poly(N-isopropylacrylamide-co-N,N'-dimethylaminopropyl methacrylamide), sensitive to both pH and temperature was synthesized and characterized for its welling behavior, lower critical solution temperature (LCST), and its appearance. The hydrogel with 5 mol% of N,N'-diemthylaminopropyl methacrylamide (DMAPMAAm) increased its volume phenomenonally in a lower pH range (ph 1~8) even at temperature ($37^{\circ}C$ and $40^{\circ}C$) higher than LCST. This behavior was unique compared to the temperature -sensitive hydrogel which did not exhibit any swelling in the same pH range. The hydrogel with 20 mol% of DMAPMAAm was swollen significantly at a higher pH of 12. With pH decrease from 12 to 2 water content in the gel increased from 38.8 wt% and 60.6 wt%, and 90.8 wt% for 5 mol% and 20 mol% gel, respectively. The transition pH that pH effect overwhelmed temperature effect occurred at a lower pH for a higher temperature ($40^{\circ}C$) and a lower mol% (5 mol%) of DMAPMAAm. Transparency and LCST of the gel increased with higher DMAPMAAm mol%.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.21 no.1
• /
• pp.81-90
• /
• 2003

To understand the thermoresponsive volume phase transition of an N-isopropyl acrylamide(NIPA) gel on water, the solubility parameter of neutral NIPA gel was determined by swelling the gel with various solvents. Water was found not to be a good solvent for NIPA gel. Equilibrium swelling curves of NIPA gel were respectively obtained by immersing in pure water, ethanol, n-propanol and some mixed solvents. On adding a small amount of alcohols to water, volume phase transition of NIPA gel in water was changed. Phase transition temperature of this gel was decreased with the increase of the carbon number of alcohol.

• Journal of the Korean Society of Radiology
• /
• v.9 no.7
• /
• pp.509-513
• /
• 2015

In this study, we evaluated the thermal denaturation characteristics of reusable NIPAM tissue mimicking (TM) Phantom by measuring the thermal sensitivity. And the changes of acoustic characteristic and thermal denaturation shape in NIPAM TM phantom according to the number of re-use time and re-use period were observed. With the result, as the sonication time is increased, the sound velocity of NIPAM phantom was decreased by 100 m/s and the attenuation was increased slightly. However, the changes according to the re-use period was not observed. In the thermal denaturation shape and size observation by ultrasound sonicaton, the remarkable changes have not been confirmed. With the result of this study, NIPAM Phantom was considered appropriate to evaluate and predict the effect of therapeutic ultrasound by in repeated sonication test.

• Polymer(Korea)
• /
• v.38 no.5
• /
• pp.626-631
• /
• 2014

Water purification requires a large amount of energy that can cause pollution problems. For this reason, forward osmosis (FO) has attracted intense interest that required a relatively low amount of energy for water purification. The forward osmosis has a serious problem that it needs drawing agents creating osmotic pressure to extract water from contaminated water. In this study, a copolymer of zwitterionic moiety and an interpenetrating polymer network (IPN) hydrogel based on thermo-responsive polymer hydrogel, poly(N-isopropylacrylamide) (PNIPAM) were prepared and attached on FO membranes, which successfully played the role of drawing agents. In the copolymer hydrogel, its swelling ratio was improved, but thermo-sensitivity was decreased. The swelling ratio and thermo-sensitivity of IPN hydrogel was lowered. We could confirm that swelling ratio is related to osmotic pressure.

• Macromolecular Research
• /
• v.16 no.2
• /
• pp.139-148
• /
• 2008

Biodegradable and elastic poly(L-lactide-co-$\varepsilon$-caprolactone) (PLCL) was electrospun to prepare nanofibers, and N-isopropylacrylamide (NIPAAm) was then grafted onto their surfaces under aqueous conditions using $^{60}Co-{\gamma}$ irradiation. The graft yield increased with increasing irradiation dose from 5 to 10 kGy and the nanofibers showed a greater graft yield compared with the firms. SEM confirmed that the PLCL nanofibers maintained an interconnected pore structure after grafting with NIPAAm. However, overdoses of irradiation led to the excessive formation of homopolymer gels on the surface of thc PLCL nanofibers. The equilibrium swelling and deswelling ratio of the PNIPAAm-g-PLCL nanofibers (prepared with 10 kGy) was the highest among the samples, which was consistent with the graft yield results. The phase-separation characteristics of PNIPAAm in aqueous conditions conferred a unique temperature-responsive swelling behavior of PNIPAAm-g-PLCL nanofibers, showing the ability to absorb a large amount of water at < $32^{\circ}C$, and abrupt collapse when the temperature was increased to $40^{\circ}C$. In accordance with the temperature-dependent changes in swelling behavior, the release rate of indomethacin and FITC-BSA loaded in PNIPAAm-g-PLCL nanofibers by a diffusion-mediated process was regulated by the change in temperature. Both model drugs demonstrated greater release rate at $40^{\circ}C$ relative to that at $25^{\circ}C$. This approach of the temperature-controlled release of drugs from PNIPAAm-g-PLCL nanofibers using gamma-ray irradiation may be used to design drugs and protein delivery carriers in various biomedical applications.