.pnipa / Fe <sub> 3 </ Sub> O <sub> 4 </ Sub> Preparation And Characterization Of The Irradiation Of The Composite Hydrogel

Hydrogels are hydrophilic but do not dissolve in water,a three-dimensional network of cross-linked polymers.Intelligent hydrogels are a series of hydrogels that can produce a sensitive response to the external environment changes,such as temperature,pH,light,ionic strength,magnetic field and electric field.Because of the unique intelligent response,intelligent hydrogels have encouraging application prospects in biomedical and biotechnological fields,including controlled drug release, sensors,switches and memory devices,tissue engineering,etc.Magnetic hydrogels can be used in controlled drug release,targeted the drug delivery.Hydrogels were prepared by conventional method -chemical initiation method which results in initiator residual in product.Magnetic hydrogels PNIPA/Fe₃O₄ were prepared by ⁶⁰Coγ-ray radiation-induced,they have the characteristic of temperature sensitivity and magnetic response.In this paper,N-isopropylacrylamide(NIPA) was choosed as a temperature-sensitive monomer,Fe₃O₄ as magnetic source.PNIPA/Fe₃O₄ magnetic hydrogels were prepared by ⁶⁰Coγ-ray radiation-induced polymerization.Swelling properties and the magnetic properties of the magnetic chydrogels were focused, furthermore,the drug controlled release properties of magnetic chydrogels were investigated.It was found that the equilibrium swelling rate of gel was reduced with the adding of nano-Fe₃O₄ magnetic particles,rather than for remaining their swelling properties and giving the magnetic properties to the hydrogel,PNIPA/Fe₃O₄ magnetic porous hydrogels were prepared by radiation-initiated polymerization.The swelling properties of porous hydrogel were studied,and the mechanism of its swelling was explored.In this paper,swelling behavior of magnetic hydrogels and magnetic porous hydrogels were investigated,the drug release of them was studied at the same time. The main contents and conclusions are as follows:(1) Fe₃O₄ magnetic nano-particles were prepared by chemical co-precipitation method under inert environment and modified by Sodium citrate.Results of XRD analysis indicated that the production of Fe₃O₄ was a spinel structure.The size of the Fe₃O₄ was about 30nm which deduced by Debye-Scherrer equation.Nano-Fe₃O₄ magnetic particles were prepared successfully.Modification of sodium citrate on Fe₃O₄ magnetic particles was effective by analyzing the FT-IR pattern of the pre-and post-modified.The magnetic properties of nano-Fe₃O₄ were tested on PPMS,and the magnetic hysteresis loops of Fe₃O₄ were defined,coercivity and residual magnetization of Fe₃O₄ nano-particles did not found on the magnetic hysteresis loop, which showed that Fe₃O₄ nanoparticles were superparamagnetic,the saturation magnetization(Ms) of Fe₃O₄ was about 65emu/g.(2) On the radiation dose in 5kGy/h,PNIPA hydrogels,PNIPA/Fe₃O₄ magnetic hydrogels respectively at 8kGy,15kGy and 22kGy were prepared successfully.Fe₃O₄ nano-magnetic particles were dispersed evenly in PNIPA/Fe₃O₄ magnetic hydrogels. With the enhancing of the irradiation dose,gel fraction increased.The addition of Fe₃O₄ reduced the equilibrium swelling rate of hydrogels,but the lower critical solution temperature(LCST) was not affected.With the increase of Fe₃O₄,the swelling rate of magnetic hydrogels reduced.With increasing of radiation dose,the compressive strength of hydrogel increased,the addition of Fe₃O₄ did not affect the compressive strength of the hydrogels.The magnetic properities of the magnetic hydrogels were tested on PPMS,the external magnetic field was -20000 Oe＜H＜20000 Oe,at room temperature(25℃).The saturation magnetization(Ms) of them increased with the increase of Fe₃O₄.(3) Magnetic porous hydrogels were prepared by irradiation polymerization through adding PEG as pore-forming agent.The hydrogels was of the clear pore structure.The maximum pore diameter size of magnetic porous hydrogels was about 40μm.The addition of pore-forming agent PEG improved the equilibrium swelling rate of composite hydrogels,with the pore-forming agent content increasing,the equilibrium swelling rate of hydrogels improving.As the pore-forming agent content up to 20%,the equilibrium swelling rate was increased by approximately 32%.With the addition of pore-forming agent,the LCST of hydrogels increased from about 33℃to 37℃and water loss rates of composite hydrogels were increased by about 52%, 75%.The swelling properties of hydrogels were not affected by the molecular weight of pore-forming agent.(4) The addition of Fe₃O₄ reduced the drug release and the earlier release rate of the hydrogels,but did not affect the balance release time,which was about four hours. The addition of pore-forming agent markedly improved the drug release of the hydrogels.The drug release of general hydrogels reached balance in four hours,but that of porous hydrogels has been increasing slowly.