Preparation And Properties Of Poly(ethyleneglycol)-poly(lactic Acid) Copolymerized Hydrogel Films

Poly(lactic acid) (PLA) is biodegradable and biocompatible aliphatic polyester. Thehydrophobicity and low degradation rate of PLA limited its application in biomedcial fields.Hydrogels are insoluble, but water-swellable three-dimensional network polymers. Hydrogelshave been widely used in biomedical areas, such as drug release and tissue engineering due totheir excellent biocompatibility, permeability and the ability to load drugs without the loss ofbioactivity. In this study, PLA-PEG-PLA copolymer end-capped with acryloyl groups, aphotopolymerizable and biodegradable macromer, was first synthesized, and then a series ofhydrogel films were prepared via copolymerization of resultant macromer withN-vinylpyrrolidone (NVP), acrylic acid (AAc) and linearβ-cyclodextrin polymer derivative(CDP-g-GMA), respectively. The structure and properties of the copolymerized gel filmswere characterized by modern analytical techniques, and drug release profiles of gel filmswere investigated by using different dye molecules as model drugs.First, Poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA)copolymers with different molecular weight were synthesized via the ring-openingpolymerization of lactide using poly(ethylene glycol) (Mn=1,000) as the initiator and stannousoctoate as the catalyst. PLA-PEG-PLA macromer (PELA-DA) was then prepared via thereaction of PLA-PEG-PLA copolymer with acryloyl chloride. PELA/NVP hydrogel filmswere prepared via copolymerization of PELA-DA macromer and NVP under UV irradiation.The structure and properties of hydrogel films were characterized. The results show that theintroduction of hydrophilic NVP monomer improved the water uptake, accelerate thedegradation, and decrease glass transition temperature (Ts show the tensile strength of gel films decreg). The mechanical propertiesmeasurementased and breaking elongationincreased with the increasing content of NVP moieties in hydrogel films. The release profileof methyl orange (MO) from hydrogel films shows that the release percentage increased withthe increase of NVP moieties.Second, pH-sensitive hydrogel films were prepared via the copolymerization of PELA-DAmacromer, AAc and NVP under UV irradiation. The pH-sensitivity of hydrogel films wasinvestigated by measuring the water uptake in different pH solutions. The results display thatthe water uptake is higher in pH7.4 PBS buffer solution. The drug-loaded methods and drugrelease profile were investigated. The result show that the drug-loaded amount of gel films viamarination-room temperature dried method is higher than that via adsorption method byelectrostatic interaction. However, the release percentage of the former is much faster than thelatter in both acid solution and basic solution. It was also observed that the release rate fromdrug-loaded gel film by adsorption is very slow even in pH7.4 PBS buffer solution.Finally, the mainly liner water-solubleβ-cyclodextrin polymer (CDP) was obtained via thecrosslinking reaction ofβ-CD and epichlorohydrin in sodium hydroxide solution in thepresence of toluene, and photopolymerizable CDP derivative (CDP-g-GMA) was obtained via the ring-opening reaction of the hydroxyl groups of CDP with the epoxy group of glycidyl methacrylate (GMA). On the basis of this, functional gel films containingβ-CD moieties were produced by free radical polymerization of PELA-DA macromer, CDP-g-GMA and NVP under UV irradiation. The incorporation of CDP derivative into the gel films improve the water uptake, increase the thermal stability, and decrease the glass transition temperature (Tg). The drug release profile of MO and methyl violet (MV) show that the release rate from drug-loaded gel film is very slow due to the formation of inclusion complexes between MO or MV and cyclodextrin moieties.