Temperature-sensitive poly(N-isopropylacrylamide)/poly(ethylene glycol) diacrylate hydrogel microspheres
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ORIGINAL RESEARCH ARTICLE
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Temperature-Sensitive Poly(N-Isopropylacrylamide)/Poly(Ethylene Glycol) Diacrylate Hydrogel Microspheres Formulation and Controlled Drug Release Xian-Zheng Zhang and Chih-Chang Chu Department of Textiles and Apparel & Biomedical Engineering Program, Cornell University, Ithaca, New York, USA
Abstract
Objective: To develop and characterize a new class of temperature-sensitive hydrogel microspheres composed of poly(N-isopropylacrylamide)/poly(ethylene glycol) diacrylate (PNIPAAm/PEG-DA). Methods: The PNIPAAm/PEG-DA hydrogel microspheres were fabricated in two aqueous systems as a result of polymer/polymer immiscibility. Both PNIPAAm and PEG-DA were used as the precursors; the PEG-DA was also used as a cross-linker for the formation of the hydrogel microspheres. Bovine serum albumin was used as the model protein drug to examine the effects of the thermo-responsive properties of the hydrogel microspheres on the release of a protein at two different temperatures (22°C and 37°C). Results: The hydrated PNIPAAm/PEG-DA hydrogel microspheres exhibited a swollen diameter of 50μm, with a narrow particle-size distribution. Scanning electron microscopy and environmental scanning electron microscopy observations revealed that, upon swelling, the resulting hydrogel microspheres had a regular spherical and rough surface morphology. The lower critical solution temperature (LCST) of the PNIPAAm/PEG-DA hydrogel microspheres was around 29.1°C, based on differential scanning calorimetric data. The release of BSA from the hydrogel microspheres at 37°C was slower than that at 22°C because of the thermo-responsive nature of PNIPAAm at temperatures above its LCST. Conclusions: We believe that these kinds of PNIPAAm/PEG-DA hydrogel microspheres may have wide applications as promising drug delivery systems, because of their intelligent nature upon external temperature change.
Introduction Researchers have been greatly interested in synthetic, intelligent, or responsive systems and have attempted to develop materials that can mimic natural feedback or response; this would contribute significantly to the advancement of novel biomaterial. This feedback concept has led to the intensive research and development of intelligent hydrogels.[1-3] Hydrogel materials have a 3-dimensional (3-D) network that can hold a large amount of water without dissolution.[4,5] In a hydrated state, the mechanical characteristic of a hydrogel is soft and similar to in vivo human tissues.[6,7] Therefore, hydrogels have been widely used as biomaterial. Intelligent hydrogels have the capability of changing their volumes with a slight variation of an external factor, such as
temperature or pH. These intelligent materials sense a stimulus as a signal and respond by changing their structures. One of the most typical applications of intelligent hydrogel-based materials is as carriers for controlled drug release. A controlled-release drug delivery system is designed to maintain the drug releas
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