Synthesis, characterization, and evaluation of copolymers based on N‐isopropylacrylamide and 2‐ethoxyethyl methacrylate for the controlled release of felodipine

Abstract

The free‐radical copolymerization of N‐isopropylacrylamide (NIPAAm) with 2‐ethoxyethyl methacrylate (EOEMA) was carried out with 2,2′‐azobisisobutyronotrile as an initiator in 1,4‐dioxane at 65°C. The resulting copolymer was characterized by Fourier transform infrared and 1H‐NMR techniques. The composition of copolymers prepared at low conversion was determined by elemental analysis. An extended Kelen–Tudos method was used to estimate the reactivity ratios. The distribution of the monomer sequence along the copolymer chain was calculated with a statistical method based on the obtained reactivity ratios. Felodipine‐loaded microspheres were prepared by the solvent evaporation technique. The effect of NIPAAm with respect to EOEMA segments on the sustained release of felodipine from the microspheres was investigated. Scanning electron micrographs of the microspheres indicated the formation of spherical microparticles in the size range 15–53 μm, even after they were loaded with the drug. The in vitro release studies of felodipine from the NIPAAm/EOEMA microspheres performed in a pH 7.4 medium showed that the rate of drug release was enhanced by an increase in the amount of NIPAAm; the size of the microspheres also increased with increasing NIPAAm in the copolymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Development of poly(N-isopropylacrylamide)/alginate copolymer hydrogel-grafted fabrics embedding of berberine nanosuspension for the infected wound treatment

“…As the temperature of the surrounding media increased above the LCST of PNIPAAm, the hydrogen bonds between water and PNIPAAm residues were disrupted. 41 As a result, the PNIPAAm component in hydrogel became hydrophobic and contracted, leading to the lower SRs and less water absorption. 42

Figure 4.The relationship between swelling ratio and temperature: (a) hydrogel-grafted nonwoven fabrics without loading of berberine nanosuspension; (b) hydrogel-grafted nonwoven fabrics loaded with berberine nanosuspension and (c) original nonwoven fabrics.

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Preparation and Characterization of a Novel Hybrid Hydrogel Composed of Bombyx mori Fibroin and Poly(N‐isopropylacrylamide)

“…Poly(N-isopropylacrylamide), with a lower critical solution temperature (LCST) around 32 ∘ C, is a typically thermoresponsive polymer which is hydrated below the LCST and undergo rapid volume decrease because of the hydrophilicity to hydrophobicity alteration. It undergoes a transition from hydrophilic to hydrophobic state in aqueous solution when the temperature is increased from below to above its LCST [31,32]. Preparation of PNIPAAm homopolymer and copolymers, such as hydrogels and micelles, have been utilized in tissue engineering [33] and drug delivery systems [34][35][36].…”