Preparation and Characterization of pH-Responsive Poly(methacrylic acid-<i>g</i>-ethylene glycol) Nanospheres

Abstract

Poly(methacrylic acid- g -ethylene glycol) (P(MAA- g -EG)) has been studied extensively in our laboratory due to its extremely promising applications in the biomedical and pharmaceutical fields. It exhibits pH-responsive interpolymer complexes that make it a promising candidate as an oral carrier for peptide and protein drug. We have developed a photoinitiated free-radical precipitation polymerization method to produce P(MAA- g -EG) nanospheres with relatively narrow size distributions. The influence of various reaction parameters, such as total monomer concentration in water, comonomer molar feed ratios, cross-linking agent concentration, and polymerization time, on the particle size and size distribution was investigated. P(MAA- g -EG) nanospheres with a relatively narrow size distribution could be produced in the size range 150−650 nm depending on the monomer concentration and comonomer molar feed ratio. The P(MAA- g -EG) nanospheres exhibited a pH-responsive swelling behavior. Increasing the concentration of the cross-linking agent during polymerization produced P(MAA- g -EG) nanospheres that swelled to a lesser degree. The morphology of the P(MAA- g -EG) nanospheres was investigated using cryogenic scanning electron microscopy.