Screening poly(ethyleneglycol) micro- and nanogels for drug delivery purposes.

This study investigates poly(ethyleneglycol) (PEG)-based micro- and nanogels, with or without lipid coating, with the aim to slowly deliver encapsulated molecules. Hydroxyethylmethacrylated PEG (PEG-HEMA), PEG-HEMA with an oligo lactate spacer (PEG-lac-HEMA), and eight-armed PEG end capped with HEMA (* -PEG-HEMA) were used. PEG-lac-HEMA matrices degraded very fast (in terms of days), while it took about 1 month for linear PEG-HEMA and several months for * -PEG-HEMA hydrogels to become degraded. PEG-based microgels were made by use of an all aqueous technique and could be lipid-coated by mixing the microgels (made positively or negatively charged through copolymerization with respectively methacrylic acid and dimethyl aminoethyl methacrylate with a suspension of oppositely charged liposomes. The release of fluorescently labeled molecules incorporated in the PEG-based microgels could be clearly governed by the type of molecules used (lasting from hours to months). PEG-based nanogels could be made using liposomes as a nanoscopic mold, resulting in particles with a PEG gel core surrounded by a lipid coating. BSA could be easily encapsulated in the PEG nanogels which released the BSA over a period of about 1 week.