A film-forming composition comprises a solvent and unimolecular nanoparticles of a self-crosslinkable nanogel star polymer. The nanogel star polymer comprises i) a crosslinked polymer core (nanogel core) and ii) 6 or more independent polymer arms covalently linked to the core by respective first end groups. A plurality of the arms comprise reactive groups for effecting crosslinking of the nanoparticles. An essentially solvent-free film layer comprising the nanoparticles self-crosslinks, optionally assisted by subjecting the film layer to a thermal treatment and/or a photochemical treatment. A surface treated article comprising the crosslinked film layer can effectively inhibit growth of and/or kill Gram-negative microbes, Gram-positive microbes, fungi, and/or yeasts.
