Polyelectrolyte capsules with metal nanoparticles in their walls and fluorescently labeled polymers as cargo inside their cavity were prepared. Capsules were ingested by living cells with no uncontrolled release of the cargo upon the incorporation process. Photoinduced heating of the metal nanoparticles in the capsule walls lead to rupture of the capsule walls, and the polymeric cargo was released to the whole cytosol. Viability tests demonstrate that opening of capsules at moderate light intensities does not impair the cellular metabolism, whereas capsule opening at high light intensities ultimately leads to cell death.