The present invention relates to particles suitable for delivery of active agents comprising a polymer containing thioester bonds which are obtained via the reaction of a thioic acid functionality and an unsaturated group. The polymer may be is linear, branched or crosslinked. The particles have an average diameter in the range of 10 nm to 1000 [mu]m, preferably in the range of 100nm-100 [mu]m. The particles may comprise an active agent selected from the group of nutrients, pharmaceuticals, proteins and peptides, vaccines, genetic materials, diagnostic agents or imaging agents. The present invention further relates to the use of the particles in dermatology, muscular skeletal, oncology, in vascular applications, in orthopaedics, in ophthamology, spinal, intestinal, pulmonary, nasal, or auricular.