You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Novel pentablock copolymer (PLA-PCL-PEG-PCL-PLA) based nanoparticles for controlled drug delivery: Effect of copolymer compositions on the crystallinity of copolymers and in vitro drug release profile from nanoparticles. The purpose of this investigation was to design novel pentablock copolymers (polylatide-polycaprolactone-polyethylene glycol- polycaprolactone-polylatide) (PLA-PCL-PEG-PCL-PLA) to prepare nanoparticle formulations which provide continuous delivery of steroids over a longer duration with minimal burst effect. Another purpose was to evaluate the effect of poly (L-lactide) (PLLA) or poly (D, L-lactide) (PDLLA) incorporation on crystallinity of pentablock copolymers and in vitro release profile of triamcinolone acetonide (selected as model drug) from nanoparticles. PLA-PCL-PEG-PCL-PLA copolymers with different block ratio of PCL/PLA segment were synthesized. Release of triamcinolone acetonide from nanoparticles was significantly affected by crystallinity of the copolymers. Burst release of triamcinolone acetonide from nanoparticles was significantly minimized with incorporation of proper ratio of PDLLA in the existing triblock (PCL-PEG-PCL) copolymer. Moreover, pentablock copolymer based nanoparticles exhibited continuous release of triamcinolone acetonide. Pentablock copolymer based nanoparticles can be utilized to achieve continuous near zero-order delivery of corticosteroids from nanoparticles without any burst effect.
{"Chemical": ["polylatide", "PDLLA", "PLLA", "PCL", "PLA", "polycaprolactone", "steroids", "poly (L-lactide)", "polyethylene glycol", "triamcinolone acetonide", "PEG", "poly (D, L-lactide)"]}