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:

Design and in vitro evaluation of a novel polymeric excipient for buccal applications. Background: The objective of this study was to develop and evaluate a more effective mucoadhesive thiomer for buccal drug-delivery systems. Methods: 2-iminothiolane was covalently attached to a chitosan backbone. A preactivation step followed, mediated by 6,6´dithionicotinamide, thiol groups were modified by disulfide bonds formation. Mucoadhesion studies were performed on buccal mucosa. In addition, water-uptake capacity, disintegration, release and cytotoxicity studies were completed. Results: The obtained chitosan-thiobutylamidine conjugate displayed 647.4 ± 85.23 µmol/g immobilized thiol groups. Due to the preactivation, approximately 60% of thiol groups were modified by formation of disulfide bonds. Chitosan-thiobutylamidine-mercaptonicotinamide displayed 1.8-fold higher stability and 1.6-fold higher mucoadhesive properties, respectively. The release study demonstrated a 1.4-fold more prolonged drug release compared with corresponding thiomers. Conclusion: According to these results, preactivated thiomers demonstrate an improved stability and increased mucoadhesive properties. Therefore, they seem to be advantageous for buccal administration over corresponding thiomers and chitosan.
{"Chemical": ["6,6\u00b4dithionicotinamide", "disulfide", "2-iminothiolane", "thiol", "mercaptonicotinamide", "thiobutylamidine"]}