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:

Progress in synthesis and antitumor activities of estradiol-linked platinum complex. Platinum complexes such as cisplatin and caboplatin are widely used in cancer chemotherapy. However, their clinical applications are substantially limited by unexpected toxic side effects. In this review, we discuss the current progress on the design and synthesis of estradiol-linked platinum complexes as the targeted antitumor drugs. Many of them display a high antitumor activity against the growth of breast cancer cell lines in vitro. The estradiol-linked platinum complexes could be used as target therapeutics for breast cancer.
{"Chemical": ["caboplatin", "cisplatin", "estradiol", "platinum", "Platinum"]}