6.1.2　Polymer nano-drug carriers

Natural and synthetic polymers are common materials for nano-drug carriers.The first polymer drug-loading system，penicillin-poly（vinyl amine）complex，was reported in 1962.In 1975，Ringsdorf proposed polymer drug carriers，in which small molecule drugs were combined with polymer carriers through covalent bonds.Compared with inorganic materials，polymers are able to undergo pH，temperature，light and other stimulus-responses，and polymers can be easily shaped into nanoparticles with different shape and size.In addition，there are a variety of polymers that are biocompatible and biodegradable，and low-or nontoxic.(https://www.daowen.com)