title: Metallic Nanoclusters for Cancer Imaging and Therapy.
abstract: BACKGROUND
  Nanoclusters are made of a few to tens of atoms with a size below 2 nm. Compared with nanoparticles, they exhibited excellent properties, such as tunable fluorescence, ease of conjugation, high quantum yield and biocompatibility, which are highly desired in the development of cancer nanotheranostics. Hence, the metallic nanoclusters have emerged as a newcomer in cancer nanomedicines. This review aims to summarize recently developed approaches to preparing metallic nanoclusters, highlight their applications in cancer theranostics, and provide a brief outlook for the future developments of nanoclusters in nanomedicine.
  
  
  METHODS
  We carried out a thorough literature search using online databases. The search was focused on a centered question. Irrelevant articles were excluded after further examination and directly relevant articles were included. The relevant articles were classified by the subjects and the information from these articles was synthesized.
  
  
  RESULTS
  One hundred and forty-three articles were included in this review. About eighty articles outlined the development in the synthetic methods of nanoclusters. The synthesis approaches include chemical reduction, photoreduction and so on. The progress in the application of gold and silver nanoclusters to cancer theranostics was described in fifteen and eight articles, respectively. The rest articles were about the advancements in the use of other metal nanoclusters and nanocluster nanocomposites as cancer theranostic agents.
  
  
  CONCLUSIONS
  This review summarizes the synthesis and use of metallic nanoclusters or their nanocomposites as cancer theranostic agents. It confirms their importance, advantages and potentials in serving as a new generation of cancer theranostics in clinics.
authors.affiliation: School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, Zhejiang, 310058, China.
authors.forename: Mingying
authors.initials: M
authors.lastname: Yang
authors.affiliation: Department of Chemistry & Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK, 73019, United States.
authors.forename: Ye
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027, China.|Department of Chemistry & Biochemistry, Stephenson Life Sciences Research Center, University of Oklahoma, 101 Stephenson Parkway, Norman, OK, 73019, United States.
authors.forename: Chuanbin
authors.initials: C
authors.lastname: Mao
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000627:therapeutic use*; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry / Q000627:therapeutic use*; D009369:Neoplasms / Q000175:diagnosis* / Q000188:drug therapy*; D000068936:Theranostic Nanomedicine / Q000379:methods*
chemical_list: D000970:Antineoplastic Agents
keywords: Metallic nanoclusters; cancer diagnosis; cancer imaging; cancer theranostics; imaging reagents; nanomedicine.