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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Adv Drug Deliv Rev. 2012 Aug 18;65(1):17–20. doi: 10.1016/j.addr.2012.07.015

Figure 1.

Figure 1

Figure 1

The number of references published under a research topic of “hydrogel” in SciFinder®. The total number of papers on hydrogel from 1950 to 2011 is 43,764. Of these, 8,554 references were on the topic of drug delivery. In the drug delivery, the subtopics of protein and gene result in 1,674 and 284 references, respectively. Of the 43,764 hydrogels references, the topics of nanotechnology and smart hydrogels result in 1,246 and 130 references, respectively.