Lanthanide-doped inorganic upconversion nanocrystals (UCNCs) are promising as fluorescent diagnostic and therapeutic agents for in vivo applications ranging from biological imaging to disease theranostics. However, all currently available lanthanide-doped inorganic UCNCs are not biodegradable and thus cannot be harmlessly eliminated from the body of living organism during a reasonable period of time, making their clinical translations nearly impossible. Here, we report a class of redemitting biodegradable UCNCs based on Yb 3+ /Er 3+ -doped inorganic potassium heptafluozirconate (K 3 ZrF 7 :Yb/Er) that features a dynamically "soft" crystal lattice containing watersoluble [ZrF 7 ] 3− cluster and a K + cation. The red-emitting K 3 ZrF 7 :Yb/Er UCNCs exhibit a pH-dependent biodegradation capability upon exposure to water both in vitro and in vivo, and the rapid biodegradation rate, monitored using the intrinsic red upconversion luminescence, can be tuned particularly in a mild acidic tumor microenvironment (pH ∼5−6). More importantly, the final biodegradation products of K 3 ZrF 7 :Yb/Er UCNCs can be excreted from the body of mice in a short period of time with no evidence of toxicity, in stark contrast to the nondegradable β-NaYF 4 :Yb/Er UCNCs that primarily accumulate in the main organs of mice. These findings described here unambiguously would benefit the future biomedical applications and clinical translations of lanthanide-doped inorganic UCNCs.

Survival and growth of the sea cucumberHolothuria leucospilota Brandt: a comparison between suspended and bottom cultures in a subtropical fish farm during summer Abstract The feasibility of co-culturing the sea cucumber Holothuria leucospilota Brandt in a subtropical fish farm was investigated in a field study. Sea cucumbers were cultured in the fish farm in cages suspended at 4 m deep (suspended culture) and directly on the seafloor (bottom culture). The survival and growth of the sea cucumbers were monitored twice during the 3-month, summer experimental period (May 26-August 14, 2010). Results showed that the suspension-cultured sea cucumbers exhibited excellent survival rate (100%) during the whole study period. There also occurred no mortality in the bottom-cultured sea cucumbers during the first culture period (May 26 -July 13); but all these died from anoxia caused by water column stratification during the second culture period (July 14-August 14). The specific growth rate of the bottom-cultured sea cucumbers (1.05 ± 0.21 % day À1 ) was nearly double that of the suspended culture animals (0.57 ± 0.21 % day À1 ) during the first culture period, and the growth rates of the suspended culture sea cucumbers in the second culture periods (0.46 ± 0.24 % day À1 ) was only a little lower than that of the first period. The sea cucumbers H. leucospilota could ingest and assimilate sediment with high organic matter content with an average assimilation efficiency of 14.9 ± 3.9%. This study indicated that fish farm detritus can be effectively used as a food source for the sea cucumber and that it can be turned into a valuable secondary crop in the form of the sea cucumber biomass.