[1] Simultaneous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during winter and summer seasons at 2003 in 14 cities in China. Daily PM 2.5 samples were analyzed for OC and EC by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance protocol. Average PM 2.5 OC concentrations in the 14 cities were 38.1 mg m À3 and 13.8 mg m À3 for winter and summer periods, and the corresponding EC were 9.9 mg m À3 and 3.6 mg m À3 , respectively. OC and EC concentrations had summer minima and winter maxima in all the cities. Carbonaceous matter (CM), the sum of organic matter (OM = 1.6 Â OC) and EC, contributed 44.2% to PM 2.5 in winter and 38.8% in summer. OC was correlated with EC (R 2 : 0.56-0.99) in winter, but correlation coefficients were lower in summer (R 2 : 0.003-0.90). Using OC/EC enrichment factors, the primary OC, secondary OC and EC accounted for 47.5%, 31.7% and 20.8%, respectively, of total carbon in Chinese urban environments. More than two thirds of China's urban carbon is derived from directly emitted particles. Average OC/EC ratios ranged from 2.0 to 4.7 among 14 cities during winter and from 2.1 to 5.9 during summer. OC/EC ratios in this study were consistent with a possible cooling effect of carbonaceous aerosols over China.
Metal–organic frameworks (MOFs)
have shown great potential
as nanophotosensitizers (nPSs) for photodynamic therapy (PDT). The
use of such MOFs in PDT, however, is limited by the shallow depth
of tissue penetration of short-wavelength light and the oxygen-dependent
mechanism that renders it inadequate for hypoxic tumors. Here, to
combat such limitations, we rationally designed core–shell
upconversion nanoparticle@porphyrinic MOFs (UCSs) for combinational
therapy against hypoxic tumors. The UCSs were synthesized in high
yield through the conditional surface engineering of UCNPs and subsequent
seed-mediated growth strategy. The heterostructure allows efficient
energy transfer from the UCNP core to the MOF shell, which enables
the near-infrared (NIR) light-triggered production of cytotoxic reactive
oxygen species. A hypoxia-activated prodrug tirapazamine (TPZ) was
encapsulated in nanopores of the MOF shell of the heterostructures
to yield the final construct TPZ/UCSs. We demonstrated that TPZ/UCSs
represent a promising system for achieving improved cancer treatment
in vitro and in vivo via the combination of NIR light-induced PDT
and hypoxia-activated chemotherapy. Furthermore, the integration of
the nanoplatform with antiprogrammed death-ligand 1 (α-PD-L1)
treatment promotes the abscopal effect to completely inhibit the growth
of untreated distant tumors by generating specific tumor infiltration
of cytotoxic T cells. Collectively, this work highlights a robust
nanoplatform for combining NIR light-triggered PDT and hypoxia-activated
chemotherapy with immunotherapy to combat the current limitations
of tumor treatment.
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