Currently, there
is great interest in the development of ways to
achieve the benefits of radiation treatments with reduced negative
effects. The present study demonstrates the utilization of radio-luminescent
particles (RLPs) as a means to achieve radio-sensitization and enhancement
and their ability to affect head- and neck-cancer-cell cultures (in
vitro) and xenografts (in vivo). Our approach utilizes a naturally
abundant radio-luminescent mineral, calcium tungstate (CaWO4), in its micro or nanoparticulate form for generating secondary
UV-A light by γ ray or X-ray photons. In vitro tests demonstrate
that unoptimized RLP materials (uncoated CaWO4 (CWO) microparticles
(MPs) and PEG–PLA-coated CWO nanoparticles (NPs)) induce a
significant enhancement of the tumor-suppressive effect of X-rays
and γ rays in both radio-sensitive- and radio-resistant-cancer
models; uncoated CWO MPs and PEG–PLA-coated CWO NPs demonstrate
comparable radio-sensitization efficacies in vitro. Mechanistic studies
reveal that concomitant CaWO4 causes increased mitotic
death in radio-resistant cells treated with radiation, whereas CaWO4 sensitizes radio-sensitive cells to X-ray-induced apoptosis
and necrosis. The radio-sensitization efficacy of intratumorally injected
CaWO4 particles (uncoated CWO MPs and PEG–PLA-coated
CWO NPs) is also evaluated in vivo in mouse head- and neck-cancer
xenografts. Uncoated CWO MPs suppress tumor growth more effectively
than PEG–PLA-coated CWO NPs. On the basis of theoretical considerations,
an argument is proposed that uncoated CWO MPs release subtoxic levels
of tungstate ions, which cause increased photoelectric-electron-emission
effects. The effect of folic acid functionalization on the in vitro
radio-sensitization behavior produced by PEG–PLA-coated CWO
NPs is studied. Surface folic acid results in a significant improvement
in the radio-sensitization efficiency of CaWO4.
Pseudomonas fluorescence KNU417 was able to degrade up to 700 mg/L of phenol in 65 h but could not degrade 1,000 mg/L of phenol. Phenol degradation rate was noticeably enhanced by pre-adaptation. In addition, the cell was able to degrade up to 1,300 mg/L of phenol by pre-adapting to 700 mg/L of phenol. Repeated adaptations to the same concentration of phenol showed negligible increase in degradation rate. Also, relatively low concentration of phenol (100-700 mg/L) required only one pre-adaptation while high concentration (1,000 mg/L) did two consecutive stepwise pre-adaptations for rapid degradation. Optimal adaptation routes were suggested for the fast phenol degradation. For example, 1,000 mg/L of phenol was degraded as fast as in 48 h when the cell was pre-adapted to 100 and 300 mg/L of phenol sequentially. The mechanism of adaptation was explained in terms of catechol 1,2-dioxygenase induction, related to aromatic ring cleavage.
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