Double-strand breaks measured along a 160 MeV proton Bragg curve using a novel FIESTA-DNA probe in a cell-free environment.

Proton radiotherapy treatment planning systems use a constant relative biological effectiveness (RBE) = 1.1 to convert proton absorbed dose into biologically equivalent high-energy photon dose. This method ignores linear energy transfer (LET) distributions, and RBE is known to change as a function of LET. Variable RBE approaches have been proposed for proton planning optimization. Experimental validation of models underlying these approaches is a pre-requisite for their clinical implementation. This validation has to probe every level in the evolution of radiation-induced biological damage leading to cell death, starting from DNA double-strand breaks (DSB). Using a novel FIESTA-DNA probe, we measured the probability of double-strand break (P DSB) along a 160 MeV proton Bragg curve at two dose levels (30 and 60 Gy (RBE)) and compared it to measurements in a 6 MV photon beam. A machined setup that held an Advanced Markus parallel plate chamber for proton dose verification alongside the probes was fabricated. Each sample set consisted of five 10 µl probes suspended inside plastic microcapillary tubes. These were irradiated with protons to 30 Gy (RBE) at depths of 5-17.5 cm and 60 Gy (RBE) at depths of 10-17.2 cm with 1 mm resolution around Bragg peak. Sample sets were also irradiated using 6MV photons to 20, 40, 60, and 80 Gy. For the 30 Gy (RBE) measurements, increases in P DSB/Gy were observed at 17.0 cm followed by decreases at larger depth. For the 60 Gy (RBE) measurements, no increase in P DSB/Gy was observed, but there was a decrease after 17.0 cm. Dose-response for P DSB between 30 and 60 Gy (RBE) showed less than doubling of P DSB when dose was doubled. Proton RBE effect from DSB, RBEP,DSB, was <1 except at the Bragg peak. The experiment showed that the novel probe can be used to perform DNA DSB measurements in a proton beam. To establish relevance to clinical environment, further investigation of the probe's chemical scavenging needs to be performed.

Purification, preliminary characterization and in vitro immunomodulatory activity of tiger lily polysaccharide.

A water-soluble polysaccharide (LLPS) from tiger lily was extracted by ultrasonic wave-assisted extraction. The LLPS, which was isolated by alcohol precipitation, was further purified by DEAE Sepharose Fast Flow and Sephadex G-100 chromatography, which resulted in LLPS fractions in LLPS-1, LLPS-2 and LLPS-3, with molecular weights of 350.5, 403.3 and 146.2kDa, respectively. LLPS-1 and LLPS-2 primarily consisted of glucose and mannose in a molar ratio of nearly 1:2 and 1:1, respectively. In contrast, LLPS-3 was primarily composed of arabinose, galactose, glucose and mannose in a molar ratio of nearly 2:2:2:1. LLPS fractions could stimulate the proliferation of macrophages. The in vitro immunomodulatory activity of the fractions was evaluated. The results showed that treatment with 25-400 µg/mL of LLPS fractions could increase phagocytic activity and nitric oxide production of macrophages in a dose-dependent manner.