No abstract

Bacillus thuringiensis (Bt) produces different types of toxin that have potent and specific insecticidal activity. In recent years, Bt toxins have been used as the safe biological control agents to protect crops replacing for chemical insecticides. Bt-based biopesticides that have been commercialized as the alternative products to control pests and insects for sustainable agriculture, contain toxicity crystals and a significant number of spores that affects to the soil microflora. These uncontrollable changes may contaminate the cultivation soil, and eventually cause adverse effects to human and animal health. Therefore, the living cells and spores existing in the Bt-biopesticides should be controlled. This study evaluates the effects of gamma radiation on spore viability, germination and growth of the existing spores after spraying on the soil and the insecticidal effectiveness of a Bt-based biopesticide (VBT) against lepidoptera larvae. We attempted to identify the optimal dose that couldinactivate Bt spores but the toxicity of Bt still retain highly. The results revealed that the dose of 20 kGy is enough to control all living cells and spores in the product that consists of approximately 5.2 × 107 spores in the initial VBT. Though the growth of existing spores after spraying on the soil reduced by 85% or more by irradiation, their insecticidal activity against Heliothis armigera larvae reduced by 20-30% only as compared to that of the initial VBT. It suggested that gamma irradiation can be applied as useful way to control the living cells and spores existing in the commercial Bt-based bio-pesticides, and the radiation dose of 20 kGy is enough to kill all spores in VBT, but still kept its insecticidal effect for Heliothis armigera larvae

Herbal eyebright products and their raw materials have been irradiated with 1, 2, 3 and 5 kGy by Co-60 gamma radiation source at Hanoi Irradiation Center for decontamination. Initial bioburdens were under the limitation levels established for the traditional medicines according to the decree of 16/2011/TT-BYT issued by Vietnam Health Ministry. These values for both bacteria and fungus slightly increased during storage to three months, reach to about 103 and 102 CFU/g for bacteria and molds, respectively. However, there are no microbial colonies that could be observed in the samples irradiated with dose higher than 3 kGy. Results suggested that the dose of 3 kGy was enough for decontamination of eyebright raw powders and products. At dose of 5 kGy, the moisture and vitamin A content of the samples were insignificantly changed. These mean the radiation treatment with low dose did not influenced the quality of eyebright products, and radiation treatment can be applied to prolong the storage of not only eyebright, but also other traditional medicines.

Poly(N-isopropylacrylamide) (PNIPAM) based hydrogels with the lower critical solution temperature (LCST) near the human body-temperature have been obtained from 10% solutions of N-isopropylacrylamide (NIPA) and N,N’-dimethyl acrylamide(DMA) mixture of 90:10 and 85:15 (w/w) by radiation copolymerization and crosslinking using a gamma Co-60 source at a dose of 20 kGy. Water swelling behaviour of the resulting hydrogels was much dependent on the initial ratio of NIPA and DMA. The hydrogels of 85:15 NIPA/DMA was chosen for further investigation for the use as drug cariers.Two kinds of drug carriers were prepared by immerging the hydrogels in solutions containing dexamethasone and tegafur. Then the drug incorporation efficiencies and in-vitro release behaviors of the ingredient were analysed. Loading capacities of the hydrogels were about 48.6 and 95.7 mg per g of dried gel for dexamethasone and tegafur, respectively. The results also revealed that the presence of ions in simulated body fluid and solution temperature much affected to the release behaviors of hydrogels for both dexamethasone and tegafur. Release rates of the ingredients were quite fast for both drug models. These drug-loaded hydrogels were biocompatibility without skin irritation suggesting that they may be used as controlled release drug carriers.

UV light has strongly influenced on the growth of E. coli as well as caused DNA damages. Configurations of both genomic DNA and pUC 19 plasmids extracted from E. coli were significantly changed by the exposure to UV light of 254 nm and DLT, an extract of Ganoderma lucidum Lingzi mushroom. The results also revealed the radio-protective effects of DLT to UV radiation. By adding 2% DLT to its culturing suspension, the growth of E. coli was significantly decreased, whereas a low DLT amount of about 0.5% slightly improved its growth, indicated that the DLT extract can be used as a promising protective substance against UV radiation. At the molecular level, the radio-protective effects of DLT were observed for both UV treated DNA and protein. Thus, DLT can protect DNA in vivo, but not in vitro. This effect was also observed for Taq polymerase, suggested that the radio-protection effect of DLT may due to it accelerated the degradation of radicals or species that produced in the suspensions during UV exposure.