Study on slow release anti-cancer drugs prepared by radiation induced polymerization

This paper reports the research results which the anticancer drugs Ara-C with controlled slow release were made by radiation induced polymerization of monomers such as methacrylates at room temperature. Our studies showed that not only hydrophilic synthetic polymers but also hydrophobic polymers such as hydrophobic methacrylates (including MMA, EMA, and BMA) could be used to the immobilization. In vitro the rate of drugs release was controlled by the many factors such as the content of drugs, the monomer material, the crosslinking agent, the irradiation dose and the water content, etc.     

Cure Kinetics of a Tetrafunctional Rubber Modified Epoxy-amine System

In this work the curing kinetics behaviour of a rubber modified epoxy amine system is investigated through calorimetric analysis. This study is part of a wider investigation on new epoxy formulations to be used as matrices of composite materials. The aim is to enhance both the processing behaviour and the mechanical properties of the matrix in order to obtain higher performance composites for more demanding applications. The epoxy system is blended with a high molecular mass rubber containing functional groups reactive towards the epoxies. The formation of a rubber/epoxy network can be achieved by means of a 'pre-reaction' between the epoxy monomers and the rubber functional groups, carried out in the presence of a suitable catalyst and before the resin is cured with the amino hardener. In this work the influence of both the rubber and the catalyst on the resin cure kinetics is analysed. This revised version was published online in July 2006 with corrections to the Cover Date.     

186Re/188Re labeled polypeptide microspheres as a potential radiation synovectomy agent

Polypeptide microspheres containing polycysteine crosslinked with polylysine were prepared and radiolabeled with¹⁸⁶Re and¹⁸⁸Re. High labeling yields with the microspheres with both¹⁸⁶Re and¹⁸⁸Re (97%) were obtained, and above 99% retention of radiolabels in water in 24 hours was obtained. Rhenum-186 labeled polycysteine and polylysine microspheres (11 ratio, 20 m as mean diameter) were injected intra-articularly into the rear stifes (knee joints) of normal New Zealand white rabbits. About 87% of injected dose was retained in rabbit stifles and adjacent tissues in 96 hours after injection, while most of the activity lost from the joints was excreted in the urine. Due to its simplicity of preparation and radiolabeling, versatility, and biodegradability, this type of conjugate system may become the therapeutics of choice for radiation synovectomy.     

Effects of γ-irradiation and cooking on vitamins B6 and B12 in grass prawns (Penaeus monodon)

The effects of irradiation doses, irradiation temperature and a combined treatment of irradiation and cooking on the vitamin B₆ and B₁₂ contents of grass prawns have been studied. Grass prawns were irradiated at refrigerated (4°C) or frozen (-20°C) temperatures with different doses. A domestic cooking procedure was followed after irradiation. The changes in vitamins B₆ and B₁₂ of both raw and cooked grass prawns were evaluated. Results showed no significant changes of vitamin B₆ and B₁₂ in grass prawns with a radiation dose up to 7 kGy at either 4°C or -20°C. Irradiation at 4°C caused more destruction of vitamin B₁₂ but not vitamin B₆ than did irradiation at -20°C in grass prawns. There was significant destruction of both vitamins B₆ and B₁₂ in unirradiated samples during cooking. The introduction of the irradiation process before cooking had no effect on either vitamin. These results indicate that the loss of vitamins B₆ and B₁₂ in the combined treatments was caused mainly by thermal destruction.     

Design and application of process control charting methodologies to gamma irradiation practices

The relationship between the contract irradiation facility and the customer has historically been based upon a “PASS/FAIL” approach with little or no quality metrics used to gage the control of the irradiation process. Application of process control charts, designed in coordination with mathematical simulation of routine radiation processing, can provide a basis for understanding irradiation events. By using tools that simulate the physical rules associated with the irradiation process, end-users can explore process-related boundaries and the effects of process changes. Consequently, the relationship between contractor and customer can evolve based on the derived knowledge. The resulting level of mutual understanding of the irradiation process and its resultant control benefits both the customer and contract operation, and provides necessary assurances to regulators.

In this article we examine the complementary nature of theoretical (point kernel) and experimental (dosimetric) process evaluation, and the resulting by-product of improved understanding, communication and control generated through the implementation of effective process control charting strategies.     

Radiolytic synthesis and characterization of Ag-PVA nanocomposites

The Ag-PVA nanocomposites with different contents of inorganic phase were prepared by reduction of Ag⁺ ions in aqueous PVA solution by gamma irradiation followed by solvent evaporation. Optical properties of the colloidal solutions and the nanocomposite films were investigated using UV-vis spectroscopy. Structural characterization of the Ag nanoparticles was performed by TEM and XRD. Interaction of the Ag nanoparticles with polymer matrix and the heat resistance of the nanocomposites were followed by IR spectroscopy and DSC analysis. IR spectra indicated that Ag nanofiller interact with PVA chain over OH groups. The changes of heat resistance upon the increase of the content of inorganic phase are correlated to the adsorption of polymer chains on the surface of Ag nanoparticles.     

Synthesis and characterisation of sulfonic acid-containing ion exchange membranes based on hydrocarbon and fluorocarbon polymers

Radiation-induced graft copolymerisation has been used to modify polymers with styrene to prepare pre-cursor copolymers that can be subsequently functionalised to produce ion exchange membranes. This paper describes the processes of simultaneous and pre-irradiation graft copolymerisation of styrene to modify hydrocarbon and fluorine-containing polymers and their sulfonation to produce hydrophilic membranes. The effect of varying the grafting conditions and their characterisation by ion exchange capacity, electrolytic resistivity and equilibrium water content is reported.     

Radiation-induced changes in carboxymethylated chitosan

This study focuses on the radiation effect of γ-ray on carboxymethylated chitosan (CM-chitosan) in solid state. The changes in molecular weight of CM-chitosan with absorbed dose were monitored by viscosity method. Experimental results indicated that random chain scissions took place under irradiation. Radiation chemical yield (G_d) of CM-chitosan in solid state with N₂-saturated was 0.49, which showed CM-chitosan has high radiation stability. Biomaterials composed of CM-chitosan can be thought to sterilize with low absorbed dose. FTIR and UV spectra showed that main chain structures of CM-chitosan were retained, carbonyl/carboxyl groups were formed and partial amino groups were eliminated in high absorbed dose. XRD patterns identified that the degradation of CM-chitosan occurred mostly in amorphous region.     

The effect of dose on light-sensitivity of radicals in alanine EPR dosimeters

In this work we present a study of light-induced effects on free radicals and their transformations in gamma-irradiated pure L-alanine and in commercially available alanine detectors: rods, pellets and films. Samples irradiated to doses from 2 Gy to 4000 kGy were exposed to light from a fluorescent lamp and to ordinary daylight. The observed changes in EPR spectra of the samples were analyzed with regard to their intensity and shape. The shape analysis was based on numerical decomposition of the measured spectra into model spectra reflecting contributions of R1, R2 and R3 radical populations in the samples. The illumination of alanine dosimeters resulted in significant decrease of the central EPR line and was accompanied by distinct variations in the shape of EPR spectra. The rate of light-induced decay in spectra amplitude was found to be dependent on dose of ionizing radiation--the sensitivity to light was decreasing with increase in dose in all detectors in the 2-5x10(5) Gy dose range. The exposure of gamma-irradiated (to 300 Gy) alanine to normal, diffused daylight resulted in decay of the signal amplitude at rate about 0.5% per week. It was shown that decay in the R1 component was responsible for the observed reduction of the spectra amplitude. The observed increase in R2 contributions in samples exposed to light confirmed a hypothesis of R-->R2 radical transformations promoted by visible light. The reported effects indicate a necessity of protection of irradiated dosimeters from their prolonged exposure to light.