We have previously demonstrated that chitosan derivative N-octyl-O-sulfate chitosan (NOSC), which presents important pharmacological properties, can suspend single walled carbon nanotubes (SWNTs) up to 20 times more effectively than other chitosan derivatives in an aqueous environment. In an attempt to further investigate the impact of different molecular weights of chitosan to the solubilization and anticoagulant properties of these hybrids an array of NOSC derivatives varying their molecular weight (low, medium and high respectively) was synthesised and characterised by means of FT-IR spectroscopy, NMR spectroscopy and thermal gravimetric analysis (TGA). Microwave and nitric acid purified SWNTs, characterised by FT-IR spectroscopy, transmission electron microscopy (TEM) and Raman spectroscopy, were colloidally stabilised by these polymers and their anticoagulant activity was assessed. The results revealed that the low molecular weight NOSC coated SWNTs exhibit the highest activity when 0.5 mg mL(-1) NOSC solutions are used, activity which is similar to that of the free polymer. Preliminary studies by exposure of these hybrids to Brine Shrimp (Artemia) cysts revealed no effect on the viability of sub-adult Artemia. Our findings suggest the possibility of tailoring these nanomaterials to bear the required properties for application as biocompatible building blocks for nanodevices including biosensors and biomaterials.

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The present study aimed to select the best medium for inactivation of Aspergillus fumigatus, Aspergillus spp. in section Nigri, A. niger, A. terreus var. terreus, A. tubingensis, Penicillium waksmanii, P. simplicissimum, and Aspergillus sp. strain no. 145 spores in clinical wastes by using supercritical carbon dioxide (SC-CO). There were three types of solutions used including normal saline, seawater, distilled water, and physiological saline with 1% of methanol; each solution was tested at 5, 10, and 20 mL of the water contents. The experiments were conducted at the optimum operating parameters of supercritical carbon dioxide (30 MPa, 75 °C, 90 min). The results showed that the inactivation rate was more effective in distilled water with the presence of 1% methanol (6 log reductions). Meanwhile, the seawater decreases inactivation rate more than normal saline (4.5 vs. 5.1 log reduction). On the other hand, the experiments performed with different volumes of distilled water (5, 10, and 20 mL) indicated that A. niger spores were completely inactivated with 10 mL of distilled water. The inactivation rate of fungal spores decreased from 6 to 4.5 log as the amount of distilled water increased from 10 to 20 mL. The analysis for the spore morphology of A. fumigatus and Aspergillus spp. in section Nigri using scanning electron microscopy (SEM) has revealed the role of temperature and pressure in the SC-CO in the destruction of the cell walls of the spores. It can be concluded that the distilled water represent the best medium for inactivation of fungal spores in the clinical solid wastes by SC-CO.

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Surface properties of bacterial cells enable them to be used in the removal of heavy metals. Moreover, the inactivation of bacterial cells via chemical or physical processes may enhance the biosorption efficiency for heavy metals. The use of supercritical carbon dioxide (SC-CO 2 ) to inactivate bacteria based on destruction of cell walls took place due to the pressurized CO 2 . In this study, the pre-treatment of Bacillus subtilis cells by SC-CO 2 (BM1), steam autoclaving (BM2), and untreated living cells (BM3) were investigated to show improvement in heavy metal removal. The removal process was optimized based on the main factors affecting bacterial biosorption, which included heavy metals ion concentrations, cell biomass concentrations, pH, time, and temperature. The efficiency of bacterial biomass in removing Ni 2þ ions in the presence of different concentrations of Pb 2þ , Cu 2þ , Zn 2þ , and Cd 2þ was also tested. BM1 and BM2 exhibited the highest potential for the removal of nickel ions in comparison to BM3. The maximum efficiency was 98.54, 99.2, and 96.3% for BM1, BM2, and BM3, respectively. Moreover, BM1 displayed a higher biosorption capacity for Ni 2þ , Cu 2þ , Zn 2þ , Pb 2þ , and Cd 2þ (>150 mg g À1 ) than BM2 and BM3. Biosorption on bacterial cell biomass of Ni 2þ ions shows lower removal affinity in the presence of other metal ions.In conclusion, the pre-treatment of bacterial cells biomass by SC-CO 2 enhanced the removal process of heavy metal ions compared to untreated living cells.