Imre Dékány

University of Szeged, Department of Physical Chemistry and Materials Science, Faculty Member

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Preface | Colloids and Surfaces A: Physicochemical and Engineering Aspects - Volume 319, Issues 1–3

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2008

Stabilisation of SWNTs by alkyl-sulfate chitosan derivatives of different molecular weight: towards the preparation of hybrids with anticoagulant properties

Nanoscale, 2011

Materials and methods Synthesis of N-octyl chitosan Chitosan (1.0 g) was suspended in methanol (5... more Materials and methods Synthesis of N-octyl chitosan Chitosan (1.0 g) was suspended in methanol (50 mL) and octaldehyde (1.02 g) was added to the suspension while stirring; the suspension obtained was stirred at room temperature for 24 hours. An aqueous solution of NaBH4 (0.5g in 5 mL) was slowly added to the reaction mixture and the resulting mixture was stirred at room temperature for further 24 hours. The reaction was stopped by neutralization with 2 M HCl. The product was filtered and repeatedly washed with methanol and water and finally dried under vacuum at 60°C to constant weight. N-octyl-O-sulphate chitosan N-octyl-chitosan (1.0 g) was suspended in DMF (40 mL). Chlorosulfonic acid (20 mL) was added dropwise to 40 mL of DMF and the mixture stirred for 1 h at 0 °C. Then the N-octyl-chitosan suspension was added to the above solution. The mixture was reacted at 40 °C for 24 hours. The reaction was stopped by neutralization with 20 % w/v NaOH, the obtained precipitate was filtered off and the filtrate was dialysed against distilled water for 3 days and then freeze dried. Purification and characterisation of SWNTs Pristine nanotubes were purified using two different methods, namely: microwave assisted purification 1 and purification by oxidation in nitric acid. 2 Microwave purification: Microwave assisted purification of SWNTs was carried out as described in literature with a slight modification. Carbon nanotubes (20.0 mg) were placed into a 100 mL conical flask and into a conventional microwave at 90 W for 5 s; the carbonaceous material was removed from the microwave, shaken and stirred with a spatula, and placed back into the microwave for another 5 s (x 60) of treatment. The SWNTs were then suspended in concentrated HCl (10 mL), the mixture obtained was centrifuged at 4,000 rpm for 5 min. After discarding the supernatant the SWNTs were further washed with water (10 mL), methanol (10 mL), and diethyl ether (10 mL). The remaining solid was dried using compressed air (10.8 mg). Nitric acid oxidation: SWNTs were oxidised by treatment in nitric acid as described in literature with modifications. HipCo SWNTs (20.0 mg) were suspended in nitric acid (4 mL) and the mixture was refluxed at 88 °C overnight. Deionised water was added to stop the reaction and the mixture was centrifuged at 4,000 rpm for 5 min. The SWNTs were washed twice with water and the final solution was neutralized with NaOH (20 % w / v). The modified SWNTs were separated by centrifugation (4,000 rpm, 5 min) and dried under a vacuum (19.6 mg). Cytotoxicity assay method Caco-2 cells were seeded in 96-well plate and incubated for 2 days in culture medium (Media 199, Invitrogen, supplemented with FCS (10 %) and penicillin / streptomycin (50 µg/mL) at 37 °C in air (95 %) : CO2 (5 %). Media was removed and cells were incubated for 2 h with polymer (500 µL) dissolved in Media 199, at concentrations of 0.1, 1 and 10 mg/mL. SDS (10 mg/mL) was used as positive control and culture media as reference for 100% cell viability. Media and test solutions were then removed after treatment time and cells washed with PBS. Freshly prepared MTT (200 µL) in Media 199 (0.5 mg/mL), without any additions, was added and cells were incubated for 1 h at 37 °C. Subsequently, MTT solutions were removed from the wells and DMSO (400 µL) was added to dissolve formed formazan crystals. After homogeneous agitation (10 min), the absorbance was read at 584 nm. In vivo biomodifcation of NOSC-SWNTs dispersions Brine Shrimp (Artemia) cysts (NT Labs, United Kingdom) were incubated in artificial sea water (Tropic Marin, Wartenberg, Germany) at 27 °C for 24 h with constant lighting until hatching. A small number of resulting larvae (about 20-25 individuals in triplicates) were incubated for 24 h at 27 °C as reported previously3 in a 48 well-plate with 20 μL of PBS and 980 μL of NOSC-SWNTs suspensions. Artemia larvae were counted and photographed with the use of a stereoscope (GX Microscopes) and a digital camera (LEICA IM50).

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