Folic acid modified clay/polymer nanocomposites for selective cell adhesion.

A folic acid (FA) modified poly(epsilon-caprolactone)/clay nanocomposite (PCL/MMT-(CH2CH2OH)2-FA) resulting in selective cell adhesion and proliferation was synthesized and characterized as a cell culture and biosensing platform. For this purpose, first the FA modified clay (MMT-(CH2CH2OH)2-FA) was prepared by treating the organo-modified clay, Cloisite 30B [MMT-(CH2CH2OH)2] with FA in chloroform at 60 °C. Subsequent ring opening polymerization of ε-caprolactone in the presence of tin octoate (Sn(Oct)2) using MMT-(CH2CH2OH)2-FA at 110 °C resulted in the formation of MMT-(CH2CH2OH)2-FA with an exfoliated clay structure. The structures of intermediates and the final nanocomposite were investigated in detail by FT-IR spectral analysis and DSC, TGA, XRD, SEM and AFM measurements. The combination of FA, PCL and clay provides a simple and versatile route to surfaces that allows controlled and selective cell adhesion and proliferation. FA receptor-positive HeLa and negative A549 cells were used to prove the selectivity of the modified surfaces. Both microscopy and electrochemical sensing techniques were applied to show the differences in cell adherence on the modified and pristine clay platforms. This approach is expected to be adapted into various bio-applications such as 'cell culture on chip', biosensors and design of tools for targeted diagnosis or therapy.

Radon measurements in the caves of Zonguldak (Turkey).

There are approximately 20 caves of limestone origin in Zonguldak (Turkey). In this study, the results of atmospheric radon measurements performed for two caves are presented. These caves, Gökgöl and Cehennemagzi, are open to tourism. Gökgöl Cave is the longer, at nearly 3,200 m in length. Cehenennemagzi is a pit-type cave with a total length of 85 m. The radon measurements were performed for 2 months between July 2004 and September 2004 using passive polycarbonate detectors. The mean radon concentrations were recorded as 1,918.8 Bq m(-3) in Gökgöl Cave and 657 Bq m(-3) in Cehennemagzi Cave. The maximum value corresponds to a site located 400 m from the entrance of Gökgöl Cave. Mean effective dose values for tourists of 0.86 microSv per visit to Cehennemagzi Cave and 3.76 microSv to Gökgöl Cave were obtained. These results show that protection against radiological hazards would not be necessary for visitors to these two caves.

Radon concentration measurements in the Amasra coal mine, Turkey.

In this study, the results of atmospheric radon measurements that were performed for the Amasra underground coal mine in Zonguldak bituminous coal basin (Turkey) are presented. The radon measurements were performed for 40 days between November 2004 and December 2004 using passive nuclear etched track detectors. The radon concentrations vary from a minimum value 49 Bq m(-3) in a site located at +40 m to a maximum value 223 Bq m(-3) in a site located at -100 m. Mean concentration is 117 (Bq m(-3)). This value is well below the action level of 500-1,500 Bq m(-3) recommended by the International Commission on Radiological Protection (ICRP) (1993). The mean effective dose value for workers of this mine of 3.4 microSv per day was obtained. This result shows that protection against radiological hazards would not be necessary for workers of this mine((2)).