الفهرس 
Sensors for Amino Acids: (Schelfer and Schubert 1992)Only 14 pages are availabe for public view
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Abstract
The amino acid Glycine shows important significance in the biological systems. Recalling the disorders associated with Glycine levels’ imbalance in the biological system, the present study is conducted to apply the blends of natural biopolymers, namely chitosan, gelatin and starch, as sensors for Glycine.
Two kinds of enhancements were carried out upon chitosan. The first one is chemical enhancement as starch and gelatin with different ratios are added separately to chitosan to form blends following the casting method. The second method is the addition of TiO2 in the form of nanoparticles (5 nm in size) in order to enhance the surface area of some selected blends.
The elongation at break, force at break, Young’s modulus, elongation at maximum and the maximum force were determined for the prepared blends to assess their mechanical properties. FTIR spectroscopy was used to follow up the structural features of the raw materials (chitosan, starch and gelatin) and subsequently the formation of the desired blends. Furthermore, UV spectroscopy was used to test the application of the prepared blends as sensors. The blend films were immersed in Glycine solutions with known concentrations for certain time. The interaction of Glycine with each blend film is then assessed with UV spectroscopy.
FTIR spectroscopy confirmed the formation of the blends. Studying the mechanical properties of the prepared blends showed that in chitosan/gelatin blend films, there were gradual increases in the values of Young’s modulus, elongation at maximum and elongation at break, and were attributed to the ability of gelatin to make elastic films. The values of maximum force and force at break also showed a gradual increase with increasing the percentage of gelatin in the blend, but when the percentage of gelatin exceeded 50% of the blend, it became less hard, leading to a gradual decrease in the values of maximum force and force at break.
As for chitosan/starch blends, there were gradual increase in the values of Young’s modulus, elongation at maximum and elongation at break which were attributed to the formation of hydrogen bonds between NH3+ of chitosan and OH- of starch. Those values then started to decrease after the percentage of starch in the blend exceeded 50% and this was attributed to the inability of starch to form elastic films. The values of maximum force and force at break showed a gradual increase and this, again, was attributed to the formation of hydrogen bonding between NH3+ of chitosan and OH- of starch. Mechanically, it was found that chitosan/gelatin and chitosan/starch blends, prepared with the above concentrations, are capable of being used as biosensors for glycine.
It was also found that films of pure chitosan, chitosan/gelatin blends and chitosan/starch blends are all sensitive to glycine but chitosan/gelatin and chitosan/starch blends showed higher sensitivity than pure chitosan. Among the prepared blends, it was found that chitosan/gelatin blends of 20% gelatin and 80% chitosan, and chitosan/starch blends of 50% starch and 50% chitosan have the highest sensitivity for glycine and were thus selected to test the effect of adding nano-TiO2 to further improve their sensitivity.
As far as TiO2 (5 nm grain size) is added to the selected blends, the blends were immersed again in glycine solution. UV spectroscopy indicated a significant increase in the sensitivity of the selected blends. This is attributed to enhancing and increasing the surface property of the blends containing nano-TiO2.