Red blood cells under varying extracellular tonicity conditions: an optical tweezers combined with micro-Raman study

Jijo Lukose, Shamee Shastry, Mithun Nelliat, Ganesh Mohan, Akheel Ahmed and C Santhosh

Extracellular tonicity has a significant influence on human red blood cell deformation capability. Advancements in the area of laser physics and optical trapping have opened up a plethora of applications for understanding cell structure and dynamics. Here, Raman Tweezers technique was employed to investigate the impact of extracellular tonicity by exposing human red blood cells to both hypertonic and hypotonic intravenous fluids. Heme aggregation was observed in hypertonic saline solution, accompanied with damage in membrane protein. Loss of intracellular hemoglobin in hypotonic solution was evident from the decrease in porphyrin breathing mode present at 752 cm−1. Oxygen binding to the central iron in the red blood cell heme was also affected under both hyper/hypo tonicity conditions. Morphological deviation of discocytes to echinocytes/spherocytes were also evident from quantitative phase imaging. Principal component analysis have showed clear differentiation of samples in order to classify the control erythrocytes and the tonicity stressed erythrocytes. Present study has also demonstrated the application of Raman Tweezers spectroscopy as a potential tool for probing red blood cell under different stress conditions.

DOI

Oxaliplatin effects on the DNA molecule studied by force spectroscopy

L Oliveira, J M Caquito Jr and M S Rocha

In the present study we investigated the binding of the anticancer compound Oxaliplatin to DNA. Using optical tweezers to perform single molecule force spectroscopy, we determined the changes of the mechanical parameters of DNA complexes formed with Oxaliplatin, at high and low ionic strengths. The interaction mechanism and the physical chemistry of the binding were determined from these measurements. In addition, kinetic information on covalent diadduct formation and on DNA compaction by Oxaliplatin were also obtained. All these results were critically compared to those obtained for the related anti-neoplastic compounds Cisplatin and Carboplatin, previously determined under similar experimental conditions. These results provide new information about the action of platinum-based compounds on DNA, being useful to the improvement of current chemotherapies and to the design of novel correlated drugs.

DOI