A Micro-Raman Study of Live, Single Red Blood Cells (RBCs) Treated with AgNO3 Nanoparticles

Abstract

Silver nanoparticles (Ag NPs) are known to exhibit broad antimicrobial activity. However, such activity continues to raise concerns in the context of the interaction of such NPs with biomolecules. In a physiological environment NPs interact with individual biological cells either by penetrating through the cell membrane or by adhering to the membrane. We have explored the interaction of Ag NPs with single optically-trapped, live erythrocytes (red blood cells, RBCs) using Raman Tweezers spectroscopy. Our experiments reveal that Ag NPs induce modifications within an RBC that appear to be irreversible. In particular we are able to identify that the heme conformation in an RBC transforms from the usual R-state (oxy-state) to the T-state (deoxy-state). We rationalize our observations by proposing a model for the nanoparticle cytotoxicity pathway when the NP size is larger than the membrane pore size. We propose that the interaction of Ag NPs with the cell surface induces damage brought about by alteration of intracellular pH caused by the blockage of the cell membrane transport.

A laser Raman tweezers study of eryptosis

“…[57] Lower pH value induces haemoglobin to release oxygen, leading to the conversion of high-affinity R state to the low-affinity T state. As has been explained in an earlier report, [58] lower pH stabilises the T state of haemoglobin. When haemoglobin is in the T state, the N-terminal amino groups of α subunits and the C-terminal histidine of the β subunits are protonated.…”

Optical tweezers combined with micro‐Raman investigation of alcohol‐induced changes on single, live red blood cells in blood plasma

“…An intense peak in 999 cm ‐1 represents the in‐plane‐mode vibration of phenylalanine. The core size band region (1,500–1,650 cm −1 ) consists of bands at 1,544; 1,561; 1,579; 1,602; 1,617; and 1,636 cm −1 , which can be attributed to the in plane porphyrin vibrational modes . The spectra obtained in normal saline and plasma exhibit major dissimilarities in terms of the oxygenation markers related to hemoglobin.…”

“…All Raman spectra were recorded within 2 hr after the blood was taken and diluted in the media solution. The power levels that are used to record the Raman spectra of control (blood plasma) and ethanol treated RBCs are well below the threshold for occurrence of photodissociation . Because the laser exposure time of each detected RBC was limited to 60 s and at a low power of ~7mW, the chance of photo damage on RBC is little and the resultant Raman spectrum will be intact and valid.…”

“…They concluded with a reduced oxygen‐affinity for the hemoglobin in a major fraction of malarial‐infected RBCs . The effect of free radicals, silver nanoparticles, glucose, and heat on RBCs that can lead to eryptosis were also investigated by monitoring the transition from relaxed to tensed state of hemoglobin …”

Probing differentiation in cancer cell lines by single-cell micro-Raman spectroscopy

“…[12][13][14][15] It is noteworthy that previous microRaman studies of differentiation have utilized four-fold high levels of incident power. 6,9 As described in other reports from our laboratory, [12][13][14][15] in which the present apparatus was used in the form of a Raman Tweezers setup, we first established the absence of significant photochemistry induced by the 785-nm laser light by recording Raman spectra of a given cell for 10 min at a time, with an interval of 1 min between subsequent measurements. We ensured that all 10 spectra, thus, obtained retained the same Raman features, providing indication that no photoinduced damage was induced in the cell in the course of the experiment.…”