biological cells. A simple and most commonly used configuration is the single beam optical trap in
which a tightly focused laser beam optically immobilizes individual cells within the laser focus. The
perturbative effect of an optical trap operating under such a tight focusing condition on the function
and biochemistry of a live cell is often a concern, with photoinduced damage typically being a primary
focus. Mechanically induced biochemical changes, however, have not been as extensively studied,
even though it is known that optical forces are imposed on a biological cell by a single beam optical
trap that are often strong enough to modify its shape. Herein, we report that a red blood cell (RBC) in a
single beam optical trap transitions from an oxygenated to a partially deoxygenated state with
increasing trapping power using laser tweezers Raman spectroscopy (LTRS). In addition, the
oxygenation states of different types of red blood cells, such as sickle cells and normal adult red blood
cells, reacts differently with the increased optical trapping power ranging from 1.6mW to 20mW,
which provides the rationale for function analysis of the oxygen carrying capacity of different types of
RBCs.