Rotational optical tweezers for active microrheometry within living cells
Mark L. Watson, Darren L. Brown, Alexander B. Stilgoe, Jennifer L. Stow, Halina Rubinsztein‐Dunlop
Abstract
Studying the mechanical properties of living cells provides opportunities to unravel the physical phenomena that govern biological functions. Macropinocytosis is a cellular pathway that involves the non-selective uptake of extracellular fluid through the formation of a macropinosome and is implicated in crucial cell-specific roles. Here, we describe an in vivo intracellular study that exploits a high-resolution rotational geometry to trap and monitor a photonic probe within a macropinosome. We use the transfer of spin angular momentum in rotational optical tweezers and show that active microrheometry methods can be successfully conducted in vivo , leading to a shear viscosity measurement of a macropinosome lumen within a living cell of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mo stretchy="false">(</mml:mo> <mml:mn>1.01</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.16</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">m</mml:mi> <mml:mi mathvariant="normal">P</mml:mi> <mml:mi mathvariant="normal">a</mml:mi> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> . This work provides a foundation for dynamic mechanobiological studies characterizing biological processes of intracellular vesicles.