Cells migrate by applying rearward forces against extracellular media. It is unclear how this is achieved in amoeboid migration, which lacks adhesions typical of lamellipodia-driven mesenchymal migration. To address this question, we developed optogenetically controlled models of lamellipodia-driven and amoeboid migration. On a two-dimensional surface, migration speeds in both modes were similar. However, when suspended in liquid, only amoeboid cells exhibited rapid migration accompanied by rearward membrane flow. These cells exhibited increased endocytosis at the back and membrane trafficking from back to front. Genetic or pharmacological perturbation of this polarized trafficking inhibited migration. The ratio of cell migration and membrane flow speeds matched the predicted value from a model where viscous forces tangential to the cell-liquid interface propel the cell forward. Since this mechanism does not require specific molecular interactions with the surrounding medium, it can facilitate amoeboid migration observed in diverse microenvironments during immune function and cancer metastasis.

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Here we report successful demonstration of a FET-like electrochemical nano-biosensor to accurately detect ultralow concentrations of adenosine triphosphate. As a 2D material, graphene is a promising candidate due to its large surface area, biocompatibility, and demonstrated surface binding chemistries and has been employed as the conducting channel. A short 20-base DNA aptamer is used as the sensing element to ensure that the interaction between the analyte and the aptamer occurs within the Debye length of the electrolyte (PBS). Significant increase in the drain current with progressive addition of ATP is observed whereas for control experiments, no distinct change in the drain current occurs. The sensor is found to be highly sensitive in the nanomolar (nM) to micromolar ( μM) range with a high sensitivity of 2.55 μA (mM) (-1), a detection limit as low as 10 pM, and it has potential application in medical and biological settings to detect low traces of ATP. This simplistic design strategy can be further extended to efficiently detect a broad range of other target analytes.