A novel way to go whole-cell in patch-clamp experiments

Achieving Automated Organelle Biopsy on Small Single Cells Using a Cell Surgery Robotic System

Single cell surgery such as manipulation or removal of subcellular components or/and organelles from single cells is increasingly used for the study of diseases and their causes in precision medicine. This paper presents a robotic surgery system to achieve automated organelle biopsy of single cells with dimensions of less than 20 μm in diameter. The complexity of spatial detection of the organelle position is reduced by patterning the cells using a microfluidic chip device. A sliding mode nonlinear controller is developed to enable extraction of organelles, such as the mitochondria and the nucleus, from single cells with high precision. An image processing algorithm is also developed to automatically detect the position of the desired organelle. The effectiveness of the proposed robotic surgery system is demonstrated experimentally with automated extraction of mitochondria and nucleus from human acute promyelocytic leukemia cells and human fibroblast cells. Extraction is followed by biological tests to indicate the functionality of biopsied mitochondria as well as the cell viability after removal of mitochondria. The results presented here have revealed that the proposed approach of automated organelle biopsy on single small cells is feasible.

Minimizing cytosol dilution in whole-cell patch-clamp experiments

During a conventional whole-cell patch clamp experiment, diffusible cytosolic ions or molecules absent in the pipette solution can become diluted by a factor of one million or more, leading to diminished current or fluorescent signals. Existing methods to prevent or limit cytosol diffusion include reducing the diameter of the pipette's orifice, adding cytosolic extract or physiological entities to the pipette solution, and using the perforated patch clamp configuration. The first method introduces measurement error in recorded signals from increased series resistance and the latter two are cumbersome to perform. In addition, most perforated patch configurations, prevent investigators from using test compounds in the pipette solution. We present a method to overcome these limitations by minimizing cytosol dilution using a novel pipette holder. Cell-attached configuration is obtained with the pipette filled with pipette solution. Most of the pipette solution is then replaced with mineral oil so that cytosol dilution can be minimized in whole-cell configuration. To accomplish this requires a suction line and two Ag/AgCl electrodes inside the pipette. Testing our novel pipette holder with Chinese Hamster Ovarian cells, we demonstrate cytosol dilution factors between 76 and 234. For large cells with somas greater than 40 μm, cytosol dilution factors of 10 or less are achievable.