AFM Microfluidic Cantilevers as Weight Sensors for Live Single Cell Mass Measurements

Gold Flake-Enabled Miniature Capacitive Picobalances

Measurement of masses of microscale objects or weak force with ultrahigh sensitivity (down to nanogram/piconewton level) and compact configuration is highly desired for fundamental research and applications in various disciplines. Here, by using freestanding gold flakes with high reflectivity (≈98% at 980 nm) as the sample tray and silica microfibers with extremely low spring constant (≈0.05 mN m-1) as the cantilever beams, miniature capacitive balances are reported with piconewton-level detection limit (picobalances) and reliable radiation force-based calibration. In the design, the gold flake is suspended by two silica microfibers, which also functions as an electrode to form a capacitor with an underneath gold electrode. Benefitting from the high reflectivity of the gold flake, the performance of picobalances can be precisely calibrated by exerting piconewton-level radiation pressure on the gold flake (working as a mirror) with a laser, showing a detection limit as low as 6.9 pN. Finally, using a fiber taper-assisted micromanipulation technique, masses of various types of pollens (with weights ranging from 4.6 to 96.3 ng) are readily measured by a picobalance at single-particle level. The miniature picobalances should find applications in precise measurement of masses of micro or nanoscale objects and various types of weak forces.

Characterizing induced pluripotent stem cells and derived cardiomyocytes: insights from nano scale mass measurements and mechanical properties

Our study reveals that the nano-mechanical measures of elasticity and cell mass change significantly through induced pluripotent stem cell (iPSC) differentiation to cardiomyocytes, providing a reliable method to evaluate such processes. The findings support the importance of identifying these properties, and highlight the potential of AFM for comprehensive characterization of iPSC at the nanoscale.

Design and Simulation of the Microcantilever Biosensor for MITF Antigen and D5 Monoclonal Antibody Interaction Finite Element Analysis, and Experimental

BACKGROUND

Biosensors and MEMS have witnessed rapid development and enormous interest over the past decades. Constant advancement in diagnostic, medical, and chemical applications has been demonstrated in several platforms and tools. In this study, the analytical and FEA of the microcantilever used in biomolecular analyses were compared with the experimental analysis results.

METHODS

In this study, MITF antigen, which is a melanoma biomarker, and anti-MITF antibody (D5) were selected as biomolecules. A MEMS-type microcantilever biosensor was designed by functionalizing the AFM cantilever by utilizing the specific interaction dynamics and intermolecular binding ability between both molecules. Surface functionalization of cantilever micro biosensors was performed by using FEA. The stress that will occur as a result of the interactions between the MITF-D5 has been determined from the deviation in the resonant frequency of the cantilever.

RESULTS

It has been found that the simulation results are supported by analytical calculations and experimental results.

CONCLUSION

The fact that the results of the simulation study overlap with the experimental and mathematical results allows us to get much cheaper and faster answers compared to expensive and time-consuming experimental approaches.

Tailoring the Sensitivity of Microcantilevers To Monitor the Mass of Single Adherent Living Cells

Microcantilevers are widely employed as mass sensors for biological samples, from single molecules to single cells. However, the accurate mass quantification of living adherent cells is impaired by the microcantilever's mass sensitivity and cell migration, both of which can lead to detect masses mismatching by ≫50%. Here, we design photothermally actuated microcantilevers to optimize the accuracy of cell mass measurements. By reducing the inertial mass of the microcantilever using a focused ion beam, we considerably increase its mass sensitivity, which is validated by finite element analysis and experimentally by gelatin microbeads. The improved microcantilevers allow us to instantly monitor at much improved accuracy the mass of both living HeLa cells and mouse fibroblasts adhering to different substrates. Finally, we show that the improved cantilever design favorably restricts cell migration and thus reduces the large measurement errors associated with this effect.