Mastering small volume measurements with QSense Omni: Setup Considerations and Example Data

In the world of surface science and molecular interaction studies, precision and efficiency are key. The QSense Omni instrument offers exceptional capabilities for small volume measurements. In this blog post, we'll explore the benefits of using QSense Omni for small volume measurements and provide a step-by-step guide on how to execute these measurements effectively. Additionally, we have included a video tutorial to help you get started.

Benefits of Small Volume Measurements with QSense Omni

Minimal Sample Requirement: The QSense Omni is designed to work with the low sample volumes, which is particularly beneficial when dealing with expensive or limited-availability samples. This is achieved through its direct-injection fluidics system, which minimizes the liquid pathway and reduces the required sample volume.

Faster Kinetics Measurements: The direct-injection system also allows for faster liquid exchange, enabling the study of rapid kinetic processes that might be missed with traditional systems.

Versatility and Automation: The QSense Omni is equipped with automated sample handling and cleaning functions, which streamline the experimental process and reduce manual labor. This automation ensures high reproducibility and efficiency in your measurements.

How to Execute Small Volume Measurements with QSense Omni

Executing small volume measurements with the QSense Omni is a straightforward process, thanks to its user-friendly design and advanced software. Here’s a step-by-step guide to help you get started:

• Sensor: Pre-clean and mount the sensor in the sensor holder and insert the sensor holder inside the chamber. Use QSoft Omni software to set the desired measurement temperature and adjust the stability criteria.
• Sample: Add your samples on the syringes mounted on the sample holder. For the small volume sample, directly pipette it on the Luer converter, or directly on the sample port. At Sample screen in QSoft Omni, choose the sample container used for your samples. For the small sample volume, choose the “port only” option.
• Start the Measurement: Use the QSoft Omni software to configure your experiment. Initiate the measurement using the QSense Omni’s intuitive interface. The system will automatically handle the sample and perform the measurement with high precision.
• Analyze the Data: Once the measurement is complete, use QSense Dfind software to analyze the data. The high-quality data generated will provide you with detailed insights into the molecular interactions at play.

Considerations for Choosing an Experimental Setup

When setting up experiments for low volume measurements with the QSense Omni, several factors should be taken into account to ensure optimal results:

• Sample Volume and Handling: The QSense Omni allows for using minimal sample volumes, starting at 90 microliters. It's crucial to handle these small volumes carefully to avoid trapping air when adding into the instrument. Slowly pipette the sample along the side of the Luer converter or sample port. Be cautious as the pipette tip is relatively large and can cause overflow if inserted too deeply.
• Sample Configuration: Depending on your sample volume, you can choose between using the Luer converter or the sample port. The Luer converter supports a maximum volume of 130 microliters, while the sample port option allows for up to 260 microliters.
• Temperature and Stability: Small volume measurements may require longer incubation times without flow. It's important to adjust the stability criteria in the QSoft Omni software to accommodate these conditions.
• Measurement Configuration: Of the 90 microliters added on the instrument, 40 microliters are available to run in your measurement, which is the minimum volume recommended to completely replace all the liquid on the sensor. This is 2 minutes script step, using standard 20µL/min flow rate. Use the pause sample period to incubate without flow.
• Data interval: For long measurements, adjust the data interval to reduce file size without compromising results, since it is expected slow kinetics in long measurements. For example, use 5 seconds interval for runs of five hours or more. Just be sure your flow rate and data interval still yield enough data points during liquid exchange. 

Example Data: Small Volume Measurement with QSense Omni

To illustrate the effectiveness of the QSense Omni in small volume measurements, let's look at an example experiment:

Experiment Setup:

• Sample: Bovine Serum Albumin (BSA) in Acetate buffer, pH 4.7. BSA concentration: 500µg/mL
• Volume: 90 microliters of sample used in the sample port configuration
• Sensor: QSX 305 Polystyrene sensor
• Flow Rate: 5 microliters per minute

 Procedure:

• Buffer baseline: 20 min
• Sample injection: 6 min
• Incubation: 3 hours of pause (no flow) after initial sample injection
• Buffer rinse: 1h

Results:

The data, Fig. 1, showed a smooth response with no air bubbles affecting the measurement. The Sauerbrey thickness indicated a 3 nm layer was quickly established, with a gradual increase over time.

Figure 1. QCM-D raw data, QSense Omni small volume measurement BSA adsorption.

Concluding remarks

This example demonstrates the QSense Omni's capability to deliver precise and reliable data even with minimal sample volumes, making it an ideal choice for studies involving expensive or rare samples. By minimizing sample requirements, the QSense Omni not only reduces costs but also opens up new possibilities for research where sample availability is limited. Its advanced fluidics and automation ensure high reproducibility and accuracy, critical for cutting-edge research in fields such as pharmaceuticals, materials science, and biotechnology.

Watch our video tutorial

For a step-by-step guide on executing small volume measurements with the QSense Omni, watch our video tutorial. This visual guide will walk you through the process, ensuring you can make the most of your QSense Omni instrument.