How to introduce a sample into the µ-volume sample holder of the ElastoSens™ Bio?
by Dimitria Camasão and Assala Larbes,
Application Scientists, Rheolution Inc.
ElastoSens™ Bio and the the µ-volume sample holder
The ElastoSens™ Bio is a compact analytical instrument that measures the viscoelastic properties of soft materials following easy and quick steps guided by the Soft Matter Analytics™ App. Prior to testing, the sample to be measured needs to be inserted into the available sample holders specifically designed for the ElastoSens™ Bio. This step plays a key role in ensuring the quality of the data obtained from the instrument.
The μ-volume sample holder was developed for applications in which sample volume is limited, such as for natural polymers, blood and plasma, cellularized hydrogels, among others. This device is completely autoclavable and designed to fit in a 12-well plate for easy sample storage. This feature together with the non destructive nature of the technology allows the same sample to be tested multiple times, enabling the tracking of its mechanical behavior over time in controlled environments.
In this technical note, two methodologies for introducing a sample into the µ-volume sample holder will be described in detail to obtain optimal results. These protocols may be preferred depending on the type of sample studied.
Methodologies for sample introduction into the µ-volume sample holder of the ElastoSens™ Bio
Methodology 1: Pouring the liquid sample from the top of the µ-volume sample holder.
This methodology is preferred for samples that are not too viscous at the liquid state and therefore they can flow easily within the cavity of the µ-volume sample holder. The pieces used in this methodology are illustrated as follows:
Figure 1: List of pieces used when pouring the liquid sample from the top of the µ-volume sample holder.
Step 1: Assembly of the loading system.
The pieces A to E need to be assembled in the following order (Figure 1) to obtain the loading system of Figure 2.
Figure 2: Assembled loading system (right).
Note: The loading system can be pre-incubated at the same temperature as the sample to be poured, ensuring homogeneous solidification specially for thermosensitive samples.
Step 2: Pouring of the liquid sample into the loading system.
The sample can be slowly poured into the loading system using a pipette (the volume required is 250 µL). It is important to make sure that the sample penetrates the cavity well and covers the entire inner space of the µ-volume sample holder (Figure 3).
Note: The sample holder can be carefully rotated in a circular manner while pipetting to fill the inner cavity first and then the center to prevent sample displayed at the bottom of Figure 3.
Figure 3: Pouring of the liquid sample into the µ-volume sample holder (left), close image featuring the cavity in which the liquid sample needs to penetrate (center), and examples of samples that were well introduced, and not well introduced (right).
Step 3: Timing for the solidification of the sample.
The loading system with the sample must be placed at the required environmental conditions to allow the sample to solidify. The sample should achieve a solid state (able to support itself over the spring) before advancing to the next step.
Note 1: It is important to place the loading system with the sample on a flat surface to ensure even solidification of the sample.
Note 2: Samples with high water content are highly prone to drying over time. To prevent sample drying, options include controlling the environmental humidity or adding mineral oil or other media onto the sample during this step, if needed.
Step 4: Disassembly of the loading system and recuperation of the µ-volume sample holder.
When the sample is ready, unscrew the piece E from the piece A (Figure 1) then carefully remove the plastic spring base (piece D) as illustrated in Figure 4A. The bottom cap of the µ-volume sample holder (piece F) can then be clipped to obtain the µ-volume sample holder with the sample (Figure 4B-C).
Figure 4: Disassembly of the loading system (A), removal of the plastic spring base (B) and recuperation of the µ-volume sample holder (C).
Note 1: A side of the spring can be held with tweezers while removing the plastic spring base (Figure 4A).
Note 2: The µ-volume sample holder with samples containing a high percentage of water should always be stored in a liquid medium when not being tested to avoid sample drying.
Step 5: Testing in the ElastoSens™ Bio.
The µ-volume sample holder with the sample only needs to be clipped to the adaptor (piece G) for testing in the ElastoSens™ Bio (Figure 5).
Figure 5: Connection with the adaptor of the ElastoSens™ Bio (left), and installation in the ElastoSens™ Bio’s mechanical unit for testing (right).
Note 1: The liquid added to the sample for storage should be removed prior to testing. If the µ-volume sample holder with the sample was immersed in liquid, it is recommended to remove the excess of liquid from the metallic pieces with an absorbent paper and remove the layer of liquid that settles over the sample with a pipette.
Note 2: It is recommended to run short tests for samples containing a high percentage of water to avoid sample drying.
Methodology 2: Introducing the liquid or solid sample from the bottom of the µ-volume sample holder.
This methodology is preferred for samples that are too viscous at the liquid state and do not flow easily within the cavity of the µ-volume sample holder, or for samples that are already solid and can be prepared at the required dimensions (thickness/height of 1.6 mm and diameter of 14 mm). The pieces used in this methodology are illustrated as follows:
Figure 6: List of pieces used when pouring the liquid sample from the bottom of the µ-volume sample holder.
Step 1: Assembly of the alternative loading system.
For this methodology, the top cap of the µ-volume sample holder (piece B) can be mounted with the cover piece (piece H) as illustrated in Figure 7.
Figure 7: Alternative loading system.
Note 1: The loading system can be pre-incubated at the same temperature as the sample to be poured, ensuring homogeneous solidification specially for thermosensitive samples.
Note 2: The addition of oil around the area where the cover piece makes contact with the sample holder can better seal the system, if needed.
Step 2: Introduction of the viscous liquid or solid sample into the loading system.
The liquid sample can be slowly poured into the loading system using a pipette (the volume required is 250 µL). It is important to make sure that the sample covers homogeneously the inner space of the µ-volume sample holder (Figure 8). Alternatively, gently place the solid sample into the cavity of the µ-volume sample holder. The spring can be added when the sample is evenly spread (allow a few seconds for liquid samples) followed by the plastic spring base.
Figure 8: Pouring of the viscous liquid sample into the µ-volume sample holder.
Step 3: Timing for the solidification of the sample.
The loading system with the sample must be placed at the required environmental conditions to allow the sample to solidify. The sample should achieve a solid state (able to support itself over the spring) before advancing to the next step.
Note 1: It is important to place the loading system with the sample on a flat surface to ensure even solidification of the sample.
Step 4: Disassembly of the loading system and recuperation of the µ-volume sample holder.
Step 5: Testing in the ElastoSens™ Bio.
The µ-volume sample holder with the sample only needs to be clipped to the adaptor (piece G) for testing in the ElastoSens™ Bio (similar to Figure 5 of previous section).
Note 1: The liquid added to the sample for storage should be removed prior to testing. If the µ-volume sample holder with the sample was immersed in liquid, it is recommended to remove the excess of liquid from the metallic pieces with an absorbent paper and remove the layer of liquid that settles over the sample with a pipette.
Note 2: It is recommended to run short tests for samples containing a high percentage of water to avoid sample drying.
Shear storage modulus (G’) of gelatin 7 % following the methodologies 1 and 2
Gelatin type B from bovine skin (Sigma-Aldrich, USA) was prepared at 7 % (%w/v) using distilled water and poured into the µ-volume sample holder following the methodologies 1 and 2. The loading systems were pre-incubated at 40 °C before sample loading (same temperature as the liquid gelatin). The loading systems with the sample were placed in the fridge at 4 °C for 30 min. They were then disassembled and the µ-volume sample holder mounting completed.
Samples were immediately tested at room temperature (23 °C) for 3 min at a temporal step of 10 s. Six samples were prepared according to each methodology (n=6). Average results are expressed as mean ± standard deviation. Statistical analysis was performed using GraphPad Prism (GraphPad Prism Software, USA) using unpaired t test with Welch’s correction. Significance was retained when p < 0.05.
Figure 9 displays the average shear storage modulus of the gelatin 7 % obtained following each methodology. No statistical difference was found between them (11 784 ± 1 128 Pa and 10 904 ± 1 471 Pa for methodology 1 and 2, respectively) confirming that the different methods of sample loading do not affect the measurements and results.
Figure 9: Average shear storage modulus (Pa) of the gelatin 7 % obtained following methodology 1 (orange) and 2 (blue).
Key takeaways
- This technical note presents two methods for sample introduction into the µ-volume sample holder together with a number of insights and recommendations to ensure their successful implementation.
- Due to the variability of materials that can be tested in the instrument, it is always recommended to practice these methodologies, verify and validate whether the samples formed inside the µ-volume sample holder respect the required geometry, and adjust these guidelines further according to their particularities.
- Users should ensure proper sample loading before starting running tests in the ElastoSens™ Bio.
ElastoSens™ Bio and the the µ-volume sample holder
The ElastoSens™ Bio is a compact analytical instrument that measures the viscoelastic properties of soft materials following easy and quick steps guided by the Soft Matter Analytics™ App. Prior to testing, the sample to be measured needs to be inserted into the available sample holders specifically designed for the ElastoSens™ Bio. This step plays a key role in ensuring the quality of the data obtained from the instrument.
The μ-volume sample holder was developed for applications in which sample volume is limited, such as for natural polymers, blood and plasma, cellularized hydrogels, among others. This device is completely autoclavable and designed to fit in a 12-well plate for easy sample storage. This feature together with the non destructive nature of the technology allows the same sample to be tested multiple times, enabling the tracking of its mechanical behavior over time in controlled environments.
In this technical note, two methodologies for introducing a sample into the µ-volume sample holder will be described in detail to obtain optimal results. These protocols may be preferred depending on the type of sample studied.
Methodologies for sample introduction into the µ-volume sample holder of the ElastoSens™ Bio
Methodology 1: Pouring the liquid sample from the top of the µ-volume sample holder.
This methodology is preferred for samples that are not too viscous at the liquid state and therefore they can flow easily within the cavity of the µ-volume sample holder. The pieces used in this methodology are illustrated as follows:
Figure 1: List of pieces used when pouring the liquid sample from the top of the µ-volume sample holder.
Step 1: Assembly of the loading system.
The pieces A to E need to be assembled in the following order (Figure 1) to obtain the loading system of Figure 2.
Figure 2: Assembled loading system (right).
Note: The loading system can be pre-incubated at the same temperature as the sample to be poured, ensuring homogeneous solidification specially for thermosensitive samples.
Step 2: Pouring of the liquid sample into the loading system.
The sample can be slowly poured into the loading system using a pipette (the volume required is 250 µL). It is important to make sure that the sample penetrates the cavity well and covers the entire inner space of the µ-volume sample holder (Figure 3).
Note: The sample holder can be carefully rotated in a circular manner while pipetting to fill the inner cavity first and then the center to prevent sample displayed at the bottom of Figure 3.
Figure 3: Pouring of the liquid sample into the µ-volume sample holder (left), close image featuring the cavity in which the liquid sample needs to penetrate (center), and examples of samples that were well introduced, and not well introduced (right).
Step 3: Timing for the solidification of the sample.
The loading system with the sample must be placed at the required environmental conditions to allow the sample to solidify. The sample should achieve a solid state (able to support itself over the spring) before advancing to the next step.
Note 1: It is important to place the loading system with the sample on a flat surface to ensure even solidification of the sample.
Note 2: Samples with high water content are highly prone to drying over time. To prevent sample drying, options include controlling the environmental humidity or adding mineral oil or other media onto the sample during this step, if needed.
Step 4: Disassembly of the loading system and recuperation of the µ-volume sample holder.
When the sample is ready, unscrew the piece E from the piece A (Figure 1) then carefully remove the plastic spring base (piece D) as illustrated in Figure 4A. The bottom cap of the µ-volume sample holder (piece F) can then be clipped to obtain the µ-volume sample holder with the sample (Figure 4B-C).
Figure 4: Disassembly of the loading system (A), removal of the plastic spring base (B) and recuperation of the µ-volume sample holder (C).
Note 1: A side of the spring can be held with tweezers while removing the plastic spring base (Figure 4A).
Note 2: The µ-volume sample holder with samples containing a high percentage of water should always be stored in a liquid medium when not being tested to avoid sample drying.
Step 5: Testing in the ElastoSens™ Bio.
The µ-volume sample holder with the sample only needs to be clipped to the adaptor (piece G) for testing in the ElastoSens™ Bio (Figure 5).
Figure 5: Connection with the adaptor of the ElastoSens™ Bio (left), and installation in the ElastoSens™ Bio’s mechanical unit for testing (right).
Note 1: The liquid added to the sample for storage should be removed prior to testing. If the µ-volume sample holder with the sample was immersed in liquid, it is recommended to remove the excess of liquid from the metallic pieces with an absorbent paper and remove the layer of liquid that settles over the sample with a pipette.
Note 2: It is recommended to run short tests for samples containing a high percentage of water to avoid sample drying.
Methodology 2: Introducing the liquid or solid sample from the bottom of the µ-volume sample holder.
This methodology is preferred for samples that are too viscous at the liquid state and do not flow easily within the cavity of the µ-volume sample holder, or for samples that are already solid and can be prepared at the required dimensions (thickness/height of 1.6 mm and diameter of 14 mm). The pieces used in this methodology are illustrated as follows:
Figure 6: List of pieces used when pouring the liquid sample from the bottom of the µ-volume sample holder.
Step 1: Assembly of the alternative loading system.
For this methodology, the top cap of the µ-volume sample holder (piece B) can be mounted with the cover piece (piece H) as illustrated in Figure 7.
Figure 7: Alternative loading system.
Note 1: The loading system can be pre-incubated at the same temperature as the sample to be poured, ensuring homogeneous solidification specially for thermosensitive samples.
Note 2: The addition of oil around the area where the cover piece makes contact with the sample holder can better seal the system, if needed.
Step 2: Introduction of the viscous liquid or solid sample into the loading system.
The liquid sample can be slowly poured into the loading system using a pipette (the volume required is 250 µL). It is important to make sure that the sample covers homogeneously the inner space of the µ-volume sample holder (Figure 8). Alternatively, gently place the solid sample into the cavity of the µ-volume sample holder. The spring can be added when the sample is evenly spread (allow a few seconds for liquid samples) followed by the plastic spring base.
Figure 8: Pouring of the viscous liquid sample into the µ-volume sample holder.
Step 3: Timing for the solidification of the sample.
The loading system with the sample must be placed at the required environmental conditions to allow the sample to solidify. The sample should achieve a solid state (able to support itself over the spring) before advancing to the next step.
Note 1: It is important to place the loading system with the sample on a flat surface to ensure even solidification of the sample.
Step 4: Disassembly of the loading system and recuperation of the µ-volume sample holder.
Step 5: Testing in the ElastoSens™ Bio.
The µ-volume sample holder with the sample only needs to be clipped to the adaptor (piece G) for testing in the ElastoSens™ Bio (similar to Figure 5 of previous section).
Note 1: The liquid added to the sample for storage should be removed prior to testing. If the µ-volume sample holder with the sample was immersed in liquid, it is recommended to remove the excess of liquid from the metallic pieces with an absorbent paper and remove the layer of liquid that settles over the sample with a pipette.
Note 2: It is recommended to run short tests for samples containing a high percentage of water to avoid sample drying.
Shear storage modulus (G’) of gelatin 7 % following the methodologies 1 and 2
Gelatin type B from bovine skin (Sigma-Aldrich, USA) was prepared at 7 % (%w/v) using distilled water and poured into the µ-volume sample holder following the methodologies 1 and 2. The loading systems were pre-incubated at 40 °C before sample loading (same temperature as the liquid gelatin). The loading systems with the sample were placed in the fridge at 4 °C for 30 min. They were then disassembled and the µ-volume sample holder mounting completed.
Samples were immediately tested at room temperature (23 °C) for 3 min at a temporal step of 10 s. Six samples were prepared according to each methodology (n=6). Average results are expressed as mean ± standard deviation. Statistical analysis was performed using GraphPad Prism (GraphPad Prism Software, USA) using unpaired t test with Welch’s correction. Significance was retained when p < 0.05.
Figure 9 displays the average shear storage modulus of the gelatin 7 % obtained following each methodology. No statistical difference was found between them (11 784 ± 1 128 Pa and 10 904 ± 1 471 Pa for methodology 1 and 2, respectively) confirming that the different methods of sample loading do not affect the measurements and results.
Key takeaways
- This technical note presents two methods for sample introduction into the µ-volume sample holder together with a number of insights and recommendations to ensure their successful implementation.
- Due to the variability of materials that can be tested in the instrument, it is always recommended to practice these methodologies, verify and validate whether the samples formed inside the µ-volume sample holder respect the required geometry, and adjust these guidelines further according to their particularities.
- Users should ensure proper sample loading before starting running tests in the ElastoSens™ Bio.
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