ForteBio Interactions Newsletter Biosensor photo

July 2008    VOLUME 1    ISSUE 2

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Technical Tip: Preserving Biosensors for Long-Term Storage

Typically, biosensors are used immediately after immobilizing the protein of interest onto the biosensor surface. However, there may be times when you want to store prepared biosensors for more than 24 hours before use. Doing so can be particularly convenient if you are using the batch-immobilization technique to prepare large numbers of biosensors at one time.

This Technical Tip outlines a preservation and storage procedure that produces stable biosensors for most proteins. A biosensor storage stability validation protocol is also provided.

Biosensor Preservation

  1. Prepare a preservation solution of 15% sucrose in PBS (w/v). A volume of 20 mL is sufficient to aliquot 200 µL per well for 96 wells. Pipette 200 µL of the solution into the appropriate wells of a 96 well plate.
  2. After completing the batch immobilization protocol, remove the biosensors from the wash solution and incubate in the sucrose solution for 1–2 minutes.
  3. Remove the biosensors from the sucrose and allow to dry. This can be done at room temperature for 5 minutes or in an incubator at 37°C for 1–2 minutes.
  4. Store preserved biosensors in the original foil pouch with desiccant at room temperature.

Assaying Stability During Storage

Stability can be determined by testing preserved biosensors against a control sample at different storage times. Correctly stabilized biosensors will not show significant deterioration in binding over time.

Assay Setup

  1. Use biosensors immediately after preservation to create a standard curve using the optimized assay protocol (this will be time point 0 days in the stability assay). Include additional replicates of a control sample at the mid-range of the assay.
  2. At desired time points after preservation (for example 1 day, 2 days, 5 days, 14 days) use the same assay protocol to run replicate data at the mid-point control concentration.

Results and Data Analysis

(Note: the instructions below are for the Octet RED system. If using the Octet QK system, see Technical Note 9, Developing a Protein-Specific Quantitation Assay Using Streptavidin Biosensors for data analysis instructions.)

  1. Load the files from the 0 day time point and analyze the standard curve from the experiment.
  2. Use the standard curve generated on Day 0 to analyze subsequent days.
  3. Compare performance over the time of storage. Correctly stabilized biosensors should show minimal loss in activity over the time they will be stored.

Time Point Tested

Average
Calculated mg/mL

%CV(n=4)

0 Days

78.75

2%

1 day

77.32

4%

2 Days

80.55

2%

5 Days

77.87

2%

14 Days

77.88

2%

Table 3: Example data showing the average calculated concentrations from a mid-point control sample. Data is shown for 5 time points ranging over 2 weeks. Replicates (n=4) were assayed at each time point. The data shows no detectable deterioration of performance and validates the stability of the preserved protein coated biosensors.

Octet RED and Octet QK Systems

Table 3 shows the average calculated concentrations from a mid-point control sample. Data is shown for 5 time points ranging over 2 weeks. Replicates (n=4) were assayed at each time point. The data shows no detectable deterioration of performance and validates the stability of the preserved protein-coated biosensors.

Detailed information on assaying stability during storage, as well as several useful assay development procedures for Streptavidin Biosensors can be found in Technical Note 9: Developing a Protein-Specific Quantitation Assay Using Streptavidin Biosensors, available for download from www.fortebio.com.

For even more Biosensor selection information visit our biosensor types page.

Biosensor Quick Reference Guide

Fortebio offers the following biosensor surface chemistries for immobilization of proteins and subsequent analysis the Octet RED and Octet QK Systems.

Biosensor

Grades

Application

Anti-human lgG Fc

Quantitation

Human lgG quantitation, Fc specific.

Anti-murine lgG

Quantitation

Mouse or rat lgG quantitation.

Protein A

Quantitation

Immunoglobulin quantitation.

Streptavidin Standard Binding

Screening &
Kinetics

Standard Strepavidin surface for biotinylated molecule analysis.

Streptavidin High Binding

Screening &
Kinetics

High Density Strepavidin surface for biotinylated molecule analysis.

Aminopropylsilane

Kinetics

General Absorption of protein to the biosensor surface.

Amine Reactive

Screening &
Kinetics

Custom ligand immobilization for analizing any protein with a primary amine group.

Super Streptavidin

Kinetics

Kinetic analysis of small peptide and/or small molecule interactions.

Kinetics Assay Biosensor Selection Guide

Factor

SBC
(Kinetics Grade)

SBC FA
(Screening Grade)

HBC
(Kinetics Grade)

HBC FA
(Screening Grade)

Super SA
(Kinetics Grade)

Amine Reactive

APS

Binding capacity

Good

Good

Excellent Excellent Excellent Good Very Good

S/N for small molecules (300-900 Daltons) on Octet RED

Not Advised

Not Advised

Not Advised Not Advised Excellent Not Advised Good

S/N for peptides (500-2000 Daltons) on Octet RED

Not Advised

Not Advised

Good Good Excellent Good Good

S/N for small proteins (5-20kD)

Good

Good

Excellent Excellent Excellent Good Good

S/N for mid sized proteins (20-150kD)

Very Good

Very Good

Excellent Excellent Excellent Very Good Excellent

S/N for large proteins (>150kD)

Excellent

Excellent

Excellent Excellent Excellent Very Good Excellent

Short kinetics assays (off rate <15min

Excellent

Excellent

Excellent Excellent Excellent Very Good Very Good

Long kinetics assays (off rate >15min)

Excellent

Good

Excellent Good Excellent Very Good Very Good

Applications at high detergent concentrations (>1%)

Good Good Excellent Excellent Excellent Good Excellent

Immobilization of non-biotinylated proteins

Not Advised Not Advised Not Advised Not Advised Not Advised Excellent Very Good

Custom quantitation

Good Very Good Excellent Excellent Very Good Not Advised Not Advised

Epitope mapping/binning

Very Good Very Good Excellent Excellent Excellent Very Good Good

Regeneration capable

Not Advised Not Advised Very Good Very Good Very Good Excellent Good
Not Advised

 = Not Advised    

Good

 = Good    

Very Good

 = Very Good    

Excellent

 = Exellent

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