In This Issue:
- Still Time to Register for the Aptamer Applications Webinar June 21st
- Meet with Base Pair scientists at DDTWC in Boston, MA July 10th – 13th
- Aptamers in Diagnostics: Lateral Flow Assays and Biosensors
- Murine IL-6 Biosensor Using Base Pair Aptamer ATW0077
It’s not too late! Register for the upcoming Aptamer Applications Webinar, June 21st, 11am EST
Aptamers are being used in place of antibodies in a growing number of applications. This webinar will give a brief overview of aptamers and discuss advancements in aptamer selection, key differences between aptamers and antibodies, aptamer advantages, and the successful use of aptamers in research, diagnostic, and therapeutic applications. View / play recording of Aptamer Applications Webinar
Meet with Base Pair scientists at DDTWC in Boston, MA, July 10th – 13th
Schedule a meeting with a Base Pair Scientist at the Drug Discovery & Therapy World Congress from July 10th to 13th in Boston, Massachusetts, USA.
Aptamers in Diagnostics: Lateral Flow Assays and Biosensors
Challenges in Diagnostics
Antibody-based diagnostics are everywhere. While monoclonal antibodies work exceptionally well for many diagnostic applications, there are some exceptions. Developing antibodies to toxic compounds, non-immunogenic compounds, and small molecules is a challenge. Distinguishing between very similar compounds is a challenge as well. Antibodies lack stability at high temperatures, making the development of field-based assays difficult. Maintaining lot-to-lot consistency in antibody production is also an ongoing concern.
Lateral Flow Assays
According to the World Health Organization, mosquito-borne diseases infect hundreds of millions of people and cause several million deaths each year. (2) In 2015, more than 10 million people were diagnosed with tuberculosis, a treatable airborne disease. Diagnostic tests that can be conducted in field locations and specific tests for drug resistant tuberculosis are lacking. (7) The simplicity and speed of lateral flow assays (LFAs) make them ideal for field-based tests.
Incorporation of temperature-stable aptamers into simple, inexpensive LFA tests enables testing in developing countries and remote, tropical regions that lack access to central testing laboratories and refrigerated storage. Unlike antibodies, aptamers can be developed under non-biological conditions for enhanced binding in urine and saliva, preferred sample types for field-based testing. (1) Aptamers can also be selected for fast on-rates, making them more suitable for LFA. Base Pair is currently working with the University of Central Florida to develop aptamers for Zika, Chikungunya, and Dengue viruses using mosquito saliva.
Biosensors
A sensor is a molecule or device that exhibits a change in a detectable signal upon interaction with a specific analyte. There are many types of sensors. Common sensors include optical sensors generating a colorimetric or fluorescent signal, electrochemical sensors detecting changes in current and plasmon resonance sensors measuring small changes in photon scattering. (3,6) Because aptamers can be selected against small and toxic compounds in a wide range of matrices, can be conjugated to a wide range of surfaces without loss of selectivity or affinity, and can be regenerated or refolded, they are ideal for use in biosensors. (6)
Researchers at the University of Jinan, China utilized selective DNA aptamers for simultaneous detection of MCF-7, HL-60, and K562 tumor cells in a fluorescent sensor based on mesoporous silica nanoparticles (MSNs) and quantum dots (QDs). (5) An electrochemical sensor utilizing an anti-IL-6 aptamer from Base Pair to detect changes in current upon IL-6 binding is described in the article below. While these sensors utilized aptamers solely for selective binding, structure-switching aptamers can be designed to generate a fluorescent signal upon binding, eliminating the need for a secondary signaling mechanism. Base Pair has developed several structure-switching aptamers for use in biosensors. Because aptamers are chemically synthesized, they offer a much greater degree of process control and enhanced lot-to-lot reproducibility.
Aptamer-Based Solutions
While antibody-based tests are currently the standard, aptamer-based diagnostic tests offer fast, simple, stable alternatives for detection of difficult targets in infectious disease, oncology, and a wide range of clinical areas. Base Pair has developed selective aptamers to opioids and opioid metabolites, pathogenic bacteria, viruses, toxins, small molecules, and many other targets for which antibody development is a challenge. The development of fast, simple, stable diagnostic tests will aid clinicians in treating and tracking disease worldwide.
For additional information on aptamer discovery and development, aptamers for LFA, and structure-switching aptamers for sensor development, please contact Base Pair.
Product Highlights:
Murine IL-6 Biosensor Using Base Pair Aptamer ATW0077
Biosensors are increasingly being used for rapid, sensitive detection of a wide range of protein biomarkers. 
While antibodies have traditionally been used in biosensor development, their large size (~10-fold larger than aptamers) can affect the distance between the binding event and the sensor surface, limiting sensitivity. For this biosensor, IL-6 aptamers were conjugated to PASE (1-Pyrenebutanoic Acid Succinimidyl Ester), then adsorbed on to single wall carbon nanotubes. When tested with 1 x PBS / 1mM MgCl2 buffer and recombinant murine IL-6, binding at concentrations as low as 1 pg/mL caused a decrease in conductance. (4)
For evaluation of IL-6 detection in serum, serum samples were diluted 1:4 in 1 x PBS with 1mM MgCl2 spiked with varying concentrations of recombinant murine IL-6. A 10 pg/mL IL-6 concentration was detected in under 2 minutes and exhibited an 8-13% drop in current. A 1,000 pg/mL concentration was detected in just under 5 minutes. (see graph below). (4)
Biosensors enable rapid detection of analytes in complex samples in diagnostic applications where quick treatment is critical. Small aptamer size and the ability to conjugate aptamers without loss of selectivity or affinity make them ideal affinity reagents for biosensor production.
Please visit the Murine IL-6 aptamer product page for more detailed product information, including dissociation constant. View Aptamer ATW0077 to Murine IL-6.
Please contact us for information about aptamer discovery & development and aptamer-based assay and sensor development.
References:
1. Chen, A. et al. Replacing antibodies with aptamers in lateral flow immunoassay. Biosensors and Bioelectronics. Sept 2015. 71:230-42.
2. Executive summary, Insect-borne diseases. World Health Organization. http://www.who.int/whr/1996/media_centre/executive_summary1/en/index9.html. Accessed June 14, 2017.
3. Fu, C., et al. Aptamer-based surface-enhanced Raman scattering-microfluidic sensor for sensitive and selective polychlorinated biphenyls detection. Anal. Chem. 2015. 87 (19):9555–9558. doi: 10.1021/acs.analchem.5b02508
4. Khosrave, F., et al. (2017). Ultrasensitive label-free sensing of IL-6 based on PASE functionalized carbon nanotube micro-arrays with RNA-aptamers as molecular recognition elements. Biosensors. 7(17), DOI:10.3390/bios7020017
5. Liang, L. et al. (June 2016). Aptamer-based fluorescent and visual biosensor for multiplexed monitoring of cancer cells in microfluidic paper-based analytical devices. Sensors and Actuators B: Chemical. 229:347-354. Doi.org/10.1016/j.snb.2016.01.137.
6. Song, S. et al. Aptamer-based biosensors. Trends in Analytical Chemistry. 2008. 27(2):108-117. doi:10.1016/j.trac.2007.12.004.
7. Tuberculosis Fact Sheet. World Health Organization. http://www.who.int/mediacentre/factsheets/fs104/en/. Accessed June 13, 2017.