22nd June 2018

Introduction:

Changes in hormone levels can be key indicators to a variety of issues, examples include testosterone levels in general health and well being(1) and diagnosing Cushing’s disease involving the steroid cortisol (2). While these small molecules and others are well documented and their role in health and disease is becoming better understood, researchers are still limited in simpler non-invasive methods that can be used to monitor their presence.

Measuring levels of a specific hormone is a challenge because they are usually only present in very low concentrations (typically in the pico- to nanomolar range). Common lab-based methods to measure these levels include gas chromatography mass spectrometry (GCMS) and HPLC. Increasing detection limits and offering alternatives to these existing methods are two exciting challenges which aptamers can address.

Solution:

Aptamers are incredibly versatile, highly specific reagents which can be applied to a multitude of conditions. Having previously demonstrated our aptamers ability to bind in vastly different and complex matrices, we tasked ourselves with adapting a commercially available biosensor to monitor expression of Cortisol in sweat. We selected a biosensor application because they have been found to be less expensive and faster than chromatographic approaches. (3)

Hormone aptamer

Fig.1 Aptamer biosensor assay targeted towards Cortisol concentration. Aptamer binding to cortisol in red, similar hormone in blue and sweat in purple.

The mechanism of action for this particular biosensor assay is comprised of a disassociation reaction of the aptamer from a sensor plate upon binding to the target. The resulting action leads to a rapid signal change.  Figure 1 shows that cortisol affinity is higher than the controls almost instantly and peaks at over 0.22nm.  The controls in comparison fail to exceed 0.15nm.

This simple exercise shows that with the use of aptamers, we can significantly enhance the binding capabilities of readily available commercial products with low cost reagents for a rapid response time.

If you want to find out more about working with aptamers, or using them to develop diagnostics, please contact us using the form below.

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  1. Bassil N, Alkaade S, Morley JE (Jun 2009). “The benefits and risks of testosterone replacement therapy: a review”. Therapeutics and Clinical Risk Management. 5 (3): 427–48. PMC 2701485 . PMID 19707253
  2. Isidori AM, Kaltsas GA, Mohammed S, et al. (November 2003). “Discriminatory value of the low-dose dexamethasone suppression test in establishing the diagnosis and differential diagnosis of Cushing’s syndrome” Clin. Endocrinol. Metab88(11): 5299–306. doi:10.1210/jc.2003-030510PMID 14602765.
  3. Advantages and limitations of on-line solid phase extraction coupled to liquid chromatography-mass spectrometry technologies versus biosensors for monitoring of emerging contaminants in water. Sara Rodriguez-Mozaz, Maria J. Lopez de Alda, Damià Barceló, J Chromatogr A. 2007 Jun 8; 1152(1-2): 97–115. Published online 2007 Jan 18. doi: 10.1016/j.chroma.2007.01.046