# Homogeneous Nuclease-Assisted SELEX for Rapid Isolation of Cross-Reactive, Functionalized Aptamers for Synthetic Cannabinoids

> **NIH NIH R21** · FLORIDA INTERNATIONAL UNIVERSITY · 2020 · $59,910

## Abstract

Synthetic cannabinoids (SCBs) are a class of designer drugs comprising more than 500 distinct compounds in
thirteen different structurally diverse families, and are widely abused as an alternative to cannabis. The effects
of consuming SCBs include adverse psychological and physiological effects and even death. SCB overdose is
currently diagnosed in emergency room (ER) settings from indirect evidence, including self-reporting or the
presence of both a cannabimimetic toxidrome and a negative drug screen. Therefore, there is a need for
accurate screening methods for SCBs/metabolites in serum that can be employed in the ER, to diagnose and
distinguish SCB overdoses from other psychiatric or neurological diseases for establishing appropriate
treatment protocols and disposition measures. Immunoassays have been developed for certain SCBs. These
assays rely on specific binding between drugs/metabolites and antibodies, offering high specificity and
sensitivity. However, minor modifications are often introduced to the SCB core structure to evade regulation.
These modifications can greatly impair binding by existing antibodies, resulting in false-negative results. With
hundreds of SCBs on the market and new compounds continuously emerging, it is therefore urgent to develop
new cross-reactive bioaffinity elements that can recognize structurally similar SCBs. To address this problem,
an original homogeneous nuclease-assisted (NA)-SELEX in conjunction with a parallel-and-serial selection
strategy is proposed to isolate a high-affinity DNA aptamer that cross reacts to all SCBs and their metabolites
from the indazole-3-carboxamide family. NA-SELEX utilizes a structured DNA library and a high-fidelity
restriction enzyme to efficiently separate target-bound aptamers from the remainder of the library. Specifically,
target binding causes aptamers to undergo a conformational change that renders them inaccessible to
enzymatic digestion, whereas unbound oligonucleotides are viable enzyme substrates and are rapidly digested
and eliminated from the next round of selection. Counter-SELEX will be performed to ensure that the isolated
aptamer does not bind to interferent molecules including phytocannabinoids, structurally-similar endogenous
substances, prescription drugs, illicit drugs as well as structurally-dissimilar drugs associated with ER visits.
This process is expected to yield the first cross-reactive aptamer capable of recognizing numerous SCBs and
metabolites based on their shared core structure, such that peripheral chemical modifications should not
meaningfully affect the aptamer's binding affinity. An electrochemical aptamer-based sensor based on this
cross-reactive aptamer will then be fabricated to sense the total serum concentration of all parent SCBs and
their metabolites, achieving a clinically relevant detection limit and long detection window. The resulting sensor
can be used in the ER to aid in the diagnosis of SCB overdose, greatly improving public he...

## Key facts

- **NIH application ID:** 9893841
- **Project number:** 5R21DA045334-02
- **Recipient organization:** FLORIDA INTERNATIONAL UNIVERSITY
- **Principal Investigator:** Yi Xiao
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $59,910
- **Award type:** 5
- **Project period:** 2019-03-15 → 2021-02-12

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9893841

## Citation

> US National Institutes of Health, RePORTER application 9893841, Homogeneous Nuclease-Assisted SELEX for Rapid Isolation of Cross-Reactive, Functionalized Aptamers for Synthetic Cannabinoids (5R21DA045334-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9893841. Licensed CC0.

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