Opioids are a group of strong analgesics used for treatment of moderate to severe pain in clinical patient care. Unfortunately, opioids are also highly addictive and if not properly administered and monitored, can lead to overdose and death. In recent decades, the use of opioids has grown exponentially, resulting in an increasing number of overdose incidents and other adverse effects. A fast and simple means to monitor blood levels of opioids would enable personalized dosing and rapid diagnosis of overdose. However, there are currently no tools to determine opioid concentrations in blood quickly and accurately at the patient's bedside. The aim of this work was to develop carbon nanomaterial-based electrochemical sensors for detection of opioids in biological matrices. Two different materials, tetrahedral amorphous carbon (ta-C) and single-walled carbon nanotube (SWCNT) networks were used for fabrication of the electrodes. An additional layer of an ion-exchange polymer, Nafion, was used as a protective membrane on top of the electrodes to reduce interference from the matrix. Carbon-based electrochemical sensors have great potential for detection of opioids in complex samples since they offer high sensitivity, fast response time, and can be miniaturized into disposable test strips. In this study the carbon-based electrodes were able to successfully detect opioids in buffer solution. Moreover, the addition of Nafion enabled detection of low levels of morphine, codeine, tramadol, and O-desmethyltramadol in diluted human plasma. The Nafion membrane was also seen to considerably alter the oxidation behavior of the analytes, resulting in increased selectivity and sensitivity. Importantly, it was observed that the opioids exhibited different electrochemical behavior on different carbon materials. While the SWCNTs showed well-defined peaks for tramadol and O-desmethyltramadol, their simultaneous detection was only possible on the Nafion/ta-C electrode due to its exceptionally wide water window. These results highlight the importance of selecting the appropriate carbon material for each specific application. Finally, SWCNT networks were fabricated into disposable Nafion-coated test strips and small concentrations of morphine in nanomolar range were measured in untreated capillary whole blood. Based on the results it was suggested that the sensor strip only measures the unbound fraction of the drug molecule in blood. However, some further experiments are needed to confirm this observation. In conclusion, the carbon nanomaterials studied in this work were found to hold great promise for simple and fast detection of opioids in biological matrices. In the future, such a tool would enable individualized pain treatment and promote accurate and safe dosing of opioids in clinical patient care.
|Translated title of the contribution||Hiilipohjaiset hybridinanomateriaalit opioidien sähkökemialliseen havaitsemiseen|
|Publication status||Published - 2021|
|MoE publication type||G5 Doctoral dissertation (article)|
- carbon nanomaterials
- electrochemical sensors
- biological matrices