Ultrasensitive covalently-linked Aptasensor for cocaine detection based on electrolytes-induced repulsion/attraction of colloids

Sanli, Serdar; Moulahoum, Hichem; Ghorbanizamani, Faezeh; Çelik, Emine Güler; Tımur, Suna

doi:10.1007/s10544-020-00507-2

Cited by 13 publications

(15 citation statements)

References 31 publications

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“…We find that the detection of meth in saliva is always less than that in buffer, namely, 63.6%, 67.3%, and 66.9% suppressed for the spiked concentrations of 50, 100, and 200 nM meth, respectively. This signal suppression is likely due to salivary proteins sequestering meth or interfering with the colorimetric response of the AuNP–aptamer system (e.g., blocking meth binding or AuNP aggregation) or perhaps both, and this kind of suppression has previously been reported in artificial saliva medium (with bovine serum albumin protein) for cocaine detection . We note that the saliva collection method needed to be highly standardized for obtaining a reliable assay response.…”

Section: Resultsmentioning

confidence: 87%

“…This signal suppression is likely due to salivary proteins sequestering meth or interfering with the colorimetric response of the AuNP−aptamer system (e.g., blocking meth binding or AuNP aggregation) or perhaps both, and this kind of suppression has previously been reported in artificial saliva medium (with bovine serum albumin protein) for cocaine detection. 41 We note that the saliva collection method needed to be highly standardized for obtaining a reliable assay response. When we tried collecting saliva in any other way (such as spitting or stimulated saliva collection) or under any other circumstance such as collecting saliva right after eating or drinking resulted in high variability and mostly failure to obtain an assay response.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Accounting for Interaction Kinetics between Gold Nanoparticles and Aptamers Enables High-Performance Colorimetric Sensors

Sen

Sester

Poulsen

et al. 2022

ACS Appl. Mater. Interfaces

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DNA aptamers have emerged as promising probes for challenging analytes that cannot be easily detected by conventional probes, including small-molecule targets. Among the different signal transduction approaches, gold nanoparticle (AuNP) aggregation assays have been widely used to generate a colorimetric response from aptamer–target interactions. This sensor design relies on the competition between the aptamer adsorbing to the AuNP surface versus interacting with the target, whereby target binding reduces the number of adsorbed aptamers that destabilizes AuNPs toward salt-induced aggregation, thereby inducing a color change. However, this thermodynamic framework overlooks the potential influence of interaction kinetics of different aptamer conformations with AuNP surfaces and with targets in solution or near surfaces. Here, we show that aptamers become more strongly adsorbed on AuNPs over time, and these trapped aptamers are less responsive toward the target analyte. By varying the sequence of addition in sensing assays, we demonstrate that these interaction kinetics have a significant effect on the sensor response and thereby produce an effective sensor for methamphetamine (meth) at biologically relevant levels in oral fluids. Along with underpinning new tools for assay development, this new knowledge also highlights the need for aptamer selection strategies that evolve aptamer sequences based on the functionality that they need to exhibit in an actual sensor.

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Section: Resultsmentioning

confidence: 87%

Section: ■ Results and Discussionmentioning

confidence: 99%

Accounting for Interaction Kinetics between Gold Nanoparticles and Aptamers Enables High-Performance Colorimetric Sensors

Sen

Sester

Poulsen

et al. 2022

ACS Appl. Mater. Interfaces

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show abstract

“…Thus, to many methods have been utilized to determine amount of cocaine, such as radioimmunoassay, enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC), and gas chromatography-mass spectrometry (GC-MS) ( Abnous et al, 2018 ). In spite of their accuracy and reliability, some disadvantages like being time-consuming, requiring complicated and expensive instruments, and dependency on skilled operators have reduced the use of these methods ( Sanli et al, 2020 ). The other method like colour tests apart from some advantages such as cost effective, simplicity, detect are limited by some drawbacks like short expiration dates and lack of proper interpretation due to discolouration during time ( Eliaerts et al, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

An ultrasensitive detection platform for cocaine: Aptasensing strategy in capillary tube

et al. 2022

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Cocaine as a detrimental addictive drug threats human health through inducing heart problem, blood pressure, anxiety, immunodeficiency, paranoia, and organ damage. Thus, the quantification of cocaine in the biological samples by a simple, high specificity, and fast method is highly urgent to decrease the harmful effect of the misuse of this drug. In this study, we constructed a novel fluorescent aptasensor by combining the fluorescein (FAM)-modified specific aptamer and AuNPs in a capillary tube as the sensing substrate for the first time. The presence of cocaine recovered the fluorescence response of the aptasensor through interaction with the aptamer and differentiation of the aptamer@AuNPs complex. By fluorescence microscopy imaging of the aptasensor substrate and its quantitative analysis, a remarkable linear range from 100 pM to 600 µM and the ultra-low limit of detection (LOD) as 0.31 pM were achieved for the target detection. Cocaine was successfully quantified in the real samples (human serum and urine) by using the aptasensor. The aptasensor is simple, easy-to-use, favorable applicability, and cost-effective; and to the best of our knowledge, it is the first use of the capillary tube as a sensing platform just by using about 3 μl of the samples. It is also an easy-to-carry tool, promising for the on-site target detection. Besides, it can be a portable device for monitoring cocaine by using a handheld single-beam fluorescence microscope. It can be an appropriate detection tool in forensic science and medicine.

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“…specific interference from certain electrolytes in saliva may be the reason which compromised the sensor capability and gave false positives. 204,121 Also, bare AuNPs in artificial saliva medium did not aggregate and remained stable suggesting the ionic strength of saliva or artificial saliva which is approximately 43 mM (final concentration in sample ~ 4 mM)…”

Section: B)mentioning

confidence: 98%

“…More recently, cocaine has been detected with a detection limit of 0.97 nM using simple unmodified AuNPs based colorimetric aptasensors strategy by Sanli et al 121 The sensor response was also validated in synthetic saliva using bovine serum albumin to mimic the biological aspect of actual oral fluid and it was found that the response of the sensor in synthetic saliva was suppressed by 64.5%. The study did not report detection in real samples which would have helped in the evaluation of the performance of the aptasensors in saliva.…”

Section: Colorimetric Aptasensors For Drugs Of Abuse Detectionmentioning

confidence: 99%

Colorimetric Aptasensors for the Detection of Methamphetamine in Saliva

Sen¹

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There has been a long-standing need and an increasing demand for a low cost, sensitive, selective, simple, and portable detector (semi quantitative/quantitative) for improved screening of drugs of abuse. Methamphetamine (meth) was chosen as the primary drug to detect due to its obvious prevalence as the most abused substance in New Zealand. Impairment caused by meth use while driving and at workplaces are a cause of serious concern which needs immediate attention of scientists so that rapid and reliable on-site applicable quantitative tests can be developed to address the growing concern. Currently, urine drug tests are most common, however these tests suffer from concerns relating to privacy invasion, or chances of adulteration when privacy is granted to the suspect. In order to overcome these issues, saliva is emerging as an alternative and promising matrix for meth detection. In this context, this project aims to develop a non-invasive assay that produces a colourimetric response in the presence of meth in human saliva. The assay features coloured gold nanoparticles (AuNPs) coated with synthetic DNA aptamers acting as the receptor for methamphetamine. Aptamers are seen as promising for biosensing applications owing to the ease of synthetically evolving nucleotide sequences to specifically bind a range of targets, along with their high stability and ease of synthesis. This colorimetric aptasensor assay not only allows the visual determination of analyte in the sample by naked eye, but simultaneously a quantitative interpretation is possible by UV/Vis spectroscopy. Using an aptamer selected to bind to meth, we first optimized the AuNPs based colorimetric assay in buffer. In this assay, colourimetric signals are generated when target binding induces aptamer dissociation from AuNP surfaces, causing them to aggregate and change colour. Whereas this assay assumes an equilibrium competition between aptamers binding to AuNPs versus the target, we discovered a pronounced time dependence in the aptamer-AuNP interactions. Over time, the aptamers became more strongly bound to the AuNPs and less available to interact with the target. This knowledge led us to demonstrate an assay with a modified sequence of steps to mitigate this problem, enabling successful detection of meth in buffer below the legal cut-off level for saliva 25 ng/mL (~ 167 nM). Our new knowledge of aptamer-AuNP interactions also suggested that traditional aptamer selection strategies are not ideal for subsequent application in colourimetric sensors. Therefore,we obtained a new meth binding aptamer that was selected via a novel method based on its association/dissociation with AuNPs in the presence of target. Indeed, we found that colourimetric sensors using the aptamer selected in this way did not suffer from the problems identified above and ultimately exhibited better sensing performance. Following this, a demonstration of meth detection in saliva was also achieved at levels of detection approaching the legal cut-off level. As well as comparing the response in saliva versus buffer and different testing protocols, successful blind tests were also conducted with unknown saliva samples. Extensive new knowledge about the nature of interactions between AuNPs and the salivary matrix was gained to underpin these sensing demonstrations, and this knowledge also highlights further challenges to overcome before these sensors can be applied outside of the lab. To facilitate the translation of the assay into an on-site applicable system, it is necessary to look for simple detection systems that are suitable for roadside or workplace applications and reliable and sensitive enough to replace the standard UV-Vis spectrophotometer for quantifying the assay. This motivated the prototype concept of a cost-effective, sensitive, and reliable single channel absorption based light meter device integrated with a sample holder and LED. The promising detection levels achieved (~ 63 nM or 9.4 ng/mL) with the device costing less than $100 showed immense scope for the future development of a simple on-site applicable quantitative drug detection device. The knowledge created in this work provide a clear picture about the challenges and opportunities in the detection of drugs and other small molecules. Provided that aptamers are selected with consideration for the downstream sensing mechanism, sensitive, robust, and simple sensing assays are close to reality for real samples such as saliva.

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Ultrasensitive covalently-linked Aptasensor for cocaine detection based on electrolytes-induced repulsion/attraction of colloids

Cited by 13 publications

References 31 publications

Accounting for Interaction Kinetics between Gold Nanoparticles and Aptamers Enables High-Performance Colorimetric Sensors

Accounting for Interaction Kinetics between Gold Nanoparticles and Aptamers Enables High-Performance Colorimetric Sensors

An ultrasensitive detection platform for cocaine: Aptasensing strategy in capillary tube

Colorimetric Aptasensors for the Detection of Methamphetamine in Saliva

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