Research
Current projects of our lab:
(1) Study the role of miRNA in neural cell-derived exosomal vesicles in drug addiction research using liquid chromatography-mass spectrometry
(2) Developing a new type of 3D microfluidic paper column-LC/MS to evaluate the association between intestinal microbiota, environmental toxins, and diseases through metabolomics
(3) Investigating metabolism of drugs of abuse in forensic toxicology using in vitro, in vivo and animal model
(4) Developing liquid phase microextraction techniques to concentrate drugs of abuse, environmental toxins and pesticides in food, biological and wastewater samples during COVID19 pandemic
miRNA in neural cell-derived exosomal vesicles for drug addiction
This study introduces an innovative method for accurately analyzing trace microRNAs (miRNAs) found in neuronal extracellular vesicles (EVs), particularly those relevant to drug addiction. Given their substantial size (usually less than 10,000 Da) and multiple negative charges, miRNAs present notable difficulties in mass spectrometry (MS) analysis. These challenges include diminished ionization efficiency in negative mode and the necessity to circumvent system charging effects. Furthermore, the nuanced sequence differences among miRNAs, especially in isomeric forms, complicate their separation with conventional reverse-phase and normal-phase chromatography techniques. This research aims to address these complexities to enhance the precision of miRNA analysis in the context of drug addiction using multi-function microfluidic paper column coupled to LC-MS.
Novel 3D printing microfluidic paper column coupled to liquid chromatography-mass spectrometry for drug analysis in plasma
Paper spray ionization, while a straightforward technique for mass spectrometry (MS) analysis without the need for sample preparation, faces limitations due to the use of paper substrates, such as short lifespan, inconsistent reproducibility, significant analyte diffusion, and inadequate chromatographic performance. To overcome these challenges, a novel approach involving a stereolithography 3D printed microfluidic paper-based column, integrated with liquid chromatography-MS (µPC-LC-MS), has been introduced. This innovative method enables the rapid creation of precise microchannels within a single paper substrate in under a second. The µPC-LC-MS system notably enhances the substrate's longevity, allowing up to 50 minutes of continuous usage per run with gradient elution at a flow rate of 20 μL/min using standard LC pumps. Additionally, a single µPC can withstand up to 5 cycles of reuse with a relative standard deviation (RSD) of 9.5%, maintaining consistent signal strength without overloading or interference. The µPC-LC-MS system's robustness and sensitivity position it as a highly promising tool for bioanalytical applications, leveraging the advantages of paper-based microfluidics.
‘A novel liquid crystal aptasensor via DNA aptamer conformational change for cocaine
detection in sewage and urine': A one-step on-site device
A pioneering single-step aptasensor based on liquid crystal (LC) technology has been innovatively designed for immediate detection of minute substances in both urine and sewage. This advanced system leverages dual mechanisms to activate the LC orientation in both the upper and lower layers simultaneously. DNA aptamers, specifically modified on a glass surface, direct the orientation of the lower layer. Focusing on cocaine detection, these asymmetric single-stranded DNA aptamers transform into a symmetrical Y-shape, prompting the LC molecules to shift from a planar alignment to a vertical (homeotropic) one. This shift induces a visible alteration in the LC display, transitioning from a luminous state to a darkened one. Remarkably, the system functions effectively with just 10 ng of dry-stored DNA aptamers. This highly sensitive, durable, and portable LC-based aptasensor represents a significant advancement for the immediate detection of trace elements in various samples.
‘Thermosensitive Nanovesicle’ - trap and release of drugs
An environmentally friendly thermosensitive nanovesicle-cloud point microextraction technique has been developed with the assistant of ultrasonic waves to determine analgesic drugs with a broad range of polarity in field water and human urine. Based on thin-film hydration, the conformation of nanovesicles was formed by a binary mixing system with the nonionic surfactants. The multilayered nano-spherical structure was able to capture polar and nonpolar compounds simultaneously by ultra-performance liquid chromatography coupled to photodiode array detection.
‘Modifier-Assisted Differential Mobility–Tandem Mass Spectrometry’-Amphetamine-type Stimulants in Urine Differential Mobility Spectrometry (DMS)
-mass spectrometry (MS) detects analytes in the gas phase on the basis of differences in ion mobility in low and high electric fields, which makes DMS-MS/MS an alternative to chromatographic separation-MS. One drawback of DMS is its limited resolution and sensitivity, especially for detecting small molecules when using a nonpolar inert gas as the carrier gas. Use of a methanol-helium mixture gave improvements in both separation and sensitivity. Nine structurally similar amphetamine-type stimulants were determined in urine without pretreatment of the samples before analysis.
‘Dilute-and-shoot Enhances MS Sensitivity ’-Phthalates in Children
Phthalates are not covalently bound to plastics. They can leach from experimental plastic devices. Due to the development of sensitive techniques, exogenous sources that interfere with the accuracy of phthalate monoester analysis can be easily detected. Here, we propose the simple and rapid dilute-and-shoot method to minimize sample handling and limit contact with laboratory apparatus, which efficiently reduced phthalate interferences mainly from experimental plasticware and improved the accuracy of analysis. Chemical additives in the mobile phase and modifiers in reconstituted solution were evaluated to improve peak shape and liquid chromatography separation.
‘The Poppy Seed Defense’
Evaluating whether a urine sample that contains morphine, in the absence of 6-MAM, is a consequence of ‘street’ heroin administration is an important analytical challenge for all drug testing laboratories. Knowledge that ingestion of a relatively small amount of poppy seeds, which naturally contain morphine and other alkaloids, can also result in a morphine positive result, has major medico-legal ramifications, including the ‘poppy seed defense’. Thebaine was acetylated and derivatives 3, 4 and 8, which have been found in 5 illicit heroin samples. These derivatives were then incubated with human liver microsomes. Metabolites from compound 4 were detected and identified by LC-MS/MS. The oxygen-linked acetyl group was labile, as expected, and yielded the free alcohol as one metabolite (ATM) whereas the acetamido group was conserved. The resulting free alcohol was then conjugated to glucuronic acid forming a second metabolite, ATMG.
Figure 1: (a) Scheme showing the generation of the new marker, ATMG. (b) Chromatograms of real samples. (c) Product ion spectrum of ATM. (d) Product ion spectrum of ATMG.