Oral Presentations 5: Analytical
Tracks
Track 1
| Monday, September 22, 2025 |
| 4:00 PM - 5:00 PM |
| Grand Copthorne Waterfront Hotel - Grand Ballroom II |
Speaker
Dr Kelvin Goh
Principal Medical Laboratory Scientist
Singapore General Hospital, Divisions of Pharmacy & Pathology (TRAIL)
MS-Based Quantification of Gemcitabine in Porcine Models: Application to Drug-Eluting Stent Development
Abstract
Background: Advanced urothelial carcinomas, particularly in upper urinary tract, can cause significant morbidity, including bleeding, obstructive uropathy, and kidney failure. Endourological treatments often result in high recurrence rates. Adjuvant localized chemotherapy using indwelling stents can reduce recurrences. However, the absence of well-designed drug-eluting stents makes this approach vulnerable to challenges such as constant urine flow, peristalsis, and an impermeable lining, which hinder effective ureteral drug delivery.
Aims: We seek to evaluate the pharmacokinetics, safety, and toxicity of administering gemcitabine via a 3D-printed, gemcitabine-infused ureteral stent in a porcine model. This approach aims to achieve targeted drug delivery to ureteral tissues, with gemcitabine detection facilitated by mass spectrometry.
Methods: Calibration curves were developed using Gemcitabine spiked in blank porcine plasma(3-1500μg/L), urine(3-1500μg/L) and tissue(0.3-500ng/g) and analyzed with a Shimadzu LCMS 9030 mass spectrometer. Tissue samples from bilateral ureters were harvested via open surgery(laparotomy) and segregated between the left ureter (drug-loaded stent) and right ureter (control stent). Pre-sacrifice and post-sacrifice bloods were drawn. Urine was collected on the day of sacrifice.
Results: Quantification of gemcitabine in plasma, urine and tissue was achieved within 4.5mins with excellent linearity(R²=0.998). Accuracy and precision were ±15% across the specified range. Gemcitabine was detected in left ureter tissues and urine but mostly absent in plasma and right ureter tissues.
Conclusion: We developed a rapid, sensitive LCMS assay to quantify gemcitabine in porcine urine, plasma, and tissue samples. Results from our assay demonstrated the utility of our novel drug-eluting stent for safe, targeted gemcitabine delivery to ureteral tissues.
Aims: We seek to evaluate the pharmacokinetics, safety, and toxicity of administering gemcitabine via a 3D-printed, gemcitabine-infused ureteral stent in a porcine model. This approach aims to achieve targeted drug delivery to ureteral tissues, with gemcitabine detection facilitated by mass spectrometry.
Methods: Calibration curves were developed using Gemcitabine spiked in blank porcine plasma(3-1500μg/L), urine(3-1500μg/L) and tissue(0.3-500ng/g) and analyzed with a Shimadzu LCMS 9030 mass spectrometer. Tissue samples from bilateral ureters were harvested via open surgery(laparotomy) and segregated between the left ureter (drug-loaded stent) and right ureter (control stent). Pre-sacrifice and post-sacrifice bloods were drawn. Urine was collected on the day of sacrifice.
Results: Quantification of gemcitabine in plasma, urine and tissue was achieved within 4.5mins with excellent linearity(R²=0.998). Accuracy and precision were ±15% across the specified range. Gemcitabine was detected in left ureter tissues and urine but mostly absent in plasma and right ureter tissues.
Conclusion: We developed a rapid, sensitive LCMS assay to quantify gemcitabine in porcine urine, plasma, and tissue samples. Results from our assay demonstrated the utility of our novel drug-eluting stent for safe, targeted gemcitabine delivery to ureteral tissues.
Biography
Dr. Kelvin Goh is a Principal Medical Laboratory Scientist in the Division of Pharmacy at the Singapore General Hospital. He has a wide range of skillsets in Organic/Inorganic Chemistry, Analytical Chemistry and Medicinal Chemistry. His current interests include mass spectrometry assay development and metabolomics approaches towards tackling real-world problems revolving around antimicrobial resistance, cancer, chronic diseases and other healthcare related challenges. He is also interested in implementation science, with most of his current works revolving around translating innovation from bench to bedside through development of lab-developed test kits and accredited lab services.
Celine Sim
Research Officer
Singapore General Hospital, Division of Pharmacy
Development of a Multi-Triazole UPLC-UV Assay in Plasma for Antifungal TDM
Abstract
Background: Triazole antifungal drugs (TADs) are pivotal in treating invasive fungal infections (IFIs) due to their broad-spectrum efficacy and relatively low toxicity. However, improper dosing can lead to adverse effects or therapeutic failure, underscoring the importance of therapeutic drug monitoring (TDM) to tailor treatments effectively. While mass spectrometry has become a preferred method for TDM assay development because of its high sensitivity, many existing high-performance liquid chromatography systems with ultraviolet detection (HPLC-UV) remain underutilized.
Aims: This study aims to develop and validate a simple, fast, and low-cost HPLC-UV method for quantifying multiple TADs in plasma.
Methods: Plasma samples containing isavuconazole(ISV), posaconazole(PCZ), voriconazole(VOC), itraconazole(ITZ) and hydroxy-itraconazole(HICZ) underwent protein precipitation with acetonitrile and separation on a C18 column using gradient elution with 10mM potassium phosphate pH2.61 buffer and acetonitrile; and quantified via UV at 270nm using naproxen as internal standard. The method was validated on accuracy, precision, limit-of-quantification(LOQ), specificity, carryover, and short-term stability based on US-FDA guidelines. The feasibility of the assay was tested in 20 clinical samples.
Results: Quantification of all TADs in plasma was achieved within 4.5 mins with excellent linearity(R²=0.998) over 0.5-40mg/L range. Accuracy and precision were ±15% across the specified range. The method fulfilled acceptance criteria according to US-FDA guidelines and successfully measured TAD in all 20 samples.
Conclusion: We developed a simple, fast, low-cost HPLC-UV assay to measure multiple TADs in plasma that can be translated for routine antifungal TDM. Continual development of HPLC-UV assay helped us to maximize existing infrastructure for TDM implementation in clinical practice.
Aims: This study aims to develop and validate a simple, fast, and low-cost HPLC-UV method for quantifying multiple TADs in plasma.
Methods: Plasma samples containing isavuconazole(ISV), posaconazole(PCZ), voriconazole(VOC), itraconazole(ITZ) and hydroxy-itraconazole(HICZ) underwent protein precipitation with acetonitrile and separation on a C18 column using gradient elution with 10mM potassium phosphate pH2.61 buffer and acetonitrile; and quantified via UV at 270nm using naproxen as internal standard. The method was validated on accuracy, precision, limit-of-quantification(LOQ), specificity, carryover, and short-term stability based on US-FDA guidelines. The feasibility of the assay was tested in 20 clinical samples.
Results: Quantification of all TADs in plasma was achieved within 4.5 mins with excellent linearity(R²=0.998) over 0.5-40mg/L range. Accuracy and precision were ±15% across the specified range. The method fulfilled acceptance criteria according to US-FDA guidelines and successfully measured TAD in all 20 samples.
Conclusion: We developed a simple, fast, low-cost HPLC-UV assay to measure multiple TADs in plasma that can be translated for routine antifungal TDM. Continual development of HPLC-UV assay helped us to maximize existing infrastructure for TDM implementation in clinical practice.
Biography
Celine Sim is a research officer at Singapore General Hospital, where she supports clinical studies in Therapeutic Drug Monitoring to enhance patient safety and treatment efficacy. She holds a bachelor’s degree in Chemistry and Biological Chemistry from Nanyang Technological University and previously interned at Shimadzu (Asia Pacific), gaining experience in spectrometry and chromatography. Her interests lie in analytical and medicinal chemistry with a focus on clinical applications.
Ms Laura Boffel
Laboratory Of Toxicology, Department Of Bioanalysis, Faculty Of Pharmaceutical Sciences, Ghent University
Antibody-Based Enrichment of Albumin-Cys34 Adducts to Monitor Drug Exposure
Abstract
Background: Although current analysis of drug biomarkers in blood and urine is well-established, compounds are only detectable for a small time period (several days). Analysis of a keratinized matrix (hair) is the only option to detect biomarkers over a longer time period (several months). However, hair analysis faces crucial technical and interpretative obstacles, complicating unambiguous interpretation of drug exposure. Monitoring drug-protein adducts, serving as biomarkers with an extended window of detection (several weeks), may offer an alternative to hair analysis.
Aims: This study aimed to develop an LC-(HR)MS/MS method to monitor and identify potential protein adducts between the Cys34 residue of human serum albumin (HSA) and drugs, with paracetamol chosen as a model analyte.
Methods: To simplify the biological matrix and improve sensitive monitoring of HSA-Cys34 adducts, a polyclonal antibody assay was designed to capture HSA-Cys34 adducts in trypsin-digested plasma. The enrichment assay and both targeted and untargeted LC-(HR)MS/MS-based detection were optimized based on monitoring of a known HSA-Cys34 adduct with N-acetyl-p-benzoquinone imine (NAPQI, a highly reactive metabolite of paracetamol).
Results: As proof-of-principle, an ‘addition-only’ protocol was optimized for 100 µL of plasma, allowing successful detection of both in vitro and in vivo (i.e., present in a post-mortem sample) generated NAPQI-Cys34 adducts using the antibody-based assay. Additionally, the presence of NAPQI-Cys34 adducts was successfully confirmed using an LC-HRMS method, enabling untargeted detection of unknown Cys34 adducts.
Conclusions: An antibody-based enrichment assay was successfully developed, optimized and applied to monitor drug-Cys34 adducts in plasma.
Key Words: Drug-Protein Adducts, Long-Term Biomarkers, LC-(HR)MS/MS
Aims: This study aimed to develop an LC-(HR)MS/MS method to monitor and identify potential protein adducts between the Cys34 residue of human serum albumin (HSA) and drugs, with paracetamol chosen as a model analyte.
Methods: To simplify the biological matrix and improve sensitive monitoring of HSA-Cys34 adducts, a polyclonal antibody assay was designed to capture HSA-Cys34 adducts in trypsin-digested plasma. The enrichment assay and both targeted and untargeted LC-(HR)MS/MS-based detection were optimized based on monitoring of a known HSA-Cys34 adduct with N-acetyl-p-benzoquinone imine (NAPQI, a highly reactive metabolite of paracetamol).
Results: As proof-of-principle, an ‘addition-only’ protocol was optimized for 100 µL of plasma, allowing successful detection of both in vitro and in vivo (i.e., present in a post-mortem sample) generated NAPQI-Cys34 adducts using the antibody-based assay. Additionally, the presence of NAPQI-Cys34 adducts was successfully confirmed using an LC-HRMS method, enabling untargeted detection of unknown Cys34 adducts.
Conclusions: An antibody-based enrichment assay was successfully developed, optimized and applied to monitor drug-Cys34 adducts in plasma.
Key Words: Drug-Protein Adducts, Long-Term Biomarkers, LC-(HR)MS/MS
Biography
In 2021, Laura graduated as a pharmacist at Ghent University. Mainly due to the interesting research she was involved in during her Master’s thesis at the Laboratory of Toxicology of prof. Christophe Stove, she decided to pursue a career in research. Shortly after graduating, she started a PhD at the Laboratory of Toxicology. Her research is mainly focused on two topics. First, she is setting up an LC-(HR)MS-MS method to monitor drug-protein adducts (in plasma), which are formed upon exposure to (illicit) drugs. Second, she is also working on different microsampling-related topics (i.e., the evaluation of novel technologies, conversion approaches, Hct determination methodologies,…).
Wen Qi Chiang
Research Officer
Singapore General Hospital, Division of Pharmacy
Utilizing Waste Plasma as a Sustainable Resource in Antibiotic TDM Assay Applications.
Abstract
Background: Bioanalytical assays are crucial for antibiotic therapeutic drug monitoring (TDM) in plasma, supporting effective antimicrobial stewardship. Plasma serves as the ideal matrix-matched standard (MMS) for calibration curves in bioanalytical assays, ensuring accurate antibiotic level measurements by minimizing matrix effects that compromise assay robustness. However, the rising cost of commercial plasma (CP) hinders the rapid adoption of TDM. TDM labs frequently generate excess leftover plasma, which is typically discarded. We propose recycling this leftover plasma to produce in-house carbon-stripped plasma (ih-CSP), reducing the reliance on fresh CP and potentially saving an estimated S$50,000 and 324kg of CO2-equivalent emission annually for a TDM service operating 2600 assays in a year.
Aims: This study evaluates ih-CSP, made from recycled leftover plasma, as a feasible alternative to fresh CP in TDM applications.
Methods: ih-CSP was prepared by treating leftover research plasma with crushed charcoal pills. Piperacillin(35mg/L), aztreonam(24mg/L), meropenem(20mg/L), doripenem(13mg/L), and tazobactam(12mg/L) were spiked into CP and ih-CSP from six patient sources. Samples were processed via protein precipitation with acetonitrile and analyzed using a Shimadzu-8060 LCMS system. Antibiotic concentrations in spiked CP and ih-CSP were compared to nominal values.
Results: All five antibiotics were quantified in CP and ih-CSP with excellent linearity (R²=0.999) across 1–400mg/L. Mean accuracies and precision were within ±15%, with negligible concentration differences (0.4–8.9%) between CP and ih-CSP.
Conclusion: Recycling leftover plasma into ih-CSP provides a cost-effective and viable alternative to CP for TDM assay application, promoting sustainable healthcare. Future research will explore its hospital-wide implementation for TDM.
Aims: This study evaluates ih-CSP, made from recycled leftover plasma, as a feasible alternative to fresh CP in TDM applications.
Methods: ih-CSP was prepared by treating leftover research plasma with crushed charcoal pills. Piperacillin(35mg/L), aztreonam(24mg/L), meropenem(20mg/L), doripenem(13mg/L), and tazobactam(12mg/L) were spiked into CP and ih-CSP from six patient sources. Samples were processed via protein precipitation with acetonitrile and analyzed using a Shimadzu-8060 LCMS system. Antibiotic concentrations in spiked CP and ih-CSP were compared to nominal values.
Results: All five antibiotics were quantified in CP and ih-CSP with excellent linearity (R²=0.999) across 1–400mg/L. Mean accuracies and precision were within ±15%, with negligible concentration differences (0.4–8.9%) between CP and ih-CSP.
Conclusion: Recycling leftover plasma into ih-CSP provides a cost-effective and viable alternative to CP for TDM assay application, promoting sustainable healthcare. Future research will explore its hospital-wide implementation for TDM.
Biography
Chiang Wenqi is a Research Officer in the Division of Pharmacy at Singapore General Hospital. She holds a Bachelor’s degree in Biological Sciences and Psychology from Nanyang Technological University. Her current research interests include Analytical Chemistry and therapeutic drug monitoring, with a focus on advancing personalised treatment in clinical settings.
Assoc Prof Mahesheema Ali
The Metro Health
Unmasking the Hidden Interference: Comparative Analysis of Solriamfetol's Effect on Amphetamine Testing
Abstract
Background:
Solriamfetol is a Schedule IV-controlled substance used to treat excessive daytime sleepiness in patients with narcolepsy and obstructive sleep apnea. It has been reported to cause false-positive amphetamine results on certain immunoassays.
Aims:
To evaluate the cross-reactivity of solriamfetol with amphetamine across four widely used urine screening platforms—Beckman Coulter, Vitros, Abbott Alinity, and Roche—and to confirm these findings using mass spectrometry.
Methods:
Negative urine samples were spiked with solriamfetol at concentrations of 0.2 µg/mL, 2 µg/mL, 200 µg/mL, and 2000 µg/mL. The samples were analyzed on all four immunoassay platforms, and mass spectrometry served as the confirmatory method.
Results:
The Beckman Coulter and Abbott Alinity assays yielded positive amphetamine results at solriamfetol concentrations exceeding 200 µg/mL, while the Vitros assay produced false positives at 2000 µg/mL. In contrast, the Roche assay showed no cross-reactivity at any concentration. Mass spectrometry confirmed negative amphetamine results for all samples.
Conclusions:
These findings emphasize the importance of confirmatory testing and careful assay selection to minimize diagnostic errors in patients taking solriamfetol.
Key Words: Schedule IV, Interference, Amphetamine, Cross reactivity
Solriamfetol is a Schedule IV-controlled substance used to treat excessive daytime sleepiness in patients with narcolepsy and obstructive sleep apnea. It has been reported to cause false-positive amphetamine results on certain immunoassays.
Aims:
To evaluate the cross-reactivity of solriamfetol with amphetamine across four widely used urine screening platforms—Beckman Coulter, Vitros, Abbott Alinity, and Roche—and to confirm these findings using mass spectrometry.
Methods:
Negative urine samples were spiked with solriamfetol at concentrations of 0.2 µg/mL, 2 µg/mL, 200 µg/mL, and 2000 µg/mL. The samples were analyzed on all four immunoassay platforms, and mass spectrometry served as the confirmatory method.
Results:
The Beckman Coulter and Abbott Alinity assays yielded positive amphetamine results at solriamfetol concentrations exceeding 200 µg/mL, while the Vitros assay produced false positives at 2000 µg/mL. In contrast, the Roche assay showed no cross-reactivity at any concentration. Mass spectrometry confirmed negative amphetamine results for all samples.
Conclusions:
These findings emphasize the importance of confirmatory testing and careful assay selection to minimize diagnostic errors in patients taking solriamfetol.
Key Words: Schedule IV, Interference, Amphetamine, Cross reactivity
Biography
Dr. Mahesheema Ali is the Medical Director of the Core laboratory, Toxicology& POCT at MetroHealth Systems and an Associate Professor of Laboratory Medicine at Case Western Reserve University School of Medicine. She is board-certified by the American Board of Clinical Chemistry and is a fellow of the ADLM Academy.
