Inkjet Printing of ‘Paperfluidic’ Devices
A simple, low-cost inkjet printing method has been developed for the preparation of immunochromatographic devices on a single piece of filter paper. This device, dubbed ‘paperfluidics‘, allows for simpler, quicker and cheaper fabrication than conventional immunochromatographic strips. The paperfluidic device was capable of detecting the model analyte IgG down to 10 µg/l, highlighting its applicability as a simple, portable test for medical, environmental and food analyses in remote or less industrialized settings.
In spring 2007, the Suzuki–Citterio research group at Keio University (Yokohama, Japan) was using piezoelectric inkjet printing to fabricate inkjet-printed chemical sensing devices. Just a few months earlier, Professor George Whitesides’ research group at Harvard University (USA) had started to work on paper-based microfluidic devices with the goal of providing simple and affordable diagnostics for developing countries. As Citterio explained to Therapeutic Delivery, “We decided to use inkjet printing technology to fabricate similar devices because it enables the rapid and highly reproducible contactless dispensing of picoliter-order liquid droplets at defined spots on a variety of surfaces. It is suitable for the deposition of materials required for optical chemical sensing into a single small-scale device. Furthermore, it allows the fabrication of patterned surfaces without having to rely on photolithography (used by Whitesides at that time). The number of required process steps is reduced and, as a further advantage, all steps can be performed using an inkjet dispenser.” The research group specializes in the development of functional organic materials for chemical sensing and in the fabrication of entire sensing devices – they have developed many functional organic dyes (fluorescent and absorbing) for use in optical chemical sensors.
Pure cellulose filter papers are not necessarily ideal substrates for immunochromatography, but the most widely-used alternative (nitrocellulose) is quite fragile and not suited to the inkjet patterning method. The inkjet printing steps had to be optimized to avoid the printed lines that mark out the test and control spots spreading out on the cellulose surface. The Suzuki–Citterio group also hope to optimize the chromatographic mobility of the gold-labeled antibodies on the cellulose substrate. So far, they have tested an assortment of cellulose substrates with varying pore sizes in combination with various blocking agents and surfactants.
For clinical diagnostics and environmental analysis (especially for water quality monitoring), chemical sensing tests alone are not sufficient. Lateral-flow immunoassays (immunochromatography) are the method of choice in low-resource settings, such as those encountered in developing countries, and a selection of devices is commercially available. However, Citterio described the drawbacks with the currently available lateral flow immunosensors: “they normally allow only one parameter to be tested with one device. For reasons of simplicity and costs, it is desirable to perform multiple tests (combining chemical and immunological parameters) simultaneously. We decided to evaluate the fabrication of lateral flow immunoassays by inkjet printing using the same approach as for our chemical sensors (patterning and printing of reagents). Finally, we demonstrated the feasibility of combining a chemical test (pH) with two immunoassays on a single piece of simple filter paper.”
Having developed the inkjet printing method to produce chemical testing devices and establishing their feasibility for testing several parameteres, the next step is to increase the number of chemical parameters that can be tested beyond just pH, test the immunoassay on real-life samples and reduce the amount of nonspecific binding. By testing alternative labeling reagents, the group hopes to improve the sensitivity.
Sources: Abe K, Kotera K, Suzuki K, Citterio D. Inkjet-printed paperfluidic immuno-chemical sensing device. Anal. Bioanal. Chem. 10.1007/s00216-010-4011-2 (2010) Epub ahead of print; Abe K, Suzuki K, Citterio D. Inkjet-printed microfluidic multianalyte chemical sensing paper. Anal. Chem. 80 (18), 6928–6934 (2008).
Rapid PCP Method May Encourage Switch from GC to LC in Forensic Labs
A new, rapid LC–MS/MS method has been developed for the determination of phencyclidine (PCP, known as ‘angel dust‘) in blood at the University of Arkansas for Medical Sciences (AR, USA). PCP, originally introduced as an anesthetic in the 1950s, is not as widely abused as other narcotics, but toxicity is observed at very low doses.
The Arkansas group are involved with collaborations to develop mAbs to treat drug abuse and are very close to having a chimeric anti-PCP mAb for use in human subjects. Lead author Howard Hendrickson explained that they “needed an analytical method that was validated for the determination of PCP in human serum samples. In order to fully validate this method, we needed authentic samples.” Since PCP is illegal, the easiest samples to obtain ethical board approval to use were postmortem samples obtained from the Arkansas State Crime Lab.
With a run time of 10 min, the new method is quicker than established GC–MS methods. Until now, forensic labs have been slow to switch from GC–MS-based methods to LC–MS/MS-based methods because of the time involved in method transfer and method validation. Hendrickson hopes that “this work may encourage the switch to higher throughput LC–MS/MS.”
Source: Chimalakonda KC, Chris Hailey C, Black R. Development and validation of an LC-MS/MS method for determination of phencyclidine in human serum and its application to human drug abuse cases. Anal. Methods DOI: 10.1039/c0ay00206b (2010) Epub ahead of print.
New Screening Test for Resistance to Imatinib
A novel fluorescence resonance energy transfer (FRET)-based biosensor has been developed to help doctors determine if a patient with chronic myeloid leukemia (CML) is resistant to imatinib (Gleevac®). Imatinib is the standard drug for treating leukemia or cancer of blood cells; however, in relapse patients, resistance can often occur and the patient’s condition can rapidly deteriorate if they are given the wrong treatment.
In a paper published in Clinical Cancer Research, Yusuke Ohba and colleagues at the Hokkaido University Graduate School of Medicine (Japan) describe how they developed and optimized a biosensor to detect BCR-ABL kinase activity in living cells. The biosensor was compared against established methods such as western blotting and flow cytometry and found to be more sensitive at measuring measuring BCR-ABL activity and its suppression by imatinib, both in detecting drug-resistant patients and identifying those susceptible to future drug resistance.
“Using this test, we are now able to identify and predict the most suitable treatment option for individual chronic myeloid leukemia patients,” said Ohba. The test can also help determine the next therapeutic option, including dose escalation, combination therapy or second-generation inhibitors. “The most critical issue in dealing with imatinib resistance is what to switch over to,” commented Ohba, “If the patient is switched to another drug to which they are also resistant, then the treatment will just be a waste of time and detrimental to the patient’s condition.”
“The entire cancer community is talking about personalized medicine, and key to that is knowing when an individual person will have a unique response,” said Yingxiao Wang (University of Illinois Urbana-Champaign, USA) in an editorial paper accompanying the research article. “This project is an important step forward.”
Sources: New lab test could identify imatinib resistance www.eurekalert.org/pub_releases/2010-07/aafc-nlt072210.php; Mizutani T, Kondo T, Darmanin S. A Novel FRET-Based Biosensor for the Measurement of BCR-ABL Activity and Its Response to Drugs in Living Cells. Clin. Cancer Res. 16, 3964-3975 (2010); Lu S, Wang Y. Clin. Cancer Res. 16(15), 3822–3824 (2010).
Saliva Monitoring of Immunosuppressants
A test being developed by the Clinical Pharmacokinetics Research Laboratory at the University of Rhode Island’s College of Pharmacy could enable clinical researchers to use saliva to easily monitor immunosuppressant drugs. Immunosuppressants are used to prevent rejection of transplanted organs and are currently monitored in blood samples, however these are invasive and so clinical researchers are looking for more patient-friendly sampling methods, such as with saliva.
Using AB SCIEX’s sensitive API 4000™ system, the Rhode Island group aim to create a simple, standardized saliva-based test that can be adopted by other clinical research laboratories around the world. The University of Rhode Island are solely responsible for advancing this test through the necessary steps to make the test meet the stringent requirements of clinical settings. Fatemeh Akhlaghi (Associate Professor of Pharmacokinetics, University of Rhode Island), whose research interests include therapeutic drug monitoring and pharmacokinetics of immunosuppressant drugs in diabetic kidney transplant patients, explained that their goal is to make it easier for laboratories to accurately analyze the effectiveness of drugs used in organ transplants: “By being able to obtain clinically-relevant results from saliva, clinical researchers can adopt a non-invasive procedure that could revolutionize the study of immunosuppressant drugs. The extremely sensitive analytical capabilities of AB SCIEX technology enables us to do what we could not previously do in our laboratory.”
Source: Clinical Researchers at University of Rhode Island Adopt AB SCIEX Technology to Develop Novel Test to Support Organ Transplants www.absciex.com/pdf/university_rhode_island_collab_pr.pdf