The Observatory
News
Origami-inspired paper sensor could test for malaria and HIV for less than a dime. Inspired by the paper-folding art of origami, chemists at the University of Texas at Austin have developed a 3-D paper sensor that may be able to test for diseases such as malaria and HIV for less than 10 cents. Such low-cost, “point-of-care” sensors could be useful in the developing world, where the resources often don't exist to pay for lab-based tests, and where infrastructure often doesn't exist to transport samples to the lab.
One-dimensional paper sensors, such as those used in pregnancy tests, are already common but have limitations. The folded, 3-D sensors can test for more substances in a smaller surface area and provide results for more complex tests. The results of the team's experiments with the origami Paper Analytical Device, or oPAD, were published in the Journal of the American Chemical Society and in Analytical Chemistry.
Researchers say that the principles underlying the sensor are related to the home pregnancy test. A hydrophobic material, such as wax or photoresist, is laid down into tiny canyons on chromatography paper. It channels the sample that's being tested—urine, blood, or saliva, for instance—to spots on the paper where test reagents have been embedded. They have also engineered a way to add a simple battery to their sensor so that it can run tests that require power. Their prototype uses aluminum foil and looks for glucose in urine.
Personalized Medicine
New study not encouraging on personalized approach to cancer treatment. No one ever said this would be easy; no one ever claimed that the conquest of cancer with drugs that target genes would be a cure or a universally effective treatment. But a study printed March 8 in the New England Journal of Medicine (NEJM) throws cold water on the idea that gene-based cancer treatment is imminent, reminding us that a molecular diagnostics approach to cancer is a work in progress. According to the authors of the study from the Cancer Research UK London Research Institute, the genetics-based treatment model may have more complexities than researchers have realized: the researchers found evidence that, within a given tumor, there may be significant variation in the location of cancer-activating genes. Also, genetic differences were uncovered between the main tumor and loci of metastases. The thrust of the research, which was based on unprecedentedly complex gene sequencing, is that a gene-based, personalized approach to cancer treatment may not be as close to realization as some have hoped. That is because single biopsies of tumors, used by clinicians to determine potential drug effectiveness, may not yield a complete picture of the tumor's biology, but rather only a minority of genetic mutations involved in the malignancy. But that is how science proceeds—two steps forward, one step back—and discovering what we don't know is part of the process of coming to know more.
New Studies
Blood test may be able to diagnose major depressive disorder. According to a study published in Molecular Psychiatry, Massachusetts General Hospital researchers, working with Ridge Diagnostics, have developed a blood test that helps to diagnose major depressive disorder (MDD). The test is not based on a single biomarker, but rather on some nine biomarkers associated with such factors as inflammation, neuron development and maintenance, and interactions among brain factors associated with stress response and other functions. Taken together, these biomarkers allow clinicians to assign a figure between one and 100, called an MDD score, that suggests the likelihood that the person being tested has major depression. The study was relatively small and quite preliminary, and its authors acknowledge that assessing its usefulness will require larger clinical trials. It might be the first step, however, on the path to diagnosing with more accuracy and specificity a very common disorder whose biochemical origins are just beginning to be understood, and which has so far resisted clear-cut mechanisms of diagnosis.
Guidelines
Standard on antimicrobial susceptibility testing of anaerobic bacteria published. The Clinical and Laboratory Standards Institute (CLSI) has published Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria; Approved Standard-Eighth Edition (M11-A8). This standard provides reference methods for the determination of minimal inhibitory concentrations of anaerobic bacteria by two end-point-determining susceptibility testing methods: agar dilution and broth microdilution. The latter is currently limited to testing of the Bacteroides fragilis group of organisms and selected antimicrobial agents. Quality control (QC) criteria for each procedure are also described.
Susceptibility testing is indicated for any organism that contributes to an infectious process warranting antimicrobial chemotherapy if its susceptibility cannot reliably be predicted from existing antibiograms. Antimicrobial resistance patterns for many anaerobic bacteria have changed significantly over the last several years, resulting in a lack of predictability for many species. Susceptibility testing of anaerobes is recommended for surveillance purposes and for specific clinical situations.
The objectives of this document are to offer useful information about methods for antimicrobial susceptibility testing of anaerobic bacteria; to provide reliable and reproducible methods that can be used for determining susceptibility for pathogens; and to present a step-by-step guide to susceptibility testing, including the number and species of organisms to test, frequency of testing, and selection of appropriate antimicrobial agents.
