NEW YORK (GenomeWeb) – Researchers at Washington University in St. Louis have developed a biospecimen preservation approach that could streamline and lower the cost of processes for shipping and storing biological samples.
Described in a study published last month in Chemistry of Materials, the approach uses nanoporous material encapsulation to preserve proteins in urine, serum, plasma, and blood samples at room temperature. This could eliminate the need for frozen shipping and storage of such samples, which is both expensive and, in some resource-constrained areas, impractical.
This is a widely acknowledge issue in clinical research and clinical testing. As Paul Kearney, president and chief scientific officer at proteomics firm Integrated Diagnostics noted in a recent interview, one of the biggest costs in clinical testing is "the cost of getting samples to your lab. It's that cost of goods where you can really make a difference."
With that in mind, a number of companies and research groups are looking into the use of dried blood spots for collection of clinical samples. Dried blood spots have advantages over conventional venipuncture samples in that they can be shipped and stored under regular refrigeration as opposed to frozen. Furthermore, the convenience of sampling, which typically involves spotting blood from a finger prick on filter paper, opens up the possibility of easy in-home self-sampling.
The approach developed by the WUSTL team similarly addresses issues around the sample shipping and storage. Instead of dried blood spots, it uses nanoporous crystals composed of a zeolitic imidazolate framework-8 (ZIF-8) to encapsulate and preserve protein biomarkers in patient samples.
To prepare samples using the process, a technician would take the plasma or serum sample of interest and add the two precursors of the ZIF-8. That starts the encapsulation process, which will take several minutes to complete, after which the encapsulated sample can be spotted and dried on a piece of filter paper, which can then be shipped and stored at room temperature with the nanoporous framework protecting the sample proteins against denaturation and degradation.
When it is time for the sample to be analyzed, the target proteins can be eluted from the paper and measured using conventional clinical assays.
Srikanth Singamaneni, associate professor of mechanical engineering and materials science at WUSTL and senior author on the study, said that development of the approach stemmed from his group's research into biosensing and, specifically, difficulties around the use of antibody-based assays in resource-limited areas.
One of Singamaneni's research focuses is simplifying immunoassays to work, for instance, on paper formats and with read-out devices like cell phones.
"But one of the problems that has always been ignored is that if you want to get at a protein, the most common bio-recognition element to use is an antibody," he said. "But antibodies are known to be unstable. They can denature. They can lose their bio-recognition capability. So we wanted to address that problem."
They did so by applying the ZIF-8 encapsulation approach, which they found allowed them to ship and store antibodies for several weeks at temperatures of 140 degrees or more. Their success with antibodies led them to consider using the approach for the biomarkers the antibodies were intended to detect, as well. Singamaneni said. "We thought, if it is possible to preserve the antibodies, why can't we use the same approach to preserve the bio-specimens?"
The method has several potential advantages compared to dried blood spots. While dried blood spots don't need to be frozen, research suggests that they should be refrigerated. The WUSTL approach, on the other hand, preserves samples at room temperature.
Additionally, dried blood spot samples are typically very low volume, less than 100 microliters. This has limited their compatibility with traditional clinical assays, which typically require larger sample volumes, especially in cases where clinicians want to look at multiple analytes. Researchers have been tackling this problem by using mass spec-based assays, which can work with smaller sample sizes. However, while mass spec continues to see increases in clinical uptake, conventional immunoassays still dominate the clinic.
The WUSTL approach allows for collection of larger sample volumes more easily compatible with conventional clinical assays. Thus far, Singamaneni and his colleagues have collected samples on the order of several milliliters but he said he thought collection of much larger sample volumes would be possible.
"You are just drying the crystals one [stack] on top of the other, and that's not going to hurt [the sample]," he said. "You can have a big stack of these crystals just dried on a piece of paper and everything can be eluted later."
The method does not necessarily tackle all the challenges around patient sampling that dried blood spot researchers are looking to address. For instance, in the case of blood, samples must be spun down and separated into plasma and/or serum prior to encapsulation. The researchers demonstrated that this could be done in resource-constrained areas using a hand-powered centrifuge, but it makes it an impractical technique for home sampling, which is a goal of many researchers interested in dried blood spots.
Singamaneni said the approach is inexpensive, adding perhaps $0.25 or less per sample, and fast, with the encapsulation process taking a few minutes and the elution process taking 40 minutes to an hour. In the CoM study he and his colleagues tested the approach with urinary NGAL, a marker of kidney dysfunction, and serum/plasma CA125, a protein marker for ovarian cancer, finding that both markers were preserved with efficiency comparable to standard sample freezing protocols.
"The technology looks very, very robust," Singamaneni said, adding that he and his colleagues are now testing it with additional proteins and in larger sample volumes. They also hope to extend the method to other biomolecules, particularly RNA, given that molecule's low stability.