Dec 20 2012
Srikanth Singamaneni, Professor of Assistant Professor in the Department of Mechanical Engineering and Materials Science at Washington University in St. Louis talks AZoSensors about Biosensor Technology for the Detection of Kidney Disease.
Can you provide the audience with a summary of your latest research on the application of a biosensor for the detection of kidney disease?
Plasmonic biosensors based on localized surface plasmon resonance (LSPR) or surface enhanced Raman scattering (SERS) hold enormous potential to provide highly sensitive, on-chip, and point-of-care diagnostic tools. However, the state of the art plasmonic biosensors are limited by the poor stability (environmental, chemical and temporal) and high cost of the natural antibodies employed as capture agents (receptors). In our latest work, we demonstrated an alternate path forward, use of artificial antibodies instead of natural antibodies as bioreceptors, which overcomes the aforementioned challenges.
As a proof of concept, we demonstrated surface molecular imprinting of gold nanorods with three different proteins, one of which is a biomarker for acute kidney injury. Furthermore, we demonstrate that with a careful control of the molecular imprinting process, the synthetic receptors can be localized at the electromagnetic hotspots of the nanorods, which are known to be most potent sites for biosensing. Investigation of bioanalytical parameters revealed the good sensitivity, selectivity and more importantly reusability of plasmonic biochips. We believe that this demonstration will open novel avenues in plasmonic biosensors for realizing inexpensive, on-chip and point-of-care diagnostic assays.
You have used biomolecular imprinting to synthesise a plasmonic biosensor. Can you briefly describe what this process is and what it involves?
A biomolecular imprinting process involves the immobilization of a template molecule (in this case the protein to be detected) on the nanotransducer (i.e., gold nanorods) followed by polymerization of small molecules bearing desired function groups (e.g., amine, carboxylic, methyl). Following the polymerization, the template molecules are removed from gold nanorods surface leaving a cavity which is complementary in shape and functionality to the protein. Essentially, we have created a binding pocket on gold nanorods which can selectively capture the protein of interest from a physiological fluid.
How does the biosensor work to detect kidney disease and how is it designed to detect the protein neutrophil gelatinase-associated lipocalin biomarker for this disease?
It has been previously reported that neutrophil gelatinase-associated lipocalin (NGAL) is an excellent predictive biomarker for acute kidney injury (AKI). Rapid quantitative detection of this biomarker in urine enables quick and easy detection of AKI. We have used NAGL as a template molecule and imprinted gold nanorods with this molecule. When these gold nanorods are exposed to physiological fluids (e.g., urine) with NAGL, it immediately binds to AuNR and causes a change in the optical properties of gold nanorods, which can be easily detected using a simple UV/visible spectrometer.
Why are we starting to see more of a shift from traditional methods to sophisticated sensor technology for the diagnosis of a particular disease?
There are numerous reasons for such a paradigm shift. Conventional biosensing approaches are time-consuming, complex (require trained personnel to run the test or the test is often performed at a remote site) and expensive. Overcoming these limitations is critical to enable point-of-care diagnostics and biodiagnosis in resource-limited settings, which is of significant interest.
What are the advantages and disadvantages to this new biosensor?
The advantages of this biosensing approach are (i) highly stable and immune to storage conditions (e.g., temperature) unlike the biosensors based on natural antibodies (ii) inexpensive (iii) simple to use and (iv) reusability. Ultimately, this technology can lead to printable biochips facilitating the detection of multiple biomarkers with a simple paper strip. The disadvantage is that the current limit of detection is slightly higher compared to the traditional biosensors. Our future work will involve the improvement of sensitivity to lower the detection limit.
How will the application of this biosensor help the patient, practitioner and healthcare costs?
The biosensor developed here is highly stable and immune to various environmental conditions (e.g., temperature and humidity). This will form an ideal platform for point-of-care diagnostic test for AKI detection. It also obviates the need for any special storage such as refrigeration and hydration. Furthermore, eliminating the use of expensive natural antibodies and reusability of the biosensor makes it inexpensive, thus significantly lowering the healthcare costs.
Is this proof-of-concept assay widely applicable to a multitude of clinical tests and biomarkers?
Yes, the current technology can be readily extended to any protein marker. However, choice of functional monomers and polymerization conditions need to be carefully optimized to maximize the template removal and sensitivity of the biosensors.
Are there any medical conditions or biochemicals that could compromise the sensitivity of this biomarker?
While the biomarker employed here needs further validation, studies so far indicate that NGAL is a good biomarker. However, current technology can be extended to any protein marker.
How does the application of this biosensor affect diagnosis time and how will this help shape healthcare resources worldwide and affect the growing prevalence rates of kidney disease?
Since the technology demonstrated here does not require highly trained personnel to run the test, it can be easily performed even in resource-limited settings.
How do you plan on developing this biosensor so that it is applicable in the detection of more than one disease?
As mentioned above, we plan on translating this to a printable version to realize a lab-on-paper strip, which enables simultaneous detection of multiple biomarkers.
About Srikanth Singamaneni
Dr. Srikanth Singamaneni is currently an Assistant Professor in the Department of Mechanical Engineering and Materials Science at Washington University in St. Louis. He obtained his PhD in Polymer Materials Science and Engineering from Georgia Institute of Technology in 2009. His current research interests include the design, synthesis and self-assembly of novel plasmonic nanostructures for various biomedical applications.
Dr. Srikanth Singamaneni has co-authored nearly 75 refereed articles (including 8 invited reviews) in archival journals, 4 book chapters, and a book (Scanning Probe Microscopy of Soft Matter: Fundamentals and Practices). He is a recipient of the Translational New Investigator Award, DOD-Army (2011), MRS Graduate Student GOLD Award (Fall 2008), and the MRS Best Poster Award (Fall 2007). He is a member of Alvin J. Siteman Cancer Center, Center for Materials Innovation and Division of Biology and Biomedical Sciences at Washington University in St. Louis.
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