Researchers have developed a biosensor – using less than a drop of blood – that could some day help identify people most at risk for osteoporosis, with early intervention being critical to reducing the morbidity and mortality of the condition.
Characterised by an increased risk of bone fractures, the condition affects about 54m people in the US alone, according to the International Osteoporosis Foundation.
While the most common technique used to measure changes in bone mineral density (BMD) – dual-energy X-ray absorptiometry – is not sufficiently sensitive to detect BMD loss until a significant amount of damage has already occurred, several genomic studies have reported genetic variations known as single nucleotide polymorphisms (SNPs) that are associated with increased risk for osteoporosis.
Using this information, Ciara O’Sullivan (Universitat Rovira i Virgili, Spain) and colleagues wanted to develop a portable electrochemical device that would allow them to quickly detect five of these SNPs in finger-prick blood samples in a step toward early diagnosis.
The device involves an electrode array to which DNA fragments for each SNP are attached. When lysed whole blood is applied to the array, any DNA matching the SNPs binds the sequences and is amplified with recombinase polymerase that incorporates ferrocene, a label that facilitates electrochemical detection.
Using this platform, the researchers detected osteoporosis-associated SNPs in 15 human blood samples, confirming their results with other methods, they wrote in their findings, published in ACS Central Science.
As the DNA does not have to be purified from the blood, the analysis can be performed quickly (about 15 minutes) and inexpensively (< $0.5 per SNP). Furthermore, because the equipment and reagents are readily accessible and portable, the researchers say that the device offers great potential for use at point-of-care settings, rather than being limited to a centralised laboratory.
The technology is also versatile and can be readily adapted to detect other SNPs, as the researchers showed previously when identifying drug resistance in tuberculosis mycobacterium from sputum and cardiomyopathy risk from blood. Although the device does not diagnose osteoporosis itself, it might help physicians identify people whom they should monitor more closely.
Study details
Generic Platform for the Multiplexed Targeted Electrochemical Detection of Osteoporosis-Associated Single Nucleotide Polymorphisms Using Recombinase Polymerase Solid-Phase Primer Elongation and Ferrocene-Modified Nucleoside Triphosphates.
Mayreli Ortiz, Miriam Jauset-Rubio, Ciara O’Sullivan, et al.
Published in ACS Central Science on 19 July 2023
Abstract
Osteoporosis is a multifactorial disease influenced by genetic and environmental factors, which contributes to an increased risk of bone fracture, but early diagnosis of this disease cannot be achieved using current techniques. We describe a generic platform for the targeted electrochemical genotyping of SNPs identified by genome-wide association studies to be associated with a genetic predisposition to osteoporosis. The platform exploits isothermal solid-phase primer elongation with ferrocene-labelled nucleoside triphosphates. Thiolated reverse primers designed for each SNP were immobilised on individual gold electrodes of an array. These primers are designed to hybridise to the SNP site at their 3′OH terminal, and primer elongation occurs only where there is 100% complementarity, facilitating the identification and heterozygosity of each SNP under interrogation. The platform was applied to real blood samples, which were thermally lysed and directly used without the need for DNA extraction or purification. The results were validated using Taqman SNP genotyping assays and Sanger sequencing. The assay is complete in just 15 min with a total cost of 0.3€ per electrode. The platform is completely generic and has immense potential for deployment at the point of need in an automated device for targeted SNP genotyping with the only required end-user intervention being sample addition.
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