Low-Cost Saliva-based Biosensor For Cancer Detection

More and more biomarkers that can help in the early diagnosis of diseases like cancer are being discovered every year, but often the effective application relies on having diagnostic methods that are both affordable and as least invasive as possible. This is definitely true in the case of breast cancers, where the standard diagnostic method after seeing something ‘odd’ on a scan is to perform a biopsy so that a tissue sample can be tested in a laboratory. What [Hsiao-Hsuan Wan] and colleagues demonstrate in a recently published research article in the Journal of Vacuum Science & Technology B is a way to use saliva on disposable test strips to detect the presence of cancer-related biomarkers. Best of all, the system could be very affordable.

The two biomarkers tested in this experiment are HER2 (in 10 – 30% of breast cancer cases) and CA 15-3, both of which are indicative of a variety of cancers, including breast cancers. According to the researchers, the levels of these biomarkers in saliva can be correlated to those in blood serum. Where other biosensors may include the read-out circuitry – making those disposable and expensive – here the disposable part is the test strips which are plated with electrodes.

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(a) Output drain voltage waveform for pure artificial saliva and HER2 protein diluted in saliva from 10−7 to 10−15 g/ml. (b) Output digital reading from PCB under different HER2 protein concentrations. (Credit: Wan et al., 2024)

” data-medium-file=”https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg?w=400″ data-large-file=”https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg?w=700″ class=”size-medium wp-image-664203″ src=”https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg?w=400″ alt=”(a) Output drain voltage waveform for pure artificial saliva and HER2 protein diluted in saliva from 10−7 to 10−15 g/ml. (b) Output digital reading from PCB under different HER2 protein concentrations. (Credit: Wan et al., 2024)” width=”400″ height=”153″ srcset=”https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg 700w, https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg?resize=250,96 250w, https://hackaday.com/wp-content/uploads/2024/02/023202_1_6.0003370.figures.online.f2.jpeg?resize=400,153 400w” sizes=”(max-width: 400px) 100vw, 400px”>

(a) Output drain voltage waveform for pure artificial saliva and HER2 protein diluted in saliva from 10−7 to 10−15 g/ml. (b) Output digital reading from PCB under different HER2 protein concentrations. (Credit: Wan et al., 2024)

Each test strip is processed by exposing it to monoclonal antibodies for the target biomarker. When the resulting strip is then exposed to a series of pulses, any antigen-antibody complexes will stretch and contract, causing a measurable change in the electrical signal. This signal is then amplified by a MOSFET, after which the data can be analyzed. According to the reported results, the experimental results matched with the (anonymized) samples from both healthy volunteers and patients with breast cancer.

Whether a saliva-based test like this will replace most biopsies remains to be seen, but if the saliva-blood serum correlation holds up in further testing, it might provide a quick and non-invasive way to test for these and other biomarkers, whether for cancer or other diseases.

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