Poster W12 - Rapid and sensitive B-type natriuretic peptide detection using a battery-free electrochemical sensing device at the point of care

Introduction: Heart failure contributes to about 36% of all cardiovascular disease deaths [1]. About one-third of the adult population in the U.S. without noticeable heart failure symptoms is at risk for developing heart failure (Stage A HF). Additionally, between 24% and 34% are in a pre-heart failure stage (Stage B HF) [2]. Monitoring biomarkers secreted in the blood is one solution for early-stage detection of heart failure and can also be used to help manage symptoms more effectively. One such biomarker doctors often use to indicate whether a person is experiencing heart failure alongside other tests is the B-type natriuretic peptide (BNP) [3]. Conventional testing for BNP necessitate clinical assistance for blood collection at the hospital and experts to perform the analysis. There are a few commercial point-of-care tests, such as the i-STAT but these are typically too expensive for patient use at nearly $50 per test [4]. So, there is an opportunity for an affordable sensing technology to continuously monitor BNP biomarker for both clinical and patient use at the point of care. Here, we present a portable, handheld device to facilitate self-monitoring and management of BNP. The portable device utilizes electrochemical sensing to measure the level of BNP and has been tested in buffer and blood serum samples. The device is powered wirelessly via a smartphone using near-field communication (NFC) technology. The electrochemical sensor has the potential to offer a cost-effective and portable platform for monitoring BNP of patients, thus contributing to the personalized management of heart failure.

Materials and

Methods: The electronic system of the handheld device comprises a potentiostat sensor with an NFC type 2 tag (SIC4341, Silicon Crafts Technology) and an antenna for wireless communication with a smartphone via Near Field Communication. Figure 1a-1d shows the design, 3D view, and photos of the circuit board, which measures approximately 4 cm × 5 cm. The circuit board is housed within a 3D-printed casing. Commercially available screen-printed electrochemical cells with a three-electrode system are utilized for analysis. The electrode surfaces are prepared by washing and connecting them to a Gamry 1010e potentiostat. Gold deposition on the electrodes with an Ag/AgCl reference is conducted by applying 5 mM gold (III) chloride trihydrate (Sigma Aldrich) in a 0.5 M H2SO4 solution, using an amperometric technique for electrochemical characterization (voltage range: -0.4 to +0.4 V; sensitivity: 10-4). Surface modification is achieved by forming a self-assembled monolayer of MUA/MCH (0.5 mM/1 mM) (Sigma Aldrich) in 200-proof ethanol, followed by EDC/NHS (25 mM/25 mM) (Thermo Fisher) coupling in 25 mM MES buffer at pH 7.4. Subsequently, BNP antibodies (Santa Cruz) in PBS solution are conjugated to the functionalized electrode surfaces. After functionalization, 0.1% BSA is used for blocking purposes. Testing of BNP at different concentrations is conducted with differential pulse voltammetry using a 1 mM potassium ferricyanide solution in 1X PBS. We are also working on developing a smartphone application to operate and calibrate the potentiostat, perform electrochemical analysis, and display the concentration of the solution being analyzed.

Results, Conclusions, and Discussions: Results and

Discussion:
Initially, the device was tested with different concentrations of ferricyanide solution using differential pulse voltammetry (DPV) analysis, and the results were validated against a standard electrochemical station. Comparison of DPV analyses, demonstrates a similar trend, thus confirming the sensor's ability to perform precise electrochemical measurements (Figure 1e and 1f). The results presented in Figure 2a show that modified surfaces exhibit a distinct peak in the DPV profile for functionalization. The DPV profiles for varying concentrations of BNP antibodies are illustrated in Figure 2b, depicting an optimal concentration of 25 µg/mL antibodies on the electrode surface for measuring 1 pg/mL BNP. The testing of the sensor’s sensitivity across a broad dynamic range (1 pg/mL to 1000 pg/mL) is depicted in Figure 2c, revealing a gradual peak rise with increasing BNP concentration in 1X PBS. The sensor’s calibration plot shows a clear relationship between DPV peak current values and BNP concentrations (Figure 2d). Further experiments on BNP sensing in serum demonstrated similar results to those tested in 1X PBS. Subsequent tests at lower BNP in serum samples (1 pg/mL to 300 pg/mL) revealed an increasing trend in current with rising BNP concentrations (Figure 2e and 2f). The calibration plot acquired by the portable device equipped with a potentiostat establishes a high correlation between varying concentrations of BNP samples, particularly at the lower concentrations, but the assay will need to be further optimized to more accurately cover the broad dynamic range beyond 50 pg/mL needed for age-adjusted BNP [5].

Conclusion:
This work focuses on developing a portable, easy-to-use device for eventual cost-effective point-of-care testing of BNP concentration to monitor heart failure at an early stage. The electrodeposition of gold nanoparticles on screen-printed electrodes significantly increased their electrochemical activity and sensitivity. Conjugation and functionalization techniques for antibodies specific to BNP were optimized, further enhancing the system's high sensitivity in the lower concentration ranges. Successful testing of the device was shown in both PBS and serum. Future work includes conducting protein interference analysis, expanding the sensitivity at the higher dynamic range, and testing with clinical samples to validate this diagnostic platform further.

Acknowledgements (Optional):

References:
[1] “Heart Failure Facts & Information.” Accessed: May 11, 2024. [Online]. Available: https://hfsa.org/patient-hub/heart-failure-facts-information
[2] B. Bozkurt et al., “Heart Failure Epidemiology and Outcomes Statistics: A Report of the Heart Failure Society of America,” J. Card. Fail., vol. 29, no. 10, pp. 1412–1451, Oct. 2023, doi: 10.1016/j.cardfail.2023.07.006.
[3] D. C. C. Lin, E. P. Diamandis, J. L. Januzzi, A. Maisel, A. S. Jaffe, and A. Clerico, “Natriuretic Peptides in Heart Failure,” Clin. Chem., vol. 60, no. 8, pp. 1040–1046, Aug. 2014, doi: 10.1373/clinchem.2014.223057.
[4] Abbott Point of Care Reagent i-STAT® Cardiac Marker / Immunoassay B-ty – Axiom Medical Supplies
[5] “What Is a BNP Test? Normal, High, and Levels” Accessed: May 14, 2024. [Online]. Available: https://www.medicinenet.com/bnp_test/article.htm