Smartphone-Assisted Detection of Homocysteine in Serum Using Boron–Nitrogen Co-doped MXene and MWCNTs

Chronic illnesses such as cardiovascular disease (CVD) are currently among the biggest risks to human health. The accumulation of homocysteine (Hcy) can result in platelet disorders, vascular damage, smooth muscle swelling, and ultimately occlusive thrombus development, all of which raise the risk of CVD. Hence, the sensitive and selective detection of Hcy, a critical biomarker for cardiovascular disorders, is vital for early diagnosis and clinical monitoring. In this study, we created an electrochemical sensor for the detection of Hcy using an electrode modified with a nanohybrid comprising boron–nitrogen (B–N) codoped MXene (BNM) and multiwalled carbon nanotubes (MWCNTs). The codoping of B and N increases the dispersion of MXenes, greatly expanding the effective surface area and giving a large number of electroactive sites for MWCNTs, while MWCNTs enhance electrocatalysis and inhibit restacking. Thus, both materials in conjunction can result in superior electrochemical properties. Under optimized conditions, the developed sensor exhibited excellent efficiency for Hcy detection, with a wide linear range of 2.5–400 μM, which covers the normal as well as clinical range. It possesses a detection limit of 0.39 ± 0.02 μM and a response time of 2.6 ± 0.14 s. The sensor demonstrated high selectivity in the presence of common interfering species and excellent reproducibility and stability, making it suitable for practical applications. Furthermore, the smartphone application “HomoCysCheck” was developed to rapidly calculate Hcy concentrations and distinguish between safe and unsafe levels in real samples. This work provides a simple and rapid detection platform for Hcy, offering significant potential for use in point-of-care applications.