Rapid Near-Patient Impedimetric Sensing Platform for Prostate Cancer Diagnosis

Abstract

With the global escalation of concerns surrounding prostate cancer (PCa) diagnosis, reliance on the serologic prostate-specific antigen (PSA) test remains the primary approach. However, the imperative for early PCa diagnosis necessitates more effective, accurate, and rapid diagnostic point-of-care (POC) devices to enhance the result reliability and minimize disease-related complications. Among POC approaches, electrochemical biosensors, known for their amenability and miniaturization capabilities, have emerged as promising candidates. In this study, we developed an impedimetric sensing platform to detect urinary zinc (UZn) in both artificial and clinical urine samples. Our approach lies in integrating label-free impedimetric sensing and the introduction of porosity through surface modification techniques. Leveraging a cellulose acetate/reduced graphene oxide composite, our sensor's recognition layer is engineered to exhibit enhanced porosity, critical for improving the sensitivity, capture, and interaction with UZn. The sensitivity is further amplified by incorporating zincon as an external dopant, establishing highly effective recognition sites. Our sensor demonstrates a limit of detection of 7.33 ng/mL in the 0.1-1000 ng/mL dynamic range, which aligns with the reference benchmark samples from clinical biochemistry. Our sensor results are comparable with the results of inductively coupled plasma mass spectrometry (ICP-MS) where a notable correlation of 0.991 is achieved. To validate our sensor in a real-life scenario, tests were performed on human urine samples from patients being investigated for prostate cancer. Testing clinical urine samples using our sensing platform and ICP-MS produced highly comparable results. A linear correlation with R² = 0.964 with no significant difference between two groups (p-value = 0.936) was found, thus confirming the reliability of our sensing platform.

Figure 1

Schematic images of the (a) chemical structure and interaction between CA/r-GO and zincon/UZn and (b) surface modification process of modified sensing platform with the CA/r-GO composite, zincon, and introducing UZn solution.

Figure 2

SEM image of the modified sensing platform without (a), with CA/r-GO modification (b), and after introducing zincon functionalization on the surface of the modified sensing platform (c). EDX analysis of the porous modified sensing platform with zincon (d), N (e) and S (f) elements individually and following the addition of UZn to the surface of the modified sensing platform (g). Also, the reduction in density of N (h) and S (i) elements is observed after the introduction of UZn.

Figure 3

EIS measurement of different concentrations of UZn from 0.1 to 1000 ng/mL for 10 mHz to 10 kHz range of frequency, when applying 10 mV input voltage. (a) Nonfaradaic Nyquist plot, Bode plot (b), phase plot angle indication of the alteration in both resistive and capacitive domains, at high frequencies toward low frequencies (c) and capacitance vs frequency (d). The nonlinear calibration curve (e) is illustrated; also, the inset image presents the calibration curve of the normalized value of different UZn levels in lab-based samples in its linear range. Selectivity of the sensing platform during the differentiation between Cu²⁺, Zn²⁺, and the mixture solution of Cu²⁺/Zn²⁺ (f) and the repeatability of the modified sensing platform after running EIS measurement seven times (f) are demonstrated. All measurements are rigorously executed at a pH of 9.8. This specific pH setting is meticulously selected due to its alignment with the optimal pH range for the UZn/zincon complex, spanning from 9.5 to 9.8. Within this range, the complex exhibits its peak performance in terms of effective molar absorption coefficients, rendering it ideal for our analytical purposes. Repeatability (g) and stability (h) of the modified porous electrode are presented.

Figure 4

Image of CA/r-GO/SPCE modified with zincon (a), schematic representation of the one-step electrochemical regeneration process on the modified sensing platform (b), and Nyquist plot of the functionalized and regenerated electrode (c). Correlative analysis of measurements obtained from the CBR material (d) and clinical samples (e). Scattered plot depicting the detection of UZn from both ICP-MS and the sensing platform results (f).