Introduction

Prostate cancer (PCa) has emerged as the second most prevalent malignancy in the male genito-urinary system1, characterized by the uncontrolled proliferation of prostate cells2. Prostate-specific antigen (PSA) detection and quantification are essential biomarkers for early PCa screening and diagnosis3,4. However, PSA detection is hampered by its limited sensitivity and specificity, which results in false-positive outcomes and needless biopsy of individuals5,6. Therefore, it is thus essential to explore new biomarkers and develop efficient screening methods for PCa diagnosis.

Sarcosine (C3H7NO2), also called N-methyl glycine, is a natural non-essential amino acid in muscles and various body tissues7. It naturally occurs as an intermediate in the choline-to-glycine metabolic pathway and is produced from the synthesis and breakdown of glycine8. Sarcosine metabolizes into glycine through sarcosine oxidase9. Sarcosine levels vary from 1.4 to 0.6 µM in healthy blood and 2–10 µM in PCa patients10. Sarcosine elevated levels in blood serve as a potential biomarker for PCa detection. Its concentration increases in invasive prostate cancer cell lines compared to benign prostate epithelial cells. The sarcosine concentration in biological samples may surpass several micromoles depending on PCa aggressiveness11. Monitoring sarcosine levels can thus provide insights into PCa progression and severity.

The methods employed for sarcosine determination are GC-MS12, HPLC with fluorescence detection13, capillary electrophoresis14, differential mobility analysis15, chemiluminescence16, fluorimetry17, surface-enhanced Raman scattering (SERS) spectroscopy18, fluorescence spectroscopy17, enzymatic colorimetry, fluorometric methods19,20, enzyme-based21, immunoassay22, and electrochemical methods23. However, these methods have limitations such as time-taking, high cost, need of skilled operator, complex sample pretreatment, sensitivity to interferences, and reduced sensitivity. Electrochemical techniques have advantages of simplicity, swift response, sensitivity, linear range, cost-effectiveness, and miniaturization24. These sensors can identify biomarkers linked to disease diagnosis via in vitro or in vivo systems25,26.

The electrochemical sensors for sarcosine predominantly use sarcosine oxidase (SOx) due to its high specificity and catalytic activity. SOx facilitates sarcosine catalysis and transforms into glycine, formaldehyde, and hydrogen peroxide8,10. Few sarcosine biosensors are based on SarOx/CHIT/CuNPs/c-MWCNT/Au8, Sox/CHIT/GNRs/AuE27, and SOx/graphene/chitosan/AgNPs/GCE28. SOx immobilization onto the working electrode is essential in these biosensors. However, directly immobilizing enzymes on support causes denaturation and reduces enzyme activity and stability. Thus, an affordable, easily operatable, and selective non-enzymatic electrochemical sensor is needed for sarcosine detection.

This study proposes a reduced graphene oxide-cobalt nickel tungsten boron oxides (CoNiWBO/rGO) nanocomposite as a non-enzymatic electrochemical sensor for sarcosine. Cobal-based composites have been widely used in electrochemical applications, including sensors and supercapacitors29,30. The electrochemical parameters of sarcosine are evaluated using CoNiWBO/rGO through LSV, DPV, and EIS. Results indicate that the CoNiWBO/rGO nanocomposite functions as a non-enzymatic electrochemical sensor with remarkable attributes, i.e., higher conductivity, selectivity, stability, rapid analysis, and cost-efficacy in sarcosine sensing. The employment of novel sensing nanocomposite for sarcosine determination presents a leap forward in analyzing the fabricated compound´s potential.

Experimental

Chemicals and reagents

Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 99%), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 99%), sodium tungstate dihydrate (Na2WO4.2H2O, ≥ 97%), graphene oxide (GO), absolute ethanol, and sodium borohydrate (NaBH4) were purchased from Sigma Aldrich, USA. Dihydrogen potassium phosphate (KH2PO4, 98.5%) and monohydrogen potassium phosphate (K2HPO4, 98%) were used for preparing 0.1 M phosphate buffer saline (PBS). All chemicals used in the experiments were of analytical grade and employed without further purification.

Synthesis of CoNiWBO/rGO nanocomposite

CoNiWBO/rGO nanocomposite was synthesized using the chemical reduction method31. Briefly, 12 mM Co(NO3)2.6H2O, 6 mM Na2WO4.2H2O, 6 mM Ni(NO3)2.6H2O, and 40 mg GO were mixed in 60 mL absolute ethanol and stirred for 24 h. Subsequently, 20 mL NaBH4 (10 wt%) solution was added to the mixture and stirred for one hour. The black product (CoNiWBO/rGO) was collected, rinsed with deionized water and absolute ethanol, and air-dried for 24 h at 25 °C. CoNiWBO/rGO was calcinated at 500 °C under nitrogen for 2 h.

$$Co(NO_{3} )_{2} .6H_{2} O + Na_{2} WO_{4} ,2H_{2} O + Ni(NO_{3} )_{2} .6H_{2} O + GO + C_{2} H_{5} OH\mathop\rightarrow\limits^{ 25^\circ {\rm C} } CoWO_{4} /NiWO_{4} /GO$$
(1)
$$Co{WO}_{4}/NiW{O}_{4}/GO+Na{BH}_{4}\to\:CoNiWBO/rGO\:\left(Grey\right)$$
(2)
$$CoNiWBO/rGO\mathop\rightarrow\limits^{500^\circ {\rm C}} CoNiWBO/rGO \left( {Black} \right)$$
(3)

Electrode fabrication

The glassy carbon electrode (GCE) used in the study was sonicated in water and methanol for 15 min. Ten mg CoNiWBO/rGO was mixed with 5 mL deionized water to make a slurry. 10 µL of this mixture was applied to the working GCE and dried. The developed electrode was used for the experiments at the electrochemical workstation (CORRTEST-CS120 model) in the three-electrode system of Ag/AgCl as the reference electrode, glassy carbon (GC) as the working electrode, and Pt wire as the counter electrode. Electrochemical measurements were made at room temperature, including CV, DPV, LSV, EIS, and chronoamperometry (CA).

Optimizations for sarcosine detection

0.1 M PBS was used as an electrolyte solution. The sarcosine sensor CoNiWBO/rGO sensitivity was assessed by recording the oxidation current as a function of applied potential from − 0.1 to 0.94 V in 30 mL solutions of increasing sarcosine concentrations (0.1–50 µM). An electrochemical response of sarcosine was examined at pH of 7.8, 7.6, 7.4, 7.2, 7.0, and 6.8 in 0.1 M PBS.

Serum sample collection and processing

Blood samples of PCa patients were obtained from MINAR Cancer Hospital, Multan, Pakistan, with prior approval by the MINAR Ethical Committee. All procedures complied with the guidelines of the Ethical Committee of MINAR Cancer Hospital, Multan, Pakistan. The blood samples were collected from the volunteers with informed consent. Samples were centrifuged for 10 min at 4000 rpm to remove solid particulate matter and stored at − 20 °C before sarcosine detection. Potentiostat was used to determine sarcosine in serum samples of PCa patients.

Results and discussion

Characterization of CoNiWBO/rGO

X-ray diffraction (XRD), UV-Vis, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) are used to examine the chemical composition and morphology. XRD analysis of CoNiWBO/rGO is conducted on Bruker D8 Advance Powder Diffractometer in the diffraction range of 5°–80°. GO diffraction peak is observed at 10°32. The inter-atomic or d-spacing is calculated using Bragg’s law33.

$$\text{d}=\frac{\text{n}{\uplambda}}{2{\text{sin}}{\uptheta}}$$
(4)

The mean inter-atomic spacing of GO is 6 Å. XRD pattern of CoNiWBO/rGO does not reveal distinct peaks and thus indicates its predominantly amorphous nature (Fig. 1A)31. The absence of GO peaks confirms the complete reduction of GO to rGO by NaBH434.

The UV spectrum of CoNiWBO/rGO has an absorbance of 243 nm (Fig. 1B), which indicates the presence of metals in the prepared nanocomposite. The presence of cobalt and nickel in CoNiWBO/rGO is confirmed because of their absorbance in the UV range of 180 to 450 nm35. TGA reveals 6.5% weight loss at 100 °C corresponding to the elimination of water molecules in the nanocomposite (Fig. 1C). There is a minor weight loss of 7.2% at 153 °C. However, CoNiWBO/rGO exhibits 13.4% weight loss from 160 to 550 °C, indicating nanocomposite degradation at elevated temperatures.

Fourier transform infrared spectroscopy (FTIR) examined (Fig. 1D) and measured the composition of GO, CoNiWBO, and CoNiWBO/rGO in the mid-infrared range (4000–400 cm− 1). The peaks located at 3400 cm− 1 are attributed to the O–H bond, and the bands at 2925 cm− 1 and 1715 cm− 1 show the stretching of the C–H bond and C=O36, while the bands at the low wavelength region (400–1100 cm− 1) show stretching vibrations of the Ni–O, W–O, and Co–O bonds31. These results indicate that the absorption bands of the metal-oxygen bond are shifted and broadened and show that Ni, Co, and W elements were oxidized in the nanocomposites.

Fig. 1
figure 1

(A) XRD, (B) UV, and (C) TGA (D) FTIR graph of CoNiWBO/rGO.

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SEM analysis provides the nanocomposite morphology (Fig. 2A), where it has well-dispersed flower-like characteristics to indicate the reduction in CoNiWBO/rGO nanoflakes due to rGO. CoNiWBO/rGO displays a porous structure formed by the aggregation of nanosheets to attain significant pore volume and surface area. ImageJ software, specifically NIH version 1.52 g, examines the fiber diameters in CoNiWBO/rGO. An average particle size of 29 nm is found for the synthesized nanocomposite (Fig. 2B). The elemental composition of CoNiWBO/rGO is determined by energy dispersive X-ray (EDS) spectroscopy, and obtained results suggest that all representative elements (C, O, Co, Ni, W, and B) are present at an appropriate ratio (Fig. 2C). Atomic force microscopy (AFM) analysis of the synthesized composite suggests that particles exhibit a rougher surface (Fig. 2D).

Fig. 2
figure 2

(A) SEM image, (B) histogram for size distribution, (C) energy dispersive X-ray spectroscopy, and (D) atomic force microscopy of CoNiWBO/rGO particles.

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Electrochemical characterization of CoNiWBO/rGO

Electrochemical measurements characterize the synthesized nanocomposite through CV, stability, scan rate, chronoamperometry, and EIS studies in 40 mM K4[Fe(CN)6].3H2O and 0.1 M KCl solutions. No redox behavior has been observed at bare GCE and reduced graphene oxide modified electrode (rGO)/GCE (Fig. 3A). Whereas CoNiWBO shows redox potential, but prominent anodic (oxidation peak at − 0.08 V with a current of 1.34 mA) and cathodic (reduction peak at − 0.2 V with a current of − 1.07 A) potential is given by CoNiWBO/rGO. The reduction peak of CoNiWBO/rGO in electrolyte solution depicts the cathodic process, and the oxidation peak depicts an anodic process. The current densities of CoNiWBO/rGO are greater when compared with other electrodes, which indicates that the synthesized nanocomposite has an active site for the redox process and shows rapid electron transfer kinetics. CV curves exhibit distinct redox peaks. B2O3 does not show electrochemical activity in the composite. However, it has a buffering role in accommodating volume changes in the charge and discharge process. The following equations can represent the faradaic reactions of surface oxidation species of the nanocomposite37,38,39,40:

$${Co}_{3}{O}_{4}+{OH}^{-}+{H}_{2}O\:\leftrightarrow\:\:3CoOOH+{e}^{-}$$
(5)
$$CoOOH+{OH}^{-}\:\leftrightarrow\:Co{O}_{2}+{H}_{2}O+{e}^{-}$$
(6)
$${Ni}_{3}{O}_{4}+{OH}^{-}+{H}_{2}O\:\leftrightarrow\:3NiOOH+{e}^{-}$$
(7)
$$NiOOH+{H}_{2}O+{e}^{-}\leftrightarrow\:Ni(OH{)}_{2}+{OH}^{-}$$
(8)
$$WO_{3} + e^{ - } + 3H_{2} O \leftrightarrow [W(OH)_{6} ]^{ - }$$
(9)

CV analyses of CoNiWBO/rGO and bare GCE illustrate different electrochemical behaviors. Bare GCE acts as a baseline in this process. CoNiWBO/rGO depicts oxidation and reduction peaks with increased current densities, suggesting better electron transfer kinetics and increased reactivity. Comparison with the literature validates that the electrochemical behavior of CoNiWBO/rGO is superior31,41.

CoNiWBO/rGO performance is assessed through 100 electrochemical cyclic stability tests. Each cycle involves repetitive redox reactions at a scan rate of 30 mVs− 1 and potential window − 0.39 V to 0.11 V. CV analysis displays consistent redox peaks to affirm the nanocomposite stability (Fig. 3B). The material can thus sustain repeated redox reactions without notable decline in electrochemical performance.

Varying scan rates affect the redox behavior of CoNiWBO/rGO. CV responses are recorded with the scan rates from 30 to 100 mVs− 1 in a potential window of − 0.39 V to 0.11 V. The redox process involving CoNiWBO/rGO exhibits rapid electron transfer with increased oxidation and reduction currents at higher scan rates (Fig. 3C). The peak current reaches a maximum at a scan rate of 100 mVs− 1. A calibration plot shows a linear correlation between scan rate and peak current (Fig. 3D). CoNiWBO/rGO current increases linearly with the scan rate, and the oxidation peaks shift to higher potential while reduction peaks to lower potential, resulting in significant potential separation31.

Fig. 3
figure 3

The electrochemical response of CoNiWBO/rGO in 0.1 M KCl and 40 mM K4[Fe(CN)6] solutions, (A) conductivity, (B) stability, (C) conductivity at varying scan rates 30 mVs-1 to 100 mVs-1, and (D) calibration plot showing linear relationship between scan rate, and oxidation and reduction currents.

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Chronoamperometry (CA)

CA experiments are conducted on CoNiWBO/rGO to explore the nature of steady-state current. CA curve in Fig. 4A provides information about the electrode’s time-dependent behavior. Despite a minor initial decrease, the curve highlights the stability of CoNiWBO/rGO-modified GCE. The voltammogram indicates a stable current for 12 h to reflect the sustained electrochemical activity of the electrode.

Electrochemical surface area (ECSA) of CoNiWBO/rGO-GCE

ECSA measurements are carried out at scan rates of 30 to 100 mVs− 142. A graph indicates the linear relationship between current density and scan rates to determine ECSA (Fig. 4B). The line graph of ECSA has a slope of 0.0002 and R2 of 0.99 (Fig. 4C). The calculated ECSA for CoNiWBO/rGO-GCE is 0.1 cm2, which is higher than bare GCE, i.e., 0.073 cm2. This suggests a larger surface area for redox reactions and the overall electrochemical activity provided by CoNiWBO/rGO. Previous study indicates that the electrochemical performance is higher for CoNiWBO/rGO electrodes, as inferred from the CV curve and corresponding area43.

Fig. 4
figure 4

Cyclic voltammograms of CoNiWBO/rGO in 0.1 M KCl and 40 mM K4[Fe(CN)6] solutions, (A) Chronoamperometric response, (B) Electrochemical Surface Area (ECSA), and (C). ECSA line graph.

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Roughness factor (Rf)

Rf is defined as the ratio of the surface area of modified GCE (A2) to that of unmodified GCE (A1). It provides information on the changes in surface area resulting from electrode modification with CoNiWBO/rGO regarding oxidation phases and overall surface area dimensions.

$${R}_{f}=\frac{{A}_{2}}{{A}_{1}}$$
(10)

ECSAs of modified GCE (A2) and bare GCE (A1) are compared to determine Rf for CoNiWBO/rGO-GCE-modified electrodes. ECSA is 0.073 cm2 for bare GCE and 0.1 cm2 for CoNiWBO/rGO-GCE. Rf is calculated as 1.43 for CoNiWBO/rGO-GCE.

Electrochemical detection of sarcosine

The sarcosine molecule undergoes oxidation in the electrochemical sensing process at appropriate electrode potentials. Figure 5 illustrates the sarcosine response in electrochemical oxidation under alkaline conditions23.

Fig. 5
figure 5

Mechanism of sarcosine electrochemical oxidation.

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Incorporating rGO in CoNiWBO enhances the electrochemical detection of sarcosine via linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). The nanocomposite provides good electrical conductivity and higher working electrode surface area when employed on the electrode. There is swift electron transfer between the target analyte and electrode for improved response and lower detection limits. The sensor sensitivity for sarcosine is assessed by measuring current versus applied potential in various sarcosine concentrations.

Linear sweep voltammetry (LSV)

LSV measurements are conducted with and without sarcosine in 0.1 M PBS. No peak exists in the potential from − 0.1 to 0.94 V for a blank solution without sarcosine. CoNiWBO/rGO serves as the sensor. An oxidation peak with a current of 13.77 µA at 0.6 V is observed by introducing 0.1 µM sarcosine to the blank solution (Fig. 6A). Peak current is linearly related to sarcosine concentration having a high correlation coefficient, i.e., R2 = 0.99 (Fig. 6B)44.

The pH’s impact on the electrochemical behavior of CoNiWBO/rGO is tested through LSV in 0.1 M PBS. The oxidation peak current shifts from pH 6.8 to 7.8 with the apex at pH 7.4 (Fig. 6C). Figure 6D shows a line graph at different pH.

Fig. 6
figure 6

LSV findings of sarcosine detection in 0.1 M PBS (pH 7.4) by CoNiWBO/rGO with different parameters, (A) concentrations of 0.1, 10, 20, 30, 40, 50 µM, (B) line graph between sarcosine concentration and current, (C) pH of 7.8, 7.6, 7.4, 7.2, 7.0, 6.8, and (D) line graph between pH and current.

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Differential pulse voltammetry (DPV)

Differences in Faradaic current and rate of charging decay are measured by differential pulse voltammetry based on applying pulsed potentials within a linear potential scanning. The baseline for this study is developed by recording DPV under optimized conditions as 0.1 M PBS solution at room temperature without sarcosine. No oxidation peak is observed using CoNiWBO/rGO as an electrochemical sensor in the potential from − 0.1 V to 0.94 V at a scan rate of 30 mVs− 1. Distinct oxidation peaks are observed at 0.6 V upon adding 0.1 µM sarcosine (Fig. 7A). DPV curves are consistent with the sarcosine concentrations of 0.1 µM to 50 µM. The oxidation peak current and sarcosine concentration have a linear trend (Fig. 7B)45.

The pH’s impact on the electrochemical behavior of 50 µM sarcosine is determined (Fig. 7C). The lowest oxidation peak with a current of 5.5 µA is observed at pH 6.8, while the highest is at pH 7.4. Figure 7D shows a line graph at different pH.

Fig. 7
figure 7

Differential pulse voltammetry (DPV) response of CoNiWBO/rGO for sarcosine sensing in 0.1 M PBS with different parameters, (A) sarcosine concentrations of 0.1, 10, 20, 30, 40, 50 µM, (B) line graph between sarcosine concentration and current, (C) pH of 7.8, 7.6, 7.4, 7.2, 7.0, 6.8, and (D) line graph between pH and current.

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Electrochemical impedance studies on CoNiWBO/rGO

Bare GCE has the highest semicircle diameter and thus elevated ohmic resistance (Fig. 8A). This implies limited electrochemical conductivity, causing impedance to charge flow. CoNiWBO/rGO exhibits enhanced electrochemical conductivity compared to GCE. The smaller semicircle in the Nyquist plot signifies lower ohmic resistance. CoNiWBO/rGO enhances charge transfer kinetics at the electrode and electrolyte interface and promotes electron transport in the electrochemical process.

The impact of varying sarcosine concentrations (0.1 µM to 50 µM) on the impedance of the CoNiWBO/rGO electrode system is explored (Fig. 8B). The lowest impedance indicates optimal charge transfer and minimal ohmic resistance occurring at sarcosine concentration of 0.1 µM and the highest at 50 µM. The pH of PBS in sarcosine sensing affects CoNiWBO/rGO electrode system impedance (Fig. 8C). Electrode showing the smallest semicircle indicates minimum charge transfer resistance for sarcosine sensing at pH 7.4.

Fig. 8
figure 8

Nyquist plots showing electrochemical impedance studies of CoNiWBO/rGO, (A) in 0.1 M KCl and 40 mM K4[Fe(CN)6] solutions, (B) at sarcosine concentrations of 0.1, 10, 20, 30, 40 and 50 µM in 0.1 M PBS of pH 7.4, and (C) pH of 7.8, 7.6, 7.4, 7.2, 7.0, 6.8 in 0.1 M PBS.

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Heterogenous rate constant (Ko)

Ko is a redox reaction’s equilibrium constant which influences reaction kinetics. A higher Ko indicates rapid and sustainable equilibrium attainment compared to that with lower Ko. Ko is calculated from the following equation46.

$$\text{K}^\circ=\frac{\text{R}\text{T}}{{{\text{F}}^{2}{\text{R}}_{\text{a}\text{c}\text{t}}\text{A}\text{C}}}$$
(11)

where Ko is the heterogeneous rate constant, F the Faraday constant (96485 Cmol− 1), T the thermodynamic temperature (298.15 K), Rct the electron transfer resistance (6842 Ω for bare GCE, 4087 Ω for CoNiWBO/rGO-GCE, and 3245 Ω for sarcosine), R the general gas constant (8.314 Jmol− 1K− 1), A the electrode surface area, and C the KCl concentration (0.1 M). Ko is 53 × 10− 6 cms− 1, 65 × 10− 6 cms− 1, and 82 × 0− 6 cms− 1 for bare GCE, CoNiWBO/rGO-GCE, and sarcosine detection by CoNiWBO/rGO.

Exponential factor

The exponential factor is calculated by the following equation:

$$Exponential\:factor=\frac{RT}{{R}^{2}+(2pif\times\:\tau{)}^{2}}$$
(12)

where R is the charge transfer resistance, pi the circle’s perimeter ~ 3.14, f the frequency i.e., 0.01 Hz, and τ the time constant. τ = R × C where C is the capacitance. The exponential factor for CoNiWBO/rGO is 2.4 × 106, for bare GCE is 1.2 × 108, and for sarcosine detection is 1.3 × 108 at optimum pH and concentration (Rct for optimum pH and concentration are 5304 Ω and 7574 Ω).

Repeatability, selectivity, and stability of the sensor

The repeatability is examined by running seven measurements under the same conditions with 50 µM sarcosine in 0.1 M PBS. DPV (Fig. 9A) and LSV (Fig. 9B) experiments support the repeatability and stability of CoNiWBO/rGO as electrochemical sensor for sarcosine detection. The selectivity of CoNiWBO/rGO-GCE electrode is assessed in the presence of 50 µM interfering substances (uric acid, glucose, and creatinine) in 0.1 M PBS of pH 7.4. The electrode performance is unaffected by the presence of these substances (Fig. 9C and D).

Fig. 9
figure 9

(A) DPV and (B) LSV repeatability and reproducibility results of CoNiWBO/rGO-GCE from successive seven readings of 50 µM sarcosine detection in 0.1 M PBS. The electrochemical response of CoNiWBO/rGO-GCE in the presence of equal concentrations (50 µM) of interfering species like uric acid, glucose, and creatinine in 0.1 M PBS via (C) DPV and (D) LSV.

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Limit of detection (LOD)

LOD is the minimum detectable quantity of analyte. It depends on reaction parameters, analyte concentration, and the detection technique. LOD is determined by the following Eq. 

$${\text{LOD}}=\frac{3\text{s}}{{\text{m}}}$$
(13)

where LOD is the detection limit, ‘s’ the standard deviation, i.e., 0.004 and 0.01 for DPV and LSV, respectively, and ‘m’ the slope, i.e., 0.26 and 0.38 for DPV and LSV. The calculated LODs for sarcosine detection are 0.04 µM and 0.07 µM by DPV and LSV, respectively.

Sarcosine determination in prostate cancer patients

The objective of this study is to assess CoNiWBO/rGO for quantifying sarcosine in human serums of PCa patients and healthy persons. The serum samples are diluted fifty times using 0.1 M PBS of pH 7.4. In this study, 50 µM sarcosine is added into serum samples, and its concentration is determined by the linear relationship depicted in Figs. 6B and 7B. Results are presented in Table 2. Higher intensities are observed in PCa patients compared to control group (Fig. 10A and B). Sarcosine concentrations in PCa patients are ~ 3 times greater than healthy donors (Fig. 10). Table 1 displays recoveries to affirm the efficacy of modified sensor for sarcosine quantification in human serum.

Table 1 Recovery study of sarcosine from human serum of prostate cancer patients.
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Table 2 The comparison of recently reported non-enzymatic electrochemical sensors for sarcosine detection.
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Fig. 10
figure 10

(A) LSV and (B) DPV voltammograms of sarcosine detection in blood serum of prostate cancer patients by CoNiWBO/rGO.

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A detailed comparison with previously published literature is given in Table 2. Comparison suggests that the designed sensors exhibits enhanced electrochemical sensing performance than several previously reported sensors.

Conclusion

An economical non-enzymatic electrochemical sensor CoNiWBO/rGO was developed to determine serum sarcosine levels, in PCa affected individuals. The working electrode modified with CoNiWBO/rGO enhanced surface area, conductivity, and accuracy for detecting micro-molar concentrations of sarcosine. CoNiWBO/rGO was prepared by co-precipitation method, and morphological and structural analysis confirms the formation of 3D flower shaped CoNiWBO/rGO. The voltametric studies, i.e., LSV and DPV demonstrates that the proposed sensor exhibits higher selectivity and sensitivity for sarcosine detection, while chronoamperometric studies shows stability of the developed sensor. The results demonstrate wide linear range from 0.1 to 50 µM and low limits of detection, i.e., 0.04 µM and 0.07 µM for DPV and LSV, respectively. The optimized sensor for sarcosine can be appropriate to screen PCa in labs via this biomarker, as it is superior to prostate specific antigen (PSA). This sensor in future can be employed as point of care devices, robotics, and automations as it depicts higher reproducibility and recovery.