Refractometric Sensing of Protein in Urine by the Photonic Crystal Fiber Biosensor in THz Regime

Rahman, Md. Moshiur; Mou, Farhana Akter; Bhuiyan, Mohammed Imamul Hassan; Islam, Mohammad Rakibul

doi:https://doi.org/10.1155/2023/6652333

International Journal of Optics

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Abstract Introduction Results Conclusion Data Availability Conflicts of Interest References Copyright Related Articles

Research Article | Open Access

Volume 2023 | Article ID 6652333 | https://doi.org/10.1155/2023/6652333

Refractometric Sensing of Protein in Urine by the Photonic Crystal Fiber Biosensor in THz Regime

Md. Moshiur Rahman,¹Farhana Akter Mou,¹Mohammed Imamul Hassan Bhuiyan,²and Mohammad Rakibul Islam³

Academic Editor: Li-Ming Si

Received03 Jun 2023

Revised22 Sept 2023

Accepted17 Oct 2023

Published26 Oct 2023

Abstract

The presence of albumin in human urine is one of the confirmed early symptoms of kidney dysfunction. A precise urine protein identification process is very important to monitor the kidney’s proper functioning. To identify the presence of albumin in urine, a refractometric protein sensing approach in the photonic crystal fiber (PCF) environment has been introduced here. A PCF geometry with suspended cladding and a circular hollow core has been proposed and investigated in the terahertz (THz) spectrum for protein identification in the liquid samples. Three levels of albumin concentrations in urine (7–125 mg/dl, 250–500 mg/dl, and 1000 mg/dl) are considered to evaluate the sensing performances of the proposed PCF. The numerical investigations are performed on the COMSOL Multiphysics platform where the finite element method (FEM) figures out the numerical outcomes. The performances of the proposed PCF exhibit highly sensitive characteristics for albumin identification in the different albumin concentration levels of urine. The sensitivity shows more than 98.5% for all the tested concentration levels due to the strategic selection of geometrical parameters and proper optimization. Alongside, negligible confinement loss of 10⁻¹⁶ cm⁻¹ is attained at the same operating point of 4.3 THz. Furthermore, dispersion profiles and practical implementation strategies are also investigated and discussed in detail.

1. Introduction

The kidneys are the vital organ in the body located in the back on either side of the vertebral column. These two bean-shaped organs are responsible for getting rid of waste products, drugs, and toxins through urine, balancing the body’s fluids, controlling the production of red blood cells, producing an active form of vitamin D, etc. So, maintaining kidney health is very significant because its performance disturbance creates an overall health disorder and even may lead to death. Regular monitoring of the kidney’s functionality is very urgent because there are no visible symptoms of kidney disorders until they are damaged. If the kidney disorder can be traced and treated early, it may be possible to stay away from any kind of worse. A blood creatinine or urine protein test can assess the kidneys’ functioning situations [1, 2].

Normally, albumin is present in the blood. The kidneys filter the blood to conserve the blood proteins and dispel waste products. The waste products are closed in urine, and the blood proteins like albumin stay in the blood vessels. If the presence of albumin is found in the urine, it definitely is an initial sign of a kidney’s abnormality that is called albuminuria or proteinuria. The functioning situation inside a healthy kidney and albuminuria conditions are displayed in Figure 1. This figure interprets that when the kidneys are performed properly, virtually no albumin is leaked into the urine. On the contrary, if the kidneys end up damaged or diseased, they will lose their competence to conserve albumin. So, albumin identification in the urine can be an effective way to trace an early kidney infection.

An incredible pace in the sensor field has emerged in the modern photonic technology after the invention of novel photonic crystal fiber (PCF). Recently, PCF has proved its potential in the sensing platform due to its highly promising guiding features, versatile diversity for applications, and faster response with precise results for detection approaches, which are an insurmountable difficulty for conventional optical fiber. The most remarkable acquisition of the PCF sensor is that it allowed greater freedom for geometrical arrangement. The optical behaviors of PCF biosensor can be modified for precise functioning by tuning the geometrical parameters such as the pattern, size, and shape of air holes [3, 4]. In addition, the PCF sensor has achieved the highest level of acceptance due to the higher sensitivity, small size, low cost, robustness, and more flexibility [5–8]. Furthermore, SPR-based PCF biosensor has a good potential for detecting biological components with high accuracy [9–14]. For these attractive features and precise level of performance, the PCF sensor has already shown evidence of its potentiality by furnishing the versatile strategies for applications in the sensing field such as chemical sensing [15], gas sensing [16], biosensing [17], RNA and DNA analysis [18, 19], genetic diagnostics [20], cancer diagnosis [21], humidity and temperature sensing [22, 23], as well as for low-loss waveguiding [24, 25] in the terahertz range. Terahertz technology already has shown numerous breakthroughs in various fields, especially biological sensing and it allows the measurement of dispersion and losses [6, 7, 7–15, 24, 25]. Highlighting the unparalleled features of this highly active area of science, we focused on developing rapid and convenient biosensors, considering the existing challenges and strategies.

Already, several pieces of research have been able to prove the potentiality of PCF devices in biosensing applications. Ahmed et al. designed a PCF geometry for blood constituent detection [7]. Nearly 80% sensitivity is achieved for all the tested blood components with negligible confinement loss. Another PCF structure has been proposed by Hossain and Podder [26] for blood component identification in the THz regime. This proposed hollow core geometry attained more than 90% sensitivity for RBCs, plasma, WBCs, hemoglobin, and water detection cases. Elhelw et al. proposed a PCF-based biosensor for blood bilirubin detection in the THz platform. A high-sensitive performance has been attained from the proposed PCF sensor with 98% sensitivity [27]. A topas-based PCF biosensor for blood cells detection has been proposed by Kumar et al. [28]. Glucose, plasma, WBC, and RBC have been considered as targeted analytes to evaluate the performance of their proposed decagonal solid-core PCF sensor. Almost 90% sensitivity is achieved for all the tested cases. A PCF biosensor has been proposed by Chopra et al. [29] for detecting molecules in biological samples and identifying different diseases. Cancerous cells, diabetes-affected cells, and different blood constituents are effectively identified in this work. A hexa-sectored square photonic crystal fiber sensor has been proposed by Assaduzzaman et al. for blood serum and plasma identification [30]. The proposed PCF sensor renders highly sensitive performance for both analyte identification cases with extremely low confinement loss and higher birefringence. For detecting the blood cholesterol, an octagonal-shaped hollow core-structured PCF has been presented by Rahman et al. [31]. Their developed PCF biosensor renders significant improvements in biological substance detection. Their proposed PCF attained 98.75% sensitivity for cholesterol detection in the THz spectrum that indicates the PCF devices have a huge potential in biosensing areas. The research works discussed above have some drawbacks such as improper core-cladding geometry, use of complex core-cladding structure, absence of crucial optical properties evaluation, higher losses, and lower sensitivity, whereas in general the issue of fabrication for practical implementation is not properly elaborated. Thus, there is ample scope to improve the performance of PCF through proper geometry selection and a simpler core-cladding structure. Besides, to the best of our knowledge, protein detection in urine concentration by a PCF sensor in the THz spectrum was not investigated before. Since PCF devices have been shown to be effective in the detection of various biological elements, there is a huge potential to develop a fabrication-friendly PCF platform with a high detection capability of protein in urine.

In this article, a circular hollow core PCF geometry has been proposed for protein detection in urine which will be applicable to identify the early kidney’s dysfunctions. This proposed PCF geometry is investigated in the THz spectrum by adding different levels of albumin concentration in urine. The sensing performances of the proposed PCF render more than 98.5% sensitivity with an extremely low confinement loss of 10⁻¹⁶ cm⁻¹ at 4.3 THz operating conditions. A fabrication-friendly PCF structure development that is applicable for biosensing applications through proper design optimization that can identify the presence of protein in urine with higher sensitivity and low losses is the key aim of this research.

2. Design Methodology of the Proposed PCF Geometry

Considering the dominance profile of the PCF platform for chemical sensing, evanescent substances, and biological detection, several PCF geometries have been proposed over the last decades. Square [32], circular [7], hexagonal [33], rhombic [34], pentagonal [35], octagonal [36], etc., have been developed and tested for different substances identification in the THz spectrum. The performance of existing PCF in sensing cases indicates that microstructured fiber can be a potential solution for sensing applications. The sensing performances of PCF devices are mostly dependent on geometrical arrangements. The geometrical arrangements of the proposed PCF are displayed in Figure 2 with the amplified view of the core, and the 3D view of developed PCF is presented in Figure 3 for better visualization. A horse-wheel-like, simple PCF geometry is developed for the biosensing applications. A circular-shaped core is considered to form the PCF core for minimizing fabrication complexity. The hollow core which is circular-shaped is constructed to enhance the interactive area of the targeted substance and light intensity. Alongside, it also helps to minimize the background material requirement that also facilitates reduction in absorption loss. Most of the previously developed PCF geometry is considered nearly 300 μm in core diameter and 3000 μm in total diameter of the sensor to investigate in the THz spectrum in case of sensing [7, 26, 28, 32–36]. For comparison of our investigated results with previously designed PCF, a 3000 μm total sensor diameter with a PML of 250 μm has been considered. 160 μm core radius r_c is considered as optimum after setting the core size at several points in the range of 145 μm to 175 μm. The core hole radius is indicated by r_h which is fixed at 152.5 μm considering the strut width of 7.5 μm. At the abovementioned geometrical conditions, the developed PCF exhibits improved sensing properties such as sensitivity, confinement loss, dispersion, effective material loss, etc. The optimized geometrical parameters are listed in Table 1. Strut width can be defined here as the material width between the core hole and the cladding hole. The strut in the cladding area indicates that the separation area between two adjacent holes is also considered the same as the core strut. A symmetrical circular manner 60° sectoring cladding structure is designed considering the fabrication complexity. Targeted stuff concentration has been applied in the core hole, and dry air is considered in the cladding holes for this investigation. Note that a small size sectoring angle will increase the number of cladding holes with lower dimensions which will increase the complexity due to the higher number of holes that need to be implemented with lower dimensions. On the other hand, a higher sectoring angle will minimize the number of holes in the cladding with large dimensions that will decrease the mechanical strength of the fiber. The lower size of the sectoring angle will increase the material requirements and enhance the material absorption probability which will slightly affect the sensitivity. Considering all the mentioned above, we have achieved better results at a 60-degree sectoring cladding structure considering all the necessary optical properties evaluated in this literature.

Usually, several polymer materials can be strong candidates as host material. Because of a higher absorption loss of polymethyl methacrylate (PMMA) and teflon, these are not considered in this case. Zeonox and Topas are the two-dominant postulants in this area with similar absorption losses (∼0.2 cm⁻¹), high glass transition points, high light transmission (91%), avoidable material dispersion, material insensitivity, etc. [37]. As per the experimental evaluation of Zeonox and Topas, there are no significant differences between them in almost all the tested properties cases [37, 38]. So, any of these can be well suited for PCF devices. In this investigation, Topas was chosen as background material. For absorbing the incident radiation produced by the light source, a perfectly matched layer has been used as an antireflecting layer in the outer region of the fiber.

3. Results and Discussions

To design the PCF geometry and analyze the sensing properties of the developed PCF, the most powerful computational technique, the finite element method has been utilized in the COMSOL Multiphysics v. 5.3a environment. Because of its lower computational time and complexity, PDE solution ability makes it the best of the other techniques for optical devices. Several steps are involved in the designing, and analysis of the proposed PCF sensor which is shown in Figure 4. At first, global variables (GVs) and structure variables (SVs) were specified in the Comsol software. After that, the geometry of the PCF was designed as per the plan. The materials of the different parts of the PCF were assigned such as topas in the strut, air in the cladding holes, and targeted analytes in the core section. The PCF meshed after setting the boundary and initial conditions for solving the differential equations. The resulting optical parameter data was collected and exported into the MATLAB software for further analysis. Necessary optical property data was observed and investigated to determine the relationship between frequency and different optical properties. If the results were not satisfactory, geometrical specifications were adjusted to the GVs and SVs, and the process was repeated until a satisfactory or desired outcome was attained. For attaining better accuracy extra-fine element size is maintained in the simulation process. The partial meshing condition of the proposed PCF is shown in Figure 5. The complete mesh of the proposed geometry consists of 46992 domain elements and 2830 boundary elements with a minimum element quality of 0.4599.

The interactive situation of targeted substances, and light intensity is presented in Figure 6 with the intensity scale in x-polarization mode. Because of the symmetrical arrangement in the cladding region with hollow core settlement both polarization modes render the same behavior. From this figure, it is clearly visualized that the interactive area is closely localized in the core area, and the light pulse and targeted substance have strongly interacted. Contrariwise, inconsequential interaction in the cladding region is noticed.

(a)

(b)

(c)

The refractive index of a substance is defined as the ratio of the velocity of light in a vacuum to the velocity of light in a certain bulk medium for a particular frequency. It is noticeable that there is no significant difference between the refractive index (RI) and the effective refractive index (ERI). Only the basic distinction for ERI is the ratio of the speed of light in a vacuum to the speed of light in the bulk media for a certain polarization in the direction of propagation in the guiding phenomenon. The effective refractive index can be estimated by the following expression [7].where β_pm is the propagation constant for a given mode and polarization, p is termed as the polarization (TE or TM), and m is the m^th mode of the given polarization, while the wave-number (k₀) in free space for a particular frequency is found by , where λ₀ denotes the wavelength in free space, and ν the frequency in all media.

On the basis of the core cladding refractive index, the refractometric PCF biosensor can sustain the light-matter interaction either by the photonic bandgap (PBG) technique or by the modified total internal reflection (MTRI) process. Because of the choise of suspended cladding with a higher air filling fraction and hollow-type core in this proposed work, the light-matter interaction is maintained by the PGB process in this case.

The response of the effective refractive index of the proposed PCF for different levels of albumin concentration in urine with respect to frequency is presented in Figure 7. In general, in the THz regime, the effective refractive index of PCF devices increases with the augmentation of frequencies that facilitates higher optical power interaction. The presented ERI response of the proposed PCF also exhibits the same manner, and this kind of behavior enhances higher-sensitivity responses.

The relative sensitivity is the key property of a sensor to assess the sensing performances of a PCF-based sensing device. The relative sensitivity coefficient expresses a clear notion about the interaction of light with the targeted samples. The amount of light-matter interaction is measured by the absorption coefficient at a certain frequency. The main concern for evaluating the sensing performance of the proposed PCF is to calculate the relative sensitivity. It can be expressed by the following equation [7]:where is the refractive index of the targeted analyte (here, = 1.335 for 7–125 mg/dl, = 1.336 for 250–500 mg/dl, = 1.337 for 1000 mg/dl) [2, 37], is the modal refractive index, and the relative sensitivity coefficient is expressed by r and p is the amount of light-matter interaction. It is calculated by [7]where E_x and E_y and H_x and H_y are the electric field and magnetic field components, accordingly.

The sensing capability of the developed PCF for protein identification as a function of frequency is presented in Figure 8. Three concentration levels of protein in urine are considered for evaluating the sensitivity of the proposed PCF. The proportion of sensitivity mostly depended on the refractive index of targeted analytes at a fixed design parameter and a certain operating region. Changes of the refractive index for different concentration levels are very tiny, as a result, the rate of sensitivity seems to be the same for all the samples. But the deviations are shown in the enlarged view of the figure. With the augmentation of frequency, light intensity strongly interacts with the targeted analytes which enhances the sensitivity. At a certain frequency, the light-matter interaction reaches its maximum level, after that the sensitivity starts to decline. It can be clearly explained that from Figure 8, at 4.3 THz operating points, the proposed PCF renders maximum sensitivity, and the proportion is 98.576% for 7–125 mg/dl albumin concentration, 98.591% for 250–500 mg/dl, and 98.607% for 1000 mg/dl concentration which is better than many of the existing works for similar application. On an average, the proposed PCF sensor exhibits 10% higher sensitivity than available in the recent literature [6, 7, 26–31].

Sensing performances can be controlled by regulating the geometrical parameters. The sensitivity of the presented PCF for protein detection by changing the core radius and strut size is shown in Figures 9 and 10, respectively. A higher core size raises the possibility of a light interaction area with the matter which helps to improve the sensing response. On the other hand, the descending values of strut have a similar impact in improving the sensitivity. The scenario of these observations is nicely visualized in Figures 9 and 10. Very insignificant sensitivity variations of 0.1% are observed compared to the optimum conditions for every 5 μm core radius changes. On the contrary, nearly 0.75% sensitivity is varied for each 1.5 μm strut size change. Alongside, it is a reality that during fabrication, maintaining an exact optimum geometrical situations is a big challenge. Considering this fact, the sensitivity of presented PCF for protein detection in urine concentration is listed in Table 2 by changing ±2% and ±5% geometrical parameters. It can be expressed that from Table 2, the impact of these geometrical variations on sensitivity is very insignificant. The subtlety of geometries can be varied up to 5% without any significant consequences.

Confinement loss (CL) is another crucial parameter of the optical device in biosensing applications. It is the competency of the sensor to resist the optical power spreading within the nominated low-loss core region. CL arises from the imperfection of the geometrical structure and the leaky nature of the modes, calculated by the imaginary part of the propagation constant as [7, 32, 34].where c stands for light velocity in vacuum, and Im(n_eff) specifies the complex part of the propagation mode, and f is the working frequency.

Dispersion is one of the momentous parameters for the optical properties, which is a quantitative analysis of the spreading light pulses when the light pulses have interacted through an optical fiber. The dispersion property of a fiber can be characterized by the following equation [27, 36]:where is the angular frequency, is the dispersion parameter, and is the effective refractive index of the material.

The variations of confinement loss for different concentrations of albumin have been demonstrated in Figure 11 with the shifting frequency. Due to the ascending manner of frequency, the propagated optical signal compactly passes inside the core region that has an impact on increasing sensitivity. It indicates that when the frequency acts in an incremental nature, the mode fields constrict more strictly towards the hollow core area, and hence, the CL curves exhibit a descending nature for the high level of frequency that neatly signifies in Figure 11. At optimal frequency conditions, the CL is investigated at 8.3 × 10⁻¹⁶ cm⁻¹, 1.07 × 10⁻¹⁶ cm⁻¹, and 3.37 × 10⁻¹⁷ cm⁻¹ for (7–125 mg/dl), (250−500 mg/dl), and 1000 mg/dl concentrations of albumin in urine accordingly which are trivial as compared to the recently proposed RI-dependent sensors for similar application in the PCF platform [5–8, 26–31].

The response of fiber dispersion for each concentration level of the analyte with an ascending frequency is shown in Figure 12 at the optimal design parameters. It can be observed that the resulting dispersion property of the proposed PCF meets a flattening region with a broad-spectrum range of 3.1 THz to 5 THz which is suitable for multichannel sensing applications. The investigated dispersion curves show a very tiny deviation for each concentration level of the sample due to the infinitesimal change of RI. It is also clearly visualized from Figure 12. At the optimal design conditions, a very near-zero dispersion of 0.039 ps/THz/cm is obtained with a dime variation of nearly ±0.032 ps/THz/cm for all the tested concentrations. The obtained dispersion by the proposed PCF sensor is highly comparable with many of the existing works for similar applications due to proper geometry selection and proper geometry optimization [7, 26, 35].

A comparison with the recently developed PCF-based THz sensor for biosensing application is presented in Table 3. It can be mentioned that from Table 3 that this proposed work not only improved the sensitivity, besides all other necessary optical properties have improved at a significant level including confinement loss, effective area, and effective material loss. The hollow core with circular-shaped PCF has a greater interactive area that enhances the interaction area between the applied analyte and light intensities. Besides, the highly porous structure of the cladding and hollow core reduces the interactive area of the light pulse with bulk material, which also helps to reduce losses. Depending on these matters, we have chosen a hollow and circular-shaped core with highly porous cladding geometry. The listed previous works in Table 3 have not considered the above-mentioned two factors together, that makes our developed structure unique with improved performances.

Recently, surface plasmon resonance- (SPR-) based PCF sensors have been reported, showing noticeable changes in outputs for small changes of refractive index among different analytes [9–14]. Resonance wavelength and peak confinement loss are very sensitive to RI of the analytes in the SPR-PCF platform [9–14]. As a result, a slight change in RI of the analytes forces to the resonance wavelength to shift right or left and the peak of the confinement loss to higher or lower level [9–14]. Thus, it could be easier to identify the unknown analyte with very tiny changes in RI using SPR-based PCF sensor. Therefore, SPR-based PCF sensor development and analysis for the identification of different analytes can be a potential research area.

4. Fabrication Feasibilities and Potential Experimental Setup of the Proposed PCF

Fabrication complexity minimization in a proper geometrical setting is a key challenge for PCF development. Keeping that in mind, symmetrical cladding and hollow-core PCF are proposed in this research. The circular hole is comparatively easily implementable by all the existing fabrication processes. It is interesting to note that Bise and Trevor already executed a PCF geometry with a circular airhole structure using sol-gel techniques [39]. Besides this, stack and draw [40], capillary stacking [41], and mechanical drilling [42], are also highly capable of implementing circular hole-structured PCF. Recently, different geometrical structure implementation possibilities are discussed including suspended structure using drilling, stacking, extrusion, and 3D printing techniques [43–49]. Talataisong et al. [45] implemented a suspended structured polymer PCF by using a 3D printing technique. Different complicated PCF geometries including suspended ones have also been fabricated by Cubillas et al. [46]. Lui et al. [47] have fabricated a suspended PCF structure in the stack and draw environment. Furthermore, several complex structures such as kagome and suspended PCF structure have been implemented by Calcerrada et al. [48]. By using the stack and draw fabrication process, different PCF geometries have been also fabricated by Lui et al. [49]. The abovementioned discussions indicate that at this stage, circular holes and suspended cladding structured PCF fabrication is not a complex task. Based on this a fabrication-friendly circular hollow core with suspended cladding-structured PCF is proposed which is easily fabricable on the many existing manufacturing platforms.

For our proposed structure, the stack and draw technique has excellent potential for fabricating the proposed PCF structure. The proposed PCF is constructed with six symmetrical capillaries in the cladding and a circular hollow structure in the core section. Fabrication steps for the proposed PCF using the stack and draw technique are shown in Figure 13. As per the stack and draw process, the first step is capillary preparation. After making solid rod capillaries, an ultrasonic mill can be used for making holes as per the desired shape. After making the cladding capillaries as per the design, these capillaries need to be stacked together inside a jacket tube. After inserting the preform stack into a glass tube and fusing during the drawing process, one obtains a microstructured preform or “cane.” The last step of this fabrication process is drawing the cane into fiber as per the design and desired dimension. Air holes size and their regularities can be controlled by applying air pressure inside the preform.

For testing the proposed PCF sensor in practice several additional arrangements are required. A possible arrangement for testing the PCF sensor is presented in Figure 14. First, a supercontinuum light source is required which has a frequency range of 1.5–5 THz. For this purpose, a SuperK compact, NKTPhotonics™ can be utilized [50]. A single-mode fiber (SMF-28) needs to be coupled between the light source and sensor through the polarizer (which is accompanied by a polarizer controller) to transport the light to the sensor. A splicing method can be used to couple the sensor with SMF-28. The Vytran FFS-2000 splicer can be utilized for splicing by using the filament fusion technique. Manual-mode translational and rotational alignment methods can be used for aligning the PCF and SMF [51]. Furthermore, SMF and PCF can also be connected by inserting an etched SMF tip into the PCF. As per the current reports, this splicing method has a coupling efficiency of more than 80% [52]. Also, free-space coupling, fiber-to-fiber coupling, etc. techniques can be also utilized for coupling purposes [53, 54]. After passing the sensor, the light needs to pass through an optical spectrum analyzer which analyzes the responses of different analytes. Yokokawa™, AQ6370C optical spectrum analyzer can be employed [50]. For injecting the analyte into the sensor, a programmable microinjector pump would be required. LongerPump™, LSP01-1A can be considered for this purpose [50]. A waste reservoir needs to be connected with an outlet channel where the used analyte will be stored. The existence of several unknown analytes causes peak shifts. These shifts can be identified by the spectrum analyzer and can be graphically displayed on the computer which will be connected to the output of the spectrum analyzer.

5. Conclusion

In this research, a refractive index-based hollow-core PCF biosensor has been proposed for albumin detection in urine on the basis of kidney dysfunctionality identification. To investigate the sensing performance of the presented PCF, three levels of protein concentration in urine have been considered. The investigated consequence of the proposed PCF reveals a superior relative sensitivity response of 98.576% for 7–125 mg/dl albumin concentration, 98.591% for 250–500 mg/dl, and 98.607% for 1000 mg/dl concentration in the terahertz spectrum. Moreover, it renders a very trivial confinement loss and a near-zero dispersion flattened profile. The investigated results of the proposed PCF and the practical implementation feasibility of state-of-the-art fabrication technology apprise that it can be a great solution for biosensing applications.

Data Availability

Data are not available anywhere. All the supporting data are reserved at the author’s end.

Conflicts of Interest

The authors declare that they have no conflicts of interest regarding the publication of this paper.

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Copyright © 2023 Md. Moshiur Rahman et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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