**3. Conclusions**

In this review, we have discussed various electrochemical sensors that have been reported in recent years which incorporate various 2D nanomaterials conjugated with metal nanoparticles towards biomarker detection that have potential suitability for clinical use and some for point-of-care applications for cancer diagnosis. Although much research has been done in the synthesis of graphene, MoS2, MXenes, MOFs, and other 2D materials incorporated with metal nanoparticles for an in vitro analysis of biomarkers. However, significant progress needs to be done in performing an in vivo analysis. Moreover, due to their inherent conductivity, these 2D nanomaterials are significantly used in electrochemical or even optical sensing. However, they are often doped with other nanomaterials to improve their electroactivity/conductivity. Further, new approaches such as nanofabrication and clinical applicability are most crucial for developing an open-use-dispose type of sensor at low cost. Furthermore, electrode-to-electrode variations upon modifications with nanomaterials largely depend on the type of functionalization method adopted, which also needed to be studied for developing electrochemical transducers with greater stability and reproducibility. Finally, the paper-based electrochemical and wearable electrochemical sensing approaches for biomarker detections are also promising due to their improved sensitivity, selectivity, and portability, such as a simple paper-based sensor that can measure with an application able to get the electrochemical signal downloaded into a smartphone is best suitable for clinical/point-of-care applications [179,180]. Though the integration of microfluidic devices with electrochemical systems possesses numerous advantages, including rapid manipulation of sample fluid, reduced reagent consumption, and low cost, commercialization of these electrochemical sensors is still in its infancy due to the challenges that these techniques are facing, such as miniaturization (multiple electrodes and channels) and integration of microfluidic systems (miniaturized flow controllers). Therefore, it is necessary to develop manufacturable biosensors that can provide accurate quantification of a biomarker of interest with a meager quantity of solutions at point-of-care with simple fabrication steps by avoiding multiple modifications on the electrode surface.

**Author Contributions:** A.K.: conceptualization, methodology, validation, writing—original draft preparation; A.K.Y.: conceptualization, methodology, validation, writing—original draft preparation; M.-H.L.: writing—review and editing, project administration, funding acquisition. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Ministry of Trade, Industry, and Energy (Grant no. 20008763 and 20009860).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **Abbreviations**



#### **References**


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