# Recent Advances of MXene-Based Electrochemical Immunosensors
## 3 Electrochemical Immunosensors Based on MXenes
### MXenes as Electrode-Modified Nanomaterials in Electrochemical Immunosensors
\begin{tabular}{c c c c c c} \hline \hline
**MXene Material [Ref.]** & **Ekchant for MXenes** & **Role** & **Analyte** & **Electrochemical** & **Limit of Detection** & **Dynamic Range** \\ \hline _f_-Ti\({}_{3}\)C\({}_{2}\)[48] & HCl/LIF & EMN & CEA & CV & 0.018 pg mL\({}^{-1}\) & 0.0001–2000 ng mL\({}^{-1}\) \\ Ti\({}_{3}\)C\({}_{2}\)[49] & HF & EMN & PSA & Capacitance & 0.031 pg mL\({}^{-1}\) & 0.1 mg mL\({}^{-1}\)50 mg mL\({}^{-1}\) \\ AuNPs\({}_{3}\)-NTO-EDOT [50] & HCl/LIF & EMN & PSA & DPV & 0.03 pg mL\({}^{-1}\) & 0.0001–200 ng mL\({}^{-1}\) \\ Ti\({}_{3}\)C\({}_{2}\)-AuNP [51] & HF & EMN & PSA & DPV & 0.31 pg mL\({}^{-1}\) & 1 pg mL\({}^{-1}\)-50 ng mL\({}^{-1}\) \\ AuNP-Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[52] & HF & EMN & CFTR21-1 & SWV & 0.1 pg mL\({}^{-1}\) & 0.5–10,000 pg mL\({}^{-1}\) \\ MXNS-AFBP [53] & HCl/LIF & EMN & Apo-A1 & DPV & 0.3 pg mL\({}^{-1}\) & 0.1 pg mL\({}^{-1}\)-50 ng mL\({}^{-1}\) \\ \({}_{3}\)T\({}_{3}\)C\({}_{2}\)[54] & HCl/LIF & EMN & NMP 22 & DPV & 0.7 pg mL\({}^{-1}\) & 0.1 pg mL\({}^{-1}\)50 ng mL\({}^{-1}\) \\ HCl/LIF & EMN & cTnI & DPV & 0.58 ng mL\({}^{-1}\) & 5–100 ng mL\({}^{-1}\) \\ AuNPs\({}_{3}\)/Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[67] & HF & EMN & cTnI & DPV & 0.069 ng mL\({}^{-1}\) & 0.1-1000 ng mL\({}^{-1}\) \\ Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[55] & HCl/LIF & EMN & Cortisol & EIS & 3.88 pM & 0.01–100 nM \\ L-cy/aNF/aNF/Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[67] & HF & EMN & Cortisol & Amperometry & 0.54 ng mL\({}^{-1}\) & 5–180 ng mL\({}^{-1}\) \\ AuNPs/a-f\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[57] & HCl/LIF & EMN & PCT & DPV & 2.0 g mL\({}^{-1}\) & 0.01–10 pg mL\({}^{-1}\) \\ AuNP/T\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[58] & HF & EMN & ALP & DPV & 4.0 U L\({}^{-1}\) & 10.0–1500 U L\({}^{-1}\) \\ Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)@AuNPs [59] & HCl/LIF & Ap\({}_{2}\)-label & PSA & DPV & 3.0 g mL\({}^{-1}\) & 0.01–10 pg mL\({}^{-1}\) \\ Ti\({}_{3}\)C\({}_{2}\)@CuAu-LDH [60] & HCl/LIF & Ap\({}_{2}\)-label & CEA & SWV & SWV: Si\({}_{3}\)S6 mL\({}^{-1}\) & 0.0001–80 ng mL\({}^{-1}\) \\ CuPtRh CNBs/NH\({}_{3}\)C\({}_{2}\)T\({}_{3}\)[61] & HCl/LIF & Ap\({}_{2}\)-label & cTnI & Amperometry & 8.3 g mL\({}^{-1}\) & 25 g mL\({}^{-1}\)-100 ng mL\({}^{-1}\) \\ C\({}_{4}\)Ca\({}_{2}\)P\({}_{2}\)S\({}_{5}\)/d-Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\)[62] & HCl/LIF & Ap\({}_{2}\)-label & h-FABP & DPV & 3.30 g mL\({}^{-1}\) & 0.01–100 g mL\({}^{-1}\) \\ PdPtBP MNPs/Ti\({}_{3}\)C\({}_{2}\)T\({}_{3}\)[63] & / & Ap\({}_{2}\)-label & KIM-1 & DPV & 86 pg mL\({}^{-1}\) & 0.5 mg mL\({}^{-1}\)–100 ng mL\({}^{-1}\) \\ \hline \hline \end{tabular} 
\begin{tabular}{c} Abbreviation: _f_-Ti\({}_{3}\)C\({}_{2}\)–(3-Aminopropyl)/triethoxysilane (APTES) functionalized Ti\({}_{3}\)C\({}_{2}\)–MXene; AuNP—gold nanoparticle; M-NTO–Ti\({}_{3}\)C\({}_{2}\) MXene-derived sodium titanate nanoribbons; MXNS—MXene-Ti\({}_{3}\)C\({}_{2}\)T\({}_{5}\) nanosheets; AFBP—PSA detection is critical for clinical diagnosis of prostate cancer. [PERSON] et al. [49] reported a horseradish peroxidase (HRP)-labeled immunosensor for the detection of PSA. The interdigitated micro-comb electrode was modified with Ti\({}_{3}\)C\({}_{2}\) MXenes, which could immobilize anti-PSA capture antibody via \(\pi\)-stacking reaction. The detection antibody was prepared with HRP-labeled AuNPs as nanocarrier, which was further enhanced with tyramine-HRP repeats. After immuno-interaction, in the presence of H\({}_{2}\)O\({}_{2}\), the tyramine-HRP oxidized 4-chloro-1-naphthol molecules into insoluble benzo-4-chlorohexadienone layer, leading to the local changes in capacitance. Combing Ti\({}_{3}\)C\({}_{2}\) MXenes electrodecodified nanomaterials with tyramine signal amplification strategy, the capacitive immunosensors achieved sensitive detection of target PSA, and exhibited good reproducibility, higher specificity and accuracy for human serum analysis in comparison with a commercial PSA enzyme-linked immunosorbent assays (ELISA) kit.