**5.4 Detection of exosomes as a source of cancer biomarkers by applying 2D MXenes**

Exosomes as type of endosome-derived cell-secreted vesicles with the structure of a lipid bilayer membrane are responsible for signal transduction in intercellular communication and extracellular matrix remodeling. In addition exosomes can also carry cargo affecting neighboring cells and they can form pre-metastatic niches [115]. Thus, exosomes are behind localized tumor development, progression and induction of distant tumors forming metastasis. The fact, that a substantially higher cellular activity of tumor cells results in the production of a greater number of exosomes than in normal/healthy cells, makes them hot candidates for cancer diagnostics in itself [115].

*Exosomes are naturally produced biological nanoparticles, with their size usually defined in the range from 30 nm up to 100 nm or sometimes up to 200 nm. Other types of extracellular vesicles (EVs) include microvesicles (50–1000 nm, which bud directly off the plasma membrane), ectosomes (vesicles assembled at and released from a plasma membrane), shedding vesicles, microparticles and apoptotic vesicles (500– 2000 nm, which bud off the membrane of cells undergoing apoptosis).*

Electrochemiluminescence (ECL) as an upcoming technique joining the benefits of both electrochemistry and chemiluminescence, has been widely applied for biomarker analysis thanks to its high sensitivity, short response time and low background signal [132]. A biosensor based on the application of MXene and ECL was developed for sensitive detection of exosomes [133]. First, MXene (*ζ* 50 mV) was modified by polyethyleneimine (PEI) (*ζ* +55 mV) through electrostatic interactions to prepare an MXene/PEI nanocomposite (*ζ* 80 mV). This positively charged nanocomposite was subsequently used in covalent immobilization of an aptamer against CD63 protein, which is present on the surface of the exosomes using an amine-coupling chemistry. In an effort to detect exosomes, the GCE was modified by AuNPs, which were next modified by ethylenediamine. In addition, free -NH2 groups of ethylenediamine were activated by EDC/NHS to deposit a polymer, which was finally used for covalent immobilization of an aptamer against the EpCAM protein present on the surface of the exosomes. The signal was generated upon completion of the sandwich configuration as shown in **Figure 5**. The biosensor was most sensitive towards exosomes produced by a breast cancer cell line MCF-7, followed by a human liver cancer cell line HepG2 and a melanoma cell line B16. Exosomes released from the MCF-7 cell line were detected in the concentration range from 500 to 5 106 particles <sup>μ</sup><sup>L</sup><sup>1</sup> with LOD of 125 particles μL<sup>1</sup> , which was more than 100 times lower than the conventional ELISA method. The biosensor exhibited an excellent performance by analysis of spiked serum samples with recovery indices of 95–104% [133]. In the later research of the same group, it was shown that, besides CD63 and EpCAM, other proteins

).

of 0.5 fM and 0.85 fM for miRNA-21 and miRNA-10b, respectively (a linear range

*(a) Illustration of the fabrication of the Ti3C2 MXenes and PAA-Ti3C2. (b) the construction of the dcDNA-Ti3C2 composite nanoprobe. (c) Multilayer imaging of plasma membrane glycoproteins MUC1 and cytoplasmic miR-21 using the dcDNA-Ti3C2 composite nanoprobe. Reprinted with permission from ref. [128].*

PSA was the both qualitatively and quantitatively examined through a sandwich-type immunoreaction and a photothermal measurement by applying Ti3C2 MXene quantum dots (QDs)-encapsulated liposome with a high photothermal efficiency [131]. Ti3C2 MXene QDs as the innovative photothermal signal beacons were entrapped in the liposome for the labeling of the secondary antibody on the surface. The sandwich-type assay was carried out by coupling a low-cost microplate with a homemade 3D printed device. Under NIR-laser irradiation of 808 nm, Ti3C2 MXene QDs converted the light energy into heat, and the shift in the temperature correlating with the analyte concentration. LOD of 0.4 ng mL<sup>1</sup> for PSA was obtained by a near-infrared (NIR) photothermal immunoassay (a linear range of 1.0 ng mL<sup>1</sup> - 50 ng mL<sup>1</sup>

The portable equipment employing a portable NIR imaging camera was able to

from 5 fM to 100 pM) [130].

**Figure 4.**

**234**

*Copyright ACS, 2019.*

*Novel Nanomaterials*

#### **Figure 5.**

*The principle of the ECL biosensor for exosomes activity detection signal amplification strategy. Reprinted with permission from Ref. [134]. Copyright ACS, 2018.*

present on the surface of the exosome can be targeted by DNA aptamers, including PSMA and PTK-7 [134]. Such a biosensor offered highly reproducible assays with RSD of 1.2% and 3.9% for detection of 10<sup>8</sup> and 10<sup>9</sup> exosomes mL<sup>1</sup> , respectively [134].

Another MXene-based biosensor for the detection of exosomes was prepared by Fang *et al*. [135] GCE was modified by SiNPs and ionic liquid with a final modification of the interface by EpCAM aptamers. In order to detect exosomes, a sandwich configuration was formed by a final incubation with a nanohybrid consisting of MXene modified by black phosphorus quantum dots, Ru(bpy)3 2+ and anti-CD63 antibodies. In addition to the ECL detection of exosomes, such a configuration also made photothermal assays possible. The ECL biosensor could detect exosomes down to 37 particles <sup>μ</sup><sup>L</sup><sup>1</sup> with a linear range of up to 5 <sup>10</sup><sup>7</sup> particles μL<sup>1</sup> . The stability of the constructed biosensor was investigated by measuring 1.1 <sup>10</sup><sup>2</sup> exosomes <sup>μ</sup><sup>L</sup><sup>1</sup> . The ECL intensity kept a relatively stable value under sequential 10 cyclic scans with relative standard deviation (RSD) of 1.1% [135].

#### **6. Conclusions**

The novel 2D nanomaterial MXene has a potential to significantly influence the field of biosensing including affinity-based biosensors with expected exponential increase in related works to be published in the years to come. MXene-based biosensors offer adequate sensitivity required for detection of cancer biomarkers present in blood down to ng mL<sup>1</sup> level or better (**Table 1**). However a great deal of effort needs to be invested into finding proper decorating strategies for MXene to simultaneously allow immobilization of biomolecules, but at the same time providing resistance towards non-specific protein binding. Matching this criteria, affinity MXene-based biosensors can be applied for analysis of complex samples such as blood serum or plasma [23]. Point-of-care tests (POC) employing MXene/based devices represent promising candidates with benefits such as adaptability in different/adverse environment,

**Target**

**237**

**Biosensor** 

**architecture**

**Detection method**

**LOD**

**Linear range**

**Reference**

**biomarker**

CEA CEA CEA MUC1 miRNA-182

miRNA-155

miRNA-21 and

ssDNAs/AuNP@

MXene/SPGE

miRNA-141

PSA PSA VEGF165

OPN Exosomes

Exosomes

Exosomes

 Cy3 labeled CD63 aptamer (Cy3-CD63

Ti3C2 MXenes

> miRNA-21 and

DNA-NaYF4:Yb,Tm/Er

 UCNPs and Ti3C2

nanosheets

energy transfer (FRET) assay

Fluorescence

 -

fluorescence

 resonance

0.62 fM

0.85 fM

(miRNA-10b)

(miRNA-21)

 and

5 fM - 100 pM

[130]

miRNA-10b

**Table 1.**

*Key* 

*characteristics*

 *of* 

*MXene-based*

*nanobiosensors*

 *for detection of cancer biomarkers.*

 aptamer)/

Ratiometric

fluorescence

 resonance

 1.4 103 particles mL1 104

 ECL probe -

AbCD63

exosomes/Apt/ILs/SiO2

MXenes-Apt2/exosomes/Apt1/PNIPAMAuNPs/

 GCE ECL

NUs/GCE

Apt/PPy@Ti3C2Tx/

 PMo12/AE (MXenesBPQDs@Ru(dcbpy)32+-PEI-

ECL

BSA/anti-PSA/AuNPs-M-NTO-PEDOT/GCE

HRP-Au-Ab2-PSA-Ab1-MXene/IDE

MB/DNA/HT/HP1/AuNPs/Ti3C2/BiVO4/GCE

Electrochemical/

Electrochemical/

Photoelectro-chemical

Electrochemical/

 EIS

 EIS, CV

 DPV

cDNA/Ti3C2T @

x

FePcQDs/AE

BSA/ssRNA/

 AuNPs/

MoS2/Ti3C2/GCE

Ab2-conjugated

cDNA-Fc/MXene/Apt/Au/

 GCE

SPA/HGNPs/N-Ti3C2-MXene

 SPR Electrochemical/

Electrochemical/

Electrochemical/

Electrochemical/

 DPV

 EIS

 DPV

 DPV

Ti3C

2 AgNPs/Ab2

MXene/AuNPs/SPA/Ab

1 and

MWCNTs-PDA-

SPR

BSA/anti-CEA/f-Ti3C2-MXene/GC

Electrochemical/

 CV

0.000018 ng mL1

0.07 fM

0.15 fM 0.33 pM

0.43 fM

4.3 aM

204 aM 138 aM

0.03 pg. L1

0.031 ng mL1

3.3 fM

0.98 fg mL1

37.0 particles μL1

125 particles μL1

1.1 102

μL1

5 102

μL1

–109 particles mL1

[134]

–5 106 particles

[97]

–1.1 107 particles

[ 135]

0.0001–20 ng mL1

0.1–50 ng mL1

10 fM - 100 nM

0.05–10,000

 pg. mL1

[ 53]

[ 120]

[121]

[ 122]

(miRNA-141)

(miRNA-21)

 and

500 aM - 50 nM

1.0 pM - 10 mM

1 fM - 0.1 nM 0.01 fM - 10 pM

0.001–1000

 pM

[127]

[117]

*DOI: http://dx.doi.org/10.5772/intechopen.94309*

[118]

[119]

[ 88]

*Ti3C2 MXene-Based Nanobiosensors for Detection of Cancer Biomarkers*

0.0001–2000

 ng mL1

[77]

 [49]


#### *Ti3C2 MXene-Based Nanobiosensors for Detection of Cancer Biomarkers DOI: http://dx.doi.org/10.5772/intechopen.94309*

**Table 1.**

*Key*

  *characteristics of MXene-based nanobiosensors for detection of cancer biomarkers.*

present on the surface of the exosome can be targeted by DNA aptamers, including PSMA and PTK-7 [134]. Such a biosensor offered highly reproducible assays with RSD of 1.2% and 3.9% for detection of 10<sup>8</sup> and 10<sup>9</sup> exosomes mL<sup>1</sup>

*The principle of the ECL biosensor for exosomes activity detection signal amplification strategy. Reprinted with*

Another MXene-based biosensor for the detection of exosomes was prepared by Fang *et al*. [135] GCE was modified by SiNPs and ionic liquid with a final modification of the interface by EpCAM aptamers. In order to detect exosomes, a sandwich configuration was formed by a final incubation with a nanohybrid consisting of MXene modified by black phosphorus quantum dots, Ru(bpy)3

and anti-CD63 antibodies. In addition to the ECL detection of exosomes, such a configuration also made photothermal assays possible. The ECL biosensor could detect exosomes down to 37 particles <sup>μ</sup><sup>L</sup><sup>1</sup> with a linear range of up to 5 <sup>10</sup><sup>7</sup>

value under sequential 10 cyclic scans with relative standard deviation (RSD) of

expected exponential increase in related works to be published in the years to come. MXene-based biosensors offer adequate sensitivity required for detection of cancer biomarkers present in blood down to ng mL<sup>1</sup> level or better (**Table 1**).

The novel 2D nanomaterial MXene has a potential to significantly influence the field of biosensing including affinity-based biosensors with

However a great deal of effort needs to be invested into finding proper decorating strategies for MXene to simultaneously allow immobilization of biomolecules, but at the same time providing resistance towards non-specific protein binding. Matching this criteria, affinity MXene-based biosensors can be applied for analysis of complex samples such as blood serum or plasma [23]. Point-of-care tests (POC) employing MXene/based devices represent promising candidates with benefits such as adaptability in different/adverse environment,

. The stability of the constructed biosensor was investigated by

. The ECL intensity kept a relatively stable

respectively [134].

*Novel Nanomaterials*

**Figure 5.**

particles μL<sup>1</sup>

1.1% [135].

**236**

**6. Conclusions**

measuring 1.1 <sup>10</sup><sup>2</sup> exosomes <sup>μ</sup><sup>L</sup><sup>1</sup>

*permission from Ref. [134]. Copyright ACS, 2018.*

,

2+

automation of tests, reduced cost, miniaturization, interference-free detection, *etc*. [50, 81, 136, 137].

PSA prostate specific antigen

SPA staphylococcal protein A SPGE screen-printed gold electrode SPR surface plasmon resonance UCNPs upconversion nanophosphors

VEGF165 vascular endothelial growth factor 165

*Ti3C2 MXene-Based Nanobiosensors for Detection of Cancer Biomarkers*

, Kishor Kumar Sadasivuni<sup>2</sup>

2 Center for Advanced Materials, Qatar University, Doha, Qatar

\*Address all correspondence to: jan.tkac@savba.sk

provided the original work is properly cited.

1 Institute of Chemistry, Slovak Academy of Sciences, Bratislava, Slovak Republic

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

, Peter Kasak<sup>2</sup> and Jan Tkac1

\*

SiO2 NUs SiO2 nanourchin

*DOI: http://dx.doi.org/10.5772/intechopen.94309*

**Author details**

Lenka Lorencova<sup>1</sup>

**239**
