NANOBIOSENSORS FOR CANCER DETECTION
Cancer is the one of the most deadly disease and current detection options are ineffective. Recently large amount of research has been done for the exposure of cancer biomarkers. There are various biosensors which are used for the recognition of cancer. In this various biosensors used are ultrasensitive fluorescence biosensors, electrochemical biosensors, fluorometric DNA nanobiosensors, cytosensing nanobiosensors, phosphoserine imprinted nanobiosensors, SERS, colorimetric aptasensors, etc. These biosensors are used for the detection of prostate, lung, breast cancer.
Nanobiosensors can be used to detect the gastric cancer. miRNAs are the biomarkers that can be estimated for the sensitive and early cancer diagnosis. Electrochemical nanobiosensors has been used to detect two gastric cancer related miRNAs. Some nanobiosensors such as Au nanoparticles- and CdSe@ CdS quantum dots that contain magnetic nanocomposite with the reduced graphene oxides show the performance in quantifying miR-106a and let-7a. With the help of cyclic voltammetry and differential pulse voltammetry not only the biosensing construction was confirmed but also its specificity, selectivity, steadiness and sensitivity was indicated.
Nanobiosensors can also be used for the finding the pancreatic cancer. Numerous proteases such as matrix metalloproteinases(MMPs), cathepsins(CTS), and urokinase plasminogen activator(UpA), offers a chance for finding the tumors with the help of liquid biopsies. Fluorescence nanobiosensors is developed for the arginase and protease detection. miRNA electrochemical biosensors are also helpful for the detection of breast cancer. This can be analysis by using miR-1999a-5p and this was designed using glassy carbon electrode with graphene oxide and gold nanorod. It was found that these nanobiosensors are very sensitive and can be used to measure low absorption of miR-199a-5p in blood serum sample. An amperometric biosensors are designed for the detection of cancer metastasis by detecting epithelial cell adhesion molecule with express the metastatic cancer cells(Ep-MCCs).
The detection relies on sandwich type approach by using bioconjugate and this is composed of reporter antibody(RepAnti), nanostructured collagen(nCOL), AuNPs, and hydrazine(Hyd). This all composition act as nonenzymatic electrocatalyst and it reduces H2O2. The binding of the cells was confirmed using electrochemical impedence spectroscopy, cyclic voltammetry and chronoamperometry and the range for the detection was found to be 45 and 100,000.  The fluorescence nanobiosensors are used for the detection of the DNA methylation. The tumor suppressor gene i. e. adenomatous polyposis coli(APC) was used for the detection to target the DNA sequence. In this the nanoparticles was determined by SEM, TEM, XRD. The pharmaceutical agent such as dipyridamole was used as fluorescence probe in which there is the interaction of the hybridized unmethylated and methylated DNA. When the ssDNA is added then the fluorescence intensity of the unmethylated ssDNA is increased while that of methylated DNA is decreased.  A sensitive fluorescent DNA nanobiosensor are used to determine DNA sequence using APC by using synthetic organic ligand as a fluorophore which was assembled on gold nanoparticles.
This was done to enhance the sensitivity. They have fast response time and the performance of the DNA biosensor was investigated and satisfactory results was obtained. An amperometric aptasensor for the lung cancer cell detection was developed. It was used for the detection of the A549 human non-small-cell lung cancer(NSCLC) cells. MUC1 aptamer was used as a recognition layer having high affinity for the lung cancer cells. It was analyzed using the chronoamperometric measurements and then the results was confirmed using DPV methods. Cancer antigen 125 (CA 125) was used for ovarian cancer. Imprinting method was used in which antipyrine europium (III) and methacryloyl antipyrine terbium (III) was used as chelating monomers and phosphoserine (PS) was used as template. Langmuir adsorption isotherms was also used. A colorimetric method was used for the recognition of the cancer cells based on the aptamer-celll interaction. Nucleolin receptors (AS 1411) were captured by the cancer cells and the binding was done for the removal of the aptamers. When there is no aptamers the colour turns red. The method can be used for the recognition of the other cells also. SERS- based biosensor was used for fast and highly sensitive detection of the prostate cancer antigen 3 (PCA3) mimic DNA.
In this there is no need for the DNA amplification process using thermo cycles in polymerase chain reaction (PCR). PCA3 mimic DNA composed of 45 nucleotide sequence and this was sandwiched between two probe DNA- immobilized particles and then the raman peak intensity was observed. This technique is useful for the early stage diagnosis.
- In the detection of gastric cancer various nanocomposite such as CdSe@CdS quantum dots used as electrochemical labels due to which this is detected at the early stage.
- Various proteases such as MMPs, CTS and UpA offers opportunity to detect early stage tumors by liquid biopsies.
- miRNA is used for the detection of breast cancer and can be used to measure the low concentration in blood serum sample.
- Amperometric biosensors are used for the detection of epithelial cells.
- A fluorimetric nanobiosensors are used for the detection of the DNA methylation for early cancer diagnosis.
- DNA nanobiosensors are used to determine DNA sequence.
- Amperometric nanobiosensors are used for the detection of the lung cancer.
- Cancer Antigen 125 is used as daigonostic biomarker for ovarian cancer.
- Colorimetric method is used for the detection of cancer cells based on aptamer cell interaction.
- SERS is used for the detection of the cancer antigen.
Nanobiosensors are used for the detection of the various types of cancer. There are detection of pancreatic cancer, gastric cancer, lung cancer, breast cancer. Nanobiosensors such as SERS, amperometric biosensors, fluorimetric biosensors, DNA nanobiosensors, colorimetric method etc. are used for the detection of the cancer. With the help of fluorescence nanobiosenser we can detect DNA methylation and by adding ssDNA how the intensity of the methylated and unmethylated DNA is affected. In the colorimetric nanobiosensors the cancer cell is detected and the binding is done after which the solution colour changes and thus detection can be easily done. By using all these biosensors we can detect the early stage of the cancer.