14 Perspectives of Aptamers for Medical Applications
419
Cancer antigen 125 (CA125) is another important biomarker for cancer diagnosis,
especially in ovarian cancer. It is a high molecular weight glycoprotein identified in
1981 with high expression in 90% of patients with epithelial ovarian cancer [67].
CA125 has been routinely used clinically as a screening indicator for epithelial
tumors including ovarian cancers [68].
Tripathi et al. [69] developed the first apta-nanozyme based lateral flow assay for
CA125 detection. This assay achieves the lowest limit of detection of 5.21 U/mL
within 20 min and costs less than 1 USD/strip. The accuracy of CA125 detection
presents a significant correlation with established CA125 chemiluminescent ELISA
with P-value < 0.0001 when tested on human serum samples. The assay has a linear
range of 7.5–200 U/mL.
Thymidine kinase 1 (TK1) [70] is traditionally a serum biomarker that is elevated
in the early stages of malignancies. It was found to be a key enzyme in DNA precursor
synthesis. since the 1980s, TK1 has been shown as a clinically valuable biomarker for
monitoring hematological malignancies as well as solid tumor such as breast cancer,
most malignant cells tend to express TK1 at higher and unregulated concentrations
than normal cells, TK1 has the definite potential to monitor therapies across a wide
range of cancer types [70, 71].
Nazari et al. [72] identified two aptamers, TK1_apta37 and TK1_apta69, for
human TK1 with high affinity and specificity. Researchers constructed a sandwich
assay platform with these aptamers to successfully detected TK1 in the concentration range of 54 − 3500 pg mL
−1 . Further clinical sample assays from 60
cancerous patients confirmed that this platform was equally efficient compared with
that using the conventional antibody-based enzyme-linked immunosorbent assay kit.
The aptamer sandwich assay achieved a dynamic range for TK1 from sub-picogram
per milliliter concentrations to clinically relevant serum levels, this approach presents
its potential applicability of the point-of-care testing system.
Aptamers have made great progress in POCTs fields. Unfortunately, most of
the aptasensor applications are still in the laboratory stage, future applications of
aptamer-related POCTs will endeavor to address more practical clinic scenarios.
14.3.2 Precision Medicine
Precision medicine [73] is an emerging discipline of prevention and treatment strategies to harness genetic and epigenetic cues for targeted treatment of a variety of
diseases, ranging from cancers, cardiovascular diseases, as well as inflammation
diseases. Aptamers are often developed via SELEX, they are also named chemical antibody because they can not only act like antibody, but also be chemically
modified, and bioconjugations can be automated on a DNA/RNA synthesizer or can
be conducted under biofriendly conditions in a low cost. Aptamers can be tagged
with fluorogenic or radioisotope reporters and conjugated with therapeutic agents for
targeted drug delivery, which pave the way for aptamers to be developed for versatile
biomedical applications such as bioimaging and targeted therapy [26, 27].
419
Cancer antigen 125 (CA125) is another important biomarker for cancer diagnosis,
especially in ovarian cancer. It is a high molecular weight glycoprotein identified in
1981 with high expression in 90% of patients with epithelial ovarian cancer [67].
CA125 has been routinely used clinically as a screening indicator for epithelial
tumors including ovarian cancers [68].
Tripathi et al. [69] developed the first apta-nanozyme based lateral flow assay for
CA125 detection. This assay achieves the lowest limit of detection of 5.21 U/mL
within 20 min and costs less than 1 USD/strip. The accuracy of CA125 detection
presents a significant correlation with established CA125 chemiluminescent ELISA
with P-value < 0.0001 when tested on human serum samples. The assay has a linear
range of 7.5–200 U/mL.
Thymidine kinase 1 (TK1) [70] is traditionally a serum biomarker that is elevated
in the early stages of malignancies. It was found to be a key enzyme in DNA precursor
synthesis. since the 1980s, TK1 has been shown as a clinically valuable biomarker for
monitoring hematological malignancies as well as solid tumor such as breast cancer,
most malignant cells tend to express TK1 at higher and unregulated concentrations
than normal cells, TK1 has the definite potential to monitor therapies across a wide
range of cancer types [70, 71].
Nazari et al. [72] identified two aptamers, TK1_apta37 and TK1_apta69, for
human TK1 with high affinity and specificity. Researchers constructed a sandwich
assay platform with these aptamers to successfully detected TK1 in the concentration range of 54 − 3500 pg mL
−1 . Further clinical sample assays from 60
cancerous patients confirmed that this platform was equally efficient compared with
that using the conventional antibody-based enzyme-linked immunosorbent assay kit.
The aptamer sandwich assay achieved a dynamic range for TK1 from sub-picogram
per milliliter concentrations to clinically relevant serum levels, this approach presents
its potential applicability of the point-of-care testing system.
Aptamers have made great progress in POCTs fields. Unfortunately, most of
the aptasensor applications are still in the laboratory stage, future applications of
aptamer-related POCTs will endeavor to address more practical clinic scenarios.
14.3.2 Precision Medicine
Precision medicine [73] is an emerging discipline of prevention and treatment strategies to harness genetic and epigenetic cues for targeted treatment of a variety of
diseases, ranging from cancers, cardiovascular diseases, as well as inflammation
diseases. Aptamers are often developed via SELEX, they are also named chemical antibody because they can not only act like antibody, but also be chemically
modified, and bioconjugations can be automated on a DNA/RNA synthesizer or can
be conducted under biofriendly conditions in a low cost. Aptamers can be tagged
with fluorogenic or radioisotope reporters and conjugated with therapeutic agents for
targeted drug delivery, which pave the way for aptamers to be developed for versatile
biomedical applications such as bioimaging and targeted therapy [26, 27].