DNA branch migration amplification cascades for enzyme-free and non-label aptamer sensing of mucin 1

Pressure and multicolor dual-mode detection of mucin 1 based on the pH-regulated dual-enzyme mimic activities of manganese dioxide nanosheets

Mucin 1 is an essential tumor biomarker, and developing cost-effective and portable methods for mucin 1 detection is crucial in resource-limited settings. Herein, the pH-regulated dual-enzyme mimic activities of manganese dioxide nanosheets were demonstrated, which were integrated into an aptasensor for dual-mode detection of mucin 1. Under acidic conditions, manganese dioxide nanosheets with oxidase mimic activities catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine sulfate, producing visible multicolor signals; while under basic conditions, manganese dioxide nanosheets with catalase mimic activities were used as catalyst for the decomposition of hydrogen peroxide, generating gas pressure signals. The proposed method allows the naked eye detection of mucin 1 through multicolor signal readout and the quantitative detection of mucin 1 with a handheld pressure meter or a UV-vis spectrophotometer. The study demonstrates that manganese dioxide nanosheets with pH-regulated dual-enzyme mimic activities can facilitate multidimensional transducing signals. The use of manganese dioxide nanosheets for the transduction of different signals avoids extra labels and simplifies the operation procedures. Besides, the signal readout mode can be selected according to the available detection instruments. Therefore, the use of manganese dioxide nanosheets with pH-regulated dual-enzyme mimic activities for dual-signal readout provides a new way for mucin 1 detection.

Aptamer-Based Probes for Cancer Diagnostics and Treatment

Aptamers are single-stranded DNA or RNA oligomers that have the ability to generate unique and diverse tertiary structures that bind to cognate molecules with high specificity. In recent years, aptamer researches have witnessed a huge surge, owing to its unique properties, such as high specificity and binding affinity, low immunogenicity and toxicity, and simplicity of synthesis with negligible batch-to-batch variation. Aptamers may bind to targets, such as various cancer biomarkers, making them applicable for a wide range of cancer diagnosis and treatment. In cancer diagnostic applications, aptamers are used as molecular probes instead of antibodies. They have the potential to detect various cancer-associated biomarkers. For cancer therapeutic purposes, aptamers can serve as therapeutic or delivery agents. The chemical stabilization and modification strategies for aptamers may expand their serum half-life and shelf life. However, aptamer-based probes for cancer diagnosis and therapy still face several challenges for successful clinical translation. A deeper understanding of nucleic acid chemistry, tissue distribution, and pharmacokinetics is required in the development of aptamer-based probes. This review summarizes their application in cancer diagnostics and treatments based on different localization of target biomarkers, as well as current challenges and future prospects.

Recent advances in the selection of cancer-specific aptamers for the development of biosensors

An early diagnosis has the potential to greatly decrease cancer mortality. For that purpose, specific cancer biomarkers have been molecularly targeted by aptamer sequences to enable an accurate and rapid detection. Aptamer-based biosensors for cancer diagnostics are a promising alternative to those using antibodies, due to their high affinity and specificity to the target molecules and advantageous production. Synthetic nucleic acid aptamers are generated by in vitro Systematic Evolution of Ligands by Exponential enrichment (SELEX) methodologies that have been improved over the years to enhance the efficacy and to shorten the selection process. Aptamers have been successfully applied in electrochemical, optical, photoelectrochemical and piezoelectrical-based detection strategies. These aptasensors comprise a sensitive, accurate and inexpensive option for cancer detection being used as point-of-care devices. This review highlights the recent advances in cancer biomarkers, achievements and optimizations made in aptamer selection, as well as the different aptasensors developed for the detection of several cancer biomarkers.