A dual-amplification system for colorimetric DNA detection based on the assembly of biomolecules

A Proton-Activatable DNA-Based Nanosystem Enables Co-Delivery of CRISPR/Cas9 and DNAzyme for Combined Gene Therapy

CRISPR/Cas9 is emerging as a platform for gene therapeutics, and the treatment efficiency is expected to be enhanced by combination with other therapeutic agents. Herein, we report a proton-activatable DNA-based nanosystem that enables co-delivery of Cas9/sgRNA and DNAzyme for the combined gene therapy of cancer. Ultra-long ssDNA chains, which contained the recognition sequences of sgRNA in Cas9/sgRNA, DNAzyme sequence and HhaI enzyme cleavage site, were synthesized as the scaffold of the nanosystem. The DNAzyme cofactor Mn²⁺ was used to compress DNA chains to form nanoparticles and acid-degradable polymer-coated HhaI enzymes were assembled on the surface of nanoparticles. In response to protons in lysosome, the polymer coating was decomposed and HhaI enzyme was consequently exposed to recognize and cut off the cleavage sites, thus triggering the release of Cas9/sgRNA and DNAzyme to regulate gene expressions to achieve a high therapeutic efficacy of breast cancer.

A sensitive platform for DNA detection based on organic electrochemical transistor and nucleic acid self-assembly signal amplification

Highly sensitive detection of DNA is of great importance for the detection of genetic damage and errors for the diagnosis of many diseases. Traditional highly sensitive organic electrochemical transistor (OECT)-based methods mainly rely on good conductivity materials, which may be limited by complex synthesis and modification steps. In this work, DNA biosensor based on OECT and hybridization chain reaction (HCR) signal amplification was demonstrated for the first time. Au nanoparticles were electrochemically deposited on the Au gate electrode to increase the surface area. Then, the HCR products, long negatively charged double-stranded DNA, were connected to the target by hybridization, which can increase the effective gate voltage offset of OECT. This sensor exhibited high sensitivity and even 0.1 pM target DNA could be directly detected with a significant voltage shift. In addition, it could discriminate target DNA from the mismatched DNA with good selectivity. This proposed method based on HCR in DNA detection exhibited an efficient amplification performance on OECT, which provided new opportunities for highly sensitive and selective detection of DNA.

A new method has been developed for DNA detection by integrating hybridization chain reaction signal amplification with organic electrochemical transistor device for the first time.

Recent Progress in DNA Hybridization Chain Reaction Strategies for Amplified Biosensing

With the continuous development of DNA nanotechnology, various spatial DNA structures and assembly techniques emerge. Hybridization chain reaction (HCR) is a typical example with exciting features and bright prospects in biosensing, which has been intensively investigated in the past decade. In this Spotlight on Applications, we summarize the assembly principles of conventional HCR and some novel forms of linear/nonlinear HCR. With advantages like great assembly kinetics, facile operation, and an enzyme-free and isothermal reaction, these strategies can be integrated with most mainstream reporters (e.g., fluorescence, electrochemistry, and colorimetry) for the ultrasensitive detection of abundant targets. Particularly, we select several representative studies to better illustrate the novel ideas and performances of HCR strategies. Theoretical and practical utilities are confirmed for a range of biosensing applications. In the end, a deep discussion is provided about the challenges and future tasks of this field.

Recent advances in nanomaterials for colorimetric cancer detection

The early diagnosis of cancer can significantly improve patient survival rates. Colorimetric methods for real-time naked-eye detection have aroused growing interest owing to their low cost, simplicity, and practicability. With the rapid development of nanotechnology, compared with conventional diagnostic methods, nanomaterials with unique physical and chemical properties were applied to improve selectivity and sensitivity in colorimetric detection of cancer biomarkers, such as MUC1 aptamer conjugated PtAuNPs to specifically recognize MUC1 proteins on the cancer cell surfaces, etching of silver nanoprisms to detect prostate-specific antigen, and aggregation or dispersion of AuNPs to sense prostate cancer antigen gene 3 or glutathione, by which the limit of detection (LOD) could approach values down to a few cancer cells per mL, several fg per mL proteins, several ng of nucleic acids, or even tens of nM of organic molecules. Herein, we review the recent progress achieved in developing colorimetric nanosensors for cancer diagnosis, particularly providing an overview of the sensing principles, target biomarkers, advanced nanomaterials employed in the fabrication of sensing platforms, and strategies for improving signal sensitivity and specificity. Finally, we sum up the nanomaterial-based colorimetric cancer detection as well as existing challenges that should be resolved to extend their clinical application.

Size-modulated optical property of gold nanorods for sensitive and colorimetric detection of thiourea in fruit juice

As an important sulfur compound, thiourea (TU) has caused great concern because of its wide application as well as its serious toxicity and hazard to the environment. Thus, it is necessary to develop a sensitive and selective method for TU analysis. In this work, gold nanorods (AuNRs) acted as an optical probe to realize the sensitive and colorimetric detection of TU. In HCl medium, Fe³⁺ at low concentration was difficult to oxide Au⁰ to form Au⁺ because of the high redox potential or the positive Gibbs free energy change. However, this process was possible when TU was present since the association constant between Au⁺ and TU is great enough to bind with TU to form a stable complex to further promote the etching of AuNRs, resulting in the lower aspect ratio of AuNRs with the blue shift and intensity decrease in extinction spectra, accompanied by the divisive colors of AuNRs solution or colorful dark-field light scattering imaging of single AuNR. The blue-shift of AuNRs longitudinal plasmon resonance absorption (LPRA) band was proportional to the concentration of TU in the range of 1-250 nM and the limit of detection (3σ/k) was as low as 0.4 nM. In addition, the colorimetric method was proven with high selectivity in the presence of potential interfering compounds, which was successfully applied to the detection of TU in fruit juice samples. This proposed colorimetric method provides a simple, sensitive yet selective measurement tool for TU sensing, which may offer new opportunities in the development of colorimetric sensors for food safety in the future.

Universal and label-free photosensitization colorimetric assays enabled by target-induced termini transformation of dsDNA resistant to Exo III digestion

A label-free and universal colorimetric assay was developed via the combination of CHA, Exo III digestion, and photosensitization colorimetry.