Development of a DNAzyme-based colorimetric biosensor assay for dual detection of Cd2+ and Hg2

Hg2+ detection and information encryption of new [1+1] lanthanide cluster

The sensing of heavy metal ion and information encryption are two very important research areas. Therefore, developing multi-functional materials capable of sensing heavy metal ions and encrypting information is highly important. In this work, three [1 + 1] lanthanide clusters [Ln(TFBA)3(dmp) (H2O)2]2 (Ln = Tb3+Tb1+1, Eu3+Eu1+1, Gd3+Gd1+1, HTFBA = 2,3,4,5-tetrafluorobenzoic acid, dmp = 4,7-dimethyl-1,10-phenanthroline) were designed and synthesized. Among them, Tb1+1 shows excellent luminescence sensing towards Hg2+ (Ex = 350 nm, Em = 545 nm). Results demonstrates the sensing with high selectivity, strong anti-interference, 20-s response time, high accuracy, excellent linear relationship in 0-20.0 μM, and a very low limit of detection (0.02 ppb). Furthermore, paper strips based on Tb1+1 is fabricated for visual detection of Hg2+ in real samples of tap water, lake water, human urine, and human serum. More interestingly, a new method for confidentiality of information is realized through multi-color anti-counterfeiting patterns with the [1 + 1] lanthanide cluster ink, based on the luminescence "on-off" sensing towards Hg2+.

An ultrasensitive Cd2+ detection biosensor based on DNAzyme and CRISPR/Cas12a coupled with hybridization chain reaction

The detection of cadmium is essential because it poses a significant threat to human health and the environment. Recent advancements in biosensors that detect nonnucleic-acid targets using CRISPR/Cas12a in combination with aptamers or DNAzymes show promising performance. Herein, we integrated DNAzyme, hybridization chain reaction (HCR) and CRISPR/Cas12a into a single biosensor for the first time and realized the ultrasensitive detection of Cd2+. A single phosphorothioate ribonucleobase (rA)-containing oligonucleotide (PS substrate) and a Cd2+-specific DNAzyme (Cdzyme) are used for Cd2+ recognition, releasing short single-stranded DNA. Then, the HCR is triggered by the cleavage products for signal transduction and amplification. Next, the trans-cleavage activity of Cas12a is activated due to the presence of crRNA complementary strands and PAM sites in the HCR products. As a result, FQ-reporters are cleaved, and the fluorescence values can be easily read using a fluorometer, allowing Cd2+ quantification by measuring the fluorescent signal. The Cd2+ detection biosensor is ultrasensitive with a detection limit of 1.25 pM. Moreover, the biosensor shows great stability under different pH and various anion conditions. The proposed sensor was utilized for environmental water sample detection, demonstrating the dependability of the detection system. Considering the high sensitivity and reliable performance of the assay, it could be further used in environmental monitoring. In addition, the design strategy reported in this study could extend the application of CRISPR/Cas12a in heavy metal detection.

Advances in colorimetric aptasensors for heavy metal ion detection utilizing nanomaterials: a comprehensive review

Heavy metal ion contamination poses significant environmental and health risks, necessitating rapid and efficient detection methods. In the last decade, colorimetric aptasensors have emerged as powerful tools for heavy metal ion detection, owing to their notable attributes such as high specificity, facile synthesis, adaptability to modifications, long-term stability, and heightened sensitivity. This comprehensive overview summarizes the key developments in this field over the past ten years. It discusses the principles, design strategies, and innovative techniques employed in colorimetric aptasensors using nanomaterials. Recent advancements in enhancing sensitivity, selectivity, and on-site applicability are highlighted. The review also presents application studies of successful heavy metal ion detection using colorimetric aptasensors, underlining their potential for environmental monitoring and health protection. Finally, future directions and challenges in the continued evolution of these aptasensors are outlined.

Recent Advances in the DNA-Mediated Multi-Mode Analytical Methods for Biological Samples

DNA-mediated nanotechnology has become a research hot spot in recent decades and is widely used in the field of biosensing analysis due to its distinctive properties of precise programmability, easy synthesis and high stability. Multi-mode analytical methods can provide sensitive, accurate and complementary analytical information by merging two or more detection techniques with higher analytical throughput and efficiency. Currently, the development of DNA-mediated multi-mode analytical methods by integrating DNA-mediated nanotechnology with multi-mode analytical methods has been proved to be an effective assay for greatly enhancing the selectivity, sensitivity and accuracy, as well as detection throughput, for complex biological analysis. In this paper, the recent progress in the preparation of typical DNA-mediated multi-mode probes is reviewed from the aspect of deoxyribozyme, aptamer, templated-DNA and G-quadruplex-mediated strategies. Then, the advances in DNA-mediated multi-mode analytical methods for biological samples are summarized in detail. Moreover, the corresponding current applications for biomarker analysis, bioimaging analysis and biological monitoring are introduced. Finally, a proper summary is given and future prospective trends are discussed, hopefully providing useful information to the readers in this research field.

Colorimetric Sensors for Chemical and Biological Sensing Applications

Colorimetric sensors have been widely used to detect numerous analytes due to their cost-effectiveness, high sensitivity and specificity, and clear visibility, even with the naked eye. In recent years, the emergence of advanced nanomaterials has greatly improved the development of colorimetric sensors. This review focuses on the recent (from the years 2015 to 2022) advances in the design, fabrication, and applications of colorimetric sensors. First, the classification and sensing mechanisms of colorimetric sensors are briefly described, and the design of colorimetric sensors based on several typical nanomaterials, including graphene and its derivatives, metal and metal oxide nanoparticles, DNA nanomaterials, quantum dots, and some other materials are discussed. Then the applications, especially for the detection of metallic and non-metallic ions, proteins, small molecules, gas, virus and bacteria, and DNA/RNA are summarized. Finally, the remaining challenges and future trends in the development of colorimetric sensors are also discussed.

Improved stability and pharmacokinetics of wogonin through loading into PASylated ferritin

Wogonin (Wog) plays an important role in human diseases, especially cancer and inflammatory diseases, but its poor solubility, unstable metabolism and low bioavailability greatly limit its application in biomedical fields. Therefore, we developed a temperature-dependent method to encapsulate wogonin into a novel ferritin-based nanocarrier. To improve the loading capacity and stability, the human H chain ferritin (HFtn) was functionalized with a repetitive polypeptide sequence composed of proline (Pro), alanine (Ala), and serine (Ser) in different residues lengths (PAS10 and PAS30). Wogonin loading and release studies demonstrated that the encapsulation efficiency and stability of the PASylated nanocarriers were significantly higher than those of the wild type. PAS-HFtn-Wog exhibited enhanced cytotoxicity to MCF-7 breast cancer cells and HepG2 liver cancer cells. Notably, the PASylated HFtn, especially PAS30-HFtn greatly prolonged the pharmacokinetics of wogonin in the mice bloodstream. Therefore, wogonin-loaded PAS-HFtn may be a promising drug candidate for cancer therapy.

Self-Powered Photoelectrochemical Assay for Hg2+ Detection Based on g-C3N4-CdS-CuO Composites and Redox Cycle Signal Amplification Strategy

A highly sensitive self-powered photoelectrochemical (spPEC) sensing platform was constructed for Hg2+ determination based on the g-C3N4-CdS-CuO co-sensitized photoelectrode and a visible light-induced redox cycle for signal amplification. Through successively coating the single-layer g-C3N4, CdS, and CuO onto the surface of an electrode, the modified electrode exhibited significantly enhanced PEC activity. The microstructure of the material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). However, the boost in photocurrent could be noticeably suppressed due to the consumption of hole-scavenging agents (reduced glutathione) by the added Hg2+. Under optimal conditions, we discovered that the photocurrent was linearly related to the Hg2+ concentration in the range of 5 pM–100 nM. The detection limit for Hg2+ was 0.84 pM. Moreover, the spPEC sensor demonstrated good performance for the detection of mercury ions in human urine and artificial saliva.

DNAzyme-based biosensors for mercury (Ⅱ) detection: Rational construction, advances and perspectives

Mercury contamination is one of the most severe issues in society due to its threats to public health and the ecological system. However, traditional methods for mercury ion detection are still limited by their time-consuming procedures, requirement of expensive instruments, and low selectivity. In recent decades, tremendous progress has been made in the development of functional nucleic acid-based, especially DNAzyme sensors for mercury (Ⅱ) (Hg²⁺) determination, including RNA-cleaving DNAzymes and G-quadruplex-based DNAzymes in particular. Researchers have heavily studied the construction of Hg²⁺ sensors, mainly originating from in vitro selection-derived DNAzymes, by incorporating T-Hg²⁺-T recognition moieties in existing DNAzyme scaffolds, and interfacing Hg²⁺-sensitive sequences with nanomaterials. In the last case, the employment of materials (as quenchers, signal transducers and DNA immobilizers) enriches the application scenarios of current Hg²⁺-DNAzymes, due to a combination of their functions. We summarize a broad range of sensing approaches, including optical, electrochemical, and other sensing methods, and compare their features. This review elaborates on the rational design strategies for engineering DNAzymes to selectively sense Hg²⁺, critically discusses their properties in different application scenarios, and summarizes recent advances in this field. Additionally, current progress, challenges and future perspectives are also discussed. This minireview provides deeper insights into the chemistry of these functional nucleic acids when working with Hg²⁺, explains the design ideas of DNAzyme-sensors in each platform, and reveals potential opportunities in developing more advanced DNAzyme sensors for the highly selective and sensitive recognition of Hg²⁺. ENVIRONMENTAL IMPLICATION: Mercury is one of the most toxic metallic contaminants due to its high toxicity, non-biodegradability, and serious human health risks when accumulated in the body. In the recent decade, intensive studies have focused on exploring mercury sensors by combining DNAzymes with various sensing methods, paving a promising avenue to gain ultra-high sensitivity and selectivity. However, so far, no review has introduced the recent advances on DNAzyme-based sensors for mercury detection in a critical way. In this review, we comprehensively summarized the studies on DNAzyme-based sensors for mercury detection using various sensing techniques including optical, electrochemical and other sensing methods.

Selection of M2+-independent RNA-cleaving DNAzymes with Sidechains Mimicking Arginine and Lysine

Sequence-specific cleavage of RNA by nucleic acid catalysts in the absence of a divalent metal cation (M 2+ ) has remained an important goal in biomimicry with potential therapeutic applications. Given the lack of functional group diversity in canonical nucleotides, modified nucleotides with amino acid-like side chains were used to enhance self-cleavage rates at a single embedded ribonucleoside site. Previous works relied on three functional groups: an amine, a guanidine and an imidazole ensconced on three different nucleosides. However, to date, few studies have systematically addressed the necessity of all three modifications, as the value of any single modified nucleoside is contextualized at the outset of selection. Herein, we report on the use of only two modified dNTPs, excluding an imidazole, i.e. 5-(3-guanidinoallyl)-2'-dUTP (dU ga TP) and 5-aminoallyl-2'-dCTP (dC aa TP), to select in-vitro self-cleaving DNAzymes that cleave in the absence of M 2+ in a pH-independent fashion. Cleavage shows biphasic kinetics with rate constants that are significantly higher than in unmodified DNAzymes and compare favorably to certain DNAzymes involving an imidazole. This work is the first report of a M2+-independent DNAzyme with two cationic modifications; as such it shows appreciable self-cleaving activity in the absence of an imidazole modification.