Based on the strong interaction between single-stranded DNA (ssDNA) and graphene material, we have designed a simple but smart platform in this work to fabricate electrochemical biosensors by using ...graphene quantum dots modified pyrolytic graphite electrode coupled with specific sequence ssDNA molecules as probes. Due to the excellent conductivity of graphene material, the modified electrode can exhibit very fine electrochemical response. Nevertheless, the probe ssDNA will inhibit the electron transfer between the electrochemical active species Fe(CN)
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3-/4- and the electrode after the probe molecules are strongly bound to the surface of the modified electrode via their interaction with graphene. However, when the target molecules such as target ssDNA or target protein also exist in the test solution, the probe ssDNA will bind with the target instead of graphene if the sequence of the probe ssDNA is designed as complementary to the target DNA or as the aptamer of the target protein. As a result, the obtained peak currents of Fe(CN)
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3-/4- will increase with the target molecules, thus various electrochemical biosensors can be easily developed with this proposed platform. The fabricated electrochemical biosensors may also have high sensitivity and selectivity, which may have potential applications in the future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A DNA-based stimulus-responsive drug delivery system for synergetic cancer therapy has been developed. The system is built on a triplex-DNA nanoswitch capable of precisely responding to pH variations ...in the range of ∼5.0–7.0. In extracellular neutral pH space, the DNA nanoswitch keeps a linear conformation, immobilizing multiple therapeutics such as small molecules and antisense compounds simultaneously. Following targeted cancer cell uptake via endocytosis, the nanoswitch inside acidic intracellular compartments goes through a conformational change from linear to triplex, leading to smart release of the therapeutic combination. This stimuli-responsive drug delivery system does not rely on artificial responsive materials, making it biocompatible. Furthermore, it enables simultaneous delivery of multiple therapeutics for enhanced efficacy. Using tumor-bearing mouse models, we show efficient gene silencing and significant inhibition of tumor growth upon intravenous administration of the smart nanoswitch, providing opportunities for combinatorial cancer therapy.
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IJS, KILJ, NUK, PNG, UL, UM
Color vision: Multicolor molecular beacons are constructed from relatively large gold nanoparticles self‐assembled with stem–loop probes and helper oligonucleotides (see picture). The nanobeacons can ...respond differentially to multiple DNA targets, emitting multiple colors.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We report a highly sensitive electrochemical sensor for the detection of Hg2+ ions in aqueous solution by using a thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe and gold nanoparticles ...(Au NPs)-based signal amplification. The MSO probe contains seven thymine bases at both ends and a “mute” spacer in the middle, which, in the presence of Hg2+, forms a hairpin structure via the Hg2+-mediated coordination of T−Hg2+−T base pairs. The thiolated MSO probe is immobilized on Au electrodes to capture free Hg2+ in aqueous media, and the MSO-bound Hg2+ can be electrochemically reduced to Hg+, which provides a readout signal for quantitative detection of Hg2+. This direct immobilization strategy leads to a detection limit of 1 μM. In order to improve the sensitivity, MSO probe-modified Au NPs are employed to amplify the electrochemical signals. Au NPs are comodified with the MSO probe and a linking probe that is complementary to a capture DNA probe immobilized on gold electrodes. We demonstrated that this Au NPs-based sensing strategy brings about an amplification factor of more than 3 orders of magnitude, leading to a limit of detection of 0.5 nM (100 ppt), which satisfactorily meets the sensitivity requirement of U.S. Environmental Protection Agency (EPA). This Au NPs-based Hg2+ sensor also exhibits excellent selectivity over a spectrum of interference metal ions. Considering the high sensitivity and selectivity of this sensor, as well as the cost-effective and portable features of electrochemical techniques, we expect this Au NPs amplified electrochemical sensor will be a promising candidate for field detection of environmentally toxic mercury.
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IJS, KILJ, NUK, PNG, UL, UM
Laborious and costly detection of miRNAs has brought challenges to its practical applications, especially for home health care, rigorous military medicine, and the third world. In this work, we ...present a pH-responsive miRNA amplification method, which allows the detection of miRNA just using a pH test paper. The operation is easy and no other costly instrument is involved, making the method very friendly. In our strategy, a highly efficient isothermal amplification of miRNA is achieved using an improved netlike rolling circle amplification (NRCA) technique. Large amounts of H+ can be produced as a byproduct during the amplification to induce significant changes of pH, which can be monitored directly using a pH test paper or pH-sensitive indicators. The degree of color changes depends on the amount of miRNA, making it possible for quantitative analysis. As an example, the method is successfully applied to quantify a miRNA (miR-21) in cancer cells. The results agree well with that from the prevalent qRT-PCR analysis. It is the first time that a paper-based point-of-care testing (POCT) is developed for the detection of miRNAs, which might promote the popularization of miRNAs working as biomarkers for diagnostic purposes.
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IJS, KILJ, NUK, PNG, UL, UM
DNA methylation, catalyzed by methylases, plays a critical role in many biological processes, and methylases have been regarded as promising targets for antimicrobial drugs. In this paper, we propose ...a simple and sensitive colorimetric assay method to detect the activity of methylases so as to monitor DNA methylation using DNA-modified gold nanoparticles (AuNPs) coupled with enzyme-linkage reactions. The duplex DNA molecules modified on the surface of AuNPs are first methylated by DNA adenine methylation (Dam) methyltransferase (MTase) and then cut by methylation-sensitive restriction endonuclease Dpn I. Removal of duplex from the AuNP surfaces by the methylation/cleavage process will destabilize the nanoparticles, resulting in aggregation of AuNPs and a red-to-blue color change. Consequently, the enzyme activity of Dam MTase can be assayed and DNA methylation can be detected. Furthermore, this study may provide a sensitive platform to screen inhibitors for Dam MTase.
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IJS, KILJ, NUK, PNG, UL, UM
The capability to encapsulate designated live cells into a biologically and mechanically tunable polymer layer is in high demand. Here, an approach to weave functional DNA polymer cocoons has been ...proposed as an encapsulation method. By developing in situ DNA-oriented polymerization (isDOP), we demonstrate a localized, programmable, and biocompatible encapsulation approach to graft DNA polymers onto live cells. Further guided by two mutually aided enzymatic reactions, the grafted DNA polymers are assembled into DNA polymer cocoons at the cell surface. Therefore, the coating of bacteria, yeast, and mammalian cells has been achieved. The capabilities of this approach may offer significant opportunities to engineer cell surfaces and enable the precise manipulation of the encapsulated cells, such as encoding, handling, and sorting, for many biomedical applications.
The rapid, accurate and sensitive determination of hydrogen peroxide (H2O2) is of great significance in the physiological, pathological and environmental fields. In this work, we have proposed a ...highly sensitive and selective amperometric biosensor for the detection of extracellular H2O2 released from human breast cancer cells with the help of a sequence-specific peptide. Since the peptide immobilized on the electrode surface can specifically bind with horseradish peroxidase (HRP) in a favorable orientation, which then well promotes the catalytic activities of the immobilized enzyme toward the reaction of o-phenylenediamine and H2O2, the proposed biosensor can detect H2O2 in a wide linear range from 1.0×10−7M to 1.0×10−4M with a low detection limit of 3.0×10−8M. It can be also directly used to efficiently trace extracellular H2O2 released from human breast cancer cells MCF-7. Furthermore, the reproducibility, stability and selectivity of the biosensor are also quite well compared with the previous report, so our biosensor might be potentially useful in physiological and pathological detection of H2O2 in the future.
► Peptides on the electrode can specifically bind with HRP in a favorable orientation. ► Immobilized HRP shows well catalytic activities toward the reaction of o-PD and H2O2. ► Proposed biosensor can detect H2O2 in a wide linear range with low detection limit. ► Proposed biosensor can efficiently trace extracellular H2O2 released from MCF-7.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Cancer imposes a severe threat to people's health and lives, thus pressing a huge medical and economic burden on individuals and communities. Therefore, early diagnosis of cancer is indispensable in ...the timely prevention and effective treatment for patients. Exosome has recently become an attractive cancer biomarker in noninvasive early diagnosis because of the unique physiology and pathology functions, which reflects remarkable information regarding the cancer microenvironment, and plays an important role in the occurrence and evolution of cancer. Meanwhile, biosensors have gained great attention for the detection of exosomes due to their superior properties, such as convenient operation, real-time readout, high sensitivity, and remarkable specificity, suggesting promising biomedical applications in the early diagnosis of cancer. In this review, the latest advances of biosensors regarding the assay of exosomes were summarized, and the superiorities of exosomes as markers for the early diagnosis of cancer were evaluated. Moreover, the recent challenges and further opportunities of developing effective biosensors for the early diagnosis of cancer were discussed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•A novel colorimetric strategy for lead ion detection has been established.•The detection relies on DNAzyme functionalized gold nanoparticles.•Target-induced cleavage can mediate ...assembly of graphene oxide.•The method displays excellent performance for the detection of lead ion.
In this paper, we report a novel colorimetric strategy for the detection of small molecules by using Pb2+ ion as an example. In this strategy, DNAzyme duplex modified gold nanoparticles (GNPs) are designed to be unable to interact with graphene oxide (GO). However, in the presence of Pb2+, the substrate strand of the DNAzyme is cleaved at its cleavage site, resulting in the disassembly of the DNAzyme duplex modified GNPs into three parts, i.e., the 3′- and 5′-fragments of substrate strand and the DNAzyme strand modified GNPs. By taking advantage of the efficient cross-linking effect of ssDNA-GNPs to GO, colorimetric sensor for the detection of the metal ion can be fabricated with a detection limit of 100pM, which is much lower than the previous reports. This colorimetric method has also been used for the determination of Pb2+ in the tap water of the local city and the water from a reservoir with satisfactory results, so it may have potential applications in the future.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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