Mechanically robust, transparent, and UV-shielding composite of Na-Alginate and maleic acid-functionalized boron nitride nanosheets with improved antioxidant property

Maleic acid functionalized boron nitride nanosheets (BNNS-MA)/Na-Alginate composite with enhanced mechanical, UV-shielding and antioxidation properties have been fabricated for the first time by solvent evaporation from a homogeneous aqueous dispersion of BNNS-MA/Na-Alginate composite solution. The composite fabrication was driven by homogenous nano-integrations and chemistry of compatibilization of BNNS-MA with Na-Alginate through H-bonding interactions between -COOH functional group of BNNS-MA and -OH, -COONa groups of Na-Alginate. The BNNS-MA/Na-Alginate composites show significant enhancement of mechanical, UV-blocking and antioxidant properties compared to the Na-Alginate. Integrating only 1 wt% BNNS-MA improved the UV-blocking, tensile strength, and antioxidant properties of Na-Alginate film by 99.1%, 73% and 60.3%, respectively. Overall, our findings of BNNS-MA integrated Na-Alginate composite films with improved physical, mechanical, UV shielding, and antioxidant functionalities is very promising to open new insight in the field of transparent UV-protected biopolymer film for consumer products, packaging, cosmetics, and engineering applications.

The cis configuration of amino-modified tetraphenylethene for selective detection of single-stranded guanine-rich DNA

The selectivity and sensitivity of amino-functionalized tetraphenylethene probes (namely Z-N2TPE and E-N2TPE) for ssDNA detection in aqueous solution were investigated. Both Z-N2TPE and E-N2TPE showed high selectivity to guanine-rich ssDNA. The sensitivity was found to be positively related to the DNA length, indicating the longer DNA could binding more probes to cause aggregation induced fluorescence. Z-N2TPE and E-N2TPE could detect guanine-rich ssDNA as short as 5 nt and 10 nt respectively. Theoretical simulation calculation shows that the amino group of the probe could simultaneously bind with guanine and phosphate ester, which contribute to high selectivity. And the cis probe could bind DNA with higher affinity than the trans one, since the two amino groups of Z-N2TPE could synergistically bind DNA while E-N2TPE could bind DNA with only one amino group.

Adsorption of DNA Oligonucleotides by Self-Assembled Metalloporphyrin Nanomaterials

Porphyrin assemblies have controllable morphology, high biocompatibility, and good optical properties and were widely used in biomedical diagnosis and treatment. With the development of DNA biotechnology, combining DNA with porphyrin assemblies can broaden the biological applications of porphyrins. Porphyrin assemblies can serve as nanocarriers for DNA, although the fundamental interactions between them are not well understood. In this work, zinc meso-tetra(4-pyridyl)porphyrin (ZnTPyP) assemblies were prepared in the presence of various surfactants and at different pH values, yielding a variety of aggregation forms. Among them, the hexagonal stacking form exposes more pyridine substituents, and the hydrogen bonding force between the substituents and the DNA bases allows the DNA to be quickly adsorbed on the surface of the assemblies. The effects of DNA sequence and length were systematically tested. In particular, the adsorption of duplex DNA was less efficient compared to the adsorption of single-stranded DNA. This fundamental study is useful for the further combination of DNA and porphyrin assemblies to prepare new functional hybrid nanomaterials.

Kinetic and Thermodynamic Control in Porphyrin and Phthalocyanine Self-Assembled Monolayers

Porphyrins and phthalocyanines are ubiquitous in modern science and technology. Their stability, redox properties, and photoresponse make them candidates for numerous applications. Many of these applications rely on thin films, and these are critically dependent on the first monolayer. In this article, we focus on noncovalently bound self-assembled monolayers of porphyrins and phthalocyanines at the solution-solid interface with special emphasis on the kinetic and thermodynamic processes that define the films and their reaction chemistry. We first discuss the difference between film-formation kinetics and desorption kinetics from fully formed films. We then present evidence that many of these monolayers are controlled by adsorption kinetics and are not in thermodynamic equilibrium. Measurement of the solution-solid interface desorption energy by scanning tunneling microscopy is discussed, and data is presented for cobalt, nickel, and free base octaethylporphyrin. The activation energy for the desorption of these compounds into phenyloctane is about half of the computed desorption energy in vacuum, and this is discussed in terms of the role of the solvent. Preexponential factors are very low compared to desorption into vacuum, and this is attributed to a reduction in the entropy of activation due to the participation of solvent in the transition state. An example of the use of relative desorption kinetics to create a new binary surface structure is given. It is suggested that this is a synthesis route that may have been missed because of the large difference in solution concentrations required to drive binary film formation. Attention then turns to the axial reaction chemistry of metalloporphyrins and metallophthalocyanines supported on conducting surfaces. We show several examples of chemistry unique to the supported complexes: cases where the metal binds ligands more readily and cases where the substrate induces ligand loss. Understanding this new axial coordination chemistry is of great importance in catalysis, sensing, and the growth of 3D materials from a self-assembled template.

Fe-nitrilotriacetic acid coordination polymer nanowires: an effective sensing platform for fluorescence-enhanced nucleic acid detection

The determination of specific nucleic acid sequences is key in identifying disease-causing pathogens and genetic diseases. In this paper we report the utilization of Fe-nitrilotriacetic acid coordination polymer nanowires as an effective nanoquencher for fluorescence-enhanced nucleic acid detection. The detection is fast and the whole process can be completed within 15 min. This nanosensor shows a low detection limit of 0.2 nM with selectivity down to single-base mismatch. This work provides us with an attractive sensing platform for applications.

[12]aneN3 Modified Tetraphenylethene Molecules as High-Performance Sensing, Condensing, and Delivering Agents toward DNAs

Four [12]aneN3 modified tetraphenylethene (TPE) compounds with different numbers of polyamine units and structure configurations, namely 1, 2, 3, and 4, were designed and synthesized. All compounds showed strong aggregation-induced emission (AIE) features. Compounds 2 and 4 showed significant emission enhancement after the addition of ssDNAs and dsDNAs of different lengths as well as calf thymus DNA (ctDNA). Compounds 1 and 3 showed very poor fluorescent responses toward DNAs. Gel electrophoresis demonstrated the abilities of 1-4 to condense DNA effectively. Complete retardation of plasmid DNA can be achieved at a concentration of 25 μM (1), 8 μM (for 2 and 3) and 4 μM (4). Experiments including fluorescent contrastive titrations, scanning electron microscopy, dynamic laser scattering, EB displacement, and gel electrophoresis demonstrated that the four compounds were able to integrate with DNA through electrostatic interactions and supramolecular stacking. A vicinal configuration around TPE (2) and more triazole-[12]aneN3 recognition sites (4) evidently enhanced the sensing capability toward oligonucleotides, and the TPE unit played an important role in the plasmid DNA condensation process because of its strong binding. With the advantages of low cytotoxicity, effective DNA sensing, and DNA condensing properties, compound 4 was successfully applied as a nonviral DNA vector and fluorescent tracer for label-free gene delivery, which is the first example of a nonviral gene vector with AIE activity.

A tetraphenylethene-based zinc complex as a sensitive DNA probe by coordination interaction

We developed a new DNA probe by utilizing the coordination interaction of Zn(2+) with DNA and the consequent emission. Because the coordination interactions do not depend on the length of the DNA, the new probe exhibited much higher sensitivity for the detection of short ssDNA than the corresponding probe based on electrostatic interactions.

Fluorescent sensors using DNA-functionalized graphene oxide

In the past few years, graphene oxide (GO) has emerged as a unique platform for developing DNA-based biosensors, given the DNA adsorption and fluorescence-quenching properties of GO. Adsorbed DNA probes can be desorbed from the GO surface in the presence of target analytes, producing a fluorescence signal. In addition to this initial design, many other strategies have been reported, including the use of aptamers, molecular beacons, and DNAzymes as probes, label-free detection, utilization of the intrinsic fluorescence of GO, and the application of covalently linked DNA probes. The potential applications of DNA-functionalized GO range from environmental monitoring and cell imaging to biomedical diagnosis. In this review, we first summarize the fundamental surface interactions between DNA and GO and the related fluorescence-quenching mechanism. Following that, the various sensor design strategies are critically compared. Problems that must be overcome before this technology can reach its full potential are described, and a few future directions are also discussed.

An amine-functionalized metal–organic framework as a sensing platform for DNA detection

An amine-functionalized metal–organic framework (MOF) as a DNA sensing platform, with possible hydrogen bond interaction between DNA and the MOF, has been developed.

Novel use of poly(3,4-ethylenedioxythiophene) nanoparticles for fluorescent nucleic acid detection

In this paper, we demonstrate the novel use of poly(3,4-ethylene dioxythiophene) (PEDOT) nanoparticle as a very effective fluorescent sensing platform for the detection of nucleic acid sequences. The principle of the assay lies in the fact that the adsorption of the fluorescently labeled single-stranded DNA (ssDNA) probe by PEDOT nanoparticle leads to substantial fluorescence quenching, followed by specific hybridization with the complementary region of the target DNA sequence. This results in desorption of the hybridized complex from PEDOT nanoparticle surface and subsequent recovery of fluorescence. A detection limit as low as 30 pM could be achieved in this sensing system. We also demonstrate its application for multiplexed detection of nucleic acid sequences. Furthermore, this sensing system can realize the detection of single-base mismatch even in multiplexed format. It is of importance to note that the successful use of this sensing platform in human blood serum system is also demonstrated.

Fluorescence resonance energy transfer dye-labeled probe for fluorescence-enhanced DNA detection: an effective strategy to greatly improve discrimination ability toward single-base mismatch

In this article, we report on the first use of fluorescence resonance energy transfer (FRET) dye-labeled probe for fluorescence resonance enhanced DNA detection to greatly improve discrimination ability toward single-base mismatch using conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) as a sensing platform. The suggested FRET dye-labeled probe contains a 5-carboxyfluorescein (FAM) group at 5' end of the oligomer as a donor and a 6-carboxy-X-rhodamine (ROX) attached to a modified cytosine (C) base as an acceptor, which were separated by three bases. The general concept used in this DNA assay is based on adsorption of the FRET dye-labeled single-stranded DNA (ssDNA) probe by PN, which is accompanied by substantial fluorescence quenching and disappearance of FRET. The subsequent specific hybridization with its target forms a double-stranded DNA (dsDNA), resulting in desorption of the hybridized duplex from PN surface accompanied by reoccurrence of FRET and fluorescence recovery. It suggests that the discrimination ability of this FRET probe based system toward single-base mismatch is about 5.2 times that of the system based on single dye-labeled probe based system.