Bifunctional MNPs@UIO-66-Arg core-shell-satellite nanocomposites for enrichment of phosphopeptides.

A facile and mild method based on self-assembled lysozyme (LYZ) to fabricate bifunctional MNPs@UIO-66-Arg core-shell-satellite nanocomposites (CSSNCs) is reported for the high-efficiency enrichment of phosphopeptides. Under physiological conditions, LYZ rapidly self-assembled into a robust coating on Fe3O4@SiO2 magnetic nanoparticles (MNPs) with abundant surface functional groups, which effectively mediate heterogeneous nucleation and growth of UIO-66 nanocrystals. Well-defined MNPs@UIO-66 CSSNCs with stacked pores, showing high specific surface area (333.65 m2 g- 1) and low mass transfer resistance, were successfully fabricated by fine-tuning of the reaction conditions including reaction time and acetic acid content. Furthermore, the UIO-66 shells were further modified with arginine to obtain bifunctional MNPs@UIO-66-Arg CSSNCs. Thanks to the unique morphology and synergistic effect of Zr-O clusters and guanidine groups, the bifunctional MNPs@UIO-66-Arg CSSNCs exhibited outstanding enrichment performance for phosphopeptides, delivering a low limit of detection (0.1 fmol), high selectivity (ß-casein/BSA, mass ratio 1:2000), and good capture capacity (120 mg g- 1). The mechanism for phosphopeptides capture may attribute to the hydrogen bonds, electrostatic interactions, and Zr-O-P bonds between phosphate groups in peptides and guanidyl/Zr-O clusters on bifunctional MNPs@UIO-66-Arg CSSNCs. In addition, the small stacking pores on the core-shell-satellite architecture may selectively capture phosphopeptides with low molecular weight, eliminating interference of other large molecular proteins in complex biological samples.

Facile fabrication of Ti4+-immobilized magnetic nanoparticles by phase-transitioned lysozyme nanofilms for enrichment of phosphopeptides.

In this study, titanium (IV)-immobilized magnetic nanoparticles (Ti4+-PTL-MNPs) were firstly synthesized via a one-step aqueous self-assembly of lysozyme nanofilms for efficient phosphopeptide enrichment. Under physiological conditions, lysozymes readily self-organized into phase-transitioned lysozyme (PTL) nanofilms on Fe3O4@SiO2 and Fe3O4@C MNP surfaces with abundant functional groups, including -NH2, -COOH, -OH, and -SH, which can be used as multiple linkers to efficiently chelate Ti4+. The obtained Ti4+-PTL-MNPs possessed high sensitivity of 0.01 fmol µL-1 and remarkable selectivity even at a mass ratio of ß-casein to BSA as low as 1:400 for phosphopeptide enrichment. Furthermore, the synthesized Ti4+-PTL-MNPs can also selectively identify low-abundance phosphopeptides from extremely complicated human serum samples and their rapid separation, good reproducibility, and excellent recovery were also proven. This one-step self-assembly of PTL nanofilms facilitated the facile and efficient surface functionalization of various nanoparticles for proteomes/peptidomes.

Antifouling Gold-Inlaid BSA Coating for the Highly Efficient Capture of Circulating Tumor Cells.

Large amounts of coexisting contamination in complex biofluid samples impede the quantified veracity of biomarkers, which is the key problem for disease confirmation. Herein, amyloid-like transformed bovine serum albumin inlaid with gold nanoparticles was used as a coating (BGC) on a substrate composed of silicon nanowires (SW; BGC-SW) under ambient conditions. After modification with the recognition group, BGC-SW could serve as an outstanding platform for the selective separation and sensitive detection of biomarkers in complicated biosamples. First, the BGC on SW with a large surface area exhibits excellent adhesion resistance. The attached amounts of contaminations in biofluids were decreased by over 78% compared with native bovine serum albumin (BSA) as the blocking agent. This is because the phase-transformed BSA coating provides stronger interactions with the SW than bare BSA, which results in a tighter attachment and more uniform coverage of the BGC. Furthermore, the gold matrix laid inside the antiadhesive coating ensures simple cross-linking with the recognition groups to selectively capture various biomarkers in complex biofluids and create a gentle release method. Circulating tumor cells (CTCs) were chosen as template biomarkers to verify the application of A-BGC-SW (BGC-SW modified with sgc8-aptamer) in various separation processes of untreated biofluids. The results showed that approximately six cells could be captured from a 1 mL fresh blood sample containing only 10 CTCs. The easy fabrication and excellent antiadhesion property endow A-BGC-SW with great potential in the field of biological separation.

C18-functionalized magnetic nanocomposites fabricated by one-step aqueous coating of tailored oligopeptides for enrichment of low-abundance peptides.

Screening and monitoring endogenous peptides from complicated biosamples is still a major challenge in mass spectrometry-based proteomics research, mainly due to their low concentration and the interference of high-abundance proteins and other contaminants in biological samples. Herein, a facile and novel approach was described for rapid fabrication of C18-functionalized magnetic nanocomposites (C18-MNCs) based on one-step aqueous coating of C18-Val-Lys-Val-Lys-Val-Lys (C18-VK-VI) for the highly selective enrichment of low-abundance endogenous peptides from biological samples. C18-VK-VI can readily self-assemble into complete monolayers mainly composed of ß-sheets with C18 hydrophobic chains erecting on the surface of GO@Fe3O4 MNCs under the physiological conditions. The resulting C18VK-VI-GO@Fe3O4 MNCs exhibited good performance for peptides enrichment from digests of standard protein (myoglobin, MYO) and human serum, such as high sensitivity (0.05 fmol µL-1) and selectivity (mass ratio of MYO digests and MYO = 1:500), rapid separation, and good reproducibility. Such a simple mild and rapid one-step aqueous coating method on the basis of oligopeptides self-assembly showed great potential in surface functionalization of various nanoadsorbents for proteome/peptidome researches.

A Light-Up Strategy with Aggregation-Induced Emission for Identification of HIV-I RNA-Binding Small Molecules.

Fluorescence methods are important tools to identify RNA-binding small molecules and further employed to study RNA-protein interactions. Most reported fluorescence strategies are based on covalent labeling of ligand or RNA, which can impede the binding between them to some extent, or light-off fluorescent indicator displacement methods, which ask for particular indicators. Herein, a label-free fluorescence strategy based on the light-on aggregation-induced emission (AIE) feature of tetraphenylethene (TPE) derivative to screen RNA-binding small molecules is presented. As a result of electrostatic interaction, the selected peptides can induce self-assembly of the TPE derivative to produce strong fluorescent emission; when the peptides are bound to RNA molecules, the TPE derivative is in the deaggregated form and shows no or minimum fluorescence. Based on the phenomenon, a competitive displacement assay combined with the TPE reporter was employed to characterize selected small molecules for their binding abilities to HIV-I RNAs. This AIE feature enables the fluorescence-off state of the TPE derivative in the presence of RNA-peptide complex to be "lightened up" quickly as the RNA-binding molecule is introduced and the peptide is competitively released. This strategy was carried out to test several small molecule binders, and the results are consistent with previous reports. This report gives an inspiring example of AIE-based fluorescent assay for HIV-I RNA-binding molecule screening, which may further be explored to build a drug screening platform for RNA-protein interference.

Specific enrichment of phosphopeptides by using magnetic nanocomposites of type Fe3O4@graphene oxide and Fe3O4@C coated with self-assembled oligopeptides.

Iron(III-immobilized magnetic nano-composites (MNCs) were first fabricated using one-step aqueous self-assembly of oligopeptides (Glu-Pro-Ala-Lys-Ala-Lys-Ala-Lys; EPAK-VI) for the highly selective capture of phosphopeptides from complex biological samples. Under physiological conditions, EPAK-VI can readily self-organize into a robust and complete coating layer mainly composed of ß-sheets and ß-turns on the surface of Fe3O4@GO and Fe3O4@C MNCs. Tailored by the cyclic structure of proline, the Glu-Pro motifs of EPAK-VI are vertically erected on the surface and thus serve as an effective linker to chelate Fe3+ through carboxyl (COO-) group in the glutamic acid (E) residues. The ionic hydrogen bonds between the ε-amino groups and the surface negative charges coupled with intermolecular hydrogen bonds render the EPAK-VI coating on the MNCs insusceptible to repeated extreme washing conditions. The Fe3+-EPAK-VI coated MNCs exhibit high enrichment efficiency for ß-casein tryptic digest (0.05 fmol µL-1), excellent selectivity from mixed digests (ß-casein/bovine serum albumin, mass ratio 1:500), and high recovery rate (over 80%). Graphical abstractSchematic representation of the fabrication of Fe3+-immobilized MNCs for phosphopeptide enrichment.

One-step fabrication of bifunctional self-assembled oligopeptides anchored magnetic carbon nanoparticles and their application in copper (II) ions removal from aqueous solutions.

Copper ion (Cu (II)) pollution has attracted much attention due to its remarkable toxic domino effect at excess amount. Efficient Cu (II) ions removal is thus a prerequisite for wastewater recycling. Herein, we present a facile and environmentally benign strategy to fabricate thiol (SH)-functionalized Fe3O4@C nanoparticles (denoted as Fe3O4@C-SH NPs) based on one-step self-assembling of a bifunctional oligopeptide with a sequence of Cys-Lys-Cys-Lys-Cys-Lys (CK-VI) for highly efficient removal of copper ions (Cu (II)) in aqueous solutions. Under the physiological conditions, CK-VI readily self-organized into a robust and tailor-made functional monolayer predominately composed of well-packed ß-sheets on the surface of Fe3O4@C NPs with their thiol groups standing on the outermost layer. The resulting Fe3O4@C-SH NPs containing abundant thiol active sites exhibited excellent adsorption capacity (up to 28.8 mg g-1) and selectivity for Cu (II) ions over coexisting ions. Compared with other covalent grafting methods with multistep processes and in harsh conditions, the proposed oligopeptides assembly-based coating method makes it possible to rapidly fabricate the Fe3O4@C-SH NPs in a simple mild one-step aqueous process with low cost. The current study provides facile and environmentally friendly approaches to rapidly tailor multifunctional surfaces of NPs for various toxic metal ions removal from wastewater.

One-step maltose-functionalization of magnetic nanoparticles based on self-assembled oligopeptides for selective enrichment of glycopeptides.

Magnetic nanoparticles (MNPs) have been widely explored in enrichment of low-abundance glycoproteins/glycopeptides prior to mass spectrometry analysis in glycoproteomics. Currently, most functional groups for recognizing glycoproteins/glycopeptides are usually immobilized on the nanomaterial surface based on covalent modification, which suffers from multistep treatment, surface-dependence, and harsh conditions. In this work, we first report a facile and rapid method for surface functionalization and subsequent glycopeptides enrichment via one-step assembly of maltose-modified oligopeptides with a sequence of Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys (AEK8-maltose). In physiological conditions, AEK8-maltose readily self-organized into a complete coating layer dominated by ß-sheets on the surface of SiO2@Fe3O4 and C@Fe3O4 MNPs, which remain intact to repeat washing with acidic organic and aqueous solutions extensively used in the sample enrichment treatments. Thus, the resulting AEK8-maltose functionalized MNPs show excellent performance in enrichment of glycopeptides in standard glycoprotein digests (24 glycopeptides from horseradish peroxidase (HRP), 31 glycopeptides from immunoglobulin (IgG)) and human serum digests (282 glycopeptides), including rapid enrichment speed (5 min), high detection sensitivity (0.001 ng/µL HRP), high selectivity (mass ratios of HRP and bovine serum albumin (BSA) digests up to 1:150), good enrichment recovery (over 86.3%), remarkable stability (repeatable for more than 8 times), and excellent renewability, which are better than or comparable with the literature results reported to date. The current work based on self-assembling oligopeptides provides a mild, economic and nontoxic procedure for one-step surface functionalization of various nanomaterials.

Versatile antifouling coatings based on self-assembled oligopeptides for engineering and biological materials.

The existence of nonspecific protein adsorption often results in significant challenges for microfluidic devices and laboratory cultureware used in biological experiments. Developing antifouling surfaces is thus increasingly desired by microfluidics engineers and biologists. Our previous studies have demonstrated that ionic hydrogen bonding between free ε-NH2 groups of the alkaline amino acids in proteins and surface negatively charged groups plays a critical role in strong adsorption of proteins onto the solid surfaces. Thus, the current work presents a facile and universal surface modification method based on self-assembly of oligopeptides with a sequence of Ala-Lys-Ala-Lys-Ala-Lys-Ala-Lys (AK-VIII) on poly(dimethylsiloxane) (PDMS) and polystyrene (PS) surfaces under physiological pH conditions. The results show that AK-VIII can self-organize into a compact amphipathic ß-sheet-rich coating layer on the PDMS and PS surfaces with similar coverage, which largely minimizes nonspecific adsorption of proteins. In addition, we compared the performances of BSA and AK-VIII used as blocking reagents to evaluate their inhibitory effect on nonspecific adsorption of the antigen and detection antibody in carcinoembryonic antigen (CEA) enzyme-linked immunosorbent assay (ELISA). The results showed that AK-VIII exhibits better performance than BSA for diminishing nonspecific adsorption of the antigen and detection antibody, thus providing lower background noise, a lower detection limit, and a wider linear range in CEA assays. This study provides a novel and versatile alternative for developing antifouling coatings to address nonspecific protein adsorption on both PDMS-based engineering and PS-based biological materials.

Chimeric Aptamers-Based and MoS2 Nanosheet-Enhanced Label-Free Fluorescence Polarization Strategy for Adenosine Triphosphate Detection.

Adenosine triphosphate (ATP) as a primary energy source plays a unique role in the regulation of all cellular events. The necessity to detect ATP requires sensitive and accurate quantitative analytical strategies. Herein, we present our study of developing a MoS2 nanosheet-enhanced aptasensor for fluorescence polarization-based ATP detection. A bifunctional DNA strand was designed to consist of chimeric aptamers that recognize and capture ATP and berberine, a fluorescence enhancer. In the absence of ATP, the DNA strand bound to berberine will be hydrolyzed when Exonuclease I (Exo I) is introduced, releasing berberine as a result. In contrast, when ATP is present, ATP aptamer folds into a G-quadruplex structure; thus, the complex can resist degradation by Exo I to maintain berberine for fluorescent detection purpose. In addition, to magnify the fluorescence polarization (FP) signal, MoS2 nanosheets were also adopted in the system. This nanosheets-enhanced FP strategy is simple and facile which does not require traditional dye-labeled DNA strands and complex operation steps. The developed fluorescence polarization aptasensor showed high sensitivity for the quantification of ATP with a detection limit of 34.4 nM, performing well both in buffer solution and in biological samples.

Ratiometric fluorescence sensor based on cholesterol oxidase-functionalized mesoporous silica nanoparticle@ZIF-8 core-shell nanocomposites for detection of cholesterol.

A novel ratiometric fluorescence sensing system based on cholesterol oxidase-functionalized dual-color mesoporous silica nanoparticles (MSNs)@metal-organic framework core-shell nanocomposite is demonstrated for cholesterol detection. MSNs were first loaded with 5-aminofluorescein (AF) inside pores and then wrapped with red-emission CdTe quantum dots (QDs) on the surface to seal in the dye molecules, forming the signal displaying unit (AF-MSN-QDs). Next, AF-MSN-QDs were encapsulated with zeolitic imidazolate framework (ZIF-8) to form a transition layer with distinct size-selectivity, which not only protected the cores from corrosion but also greatly decreased background interference from large molecules. More significantly, the ZIF-8 shells showed high affinity for most enzymes, which made it possible for cholesterol oxidase (ChOx) to self-organize on the surface of ZIF-8-encapsulated AF-MSN-QDs via chemo-physical adsorption, forming novel core-shell nanocomposites (AF-MSN-QD@ZIF-8-ChOx) as a sensing platform for cholesterol detection. The detectable signal was monitored by enzymatic product-quenching fluorescence of the QDs. The fluorescence changes of I520/I618 showed excellent linearity with H2O2 concentrations in the range of 5-100 nM, with a limit of detection (LOD) as low as 0.89 nM. As a proof-of-concept, cholesterol was selectively detected with beneficial LOD as low as 0.923 µg/mL, demonstrating the great potential of this biosensor platform for other biologically important molecules with H2O2-producing oxidases.

A novel peptide/Fe3O4@SiO2-Au nanocomposite-based fluorescence biosensor for the highly selective and sensitive detection of prostate-specific antigen.

Highly selective and sensitive detection methods are very important for the early diagnosis of prostate-specific antigen (PSA). Here, we present a novel peptide/Fe3O4@SiO2-Au nanocomposite-based fluorescence biosensor for highly selective and sensitive detection of PSA. The biosensor was made by self-organizing 5-FAM labeled peptides onto the surface of magnetic Fe3O4@SiO2-Au nanocomposites (MNCPs), resulting in efficient quenching of the FAM fluorescence. The PSA specifically recognized and cleaved the 5-FAM-labeled peptides, leading to the fluorescence recovery. This is the first report of the MNCPs by in situ growth of Au nanoparticles (AuNPs) on the SiO2 encapsulated single Fe3O4 nanocubes. The MNCPs feature robust salt stability, and allow for effective fluorescence quenching and easy magnetic separation, which greatly decrease the background fluorescence. The peptide/MNCPs-based fluorescence biosensor measure a wide range of concentrations of PSA, from 1.0 × 10-12 to 1.0 × 10-9g/mL, with a limit of detection (LOD) of 3.0 × 10-13g/mL in both standard solutions and serum samples, demonstrating the great potential of this biosensor platform for use in clinical and biological assays.

Fabrication of a porous ß-cyclodextrin-polymer-coated solid-phase microextraction fiber for the simultaneous determination of five contaminants in water using gas chromatography-mass spectrometry.

A novel solid-phase microextraction fiber coated with a porous ß-cyclodextrin polymer was developed. The porous ß-cyclodextrin polymer cross-linked using tetrafluoroterephthalonitrile, possessed well-distributed pores and the largest surface area among current ß-cyclodextrin polymers. Scanning electron microscopy revealed that the coating had a continuous wrinkled and folded structure, which guarantees a sufficient loading capacity for contaminants. The properties of the developed fiber were evaluated using headspace solid-phase microextraction of five contaminants as model analytes coupled with gas chromatography-mass spectrometry. Owing to the advantages of a large surface area and three-dimensional cavities, the novel fiber exhibited excellent operational stability and extraction ability. After optimisation of the extraction conditions, including extraction temperature, extraction time, salt effect, and desorption time, validation of the method with water samples achieved good linearity over a wide range (0.01-120 µg L-1) and low detection limits (0.003-1.600 µg L-1). The single-fiber and fiber-to-fiber repeatabilities were 1.7-11.0% and 1.9-11.0%, respectively. The method was applied to the simultaneous analysis of five analytes with satisfactory recoveries (76.6-106.0% for pond water and 89.0-105.9% for rainwater).

A fluorescence aptasensor based on two-dimensional sheet metal-organic frameworks for monitoring adenosine triphosphate.

In the present study, a facile fluorescence aptasensor based on two-dimensional sheet metal-organic frameworks of N,N-bis(2-hydroxyethyl)dithiooxamidato copper(II) (H2dtoaCu) was developed for the sensitive detection of adenosine triphosphate (ATP). The sensing mechanism was based on the noncovalent interaction between FAM-labeled (fluorescein amidite) ATP aptamers and H2dtoaCu. In the absence of ATP, the FAM-labeled aptamer readily adsorbs onto H2dtoaCu, mainly via π-π stacking and hydrogen bond interactions between the nucleotide bases and the H2dtoaCu surface, leading to the reduction of fluorescence intensity of the FAM by photoinduced electron transfer (PET). In the presence of ATP, the FAM-labeled aptamer specifically forms ATP-binding aptamer complexes which exhibit only weak adsorption on the H2dtoaCu surface. Thus, the fluorescence of the FAM-labeled ATP aptamer remained largely unchanged. The fluorescence aptasensor exhibited a good linear relationship between the fluorescence intensity and the logarithm concentration of ATP over a range of 25-400 nM, with a detection limit of 8.19 nM (3S/N). ATP analogs such as guanosine triphosphate, uridine triphosphate, and cytidine triphosphate have negligible effect on the aptasensor performance due to the high selectivity of the ATP aptamer to its target, showing promising potential in real sample analysis.

Spectroscopic quantification of 5-hydroxymethylcytosine in genomic DNA using boric acid-functionalized nano-microsphere fluorescent probes.

5-hydroxymethylcytosine (5hmC) is the sixth base of DNA. It is involved in active DNA demethylation and can be a marker of diseases such as cancer. In this study, we developed a simple and sensitive 2-(4-boronophenyl)quinoline-4-carboxylic acid modified poly (glycidyl methacrylate (PBAQA-PGMA) fluorescent probe to detect the 5hmC content of genomic DNA based on T4 ß-glucosyltransferase-catalyzed glucosylation of 5hmC. The fluorescence-enhanced intensity recorded from the DNA sample was proportional to its 5-hydroxymethylcytosine content and could be quantified by fluorescence spectrophotometry. The developed probe showed good detection sensitivity and selectivity and a good linear relationship between the fluorescence intensity and the concentration of 5 hmC within a 0-100nM range. Compared with other fluorescence detection methods, this method not only could determine trace amounts of 5 hmC from genomic DNA but also could eliminate the interference of fluorescent dyes and the need for purification. It also could avoid multiple labeling. Because the PBAQA-PGMA probe could enrich the content of glycosyl-5-hydroxymethyl-2-deoxycytidine from a complex ground substance, it will broaden the linear detection range and improve sensitivity. The limit of detection was calculated to be 0.167nM after enrichment. Furthermore, the method was successfully used to detect 5-hydroxymethylcytosine from mouse tissues.

Size-selective QD@MOF core-shell nanocomposites for the highly sensitive monitoring of oxidase activities.

In this work, we proposed a novel and facile method to monitor oxidase activities based on size-selective fluorescent quantum dot (QD)@metal-organic framework (MOF) core-shell nanocomposites (CSNCPs). The CSNCPs were synthesized from ZIF-8 and CdTe QDs in aqueous solution in 40min at room temperature with stirring. The prepared CdTe@ZIF-8 CSNCPs , which have excellent water dispersibility and stability, displays distinct fluorescence responses to hole scavengers of different molecular sizes (e.g., H2O2, substrate, and oxidase) due to the aperture limitation of the ZIF-8 shell. H2O2 can efficiently quench the fluorescence of CdTe@ZIF-8 CSNCPs over a linearity range of 1-100nM with a detection limit of 0.29nM, whereas large molecules such as substrate and oxidase have very little effect on its fluorescence. Therefore, the highly sensitive detection of oxidase activities was achieved by monitoring the fluorescence quenching of CdTe@ZIF-8 CSNCPs by H2O2 produced in the presence of substrate and oxidase, which is proportional to the oxidase activities. The linearity ranges of the uricase and glucose oxidase activity are 0.1-50U/L and 1-100U/L, respectively, and their detection limits are 0.024U/L and 0.26U/L, respectively. Therefore, the current QD@MOF CSNCPs based sensing system is a promising, widely applicable means of monitoring oxidase activities in biochemical research.

Carbohydrate analysis on hybrid poly(dimethylsiloxane)/glass chips dynamically coated with ionic complementary peptide.

A facile and efficient dynamic coating method using an ionic complementary peptide was established for high-performance separation of 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-labeled carbohydrates in a hybrid poly(dimethylsiloxane) (PDMS)/glass microfluidic channel. EAK16-II with a sequence of [(Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys)2] can readily self-organize into a complete coating layer tightly adsorbed on both hydrophobic PDMS and hydrophilic glass surfaces, which efficiently suppressed nonspecific analyte adsorption and minimized electroosmotic flow (EOF). Separation conditions were systematically investigated with respect to EAK16-II concentration, running buffer, buffer pH, and field strength (Esep). Under the optimal conditions, rapid and reproducible separations of maltodextrin ladder, glycans from glucosamine capsules, tablets, and pomegranate peel extracts were achieved with over 450000 theoretical plates per meter in the hybrid PDMS/glass microchannels dynamically coated with 1.0mg/mL EAK16-II-0.05% n-dodecyl ß-d-maltoside (DDM), and the relative standard deviation (RSD) values were less than 3.2% (n=4) for the migration times. The present work provides a facile and efficient means to minimize EOF and nonspecific analyte adsorption in microfluidic chips fabricated in various substrates, thereby broadening the applications of microfluidic chips in complicated biological assays.

Fluorescent DNA-Protected Silver Nanoclusters for Ligand-HIV RNA Interaction Assay.

Studying ligand-biomacromolecule interactions provides opportunities for creating new compounds that can efficiently regulate specific biological processes. Ribonucleic acid (RNA) molecules have become attractive drug targets since the discovery of their roles in modulating gene expression, while only a limited number of studies have investigated interactions between ligands and functional RNA molecules, especially those based on nanotechnology. DNA-protected silver nanoclusters (AgNCs) were used to investigate ligand-RNA interactions for the first time in this study. The anthracycline anticancer drug mitoxantrone (MTX) was found to quench the fluorescence of AgNCs. After adding human immunodeficiency virus trans-activation responsive region (TAR) RNA or Rev-response element (RRE) RNA to AgNCs-MTX mixtures, the fluorescence of the AgNCs recovered due to interactions between MTX with RNAs. The binding constants and number of binding sites of MTX to TAR and RRE RNA were determined through theoretical calculations. MTX-RNA interactions were further confirmed in fluorescence polarization and mass spectrometry experiments. The mechanism of MTX-based fluorescence quenching of the AgNCs was also explored. This study provides a new strategy for ligand-RNA binding interaction assay.

Surface Modification of Poly(dimethylsiloxane) Using Ionic Complementary Peptides to Minimize Nonspecific Protein Adsorption.

Poly(dimethylsiloxane) (PDMS) has become a widely used material for microfluidic and biological applications. However, PDMS has unacceptably high levels of nonspecific protein adsorption, which significantly lowers the performance of PDMS-based microfluidic chips. Most existing methods to reduce protein fouling of PDMS are to make the surface more hydrophilic by surface oxidization, polymer grafting, and physisorbed coatings. These methods suffer from the relatively short-term stability, the multistep complex treatment procedure, or the insufficient adsorption reduction. Herein, we developed a novel and facile modification method based on self-assembled peptides with well-tailored amino acid composition and sequence, which can also interact strongly with the PDMS surface in the same way as proteins, for suppressing the nonspecific protein fouling and improving the biocompatibility of PDMS-based microfluidic chips. We first demonstrated that an ionic complementary peptide, EAR16-II with a sequence of [(Ala-Glu-Ala-Glu-Ala-Arg-Ala-Arg)2], can readily self-assemble into an amphipathic film predominantly composed of tightly packed ß-sheets on the native hydrophobic and plasma-oxidized hydrophilic PDMS surfaces upon low concentrations of carbohydrates. The self-assembled EAR16-II amphipathic film exposed its hydrophobic side to the solution and thus rendered the PDMS surface hydrophobic with water contact angles (WCAs) of around 110.0°. However, the self-assembled EAR16-II amphipathic film exhibited excellent protein-repelling and blood compatibility properties comparable to or better than those obtained with previously reported methods. A schematic model has been proposed to explain the interactions of EAR16-II with the PDMS surface and the antifouling capability of EAR16-II coatings at a molecular level. The current work will pave the way to the development of novel coating materials to address the nonspecific protein adsorption on PDMS, thereby broadening the potential uses of PDMS-based microfluidic chips in complex biological analysis.

Biomass-derived highly porous functional carbon fabricated by using a free-standing template for efficient removal of methylene blue.

Banana peel (BP), a biomass waste, was converted into a valuable highly porous functional carbon material (HPFCM) by a general chelate-assisted co-assembly process. The HPFCMs were fabricated by using Al(III)-based metal-organic framework-like as a free-standing template and commercial Pluronic F127 as a microstructure-directing agent. Several critical variables for fabrication including doses of Al(III) and F127, carbonization temperature had been optimized and the adsorption behavior of HPFCMs was examined by using methylene blue as dye model compound. The optimal adsorbent was validated as HPFCMs-5-1-800, and its equilibrium data were well fitted to the Langmuir isotherm model with a monolayer adsorption capacity of 385.12 mg g(-1) at ambient temperature. The surface physical properties of HPFCMs-5-1-800 were also exemplarily characterized. The findings revealed that the free-standing template is a potential route for preparation of HPFCM from waste BP.