Positively-charged Molecules Research Articles

In situ fabrication of fully negatively-charged layer-by-layer nanofilms on a living cell surface.

Fully negatively-charged (FNC) layer-by-layer nanofilms were successfully assembled on a living cell surface for the first time using only poly(acrylic acid) (PAA) by introducing strain-promoted click chemistry to crosslink PAA layers. The resulting nanofilms retained their negative charges and showed higher adsorption of positively-charged molecules without affecting the cell viability.

Smart hybrid copolymer-coated silica nanosystems with dual responsiveness as a carrier for positive charged molecules

Smart nanosystems consisting of inorganic particles and responsive polymers display significant and remarkable aspects. Such combined work exploits a facile path for multifunctional nanomaterials and facilitates various novel technological applications due to “live” polymer components. Here, we report the design and synthesis of a new platform of smart hybrid nanosystems (SHN) for positively charged probe loading and specific release under pH and temperature-controlled conditions. The SHN was prepared by a simple sequential method that produced an integrated core–shell nanomaterial with a dual stimulus response and excellent colloidal stability. Further, we demonstrate by crossing DLS and NMR results that these core–shell nanosystems present transduction from both stimuli to a mechanical shrinkage of the polymeric shell, leading to a remote-controlled dual response that can be synthetically tuned by controlling the molar ratio between monomers. Finally, we studied the potential of these SHN as molecular carriers and demonstrated that they are useful for selective ionic encapsulation of positively charged molecules, which release is controlled by the dual responsiveness. We successfully extended this concept to doxorubicin release triggered by T and pH changes, which opens possibilities of using these SHN improving results and patient compliance in chemotherapy treatments.

Numerical Study of Single Molecular Charge Sensing by FET-Integrated Nanopore Biosensor

This report studies the charge-based sensing modality of FET-embedded nanopore biosensors through FEM simulation. PNP equation is solved to analyze the mirror charge introduced by charged biomolecule while threading through the nanopore-FET sensor. Negative and positive charged molecules are analyzed respectively. Obvious local potential change induced by the presenting of charged molecules nearby is observed. In addition, the transport-induced descreening effect is observed under intensive bias, which might explain the capability of charge sensing even under high concentrations such as 1 M for FET-nanopore biosensors.

Tuning of nanofiltration membrane by multifunctionalized nanovesicles to enable an ultrahigh dye/salt separation at high salinity

A nanofiltration (NF) membrane capable of efficiently separating dye and salt at high-salinity is of great interest for the effective treatment of the textile wastewater. However, existing NF membranes exhibit either an excessively high salt rejection or a compromised dye rejection at high salinity. To overcome these challenges, herein the highly uniform nanovesicles functionalized with positively-charged molecules and nonreactive polymers were employed to tune the surface charge density and pore size of the thin-film composite (TFC) NF membrane via interfacial polymerization. The tuning proved efficient to simultaneously reduce surface charge density and enlarge pore size to the desired extent, which enabled a very low retention of salts (∼7% for NaCl) while maintaining a rather high dye rejection (∼99.8% for Direct red 23) with a high salt/dye separation factor of 464. Additionally, the separation stability of the finely-tuned membrane was superior to most of other reported NF membranes when treating a high-salinity dye/salt mixture. Meanwhile, the water permeability of the modified TFC membrane was enhanced by a factor of 2.6, reaching up to 205.8 L m−2 h−1 MPa. This study paves a new route to the high-performance NF membrane for an effective treatment of the high-salinity textile wastewater.

Bioinspired redox-driven NAD+ pump membranes with composition of annulated and cylindrical channel

In nature, ion transportation across cell membranes promotes the conduction of biological signals. Inspired by these gorgeous phenomena of nature, we construct a new artificial nanochannel membrane can well recurrence the ion transportation character of the biological ion pump by varying surface properties and present similar regulation mechanism by direct precisely controllable ion transportation. What counts is two separate channels including annulated and cylindrical channel, where the controllable translocation of ion influx across the membrane due to the change of surface charges and asymmetric structure. Notably, the mechanism of this system is that the highly positive charged molecules Nicotinamide adenine dinucleotide oxidized form cations (NAD+) are driven to into nanochannels membrane due to the redox reaction, which is carried out by an energy-transducing oxidoreduction from its reduced form (NADH) to product its oxidized form (NAD+) by O2. As a light-controlled ion pump, this SiO2 membrane system can selectively restrict NADH flux. Such a new ion pump could not only provide the emergence of an in-depth mechanistic understanding on smart ion pump behavior in living organism but also promotes the development of artificial ion pump devices in power source, seawater desalination and biosensor.

Investigating Novel Syntheses of a Series of Unique Hybrid PLGA-Chitosan Polymers for Potential Therapeutic Delivery Applications.

Discovering new materials to aid in the therapeutic delivery of drugs is in high demand. PLGA, a FDA approved polymer, is well known in the literature to form films or nanoparticles that can load, protect, and deliver drug molecules; however, its incompatibility with certain drugs (due to hydrophilicity or charge repulsion interactions) limits its use. Combining PLGA or other polymers such as polycaprolactone with other safe and positively-charged molecules, such as chitosan, has been sought after to make hybrid systems that are more flexible in terms of loading ability, but often the reactions for polymer coupling use harsh conditions, films, unpurified products, or create a single unoptimized product. In this work, we aimed to investigate possible innovative improvements regarding two synthetic procedures. Two methods were attempted and analytically compared using nuclear magnetic resonance (NMR), fourier-transform infrared spectroscopy (FT-IR), and dynamic scanning calorimetry (DSC) to furnish pure, homogenous, and tunable PLGA-chitosan hybrid polymers. These were fully characterized by analytical methods. A series of hybrids was produced that could be used to increase the suitability of PLGA with previously non-compatible drug molecules.

Shape-controlled synthesis of liquid metal nanodroplets for photothermal therapy

The capping agents for liquid metal (LM) nanodroplets in aqueous solutions are restricted to thiol-containing and positively-charged molecules or macromolecules. However, both thiolate-metal complex and electrostatic interaction are liable to detachment upon strong mechanical forces such as sonication, leading to limited stability and applications. To address this, we utilized ultrasmall water soluble melanin nanoparticles (MNPs) as the capping agent, which exhibited strong metal binding capability with the oxide layer of gallium based LMs and resulted in enhanced stability. Interestingly, shape-controlled synthesis of LM nanodroplets can be achieved by the incorporation of MNPs. Various EGaIn nanostructures including nanorice, nanosphere and nanorod were obtained by simply tuning the feed ratio, sonication time, and suspension temperature. Among these shapes, EGaIn nanorice has the best photothermal conversion efficiency, which could be leveraged for photothermal therapy.

Coxsackievirus B3 Responds to Polyamine Depletion via Enhancement of 2A and 3C Protease Activity.

Polyamines are small positively-charged molecules abundant in eukaryotic cells that are crucial to RNA virus replication. In eukaryotic cells, polyamines facilitate processes such as transcription, translation, and DNA replication, and viruses similarly rely on polyamines to facilitate transcription and translation. Whether polyamines function at additional stages in viral replication remains poorly understood. Picornaviruses, including Coxsackievirus B3 (CVB3), are sensitive to polyamine depletion both in vitro and in vivo; however, precisely how polyamine function in picornavirus infection has not been described. Here, we describe CVB3 mutants that arise with passage in polyamine-depleted conditions. We observe mutations in the 2A and 3C proteases, and we find that these mutant proteases confer resistance to polyamine depletion. Using a split luciferase reporter system to measure protease activity, we determined that polyamines facilitate viral protease activity. We further observe that the 2A and 3C protease mutations enhance reporter protease activity in polyamine-depleted conditions. Finally, we find that these mutations promote cleavage of cellular eIF4G during infection of polyamine-depleted cells. In sum, our results suggest that polyamines are crucial to protease function during picornavirus infection. Further, these data highlight viral proteases as potential antiviral targets and highlight how CVB3 may overcome polyamine-depleting antiviral therapies.

Alternative <em>In Vitro</em> Methods for the Determination of Viral Capsid Structural Integrity

Human norovirus exacts considerable public health and economic losses worldwide. Emerging in vitro cultivation advances are not yet applicable for routine detection of the virus. The current detection and quantification techniques, which rely primarily on nucleic acid amplification, do not discriminate infectious from non-infectious viral particles. The purpose of this article is to present specific details on recent advances in techniques used together in order to acquire further information on the infectivity status of viral particles. One technique involves assessing binding of a norovirus ssDNA aptamer to capsids. Aptamers have the advantage of being easily synthesized and modified, and are inexpensive and stable. Another technique, dynamic light scattering (DLS), has the advantage of observing capsid behavior in solution. Electron microscopy allows for visualization of the structural integrity of the viral capsids. Although promising, there are some drawbacks to each technique, such as non-specific aptamer binding to positively-charged molecules from sample matrices, requirement of purified capsid for DLS, and poor sensitivity for electron microscopy. Nonetheless, when these techniques are used in combination, the body of data produced provides more comprehensive information on norovirus capsid integrity that can be used to infer infectivity, information which is essential for accurate evaluation of inactivation methods or interpretation of virus detection. This article provides protocols for using these methods to discriminate infectious human norovirus particles.

Alternative In Vitro Methods for the Determination of Viral Capsid Structural Integrity.

Human norovirus exacts considerable public health and economic losses worldwide. Emerging in vitro cultivation advances are not yet applicable for routine detection of the virus. The current detection and quantification techniques, which rely primarily on nucleic acid amplification, do not discriminate infectious from non-infectious viral particles. The purpose of this article is to present specific details on recent advances in techniques used together in order to acquire further information on the infectivity status of viral particles. One technique involves assessing binding of a norovirus ssDNA aptamer to capsids. Aptamers have the advantage of being easily synthesized and modified, and are inexpensive and stable. Another technique, dynamic light scattering (DLS), has the advantage of observing capsid behavior in solution. Electron microscopy allows for visualization of the structural integrity of the viral capsids. Although promising, there are some drawbacks to each technique, such as non-specific aptamer binding to positively-charged molecules from sample matrices, requirement of purified capsid for DLS, and poor sensitivity for electron microscopy. Nonetheless, when these techniques are used in combination, the body of data produced provides more comprehensive information on norovirus capsid integrity that can be used to infer infectivity, information which is essential for accurate evaluation of inactivation methods or interpretation of virus detection. This article provides protocols for using these methods to discriminate infectious human norovirus particles.

Natural Non-Mulberry Silk Nanoparticles for Potential-Controlled Drug Release.

Natural silk protein nanoparticles are a promising biomaterial for drug delivery due to their pleiotropic properties, including biocompatibility, high bioavailability, and biodegradability. Chinese oak tasar Antheraea pernyi silk fibroin (ApF) nanoparticles are easily obtained using cations as reagents under mild conditions. The mild conditions are potentially advantageous for the encapsulation of sensitive drugs and therapeutic molecules. In the present study, silk fibroin protein nanoparticles are loaded with differently-charged small-molecule drugs, such as doxorubicin hydrochloride, ibuprofen, and ibuprofen-Na, by simple absorption based on electrostatic interactions. The structure, morphology and biocompatibility of the silk nanoparticles in vitro are investigated. In vitro release of the drugs from the nanoparticles depends on charge-charge interactions between the drugs and the nanoparticles. The release behavior of the compounds from the nanoparticles demonstrates that positively-charged molecules are released in a more prolonged or sustained manner. Cell viability studies with L929 demonstrated that the ApF nanoparticles significantly promoted cell growth. The results suggest that Chinese oak tasar Antheraea pernyi silk fibroin nanoparticles can be used as an alternative matrix for drug carrying and controlled release in diverse biomedical applications.

Cell Adhesion Strength is Reduced by the Presence of Pericellular Matrix Patches

We present a detailed characterization of the organization of hyaluronan and bottlebrush proteoglycans in the pericellular matrix (PCM) of rat chondrocyte cells (RCJ-P) and PC3 prostrate cancer cells, and then use that insight to understand how the PCM impacts the transport of nanoparticles and charged molecules to the cell surface, and the cell's adhesion to substrates. Our studies reveal that the PCM strongly impacts the flux of nanoparticles to the cell surface in a size-dependent fashion. Further, the concentration of bottlebrushes (e.g. aggrecan, versican) in the PCM determines a maximal particle size that can reach the cell surface, ∼400nm for both cell lines but only ∼200nm when the PCM is saturated with proteoglycans. These observations have direct implications for studies of drug delivery vehicles and exosomes, whose particle sizes fall in this range. Our studies also provide evidence that negatively-charged chondroitin sulfates in the bottlebrush proteoglycans are available for binding to positively-charged molecules (e.g. growth factors), sequestering and concentrating molecules near the cell surface, as well as protecting them from enzymatic degradation. Super-resolution imaging of PCM at the cell-substrate interface reveals patches of PCM in co-existence with vinculin-rich adhesions. In order to address whether the PCM acts as a repulsive cushion, we quantify the cell adhesion strength versus enzymatic degradation of the PCM using a spinning disk apparatus. The studies show that the adhesion strength increases by ∼24% for RCJP cells enzymatically-treated with hyaluronidase and by a factor of ∼39% for PC3 cells. A similar increase in adhesion occurs with chondroitinase-ABC treatment. Together, these quantitative measurements of the pericellular matrix indicate that this common but neglected in vitro and in vivo structure deserves further attention to understand how it regulates cells’ interactions with their surroundings. Funding: NSF CAREER-DMR-0848797.

Heparin-based hydrogels with tunable sulfation & degradation for anti-inflammatory small molecule delivery.

Sustained release of anti-inflammatory agents remains challenging for small molecule drugs due to their low molecular weight and hydrophobicity. Therefore, the goal of this study was to control the release of a small molecule anti-inflammatory agent, crystal violet (CV), from hydrogels fabricated with heparin, a highly sulfated glycosaminoglycan capable of binding positively-charged molecules such as CV. In this system, both electrostatic interactions between heparin and CV and hydrogel degradation were tuned simultaneously by varying the level of heparin sulfation and varying the amount of dithiothreitol within hydrogels, respectively. It was found that heparin sulfation significantly affected CV release, whereby more sulfated heparin hydrogels (Hep and Hep(-N)) released CV with near zero-order release kinetics (R-squared values between 0.96-0.99). Furthermore, CV was released more quickly from fast-degrading hydrogels than slow-degrading hydrogels, providing a method to tune total CV release between 5-15 days while maintaining linear release kinetics. In particular, N-desulfated heparin hydrogels exhibited efficient CV loading (∼90% of originally included CV), near zero-order CV release kinetics, and maintenance of CV bioactivity after release, making this hydrogel formulation a promising CV delivery vehicle for a wide range of inflammatory diseases.

Induced Formation of Dominating Polar Phases of Poly(vinylidene fluoride): Positive Ion–CF2 Dipole or Negative Ion–CH2 Dipole Interaction

The "ion-dipole" interaction has been the most widely accepted mechanism for the direct formation of polar phases (β, γ) of poly(vinylidene fluoride) (PVDF), which have been widely used as transducers, actuators, and sensors. However, the type of charged ions is still controversial. In order to throw light upon this issue, two types of charged small organic molecules that are in different physical states (melt or solid) during the crystallization of PVDF were melt-blended with PVDF resin. Results revealed that only the incorporation of positive charged molecules can lead to the formation of polar phases. Additionally, it is interesting to find that during the crystallization of PVDF, molten positively charged molecules resulted in β-phase dominating, while solid positively charged molecules exclusively induced γ-phase. These results lead to the understanding that the induced formation of polar phases of PVDF is due to the "positive ion-CF2 dipole" interaction.

Mussel-inspired protein-mediated surface functionalization of electrospun nanofibers for pH-responsive drug delivery

pH-responsive drug delivery systems could mediate drug releasing rate by changing the pH values at specific times as per the pathophysiological need of the disease. This paper demonstrates that a mussel-inspired protein polydopamine coating can tune the loading and releasing rate of charged molecules from electrospun poly(ε-caprolactone) (PCL) nanofibers in solutions with different pH values. In vitro release profiles show that the positive charged molecules release significantly faster in acidic than those in neutral and basic environments within the same incubation time. The results of fluorescein diacetate staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays show the viability of cancer cells after treatment with doxorubicin-released media at different pH values qualitatively and quantitatively, indicating that the media containing doxorubicin that were released in solutions at low pH values could kill a significantly higher number of cells than those released in solutions at high pH values. Together, the pH-responsive drug delivery systems based on polydopamine-coated PCL nanofibers could have potential application in the oral delivery of anticancer drugs for treating gastric cancer and in vaginal delivery of anti-viral drugs or anti-inflammatory drugs, which could raise their efficacy, deliver them to the specific target and minimize their toxic side effects.

Histones, Like Platelet Factor 4 (PF4), Affect Generation of Activated Protein C: Implications for the Pathogenesis of Severe Sepsis

Abstract 530Platelet factor 4 (PF4) increases aPC generation by the thrombin (IIa)/thrombomodulin (TM) complex and may impact outcome in sepsis. PF4’s effect on aPC generation follows a biphasic curve when tested in solution, on human TM expressing HEK293, and on primary endothelial cells (ECs) with a peak concentration at around 25 μg/ml. Formation of complexes at a specific molar ratio between positively-charged tetramers of PF4 and negatively-charged chondroitin sulfate (CS) on the TM glycosaminoglycan (GAG) is crucial for the increase in aPC generation. Other positively-charged molecules like protamine sulfate (PRT) affect aPC generation in a similar manner, and heparin, which is known to bind PF4 and PRT more avidly than CS, lowers effective PF4 or PRT concentrations. Here we examined whether histones, that are also small positively-charged molecules, affect aPC generation. Histones released from cells in sepsis are cytotoxic toward ECs and lethal when injected into mice, and aPC reverses this lethality. May histones affect aPC generation by the same mechanism as other positively-charged molecules, and how does the presence of PF4 or heparin influence this effect? We have addressed these questions both in solution and with TM-expressing cells, in the absence or presence of endothelial protein C receptor. We found that individual, or mixed histones affect aPC formation following a similar biphasic curve seen with PF4 with a peak effect at around 10 μg/ml but to lesser extent (2-fold maximal increase compared to 6-fold for PF4). Histones and PF4 are additive at low concentrations; however, more importantly, histones only decreased aPC generation when tested in the presence of optimal or higher PF4 concentration (>25 μg/ml). Just as with PF4, added heparin decreased effective histone concentration and shifted the curve for aPC generation to the right, both in the absence or presence of PF4. We hypothesize that normally PF4 released from platelets augments aPC generation and low concentration of histones have similar effect. But when histones are released in sepsis in high concentrations, their interaction with CS on TM blocks formation of complexes between PF4 and TM’s CS that are optimal for maximal increase of aPC generation. Further we tested the effect of histones on aPC generation in vivo. Injection of histones in mice increased IIa-induced (2U/kg) aPC generation in plasma. This increase was concentration dependent (at 1 to 20 mg/kg increasing aPC generation up to 10-fold), but injection of higher amount of histones (40 mg/kg) became lethal. Mice that were overexpressing human PF4 had an increased lethality when histones at 40 mg/kg were co-injected with thrombin (2U/kg) over the littermate mice deficient in murine PF4 (60% vs. 0% mortality, respectively, n=5 for each group) suggesting that in vivo histones may also act additively with PF4 on aPC generation. We propose that in severe septic patients, especially those with high levels of released PF4, concurrently available histones suppress aPC generation. By binding to the excess of PF4 and/or histones, heparin may be beneficial in severe sepsis by allowing improved aPC generation. Disclosures:No relevant conflicts of interest to declare.

Influence of particle size and salinity on adsorption of basic dyes by agricultural waste: dried Seagrape (Caulerpa lentillifera)

Green macroalga Caulerpa lentillifera was found to have reasonable adsorption capacity for basic dyes, Astrazon Blue FGRL (AB), Astrazon Red GTLN (AR), and Astrazon Golden Yellow GL-E (AY). The initial dye concentration was in the range of 100-1,800 mg/L. The dried algal sorbent was ground and sieved into 3 sizes: S (0.1-0.84 mm), M (0.84-2.0 mm), and L sizes (larger than 2.0 mm). For all conditions examined in this work (at 25 degrees C in batch systems), the adsorption reached equilibrium within the first hour. The kinetic data corresponded well with the pseudo second order kinetic model where the rate constant, k2, decreased as the sorbent size increased for all dyes. The adsorption isotherms followed both Langmuir and Freundlich models. Among three sorbent sizes, S size gave the highest adsorption capacity followed by M and L sizes. A reduction of sorbent size increased the specific surface area for mass transfer, and also increased the total pore volume, thus providing more active sites for adsorption. The adsorption of AB was adversely influenced by the protonation of algal surface at low pH. On the other hand, the adsorption of AR and AY could be due to weak electrostatic interaction, which was not significantly affected by pH. Increasing salinity of the system caused a decrease in adsorption capacity possibly due to the competition between Na+ and the dye cations for the binding sites on algal surface. Moreover, an increase in salinity generated a compressed electrical double layer on the algal surface which exerted repulsive force, retarding the adsorption of positive charged molecules such as the basic dyes.

Permeation of permanently positive charged molecules through artificial membranes—Influence of physico-chemical properties

The aim of this study was to investigate the permeation properties of 20 permanently positive charged molecules in the parallel artificial membrane permeability assay (PAMPA). Eight of them were derivatives of the N-alkyl-isoquinolinium salt and 12 were congeners of the dye rhodamine 110. Five out of 12 molecules from the rhodamine 110 series have one additional carboxylic group and two have two carboxylic acids. The experimentally derived effective permeability values ( P e) cover a range of 3–4 log units. Ten compounds showed low permeabilities ( P e < 0.1 × 10 −6 cm/s), four medium permeabilities (0.1 × 10 −6 ≤ P e < 1 × 10 −6 cm/s) and six were highly permeable ( P e ≥ 1 × 10 −6 cm/s). In addition, computational models were built with a number of calculated molecular descriptors and evaluated for their ability to predict membrane permeability. It turned out that the experimental P e values can be explained by electronic properties and parameters describing the shape of molecules. This work provides evidence that permanently charged molecules can have high passive membrane permeabilities provided that the charge can be spread over several aromatic ring systems.

To Construct “Ion Traps” for Enhancing the Permselectivity and Permeability of Polyelectrolyte Multilayer Films

We introduced single-charged molecules into layer-by-layer film of polymers by mixing polyelectrolyte and single-charged molecules with an appropriate ratio to form polymer complex and then deposition in alternation with counter-polyelectrolyte. By immersing the layer-by-layer film into aqueous solution of electrolytes, the single-charged molecules could be released from the layer-by-layer film. An interesting finding is the releasing of the single-charged molecules gave the multilayer film the permselectivity. For example, cations would be trapped and anions be repelled if positive-charged molecules were used. Multilayer films able to trap either cations or anions could be fabricated, depending on the nature of single-charged template molecules used. Thus, the ion permselectivity of multilayer film was enhanced. Moreover, the permeability of the film was also dramatically increased, suggesting the potential application of layer-by-layer films as highly efficient ion-permselective membranes.

Eurocorr 2004 – Part 2

(2005). Eurocorr 2004 – Part 2. Corrosion Engineering, Science and Technology: Vol. 40, No. 1, pp. 5-15.