Thermotropic "Plumber's Nightmare"-A Tight Liquid Organic Double Framework

Gyroid, double diamond and the body-centred "Plumber's nightmare" are the three most common bicontinuous cubic phases in lyotropic liquid crystals and block copolymers. While the first two are also present in solvent-free thermotropics, the latter had never been found. Containing six-fold junctions, it was unlikely to form in the more common phases with rod-like cores normal to the network columns, where a maximum of four branches can join at a junction. The solution has therefore been sought in side-branched mesogens that lie in axial bundles joined at their ends by flexible "hinges". But for the tightly packed double framework, geometric models predicted that the side-chains should be very short. The true Plumber's nightmare reported here, using fluorescent dithienofluorenone rod-like mesogen, has been achieved with, indeed, no side chains at all, but with 6 flexible end-chains. Such molecules normally form columnar phases, but the key to converting a complex helical column-forming mesogen into a framework-forming one was the addition of just one methyl group to each pendant chain. A geometry-based explanation is given.

Supertwisted Chiral Gyroid Mesophase in Chiral Rod-Like Compounds

Among the intriguing bicontinuous self-assembled structures, the gyroid cubic is the most ubiquitous. It is found in block and star polymers, surfactants with or without solvent, in thermotropic liquid crystals with end- or side-chains, and in biosystems providing structural color and modelling cell mitosis. It contains two interpenetrating networks of opposite chirality and is thus achiral if, as usual, the content of the two nets is the same. However, we now find that this is not the case for strongly chiral compounds. While achiral molecules follow the opposite twists of nets 1 and 2, molecules with a chiral center in their rod-like core fail to follow the 70° twist between junctions in net 2 and instead wind against it by -110° to still match the junction orientation. The metastable chiral gyroid is a high-entropy high-heat-capacity mesophase. The homochirality of its nets makes the CD signal of the thienofluorenone compounds close to that in the stable I23 phase with 3 isochiral nets.

Mesoporous Silica-Based Nanoplatforms Are Theranostic Agents for the Treatment of Inflammatory Disorders

Complete recovery from infection, sepsis, injury, or trauma requires a vigorous response called inflammation. Inflammatory responses are essential in balancing tissue homeostasis to protect the tissue or resolve harmful stimuli and initiate the healing process. Identifying pathologically important inflammatory stimuli is important for a better understanding of the immune pathways, mechanisms of inflammatory diseases and organ dysfunctions, and inflammatory biomarkers and for developing therapeutic targets for inflammatory diseases. Nanoparticles are an efficient medical tool for diagnosing, preventing, and treating various diseases due to their interactions with biological molecules. Nanoparticles are unique in diagnosis and therapy in that they do not affect the surroundings or show toxicity. Modern medicine has undergone further development with nanoscale materials providing advanced experimentation, clinical use, and applications. Nanoparticle use in imaging, drug delivery, and treatment is growing rapidly owing to their spectacular accuracy, bioavailability, and cellular permeability. Mesoporous silica nanoparticles (MSNs) play a significant role in nano therapy with several advantages such as easy synthesis, loading, controllability, bioavailability over various surfaces, functionalization, and biocompatibility. MSNs can be used as theranostics in immune-modulatory nano systems to diagnose and treat inflammatory diseases. The application of MSNs in the preparation of drug-delivery systems has been steadily increasing in recent decades. Several preclinical studies suggest that an MSN-mediated drug-delivery system could aid in treating inflammatory diseases. This review explains the role of nanoparticles in medicine, synthesis, and functional properties of mesoporous silica nanoparticles and their therapeutic role against various inflammatory diseases.

Mesoporous Silica Nanoparticles Functionalized with Amino Groups for Biomedical Applications

The synthesis and characterization of amino-functionalized mesoporous silica nanoparticles are presented following two different synthetic methods: co-condensation and post-synthesis grafting of 3-aminopropyltriethoxysilane. The amino groups' distribution on the mesoporous silica nanoparticles was evaluated considering the aggregation state of a grafted photosensitizer (Verteporfin) by using spectroscopic techniques. The homogeneous distribution of amino groups within the silica network is a key factor to avoid aggregation during further organic functionalization and to optimize the performance of functionalized silica nanoparticles in biomedical applications. In addition, the formation of a protein corona on the external surface of both bare and amino-functionalized mesoporous silica was also investigated by adsorbing Bovine Serum Albumin (BSA) as a model protein. The adsorption of BSA was found to be favorable, reducing the aggregation phenomena for both bare and amino-modified nanoparticles. Nevertheless, the dispersant effect of BSA was much more evident in the case of amino-modified nanoparticles, which reached monodispersion after adsorption of the protein, thus suggesting that amino-modified nanoparticles can benefit from protein corona formation for preventing severe aggregation in biological media.

Computational Reverse-Engineering Analysis for Scattering Experiments of Assembled Binary Mixture of Nanoparticles

In this paper, we describe a computational method for analyzing results from scattering experiments on dilute solutions of supraparticles, where each supraparticle is created by the assembly of nanoparticle mixtures. Taking scattering intensity profiles and nanoparticle mixture composition and size distributions in each supraparticle as input, this computational approach called computational reverse engineering analysis for scattering experiments (CREASE) uses a genetic algorithm to output information about the structure of the assembled nanoparticles (e.g., real space pair correlation function, extent of nanoparticle mixing/segregation, sizes of domains) within a supraparticle. We validate this method by taking as input in silico scattering intensity profiles from coarse-grained molecular simulations of a binary mixture of nanoparticles, forming a close-packed structure and testing if our computational method can correctly reproduce the nanoparticle structure observed in those simulations. We test the strengths and limitations of our method using a variety of in silico scattering intensity profiles obtained from simulations of a spherical or a cubic supraparticle comprising binary nanoparticle mixtures with varying chemistries, with and without dispersity in sizes, that exhibit well-mixed to strongly segregated structures. The strengths of the presented method include its capability to analyze scattering intensity profiles even when the wavevector q range is limited, to handily provide all of the pairwise radial distribution functions, and to correctly determine the extent of segregation/mixing of the nanoparticles assembled in complex geometries.

Insights into the Formation Pathway of Templated Ordered Nanostructured Carbonaceous Particles under Hydrothermal Conditions

Ordered nanostructured materials and their porous counterparts are important for numerous applications in sorption and separation sciences, electrochemistry, catalysis, and photonics. They can be synthesized by introducing surfactant or amphiphilic polymer template(s) into the condensation stage of a developing solid. Understanding the pathways involved in the formation of these materials is of great interest and will help in the development of future synthesis schemes for designing nanomaterials with controlled nanostructures, pore sizes and shapes, and particle morphologies. In this work, the formation pathway of carbonaceous particles, with cubic-type ordered nanostructures, in the polymer amphiphile-templated hydrothermal condensation of sugar was investigated. A detailed transmission electron microscopy study revealed the initial formation of ∼50 nm sized nanoparticles and the structure attributable to assembled nanoparticles to form larger microparticle volumes. Small-angle X-ray scattering analysis showed the time-dependent development of the ordered structures in the carbonaceous particles. A dynamic stabilization-destabilization of the ordered phase was suggested through the analysis of the liquid crystalline gel-like matrix. The growing carbonaceous body inherited the final liquid crystalline phase, giving the microparticles a well-ordered cubic nanostructure. An additional internal domain texture was also revealed inside the microparticles. The proposed pathway will contribute toward establishing strategies for precisely manipulating nanostructured bodies as well as acquiring an in-depth understanding of the templated precipitations, including those in the natural systems.

Studies of nanoparticle delivery with in vitro bio-engineered microtissues

A variety of engineered nanoparticles, including lipid nanoparticles, polymer nanoparticles, gold nanoparticles, and biomimetic nanoparticles, have been studied as delivery vehicles for biomedical applications. When assessing the efficacy of a nanoparticle-based delivery system, in vitro testing with a model delivery system is crucial because it allows for real-time, in situ quantitative transport analysis, which is often difficult with in vivo animal models. The advent of tissue engineering has offered methods to create experimental models that can closely mimic the 3D microenvironment in the human body. This review paper overviews the types of nanoparticle vehicles, their application areas, and the design strategies to improve delivery efficiency, followed by the uses of engineered microtissues and methods of analysis. In particular, this review highlights studies on multicellular spheroids and other 3D tissue engineering approaches for cancer drug development. The use of bio-engineered tissues can potentially provide low-cost, high-throughput, and quantitative experimental platforms for the development of nanoparticle-based delivery systems.

Enhanced Phenol Tert-Butylation Reaction Activity over Hierarchical Porous Silica-Alumina Materials

Hierarchical aluminum-silicon materials have been successfully prepared by mixing pre-crystallization of silica-alumina sol and citric acid under hydrothermal conditions. The influence of pre-crystallization time on the micro-mesoporous structure is studied using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), N2 physical adsorption, and high-resolution transmission electron microscopy (HRTEM). The catalytic performance of hierarchical silica-alumina material is evaluated by alkylation of phenol with tert-butanol. The results show that the silica-alumina materials with a pre-crystallization time of 16 h show micro-mesoporous structure and excellent catalytic activity.

Recent advances in hexavalent chromium removal from aqueous solutions by adsorptive methods

Chromium exists mainly in two forms in environmental matrices, namely, the hexavalent (Cr(vi)) and trivalent (Cr(iii)) chromium. While Cr(iii) is a micronutrient, Cr(vi) is a known carcinogen, and that warrants removal from environmental samples. Amongst the removal techniques reported in the literature, adsorption methods are viewed as superior to other methods because they use less chemicals; consequently, they are less toxic and easy to handle. Mitigation of chromium using adsorption methods has been achieved by exploiting the physical, chemical, and biological properties of Cr(vi) due to its dissolution tendencies in aqueous solutions. Many adsorbents, including synthetic polymers, activated carbons, biomass, graphene oxide, and nanoparticles as well as bioremediation, have been successfully applied in Cr(vi) remediation. Initially, adsorbents were used singly in their natural form, but recent literature shows that more composite materials are generated and applied. This review focused on the recent advances, insights, and project future directions for these adsorbents as well as compare and contrast the performances achieved by the mentioned adsorbents and their variants.

pH-mediated control over the mesostructure of ordered mesoporous materials templated by polyion complex micelles

Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH.

Synthesis and compatibility evaluation of versatile mesoporous silica nanoparticles with red blood cells: an overview

Protean mesoporous silica nanoparticles are propitious candidates over decades for nanoscale drug delivery systems due to their unique characteristics, including changeable pore size, mesoporosity, high drug loading capacity and biodegradability.

Rod-shaped mesoporous silica nanoparticles for nanomedicine: recent progress and perspectives

INTRODUCTION

Interest in mesoporous silica nanoparticles for drug delivery has resulted in a good understanding of the impact of size and surface chemistry of these nanoparticles on their performance as drug carriers. Shape has emerged as an additional factor that can have a significant effect on delivery efficacy. Rod-shaped mesoporous silica nanoparticles show improvements in drug delivery relative to spherical mesoporous silica nanoparticles.

AREAS COVERED

This review summarises the synthesis methods for producing rod-shaped mesoporous silica nanoparticles for use in nanomedicine. The second part covers recent progress of mesoporous silica nanorods by comparing the impact of sphere and rod-shape on drug delivery efficiency.

EXPERT OPINION

As hollow mesoporous silica nanorods are capable of higher drug loads than most other drug delivery vehicles, such particles will reduce the amount of mesoporous silica in the body for efficient therapy. However, the importance of nanoparticle shape on drug delivery efficiency is not well understood for mesoporous silica. Studies that visualize and quantify the uptake pathway of mesoporous silica nanorods in specific cell types and compare the cellular uptake to the well-studied nanospheres should be the focus of research to better understand the role of shape in uptake.

Mesoporous Silica Nanoparticles: A Comprehensive Review on Synthesis and Recent Advances

Recent advancements in drug delivery technologies utilizing a variety of carriers have resulted in a path-breaking revolution in the approach towards diagnosis and therapy alike in the current times. Need for materials with high thermal, chemical and mechanical properties have led to the development of mesoporous silica nanoparticles (MSNs). These ordered porous materials have garnered immense attention as drug carriers owing to their distinctive features over the others. They can be synthesized using a relatively simple process, thus making it cost effective. Moreover, by controlling the parameters during the synthesis; the morphology, pore size and volume and particle size can be transformed accordingly. Over the last few years, a rapid increase in research on MSNs as drug carriers for the treatment of various diseases has been observed indicating its potential benefits in drug delivery. Their widespread application for the loading of small molecules as well as macromolecules such as proteins, siRNA and so forth, has made it a versatile carrier. In the recent times, researchers have sorted to several modifications in the framework of MSNs to explore its potential in drug resistant chemotherapy, antimicrobial therapy. In this review, we have discussed the synthesis of these multitalented nanoparticles and the factors influencing the size and morphology of this wonder carrier. The second part of this review emphasizes on the applications and the advances made in the MSNs to broaden the spectrum of its use especially in the field of biomedicine. We have also touched upon the lacunae in the thorough understanding of its interaction with a biological system which poses a major hurdle in the passage of this carrier to the clinical level. In the final part of this review, we have discussed some of the major patents filed in the field of MSNs for therapeutic purpose.

Growth of 2D Mesoporous Polyaniline with Controlled Pore Structures on Ultrathin MoS2 Nanosheets by Block Copolymer Self-Assembly in Solution

The development of versatile strategies toward two-dimensional (2D) porous nanocomposites with tunable pore structures draws immense scientific attention in view of their attractive physiochemical properties and a wide range of promising applications. This paper describes a self-assembly approach for the directed growth of mesoporous polyaniline (PANi) with tunable pore structures and sizes on ultrathin freestanding MoS₂ nanosheets in solution, which produces 2D mesoporous PANi/MoS₂ nanocomposites. The strategy employs spherical and cylindrical micelles, which are formed by the controlled solution self-assembly of block copolymers, as the soft templates for the construction of well-defined spherical and cylindrical mesopores in the 2D PANi/MoS₂ nanocomposites, respectively. With potential applications as supercapacitor electrode materials, the resultant 2D composites show excellent capacitive performance with a maximum capacitance of 500 F g^-1 at a current density of 0.5 A g^-1, good rate performance, as well as outstanding stability for charge-discharge cycling. Moreover, the 2D mesoporous nanocomposites offer an opportunity for the study on the influence of different pore structures on their capacitive performance, which helps to understand the pore structure-property relationship of 2D porous electrode materials and to achieve their electrochemical performance control.

Mesostructure of Mesoporous Silica/Anodic Alumina Hierarchical Membranes Tuned with Ethanol

Hierarchically structured membranes composed of mesoporous silica embedded inside the channels of anodic alumina (MS-AAM) were synthesized using the aspiration method. Ethanol is shown to have a significant effect on the type and organization of the mesoporous silica phase. Detailed textural analysis revealed that the pore size distribution of the mesoporous silica narrows and the degree of ordering increases with decreasing ethanol concentration used in the synthesis mixture. The silica mesopores were synthesized with pores as small as 6 nm in diameter, with the channel direction oriented in lamellar, circular, and columnar directions depending on the ethanol content. This study reveals ethanol concentration as a key factor behind the synthesis of an ordered mesoporous silica-anodic alumina membrane that can increase its functionality for membrane-based applications.

Identification of a major intermediate along the self-assembly pathway of an icosahedral viral capsid by using an analytical model of a spherical patch

Viruses are astonishing edifices in which hundreds of molecular building blocks fit into the final structure with pinpoint accuracy. We established a robust kinetic model accounting for the in vitro self-assembly of a capsid shell derived from an icosahedral plant virus by using time-resolved small-angle X-ray scattering (TR-SAXS) data at high spatiotemporal resolution. By implementing an analytical model of a spherical patch into a global fitting algorithm, we managed to identify a major intermediate species along the self-assembly pathway. With a series of data collected at different protein concentrations, we showed that free dimers self-assembled into a capsid through an intermediate resembling a half-capsid. The typical lifetime of the intermediate was a few seconds and yet the presence of so large an oligomer was not reported before. The progress in instrumental detection along with the development of powerful algorithms for data processing contribute to shedding light on nonequilibrium processes in highly complex systems such as viruses.

A New Insight into Growth Mechanism and Kinetics of Mesoporous Silica Nanoparticles by in Situ Small Angle X-ray Scattering

The growth mechanism and kinetics of mesoporous silica nanoparticles (MSNs) were investigated for the first time by using a synchrotron time-resolved small-angle X-ray scattering (SAXS) analysis. The synchrotron SAXS offers unsurpassed time resolution and the ability to detect structural changes of nanometer sized objects, which are beneficial for the understanding of the growth mechanism of small MSNs (∼20 nm). The Porod invariant was used to quantify the conversion of tetraethyl orthosilicate (TEOS) in silica during MSN formation, and the growth kinetics were investigated at different solution pH and temperature through calculating the scattering invariant as a function of reaction time. The growth of MSNs was found to be accelerated at high temperature and high pH, resulting in a higher rate of silica formation. Modeling SAXS data of micelles, where a well-defined electrostatic interaction is assumed, determines the size and shape of hexadecyltrimethylammonium bromide (CTAB) micelles before and after the addition of TEOS. The results suggested that the micelle size increases and the micelle shape changes from ellipsoid to spherical, which might be attributed to the solubilization of TEOS in the hydrophobic core of CTAB micelles. A new "swelling-shrinking" mechanism is proposed. The mechanism provides new insights into understanding MSN growth for the formation of functional mesoporous materials exhibiting controlled morphologies. The SAXS analyses were correlated to the structure of CTAB micelles and chemical reaction of TEOS. This study has provided critical information to an understanding of the growth kinetics and mechanism of MSNs.

Interplay of carbon-silica sources on the formation of hierarchical porous composite materials for biological applications such as lipase immobilization

The porous inorganic materials, with hierarchical structures, find application in many processes where the chemical stability and pore connectivity are key points, such as separation, adsorption and catalysis. Here, we synthesized carbon-silica composite materials, which combine hydrolytic stability of the carbon with the surface chemical reactivity of silica in aqueous media. The polycondensation of carbonaceous and siliceous species from sucrose, Triton X-100 surfactant and tetraethylortosilicate during the hydrothermal synthesis led to the formation of hydrochar composite materials. The subsequent carbonization process of these composite hydrochars gave carbon-silica hierarchical porous materials. The study of the micellar reaction system and the characterization of the derivate materials (carbon-silica composite, carbon and silica) were carried out. The results indicate that synthesis conditions allowed the formation of a silica network interpenetrated with a carbon one, which is produced from the incorporated organic matter. The control of the acidity of the reaction medium and hydrothermal conditions modulated the reaction yield and porous characteristics of the materials. The composite nature in conjunction with the hierarchical porosity increases the interest of these materials for future biological applications, such as lipase immobilization.

Dendrimer-surfactant interactions

In this article, we reviewed the interactions between dendrimers and surfactants with particular focus on the interaction mechanisms and physicochemical properties of the yielding dendrimer-surfactant aggregates. In order to provide insight into the behavior of dendrimers in biological systems, the interactions of dendrimers with bio-surfactants such as phospholipids in bulk solutions, in solid-supported bilayers and at the interface of phases or solid-states were discussed. Applications of the dendrimer-surfactant aggregates as templates to guide the synthesis of nanoparticles and in drug or gene delivery were also mentioned.

On the role of specific interactions in the diffusion of nanoparticles in aqueous polymer solutions

Understanding nanoparticle diffusion within non-Newtonian biological and synthetic fluids is essential in designing novel formulations (e.g., nanomedicines for drug delivery, shampoos, lotions, coatings, paints, etc.), but is presently poorly defined. This study reports the diffusion of thiolated and PEGylated silica nanoparticles, characterized by small-angle neutron scattering, in solutions of various water-soluble polymers such as poly(acrylic acid) (PAA), poly(N-vinylpyrrolidone) (PVP), poly(ethylene oxide) (PEO), and hydroxyethylcellulose (HEC) probed using NanoSight nanoparticle tracking analysis. Results show that the diffusivity of nanoparticles is affected by their dimensions, medium viscosity, and, in particular, the specific interactions between nanoparticles and the macromolecules in solution; strong attractive interactions such as hydrogen bonding hamper diffusion. The water-soluble polymers retarded the diffusion of thiolated particles in the order PEO > PVP > PAA > HEC whereas for PEGylated silica particles retardation followed the order PAA > PVP = HEC > PEO. In the absence of specific interactions with the medium, PEGylated nanoparticles exhibit enhanced mobility compared to their thiolated counterparts despite some increase in their dimensions.

Triblock siloxane copolymer surfactant: template for spherical mesoporous silica with a hexagonal pore ordering

Ordered mesoporous silica materials with a spherical morphology have been prepared for the first time through the cooperative templating mechanism (CTM) by using a silicone triblock copolymer as template. The behavior of the pure siloxane copolymer amphiphile in water was first investigated. A direct micellar phase (L(1)) and a hexagonal (H(1)) liquid crystal were found. The determination of the structural parameters by SAXS measurements leads us to conclude that in the hexagonal liquid crystal phase a part of the ethylene oxide group is not hydrated as observed for the micelles. Mesoporous materials were then synthesized from the cooperative templating mechanism. The recovered materials were characterized by SAXS measurements, nitrogen adsorption-desorption analysis, and transmission and scanning electron microscopy. The results clearly evidence that one can control the morphology and the nanostructuring of the resulting material by modifying the synthesis parameters. Actually, highly ordered mesoporous materials with a spherical morphology have been obtained with a siloxane copolymer/tetramethoxysilane molar ratio of 0.10 after hydrothermal treatment at 100 °C. Our study also supports the fact that the interactions between micelles and the hydrolyzed precursor are one of the key parameters governing the formation of ordered mesostructures through the cooperative templating mechanism. Indeed, we have demonstrated that when the interactions between micelles are important, only wormhole-like structures are recovered.

Self-assembled liposomal nanoparticles in photodynamic therapy

Photodynamic therapy (PDT) employs the combination of non-toxic photosensitizers (PS) together with harmless visible light of the appropriate wavelength to produce reactive oxygen species that kill unwanted cells. Because many PS are hydrophobic molecules prone to aggregation, numerous drug delivery vehicles have been tested to solubilize these molecules, render them biocompatible and enhance the ease of administration after intravenous injection. The recent rise in nanotechnology has markedly expanded the range of these nanoparticulate delivery vehicles beyond the well-established liposomes and micelles. Self-assembled nanoparticles are formed by judicious choice of monomer building blocks that spontaneously form a well-oriented 3-dimensional structure that incorporates the PS when subjected to the appropriate conditions. This self-assembly process is governed by a subtle interplay of forces on the molecular level. This review will cover the state of the art in the preparation and use of self-assembled liposomal nanoparticles within the context of PDT.