Stimuli-responsive liquid foams: From design to applications

Stimuli-responsive liquid foams and bubbles are systems for which the stability, structure, shape, and movement can be controlled by the application of stimuli. The foam stability can be modified by a stimulus which can change solution condition (pH, temperature, and ionic strength) or with the application of an external field (light and magnetic). Different foam stabilizers have been described in the literature to design these responsive foams systems ranging from surfactants, peptides, polymers, soft polymer particles, surfactants self-assembly, crystalline particles, emulsion droplets, and solid particles. This review aims to cover the recent advances of the design of stimuli-responsive liquid foams and their applications. Responsive liquid foams are attractive in textile coloring process, biomedical application, washing, and material recovery processes.     

Recent advances of multidimensional sensing: from design to applications

Recently, multidimensional(or multi-channel) sensing methodology has attracted broad attention in the field of analytical chemistry due to its fascinating merits. A variety of multidimensional sensors based on sensor arrays, lab-on-a-molecule/nanoparticle and smart chip strategies have been designed to differentiate chemical structure and property similar analytes and complex samples. Pattern recognition algorithms are usually used and allow these sensors to fulfill such proposes. In this review,the recent advances of multidimensional sensor devices were firstly summarized, and particularly focused on their design strategies and applications in monitoring of biological active molecules, biomarkers, microbes, foods and beverages, etc. Then,some limitations and possible solutions of multidimensional sensors were discussed. And finally, potential applications of this technique in the future were proposed. This review would help the readers who are interested in multidimensional sensing methodology to understand the research progresses and trends.     

Active colloids: Progress and challenges towards realising autonomous applications

Active colloids are small scale materials capable of producing enhanced motion within fluid environments. The field of active colloids has grown rapidly over the last ten years and is approaching maturity where viable applications are within reach. In this review, recent advances are surveyed with a strong emphasis on developments that can enable autonomous applications, where colloids execute useful tasks without external interventions. These applications are likely to prove transformative as the resulting technologies will be significantly less complex than current methods. A survey of the requirements to achieve autonomous applications is provided, considering guidance, solution compatibilities, manufacture and function; with reference to recent developments in these capacities. Following on from this, progress towards applications in environmental remediation, lab-on-a-chip microfluidics and in vivo drug delivery is highlighted.     

Nanocellulose properties and applications in colloids and interfaces

In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphology, low density, chirality and thermo-mechanical performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air–solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liquid–liquid and air–liquid interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufactured via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.     

Hybrid linear dendritic macromolecules: From synthesis to applications

Linear‐dendritic copolymers are intriguing macromolecules, which offer challenge and fascination as purely synthetic objects at the crossroad of organic and polymer chemistry and as promising materials for diverse advanced applications. This review traces their discovery and highlights the synthetic strategies used for their construction. The ambivalent character of the linear‐dendritic architecture opens numerous avenues towards emerging and potential applications. Specific solution properties enable the construction of nanometer‐sized nanoreactors for reactions in environmentally friendly media, and the creation of “nanosponges” for selective passive binding of fluorescent pH‐indicators for environmental or biomonitoring. Another structure–property relationship is used for noncovalent and site‐specific modification of glycoproteins, which leads to the formation of “semiartificial” enzymes with enhanced and broadened catalytic activity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5295–5314, 2008     

High-strength hydrogels: Microstructure design,characterization and applications

Hydrogels are a class of polymeric network materials embedded in a water-rich environment. They are widely applied in drug delivery, actuator, and sensor. However, conventional hydrogels encountered limits from their poor mechanical property. Recent researches in hydrogels have been focusing on mechanical enhancement, ranging from design of microstructures to adjustment of compositions in hydrogels. Here, the design and fabrication strategies of high-strength hydrogels, as well as major progress in their typical strength-support applications are systemically reviewed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1325–1335     

Hybrid lipid oligonucleotide conjugates: synthesis, self-assemblies and biomedical applications

Hybrid lipid oligonucleotide conjugates are finding more and more biotechnological applications. This short critical review highlights their synthesis, supramolecular organization as well as their applications in the field of biotechnology (111 references).     

Recent advances in short peptide self-assembly: from rational design to novel applications

Owing to their structural simplicity and robust self-assembled nanostructures, short peptides prove to be an ideal system to explore the physical processes of self-assembly, hydrogels, semi-flexible polymers, quenched disorder, and reptation. Rational design in peptide sequences facilitates cost-effective manufacturing, but the huge number of possible peptides has imposed obstacles for their characterization to establish functional connections to the primary, secondary, and tertiary structures. This review aims to cover recent advances in the self-assembly of designed short peptides, with a focus on physical driving forces, design rules, characterization methods, and exemplar applications. Super-resolution microscopy in combination with modern image analysis have been applied to quantify the structure and dynamics of peptide hydrogels, while small-angle neutron scattering and solid-state nuclear magnetic resonance continue to provide valuable information on structures over complementary length scales. Short peptides are attractive in biomedicine and nanotechnology, e.g., as antimicrobials, anticancer agents, vehicles for controlled drug release, peptide bioelectronics, and responsive cell culture materials.     

Quinolactacins revisited: from lactams to imide and beyond

Chemical analysis of a solid phase fermentation of an Australian Penicillium citrinum strain has returned all known examples of a rare class of N-methyl quinolone lactams, quinolactacins A2 (1), B2 (2), C2 (3) and A1 (4), together with the new quinolactacins B1 (5), C1 (6), D1 (7) and D2 (8), and the novel derivatives quinolonimide (9) and quinolonic acid (10). Complete stereostructures were assigned to all these compounds by detailed spectroscopic analysis and chemical interconversion. Carefully controlled and monitored decomposition studies have confirmed that quinolactacins readily undergo C-3 epimerization and oxidation, and under appropriate conditions convert to quinolonimide and quinolonic acid. Mechanisms for key transformations are proposed. The decomposition studies suggested that only quinolactacins A2 (1) and B2 (2) are genuine natural products, with all other isolated compounds being decomposition artefacts. Quinolactacins C1 (6), C2 (3), and the racemic mixture of quinolactacins D1/D2 (8/7) all displayed notable cytotoxic activity.     

Citrinin revisited: from monomers to dimers and beyond

Detailed chemical analysis of the solid phase fermentation of an Australian Penicillium citrinum isolate has returned the known compounds citrinin (1), phenol A acid (6), dihydrocitrinone (7) and dihydrocitrinin (8), together with a novel cytotoxic dimer, dicitrinin A (5). Dicitrinin A (5) was determined to be a dimerised artefact of the major co-metabolite citrinin, and its structure solved by spectroscopic analysis and chemical modification. Analysis of the products encountered during the controlled decomposition of citrinin led to the discovery of additional citrinin dimers and delineated a plausible mechanistic pathway linking all monomeric and dimeric citrinin degradation products.     

Double-lanthanide-binding tags: design, photophysical properties, and NMR applications

Lanthanide-binding tags (LBTs) are peptide sequences of up to 20 encoded amino acids that tightly and selectively complex lanthanide ions and can sensitize terbium (Tb3+) luminescence. On the basis of these properties, it was predicted that increasing the number of bound lanthanides would improve the capabilities of these tags. Therefore, using a structurally well-characterized single-LBT sequence as a starting point, a "double-LBT" (dLBT), which concatenates two lanthanide-binding motifs, was designed. Herein we report the generation of dLBT peptides and luminescence and NMR studies on a dLBT-tagged ubiquitin fusion protein. These lanthanide-bound constructs are shown to be improved luminescent tags with avid lanthanide binding and up to 3-fold greater luminescence intensity. NMR experiments were conducted on the ubiquitin construct, wherein bound paramagnetic lanthanides were used as alignment-inducing agents to gain residual dipolar couplings, which are valuable restraints for macromolecular structure determination. Together, these results indicate that dLBTs will be valuable chemical tools for biophysical applications leading to new approaches for studying the structure, function, and dynamics of proteins.     

Blood substitutes and other potential biomedical applications of fluorinated colloids

An oxygen carrying, heat-sterilized phospholipid-based emulsion of a fast excreted lipophilic fluorocarbon, perfluorooctyl bromide (perflubron), stabilized against molecular diffusion, has been developed to serve as a temporary blood substitute. It is expected to reduce exposure to donor blood and thereby help mitigate the pressure on our blood supply. A phase III clinical trial in Europe has demonstrated that use of the emulsion resulted in avoidance and reduction of donor blood transfusion in surgery patients. Further potential applications for fluorocarbon emulsions include use as a bridge to transfusion, treatment of myocardial ischemia and stroke, potentiation of radio and chemotherapy and preservation of organs destined for transplantation. Echogenic, injectable gaseous microbubbles, osmotically stabilized by perfluorohexane, provide an effective contrast agent for ultrasound imaging. Clinical trials have established improved imaging of the walls of the heart and, hence, assessment of cardiac function. The ability of improving detection of myocardial perfusion, blood flow abnormalities and solid tumors is also being investigated. Various families of fluorinated amphiphiles with modular molecular structures and polar heads derived from natural products have been synthesized. Due to their highly hydrophobic perfluoroalkylated tail chains, these amphiphiles readily self-assemble into stable fluorinated vesicles, tubules and other organized molecular systems with distinctive properties. Fluorosurfactants also allowed preparation of direct, reverse, apolar and multiple emulsions and gels. These fluorinated colloids have potential for the delivery of drugs and other bioactive materials, and provide unique tools in biomedical research.     

Self-formation phenomenon to hierarchically structured porous materials: design, synthesis, formation mechanism and applications

In this paper, we will thoroughly review a novel and versatile self-formation phenomenon that can be exploited to target porous hierarchies of materials without need of any external templates only on the basis of the chemistry of metal alkoxides and alkylmetals. These hierarchically porous materials have unique structures, which are made of either parallel funnel-like/straight macrochannels or 3D continuous interconnected macroporous foams with micro/mesoporous walls. The self-generated porogen mechanism has been proposed, leading to a series of techniques to tailor porous hierarchy, i.e. the use of different chemical precursors (single metal alkoxides, mixed metal alkoxides, single molecular precursors with two different alkoxide functionalities, alkylmetals, etc., …), the control of their hydrolysis and condensation rates (pH, chelating agents,…) and the addition of alkoxysilanes as co-reactant. Various chemical compositions from single or binary metal oxides, to aluminosilicates, aluminophosphates, silicoaluminophosphates, metallophosphates,… can be prepared, offering a panel of potential applications. Some perspectives have been proposed to transform the synthesized materials with a hierarchy of pore sizes to micro-meso-macroporous crystalline materials with zeolite architectures. The advantages of this self-formation preparation method have been discussed compared to traditional templating methods. The possibility to combine with other strategies, for example soft or hard templating, to target even more sophisticated hierarchically meso-macroporous materials with specific structure and function for various applications has been presented. The "hierarchical catalysis" concept has been re-visited.     

SERS as a bioassay platform: fundamentals, design, and applications

Bioanalytical science is experiencing a period of unprecedented growth. Drivers behind this growth include the need to detect markers central to human and veterinary diagnostics at ever-lower levels and greater speeds. A set of parallel arguments applies to pathogens with respect to bioterrorism prevention and food and water safety. This tutorial review outlines our recent explorations on the use of surface enhanced Raman scattering (SERS) for detection of proteins, viruses, and microorganisms in heterogeneous immunoassays. It will detail the design and fabrication of the assay platform, including the capture substrate and nanoparticle-based labels. The latter, which is the cornerstone of our strategy, relies on the construction of gold nanoparticles modified with both an intrinsically strong Raman scatterer and an antibody. This labelling motif, referred to as extrinsic Raman labels (ERLs), takes advantage of the well-established signal enhancement of scatterers when coated on nanometre-sized gold particles, whereas the antibody imparts antigenic specificity. We will also examine the role of plasmon coupling between the ERLs and capture substrate, and challenges related to particle stability, nonspecific adsorption, and assay speed.     

Enzyme inhibitors as chemical tools to study enzyme catalysis: rational design, synthesis, and applications

Carefully designed molecules that are intimately related to the reaction mechanism of enzymes are often highly selective and potent inhibitors that serve as extremely useful chemical probes for understanding the reaction mechanism and structure of enzymes. This article describes the design, synthesis, and applications of specific inhibitors of two mechanistically distinct groups of enzymes, ATP-dependent amide ligases and Ser- and Thr-hydrolases. Our strategy is based on the premise that stable analogues of the transition state (transition-state analogues) are highly potent inhibitors that serve as good mechanistic probes, and that a key structure of a good inhibitor of one enzyme is also utilized for the inhibitors of other enzymes that share the same chemistry in their catalyzed reactions, irrespective of the degree of structural similarity and evolutionary link between the enzymes. According to these principles, we designed and synthesized a series of phosphinate- and sulfoximine-based transition-state analogue inhibitors of glutathione synthetase, gamma-glutamylcysteine synthetase and asparagine synthetase. For the second group of enzymes, we synthesized a gamma-monofluorophosphono glutamate analogue for mechanism-based affinity labeling of gamma-glutamyltranspeptidase and fluorescent phosphonic acid esters for the active-site titration of lipase. These inhibitors were used successfully as ligands for detailed kinetic analyses, X-ray crystallography, and mass analysis of the enzymes to identify the key amino acid residues responsible for catalysis and substrate recognition in the transition state.     

Recent developments on chiral ionic liquids: design, synthesis, and applications

The recent progress in chiral ionic liquids with respect to their syntheses and applications in enantioselective reactions and chiral recognition is described. In addition to the conventional chiral ionic liquids derived from chiral natural products, a library of novel chiral spiro compounds, including spiro bis(pyridinium) and spiro bis(imidazolium) salt, is also described.     

Symbolic equations and their applications to reaction design

The application of symbolic equations to problems of reaction design is described. Problems in their analytical and constructive enumeration are formulated in terms of graph and permutation group theories. Some features of the combinatorial algorithm and of its computer implementations are described. Several hypothetical processes corresponding to unknown types of reaction are outlined.     

Inverse patchy colloids: Synthesis,modeling and self-organization

Inverse patchy colloids are nano- to micro-scale particles with a surface divided into differently charged regions. This class of colloids combines directional, selective bonding with a relatively simple particle design: owing to the competitive interplay between the orientation-dependent attraction and repulsion — induced by the interactions between like/oppositely charged areas — experimentally accessible surface patterns are complex enough to favor the stabilization of specific structures of interest. Most important, the behavior of heterogeneously charged units can be ideally controlled by means of external parameters, such as the pH and the salt concentration. We present a concise review about this class of systems, spanning the range from the synthesis of model inverse patchy particles to their self-assembly, covering their coarse-grained modeling and the related numerical/analytical treatments.     

Purification of biomimetic apatite-based hybrid colloids intended for biomedical applications: A dialysis study

The field of nanobiotechnology has lately attracted much attention both from therapeutic and diagnosis viewpoints. Of particular relevance is the development of colloidal formulations of biocompatible nanoparticles capable of interacting with selected cells or tissues. In this context, the purification of such nanoparticle suspensions appears as a critical step as residues of unreacted species may jeopardize biological and medical outcomes, and sample purity is thus increasingly taken into account by regulatory committees. In the present work, we have investigated from a physico-chemical point of view the purification by dialysis of recently developed hybrid colloids based on biomimetic nanocrystalline apatites intended for interacting with cells. Both Eu-doped (2mol.% relative to Ca) and Eu-free suspensions were studied. The follow-up of the dialysis process was carried out by way of FTIR, TEM, XRD, pH and conductivity measurements. Mathematical modelling of conductivity data was reported. The effects of a change in temperature (25 and 45°C), dialysis medium, and starting colloid composition were evaluated and discussed. We show that the dialysis method is a well-adapted and cheap technique to purify such mineral-organic hybrid suspensions in view of biomedical applications, and we point out some of the characterization techniques that may prove helpful for following the evolution of the purification process with time.