We investigate, by means of computer simulations, the formation of soft nanoparticles by irreversible intramolecular cross-linking of homofunctional polymer precursors in good solvent. Simulations reveal that the early and intermediate stages of the cross-linking process are dominated by bonding at short contour distances. Because of the initial selfavoiding character of the precursor, bonding at long contour distances, which is the efficient mechanism for global compactation, is a rare event that essentially occurs in the late stage of cross-linking. Thus, irreversible cross-linking of precursors with identical molecular weight and linker fraction produces both compact and sparse objects. This is confirmed by a detailed analysis of the size and shape distribution of the fully cross-linked nanoparticles. We also investigate intramolecular cross-linking of heterofunctional polymers with two species of orthogonal linkers, bonding between distinct species being forbidden. It is found that simultaneous cross-linking of both species and sequential cross-linking (activation of one species after full cross-linking of the other) lead to the same structural properties for the resulting nanoparticles. The heterofunctional nanoparticles are on average smaller and more spherical than the homofunctional counterparts, though still a significant fraction of sparse objects is found. The simulation results are compared with results from SEC/MALLS and SAXS experiments in real polymeric nanoparticles.
ABSTRACT:We report herein a very efficient synthesis strategy for the construction of artificial transient-binding protein-mimic nano-objects. Michael addition-mediated multidirectional self-assembly of individual polymeric chains at r.t. leads to "Michael" nanocarriers that in solution resemble disordered multidomain proteins, as revealed by a combination of small angle neutron scattering (SANS) measurements and coarse-grained molecular dynamics (MD) results, whereas in the dry state adopt a collapsed, globular morphology, as observed by transmission electron microscopy (TEM). This extended-to-compact morphology transition taking place upon solvent removal is of paramount importance, among other applications, for the construction of efficient biosensors based on immobilized protein-mimic nano-objects and for the development of transient vitamin-binding systems. As a proof of concept, we show the controlled delivery of vitamin B 9 from these novel transient-binding nanocarriers.Nature is a continuous source of inspiration for scientists across different disciplines.1 In particular, the specific -native-conformation of proteins allowing these large biomolecules to carry out sophisticated tasks such as catalysis inspired the construction of a first generation of artificial enzymes based on a variety of molecular and macromolecular structures such as macrocyclic compounds, 2 star and helical polymers, 3 dendrimers 4 and micelles.
Mimicking the substrate specificity and catalytic activity of enzymes is of great interest for different fields (e.g., chemistry, biology, nanomedicine). Enhanced reaction rates using artificial, enzyme-mimic catalysts based on a variety of molecular structures and nano-entities (e.g., macrocyclic compounds, star and helical polymers, dendrimers) have been previously reported. However, examples of enzyme-sized soft entities displaying substrate specificity are certainly scarce. Herein, we report the synthesis and characterization of single-chain nanoparticles based on metallo-folded polymer chains containing complexed Cu(II) ions showing catalytic specificity during the oxidative coupling of mixtures of chemically related terminal acetylene substrates. This work paves the way for the easy and efficient construction of other Pd, Ni, Co, Fe, Mn or Mo-containing soft nano-entities approaching the substrate specificity of natural enzymes for a variety of organic reactions.
Single-chain polymeric nanoparticles are artificial folded soft nano-objects of ultra-small size which have recently gained prominence in nanoscience and nanotechnology due to their exceptional and sometimes unique properties. This review focuses on the current state of the investigations of click chemistry techniques for highly-efficient single-chain nanoparticle construction. Additionally, recent progress achieved for the use of well-defined single-chain nanoparticles in some promising fields, such as nanomedicine and catalysis, is highlighted.
Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (conductivity, stability, transparency and biocompatibility). The gold standard material is the commercially available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biology and electronics, PEDOT:PSS presents some limitations associated with its low (bio)functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed analysis of the different synthetic routes to (bio)functional dioxythiophene monomer/polymer derivatives. Second, we focus on the preparation of PEDOT dispersions using different biopolymers and biomolecules as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiology, implantable electrodes, stimulation of neuronal cells or pan-bio electronics.
Nanog is involved in controlling pluripotency and differentiation of stem cells in vitro. However, its function in vivo has been studied only in mouse embryos and various reports suggest that Nanog may not be required for the regulation of differentiation. To better understand endogenous Nanog function, more animal models should be introduced to complement the murine model. Here, we have identified the homolog of the mammalian Nanog gene in teleost fish and describe the endogenous expression of OlNanog mRNA and protein during medaka (Oryzias latipes) embryonic development and in the adult gonads. Using medaka fish as a vertebrate model to study Nanog function, we demonstrate that Ol-Nanog is necessary for Sphase transition and proliferation in the developing embryo. Moreover, inhibition or overexpression of OlNanog does not affect gene expression of various pluripotency and differentiation markers, suggesting that this transcription factor may not play a direct role in embryonic germ layer differentiation.
Structurally dynamic single-chain polymer nanoparticles that can reversibly undergo a coil to particle transition via formation and cleavage of intramolecular dynamic enamine cross-links are reported.
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