Facile Synthesis of Multivalent Water-Soluble Organic Nanoparticles via “Surface Clicking” of Alkynylated Surfactant Micelles

Multivalent interactions occur frequently between biological entities.1 When strong binding is not achievable with a single receptor-ligand pair, multivalency, or simultaneous binding between multiple receptors and ligands, becomes an effective strategy to enhance the binding. Significant efforts have been devoted in recent years to synthetic multivalent ligands and their interactions with biological hosts.2 Two of the most widely used scaffolds in multivalency are dendrimers and gold nanoparticles protected with functionalized thiols

Template Synthesis of Subnanometer Gold Clusters in Interfacially Cross-Linked Reverse Micelles Mediated by Confined Counterions

A cationic surfactant with a triallylammonium headgroup was cross-linked photochemically in the presence of a hydrophilic dithiol in the reverse micelle (RM) configuration. The interfacially cross-linked reverse micelles (ICRMs) are unusual templates for nanomaterials synthesis. Our previous work indicated that the ICRMs could extract anionic metal salts such as tetracholoroaurate into the hydrophilic interior, and the entrapped aurate was reduced without externally added reducing agent to form subnanometer luminescent gold clusters [Zhang, S.; Zhao, Y. ACS Nano2011, 5, 2637–2646]. In this work, the bromide counterions were established as the reducing agent in the template synthesis. The reduction of tetrachloroaurate was proposed to happen through ligand exchange on the aurate by the bromide ions, reductive elimination of halogen, and disproportionation of the Au(I) intermediate. The size of the gold clusters could be tuned rationally by the water-to-surfactant ratio (W0) and the reducing agent. Monodisperse Au4 and Au9–10 clusters as well as larger Au18 and Au23 clusters were obtained from the ICRM templates. The as-prepared, metastable gold clusters were subject to reconstruction triggered by ligand exchange on the surface but could be stabilized through proper surface protection using a chelating dithiol

Rapid Release of Entrapped Contents from Multi-Functionalizable, Surface Cross-Linked Micelles upon Different Stimulation

Hydrophobic guests such as pyrene could be readily trapped inside the micelles of an alkynylated surfactant in the presence of an azide-functionalized cross-linker using the click reaction. The cross-linker was designed to contain cleavable bonds such as geminal diol, disulfide, and acetal. The resulting pyrene-containing water-soluble nanoparticle was under electrostatic stress when diluted below the CMC of the surfactant. Extremely rapid (\u3c1 min) release of the hydrophobic content was observed when the cross-linker was cleaved. This method combines the ease of physical entrapment and the precision of chemical ligation, and potentially is highly useful in the delivery and controlled release of pharmaceutical agents

Effects of Micelle Properties on the Conformation of Oligocholates and Importance of Rigidity of Foldamers

The conformation of a cholate hexamer with a clicked tether in between two tricholate units and pyrene groups at the chain ends was studied by fluorescence spectroscopy. In contrast to the parent cholate hexamer that folded in all micelles investigated, the folding of the clicked hexamer was highly dependent on the type of surfactant used to solubilize the compound. The clicked oligocholate folded in the Brij 35 micelle, possibly due to the latter’s small size and strong internal hydrophobicity. The oligocholate formed intermolecular aggregates in SDS solutions below the CMC of the surfactant. The aggregates were dissociated by the SDS micelles but the individual oligocholate stayed unfolded. In Triton X-100 and sodium cholate solutions, the aggregated, unfolded, and folded oligocholates coexisted and gradual unfolding occurred with an increasing concentration of the surfactant. The conformation of the clicked oligocholate was sensitive to the nonideal mixing of ionic/nonionic micelles and to the unconventional aggregation of sodium cholate

Graph Search and its Application in Building Extraction from High Resolution Remote Sensing Imagery

Building extraction using Hough transformation and cycle detection

Conformationally Controlled Oligocholate Membrane Transporters: Learning through Water Play

Controlled translocation of molecules and ions across lipid membranes is the basis of numerous biological functions. Because synthetic systems can help researchers understand the more complex biological ones, many chemists have developed synthetic mimics of biological transporters. Both systems need to deal with similar fundamental challenges. In addition to providing mechanistic insights into transport mechanisms, synthetic transporters are useful in a number of applications including separation, sensing, drug delivery, and catalysis

Modelling Stretch Blow Moulding of Poly (l-lactic acid) for the Manufacture of Bioresorbable Vascular Scaffold

Stretch blow moulding (SBM) has been employed to manufacture bioresorbable vascular scaffold (BVS) from poly (l-lactic acid) (PLLA), whilst an experience-based method is used to develop the suitable processing conditions by trial-and-error. FEA modelling can be used to predict the forming process by the scientific understanding on the mechanical behaviour of PLLA materials above the glass transition temperature (Tg). The applicability of a constitutive model, the ‘glass-rubber’ (GR) model with material parameters from biaxial stretch was examined on PLLA sheets replicating the biaxial strain history of PLLA tubes during stretch blow moulding. The different stress–strain relationship of tubes and sheets under equivalent deformation suggested the need of re-calibration of the GR model for tubes. A FEA model was developed for PLLA tubes under different operation conditions, incorporating a virtual cap and rod to capture the suppression of axial stretch. The reliability of the FEA modelling on tube blowing was validated by comparing the shape evolution, strain history and stress–strain relationship from modelling to the results from the free stretch blow test