Search

One-dimensional K2CuBr3 single crystals are demonstrated for visible light communication with a high data transmission rate of 248 Mbps, which is more than 33-fold the −3 dB bandwidth.

We demonstrated a clear and comprehensive description of the solution state, dissolution process, and regulation principle of cellulose in ionic liquids (ILs) and IL/co-solvent systems.

Artificial protocells operating under non-equilibrium conditions offer a new approach to achieve dynamic features with life-like properties. Using coacervate micro-droplets comprising polylysine (PLL) and a short single-stranded oligonucleotide (ss-oligo) as a membrane-free protocell model, we demonstrate that circulation and vacuolization can occur simultaneously inside the droplet in the presence of an electric field. The circulation is driven by electrohydrodynamics and applies specifically to the major components of the protocell (PLL and ss-oligo). Significantly, under low electric fields (E = 10 V cm-1) the circulation regulates the movement of the vacuoles, while high levels of vacuolization produced at higher electric fields can deform or reshape the circulation. By taking advantage of the interplay between vacuolization and circulation, we achieve dynamic localization of an enzyme cascade reaction at specific droplet locations. In addition, the spatial distribution of the enzyme reaction is globalized throughout the droplet by tuning the coupling of the circulation and vacuolization processes. Overall, our work provides a new strategy to create non-equilibrium dynamic behaviors in molecularly crowded membrane-free synthetic protocells.

The mutual interaction between enzymes and their environments plays a key role in various life processes. In this study, using the complexes formed by salmon DNA and a de novo designed peptide, Ac-RRRRRRRRRGALGLPGKGGGLQRLTALDGR-NH2 (abbreviated as RR-30), as a model, we studied the activity of collagenase encapsulated inside the complex. Collagenase is able to cleave RR-30 at a LG/LP site, generating two shorter length peptides, which decreases the stability of the complex. Results show that the complex dissociates with time in the presence of collagenase. The dissociation rate is linearly proportional to the collagenase concentration. On the other hand, the collagenase activity is severely deteriorated inside the complex, where only 1/3 of the enzyme is active. We attribute it to the electrostatic interaction and hydrophobic interaction between collagenase and the components of the complex. Therefore, the mutual interaction determines the structure and kinetics of the DNA/peptide complex.

Oxidation stress has been becoming an important target for the development of smart nanomedicines, triggering research interest in oxidation responsive polymers. Herein, we report a new type of temperature/oxidation dual responsive copolymer. They were synthesized by the sequential atom transfer radical copolymerization (ATRP) of N-isopropylacrylamide (NIPAM, M1) and a phenylboronic pinacol ester-containing acrylate (M2) and dialysis against water to remove the pinacol protecting groups. The copolymers with a small amount of phenylboronic acid units (

Kanamycin A, an amino modified sugar, can interact with poly(ethylene glycol)-block-poly(glutamate sodium) (PEG114-PGlu64) via electrostatic interactions (with PGlu) and hydrogen bonding (with PEG). The interplay of these two forces determines the assembly process and the resulting structure. In deionized water, kanamycin A and PEG114-PGlu64 form a spherical structure at [+]/[-] = 3.5. This structure dissociates instantly and completely in the presence of 30 mM NaCl. However, a new structure is reassembled in about 2 hours. A similar phenomenon is observed when the buffer pH is increased from 7.8 to 8.3. We attribute the distinct dissociation/reassembly process to the reestablishment of the balance between electrostatic interactions and hydrogen bonding. The dissociation/reassembly process in response to environmental changes offers a novel approach to release the loaded cargo in a controlled manner.

Polyelectrolyte complexes (PECs) are of great importance in drug delivery and gene therapy. The density and the distribution of the charges are key parameters of a polyelectrolyte, determining the structure of the complex and the kinetics of the complexation. Using peptides of precisely-controlled charge density as model molecules, we showed that the presence of weakly-charged peptides, (KGGG)5 or (KGKG)5, did not affect the complexation of highly-charged peptides (KKKK)5 with 21 bp oligonucleotides. However, peptide containing blocks of different charge densities, such as (KKKK)5-b-(KGGG)5 or (KKKK)5-b-(KGKG)5, exhibited superior performance during complexation. With a relatively uniform small size, the complex was also stable in serum. More importantly, the cellular uptake of the complex was greatly enhanced by a ratio of 40-60%, compared to that of the complex formed by uniformly-charged peptides. We attributed the improvement to the structure of the complex, in which the highly-charged blocks form the core with the oligonucleotide whilst the weakly-charged blocks dangle outside, preventing the complexes from further aggregation.

Under an electric field, the complexes formed by DNA and polylysine exhibit novel features, such as selective merging of particles, ejecting of daughter vehicles, and differentiation of particles of varying mobility. The mobility of the complex could be three times faster than that of free DNA.

The mechanism of DNA assembly is revealed by analyzing the energy barriers during nucleation and growth. The assembly is controlled by two competing parameters: the conformation adjustment rate of DNA strands and the spreading rate of new strands on the nuclei surface, both of which are temperature dependent and can be tuned by sequence design.

Penetration and partition of C60 to the lipid bilayer core are both relevant to C60 toxicity, and useful to realise C60 biomedical potential. A key aspect is the effect of C60 on bilayer mechanical properties. Here, we present an experimental study on the mechanical effect of the incorporation of C60 into the hydrophobic core of fluid and gel phase zwitterionic phosphatidylcholine (PC) lipid bilayers. We demonstrate its incorporation inside the hydrophobic lipid core and the effect on the packing of the lipids and the vesicle size using a combination of infrared (IR) spectroscopy, atomic force microscopy (AFM) and laser light scattering. Using AFM we measured the Young's modulus of elasticity (E) of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) in the absence (presence) of intra-membranous C60 at 24.5 °C. E of fluid phase supported bilayers is not altered by C60, but E increases with incorporation of C60 in gel phase bilayers. The increase is higher for longer hydrocarbon chains: 1.6 times for DPPC and 2 times for DSPC. However the mechanical resistance of gel phase bilayers of curved bilayered structures decreases with the incorporation of C60. Our combined results indicate that C60 causes a decrease in gel phase lipid mobility, i.e. an increase in membrane viscosity.

A series of three-dimensional shape-persistent molecules with three conjugated arms perpendicular to a planar core were developed to self-assemble into supramolecular polymeric nanowires through multiple hydrogen-bonding interactions. After introducing bulky functional groups, aggregation of the nanowires was inhibited, and single molecular nanowires were obtained in concentrated solutions. Therefore, these nanowires had large surface areas with functional groups appended on the surface. Moreover, the photophysical properties of the functional groups including emission peaks and fluorescent lifetime were not changed after self-assembly. Some nanowires emitted high fluorescence after incorporating various chromophores on the side chains of the three-dimensional skeleton through effective fluorescence resonance energy transfer. For example, 1-BTHex showed a quantum efficiency of about 7.9% in solution, similar to the model compound DHBT. However, in the solid state the fluorescence of DHBT was almost quenched with a quantum efficiency lower than 1% due to π–π interactions, but 1-BTHex also gave much higher quantum efficiency, about 6%, which was close to that in solution.

A noncovalent strategy is proposed for endowing responseless catanionic surfactant (a mixture of cationic and anionic surfactants) aggregates with responsive abilities by addition of a responser. In this strategy, the composition of catanionic surfactant can be carefully selected to render aggregates sensitive to added responsers, and the responsers can be chosen from plenty of commercialized candidates, which bear responsive groups and will be noncovalently incorporated into the aggregates. In this paper, we report an illustrative example for the strategy: dual-responsive vesicles are realized by simply adding a responser, SC (sodium cholate), to a stimuli-inert DEAB/SDS (dodecyl triethyl ammonium bromide/sodium dodecyl sulfate) vesicular aqueous solution at a low responser/surfactant molar ratio of 0.045. The resultant DEAB/SDS/SC aggregates undergo reversible transitions between vesicles and micelles in response to temperature or pH variations. Possible mechanisms for these responsive behaviors are speculated, where the temperature-responsive hydroxyl groups and pH-responsive carboxylate group of SC are thought to be crucial. This responsive ability-endowing noncovalent strategy shows potential as a general, versatile, and economical method for fabricating stimuli-responsive self-assemblies.

Aminoglycosides are capable of expelling water molecules when forming a complex with DNA via electrostatic interaction. The "water-proof" nature of the complex leads to the formation of capsules, which possess hierarchical shell structures with a smooth and rigid outer layer and a viscoelastic inner layer.

A family of amphiphilic block copolymers with pendent ortho ester groups were synthesized by modifying the double hydrophilic block copolymer PEO114-b-PVA240 with 2-ethylidene-4-methyl-1,3-dioxolane (EMD) under mild conditions (30 °C). The degree of modification (DM) of the ortho ester groups can be tuned by simply varying the feed ratio of EMD to the hydroxyl groups in the PVA block. These block copolymers are stable in an anhydrous environment. Laser light scattering (LLS) and transmission electron microscopy (TEM) measurements revealed that in weakly basic aqueous buffer, these amphiphilic block copolymers self-assembled into aggregates with different size and morphology, ranging from solid-like spherical nanoparticles to polymersomes as the DM increased. The acid-triggered dissociation behaviour of the aggregates were studied by LLS, nile red (NR) fluorescence and TEM. The copolymer aggregates dissociated faster in a buffer with the lower pH; the dissociation rate of the aggregates became faster for the copolymers with lower DM. The polymersomes can load both hydrophilic biomacromolecules like lysozyme and hydrophobic anticancer drug doxorubicin (DOX). The drug-loaded polymersomes were stable in neutral phosphate buffer for at least 6 h with a payload leakage of less than 25% in 12 h at 37 °C; however, significant acid-triggered payload release was accomplished even at a mildly acidic pH (6.0). Finally, the DOX-loaded polymersomes exhibited a concentration-dependent toxicity to MCF-7 and HeLa cells while the copolymers themselves are non-toxic.

Polycations and cationic lipids have been widely employed as non-viral vectors for siRNA delivery. However, the stability of siRNA–polycation complexes is still rarely reported. Using highly charged dendrimer poly(amidoamine) (PAMAM) as an example, we studied the complexation of siRNA with a polycation by laser light scattering and atomic force microscopy. PAMAM forms a complex of more than 100 nm in diameter with siRNA right after mixing. However, the complex is not stable. It experiences an interesting kinetic process of aggregation, followed by phase separation. The rate of phase separation is related to the chemical composition of the polycations. Gene expressions on A549 cells and Hela cells demonstrate that the transfection efficiency decreases with the kinetics of the complexes. Cross-linking of the primary amino group of the PAMAM stabilizes the siRNA complex and causes the transfection results to be steady with time.

Polycations and cationic lipids have been widely used as non-viral vectors for the delivery of plasmid DNA, siRNA and anti-sense oligonucleotides. To demonstrate that one polycation can form a complex with several types of DNA, we conducted a comparative study on the complexation of poly(L-lysine) (PLL) with 2000 bp salmon testes DNA (dsDNA), 21 bp double-stranded oligonucleotides (ds-oligo), and 21 nt single-stranded oligonucleotides (ss-oligo) in PBS buffer. The complexes are prepared by a titration method and the process is monitored by laser light scattering. It was found that in most cases, ss-oligo and ds-oligo form complexes with higher molecular weights than the complex formed by dsDNA at the same +/- ratio immediately after mixing. More importantly, the complexes formed by oligonucleotides are not stable, the scattered intensity gradually decreases to the level of the solvent in weeks. Atomic force microscopy measurements also indicate that the freshly prepared complex is subject to environmental changes and could dissociate very quickly. The behaviour of oligonucleotides cannot be predicted by the classical polyelectrolyte theories.

Supramolecular polymerization follows a nucleation-elongation mechanism; however, after the supramolecular polymerization, what happens while forming nanowires? In order to answer this question, we systematically investigated the molecular packing and growth mechanism of a series of supramolecular polymeric nanowires. We carefully analyzed the molecular packing in the nanowires and proposed a packing model through X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). We used dynamic light scattering (DLS) to investigate in situ the growth process of these nanowires. The DLS results showed that after nucleation growth, a mesoscale assembly existed as an intermediate, which then formed the nanowires. This is the first example to directly monitor the growth of organic nanowires in solution. We also investigated the solvent effect on the self-assembly process of the side-chain functionalized monomers. Our investigation demonstrates that the weaker the interactions between the lateral groups, and the stronger the interactions of the lateral groups with the solvent are, the more obvious the tendency to 1D growth. Based on these results, we proposed that an “oriented-attachment” growth mechanism existed in this system after the supramolecular polymerization. Furthermore, single molecular nanowires and side-by-side attached single molecular nanowires were also observed through atomic force microscopy (AFM), which further supported the “oriented-attachment” mechanism. Accordingly, we demonstrate that after the supramolecular polymerization, “oriented attachment” growth mechanism is another critical process for the construction of large anisotropic organic assemblies, such as organic nanowires.

Liposome-embedded hydrogels have been widely used for controlled drug release. In this work, by embedding egg phosphatidylcholine (EPC) liposome into a poly(N-isopropylacrylamide) (PNIPAm) hydrogel via chemical cross-linking, we systemically studied the physical interactions between the liposome and hydrogel matrix, as well as the release mechanism of the encapsulated content in the liposome at varying temperatures. It was found that the confinement of the network and the hydrophobic interactions between the liposome and PNIPAm determined the integrity of the liposome and, more importantly, the release profile of the encapsulated content, such as calcein. This liposome-embedded stimuli-responsive system is suitable for the delivery of mixed drugs with different release profiles, and easily achieves on-demand release.

Block copolymers containg poly(ethylene oxide) (PEO) have been widely used in biomedical applications. The PEO block is generally treated as the hydrophilic moiety. In this work, we demonstrated that PEO could serve as the “hydrophobic” block under certain conditions by using PEO-b-poly(vinyl alcohol) (PEO-b-PVA) as the example. Water is a non-selective solvent for both of the blocks, however, the addition of NaCl decreases the solubility of PEO in aqueous solution while it shows no effect on the PVA block. With the solubility of PEO being deteriorated by adding NaCl, PEO-b-PVA exhibited amphiphilic feature in aqueous solution with PEO being the “hydrophobic” block. Therefore, by just adding salts, uniform gel-like particles were formed by PEO-b-PVA of proper block ratio. These solid particles formed by dual hydrophilic copolymers with excellent biocompability may have great potential in biomedical applications.

Ethyl carbamylated polyrotaxane (ECPR) and propyl carbamylated polyrotaxane (PCPR) were prepared based on the reactions between ethyl/propyl isocyanate and polyrotaxane (PR) in anhydrous DMSO under an argon atmosphere. By changing the alkyl type and substitution ratio, the PR derivative with good water-solubility was obtained and its solutions showed reversible sol–gel phase transition. During the heating process, transition temperature from sol to gel decreased from 32 °C to 18 °C with increasing the solution concentration from 2.44% to 13.5%, while in the cooling process, all the gels with various concentration did not turn into sols until the temperature decreased to 1 °C, exhibiting large hysteresis between heating and cooling.

C60(OH)8 is a fullerenol with all the hydroxyl groups located in the same hemisphere. It combines the fascinating assembly behaviour of a Janus particle and the unique properties of a fullerene. Since the range of interparticle hydrophobic attraction in water is much longer than the particle size, C60(OH)8 has a strong tendency to form aggregates. At concentrations above 1.0 × 10−6 M, the Rg of the aggregate is 110 nm and the aggregation number reaches 2.5 × 105. However, the conformation of the aggregate is not condensed, C60(OH)8 can still adjust its position by transportation or rotation. Therefore, when deposited on the surface, C60(OH)8 assembles into a spherical structure or a single-layered fiber on the hydrophilic surface, but it forms a toroidal structure with concentric rings on the hydrophobic surface. If illuminated with light during assembly, fibers composed of multi-braids are observed on the hydrophilic surface. Our work demonstrated that the assembly of Janus fullerenol offered a new approach to prepare novel carbon structures.

As part of our continuing research work, studies toward the self-aggregation behaviour of amphiphilic triblock copolymers containing β-CD-Pluronic F127 polyrotaxane as a central block and hydrophilic brush-like PPEGMA as flanking blocks in aqueous solution were conducted by using dynamic and static light scattering (DLS and SLS) analyses and transmission electron microscopy (TEM). These self-aggregates are characterized by a unique random coil structure. Their hydrodynamic radius (Rh) and radius of gyration (Rg) decrease as the number of the entrapped β-CD molecules increases, while the core of the random coils becomes looser due to the increase of the rigidity and steric hindrance of the brush-like polymer chains. Interestingly, it was observed that the morphology of the aggregates changes greatly after loading amphotericin B (AmB). According to the DLS/SLS and TEM results, it was speculated that a solid sphere is formed, and that the density of spheres increases as the number of entrapped β-CDs increases. For these self-aggregates, as the number of entrapped β-CDs increases, their drug-loading content (DLC) and drug-loading efficiency (DLE) for AmB increases, while their hemolytic activity against rabbit erythrocytes decreases. It appears that the multiple hydrogen-bonding interactions between AmB and the entrapped β-CDs make a significant contribution to the morphology change of the self-aggregates and their high loading capability for AmB.