Small-Angle X-ray Scattering for PEGylated Liposomal Doxorubicin Drugs: An Analytical Model Comparison Study.

Liposomal delivery systems are recognized as efficient and safe platforms for chemotherapeutic agents, with doxorubicin-loaded liposomes being the most representative nanopharmaceuticals. Characterizing the structure of liposomal nanomedicines in high spatial and temporal resolution is critical to analyze and evaluate their stability and efficacy. Small-angle X-ray scattering (SAXS) is a powerful tool increasingly used to investigate liposomal delivery systems. In this study, we chose a Doxil-like PEGylated liposomal doxorubicin (PLD) as an example and characterized the liposomal drug structure using synchrotron SAXS. Classical analytical models, including the spherical-shell or flat-slab geometries with Gaussian or uniform electron density profiles, were used to model the internal structure of the liposomal membrane. A cylinder model was applied to fit the scattering from the drug crystal loaded in the liposomes. The high-resolution structures of the original drug, Caelyx, and a similar research drug prepared in our laboratory were characterized using these analytical models. The structural parameters of PLDs, including the thickness of the liposomal membrane and morphology of the drug crystal, were further compared. The results demonstrated that both spherical-shell and flat-slab geometries with Gaussian electron density distribution were suitable to elucidate the structural features of the liposomal membrane under a certain range of scattering vectors, while models with uniform electron density distribution exhibited poor fitting performance. This study highlights the technical features of SAXS, which provides structural information at the nanoscale for liposomal drugs. The demonstrated methods are reliable and easy-to-use for the structural analysis of liposomal drugs, which are helpful for a broader application of SAXS in the production and regulation of nanopharmaceuticals.

Chiral Adaptive Induction of an Achiral Cucurbit[8]uril-Based Supramolecular Organic Framework by Dipeptides in Water.

Chiral induction by natural biomolecules can reveal the indispensable role of chiral structures in life and can be used to develop the chirality-sensing biomolecular recognition. Here, we present the synthesis and characterization of an achiral supramolecular organic framework (SOF-1) constructed from cucurbit[8]uril (CB[8]) and hexaphenylbenzene (HPB) derivative (1) in water. Due to the propeller-like rotational chiral conformation of HPB units and the specific recognition properties of CB[8], SOF-1 demonstrates chiral adaptive induction in water when interacting with the N-terminal Trp-/Phe-containing dipeptides including L-TrpX and L-PheX (X is an amino acid residue), respectively, exhibiting contrasting circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. Consequently, SOF-1 has been developed as a supramolecular host and chiroptical sensor capable of recognizing and distinguishing the sequence-opposite Trp-/Phe-containing dipeptide pairs including L-TrpX/L-XTrp and L-PheX/L-XPhe based on the sequence-selective CD responses.

Adaptive Chirality of an Achiral Cucurbit[8]uril-Based Supramolecular Organic Framework for Chirality Induction in Water.

Chiral framework materials have been developed for many applications including chiral recognition, chiral separation, asymmetric catalysis, and chiroptical materials. Herein, we report that an achiral cucurbit[8]uril-based supramolecular organic framework (SOF-1) with the dynamic rotational conformation of tetraphenylethene units can exhibit adaptive chirality to produce M-SOF-1 or P-SOF-1 with mirror-image circular dichroism (CD) with gabs ≈±10-4 and circularly polarized luminescence (CPL) with glum ≈±10-4 induced by L-/D-phenylalanine in water, respectively. The chirality induction in CD (gabs ≈-10-4 ) and CPL (glum ≈-10-4 ) of P-SOF-1 from achiral SOF-1 can be presented by using a small amount of adenosine-5'-triphosphate disodium (ATP) or adenosine-5'-diphosphate disodium (ADP) (only 0.4 equiv) in water. Furthermore, the adaptive chirality of SOF-1 can be used to determine dipeptide sequences (e.g., Phe-Ala and Ala-Phe) and distinguish polypeptides/proteins (e.g., somatostatin and human insulin) with characteristic CD spectra. Therefore, achiral SOF-1 as an ideal chiroptical platform with adaptive chirality may be applied to determine the enantiopurity of amino acids (e.g., L-/D-phenylalanine), develop aqueous CPL materials, and distinguish biological chiral macromolecules (e.g., peptides/proteins) via chirality induction in water.

Diamondoid Frameworks via Supramolecular Coordination: Structural Characterization, Metallogel Formation, and Adsorption Study.

Supramolecular coordination has been developed as an efficient tool to construct a variety of discrete metallacycles and metallacages with well-defined shapes and sizes. However, its application in framework construction has been barely exploited. In this paper, we report the direct synthesis of two diamondoid frameworks from a simple tetrahedral precursor, tetra(4-(4-pyridinyl)phenyl)methane, and two linear difunctional platinum(II) ligands via one-step supramolecular coordination. Controlled by the specific angularity and geometry of the tetrahedral and linear subunits, these frameworks possess a well-defined diamondoid topology with highly regulated periodicity and three-dimensional porosity. Moreover, these rigid frameworks can be directly changed into a metallogel when prepared in DMSO at high concentrations. Interestingly, these diamondoid frameworks exhibit a cationic nature and stimuli-responsive behavior, which potentially endow them with the selective adsorption and controlled release for anionic dyes and drugs in aqueous environments. Thus, this study demonstrates that supramolecular coordination is a facile and efficient approach for the preparation of functional framework materials containing predesigned and well-defined supramolecular coordination assemblies as molecular skeletons.

Lipid-Based Liquid Crystalline Nanoparticles Facilitate Cytosolic Delivery of siRNA via Structural Transformation.

RNA interference (RNAi) technology has shown great promise for the treatment of cancer and other genetic disorders. Despite the efforts to increase the target tissue distribution, the safe and effective delivery of siRNA to the diseased cells with sufficient cytosolic transport is another critical factor for successful RNAi clinical application. Here, the constructed lipid-based liquid crystalline nanoparticles, called nano-Transformers, can transform thestructure in the intracellular acidic environment and perform high-efficient siRNA delivery for cancer treatment. The developed nano-Transformers have satisfactory siRNA loading efficiency and low cytotoxicity. Different from the traditional cationic nanocarriers, the endosomal membrane fusion induced by the conformational transition of lipids contributes to the easy dissociation of siRNA from nanocarriers and direct release of free siRNA into cytoplasm. We show that transfection with cyclin-dependent kinase 1 (CDK1)-siRNA-loaded nano-Transformers causes up to 95% reduction of relevant mRNA in vitro and greatly inhibits the tumor growth without causing any immunogenic response in vivo. This work highlights that the lipid-based nano-Transformers may become the next generation of siRNA delivery system with higher efficacy and improved safety profiles.

Diamondoid Supramolecular Coordination Frameworks from Discrete Adamantanoid Platinum(II) Cages.

Recently, porous framework materials with various network-type structures have been constructed via several different approaches, such as coordination interactions, reversible covalent bonds, and non-covalent interactions. Here, we have combined the concepts of supramolecular coordination complex (SCC) and metal-organic framework to offer a new strategy to construct a diamondoid supramolecular coordination framework (SCF) from an adamantanoid supramolecular coordination cage as the tetrahedral node and a difunctional Pt(II) ligand as the linear linker via stepwise orientation-induced supramolecular coordination. The adamantanoid supramolecular coordination cage has four uncoordinated pyridyl groups, which serve as the four vertexes of the tetrahedral geometry in the diamondoid framework. As a result, this diamondoid SCF exhibits an adamantanoid-to-adamantanoid substructure with two sets of pores, including the interior cavity of the adamantanoid cage and the extended adamantanoid space between the individual cages in the framework. In addition, the shape-controllable and highly ordered self-assembly of nanometer-sized diamondoid SCF is observed as micrometer-sized regular octahedrons by evaporation under heating in DMSO. This study demonstrates the potential application of supramolecular coordination complexes in the precise construction of highly regulated porous framework materials.

Shape-Controllable and Fluorescent Supramolecular Organic Frameworks Through Aqueous Host-Guest Complexation.

Two kinds of shape-controllable and fluorescent supramolecular organic frameworks (cuboid or spheroid) are constructed hierarchically from CB[8] and tetraphenylethylene derivatives through host-guest interaction in water. These two fluorescent SOFs exhibit intriguing and varied photophysical properties, including large red-shifts (up to 82 nm) and stimuli-responsive behavior to competitive guest by binding with CB[8], the turn-on fluorescence of which is applied in cellular imaging.

Synthesis and Self-Assembly of Shape Amphiphiles Based on POSS-Dendron Conjugates.

Shape has been increasingly recognized as an important factor for self-assembly. In this paper, a series of shape amphiphiles have been built by linking polyhedral oligomeric silsesquioxane (POSS) and a dendron via linkers of different lengths. Three conjugates of octahedral silsesquioxanes (T8-POSS) and dendron are designed and synthesized and are referred to as isobutyl T8-POSS gallic acid derivatives (BPOSS-GAD-1, BPOSS-GAD-2, BPOSS-GAD-3). These samples have been fully characterized by ¹H-NMR, 13C-NMR, Fourier transform infrared (FT-IR) spectroscopy and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry to establish their chemical identity and purity. Driven by different interactions between POSS and dendron, ordered superstructure can be found upon self-assembly. The stabilities and structures of these samples are further studied by using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXD), and molecular simulations. The results show that their melting points range from 74 °C to 143 °C and the molecular packing schemes in the assemblies can form lamellar structure of BPOSS-GAD-3 as determined by the different linkers.

Extraction of cellulose nanofibrils from pine sawdust by integrated chemical pretreatment.

Reducing energy consumption is major challenge in the industrialization of chemical pretreatments for the extraction of cellulose nanofibrils (CNF). In this study, an integrated chemical pretreatment with alkaline/acid-chlorite/TEMPO-oxidant was used for the nano-fibrillation of CNF from pine sawdust (WS). The alkaline and acid-chlorite pretreatments effectively eliminated the non-cellulosic components present in WS, resulting in the delamination of individual cell layers and swelling of the internal structures within the cellulose fiber bundles and cellulose microfibrils that form these layers. The spacing between CNF within the cellulose microfibrils increased from 3.7 nm to 5.5 nm. These loosely packed hierarchical structures facilitated the penetration of the reagent, which led to an increase in the specific surface area during the TEMPO-oxidant reaction and consequently accelerated the reaction rate. The WS was pretreated in a very dilute solution (1 % NaOH and 0.5 % NaClO2) under mild conditions (70 °C for 1 h), which resulted in a significant reduction of the TEMPO reaction time (from 3 h to 30 min) and a lower consumption of the reaction reagent (one fourth of the amount consumed compared to the direct oxidation of WS to achieve the same degree of cellulose nano-fibrillation).

Effect of Length of Cellulose Nanofibers on Mechanical Reinforcement of Polyvinyl Alcohol.

Cellulose nanofibers (CNF), representing the nano-structured cellulose, have attained an extensive research attention due to their sustainability, biodegradability, nanoscale dimensions, large surface area, unique optical and mechanical performance, etc. Different lengths of CNF can lead to different extents of entanglements or network-like structures through van der Waals forces. In this study, a series of polyvinyl alcohol (PVA) composite films, reinforced with CNF of different lengths, were fabricated via conventional solvent casting technique. CNF were extracted from jute fibers by tuning the dosage of sodium hypochlorite during the TEMPO-mediated oxidation. The mechanical properties and thermal behavior were observed to be significantly improved, while the optical transparency decreased slightly (Tr. > 75%). Interestingly, the PVA/CNF20 nanocomposite films exhibited higher tensile strength of 34.22 MPa at 2 wt% filler loading than the PVA/CNF10 (32.55 MPa) while displayed higher elastic modulus of 482.75 MPa than the PVA/CNF20 films (405.80 MPa). Overall, the findings reported in this study provide a novel, simple and inexpensive approach for preparing the high-performance polymer nanocomposites with tunable mechanical properties, reinforced with an abundant and renewable material.

A tunable alkaline/oxidative process for cellulose nanofibrils exhibiting different morphological, crystalline properties.

This study describes a two-step alkali/oxidation process to efficiently convert waste sugarcane bagasse (SCB) into cellulose nanofibrils (CNF) whose structures have been characterized using a range of analytical techniques (SR-WAXS, IR, TEM and DLS). Increasing the concentration of the NaOH solution from 10 to 16 wt% in the first step results in a gradual increase in cellulose II content from 0 to >99 %, which also produces a corresponding increase in fiber crystallinity index from 32 to 61 %. Varying the concentration of NaClO used in the second oxidative step enables the morphologies of the CNF to be reliably controlled, with fiber lengths decreasing from micrometer to nanometer levels as the amount of NaClO oxidant used is increased. This simple two-step alkaline/oxidative treatment process enables SCB to be converted into CNF exhibiting different polymorphic and morphological properties, thus enabling their economic and reproducible production as nanostructured materials for numerous applications.

Constructing Conductive Channels between Platinum Nanoparticles and Graphitic Carbon Nitride by Gamma Irradiation for an Enhanced Oxygen Reduction Reaction.

Electrocatalytic performance of low-cost graphitic carbon nitride (g-C3N4) is greatly limited by its conductivity. In this work, an innovative method, gamma irradiation technology, was used to efficiently synthesize g-C3N4/Pt nanoparticle (CN/Pt) nanocomposites, which can construct conductive channels between the nanostructure g-C3N4 and supported platinum nanoparticles (PtNPs). Then, the as-prepared CN/Pt nanocomposites were applied in the oxygen reduction reaction (ORR) as an electrocatalyst, which shows a small Tafel slope and the fast four-electron transfer path in the ORR. The oxygen reduction performance over the CN/Pt nanocomposite is much superior to that of the commercial Pt/C and mostly reported in g-C3N4-based electrodes. Experimental results have confirmed the fast charge transfer between PtNPs and g-C3N4 through a metal-support interaction, and using gamma irradiation technique to disperse PtNPs on g-C3N4 proves to be an effective strategy to enhance the catalytic performance of g-C3N4 in ORR. Therefore, gamma irradiation may possess great potential for preparing CN/Pt nanocomposites as a highly efficient ORR catalyst.

Tetraphenylethene-Based Supramolecular Coordination Frameworks with Aggregation-Induced Emission for an Artificial Light-Harvesting System.

Supramolecular coordination is an efficient strategy to construct supramolecular coordination frameworks with predesigned structures, assembled shapes, and specific function. In this work, we report the synthesis, structural characterization, and photophysical property of two tetraphenylethene-based supramolecular coordination frameworks 1a and 1b formed from 1,1,2,2-tetrakis(4-(pyridin-4-yl)phenyl)ethene (2a) or 1,1,2,2-tetrakis(4-((E)-2-(pyridin-4-yl)vinyl)phenyl)ethene (2b) and a linear difunctional platinum(II) ligand (3a) via coordination-driven self-assembly. Controlled by the specific angularity and geometry of tetraphenylethene (with 60° and 120°) and difunctional Pt(II) linker (with 180°), these supramolecular coordination frameworks possess a well-defined and two-dimensional (2D) rhombic network-type topology with good periodicity and porosity. Given the aggregation-induced emission (AIE) property of tetraphenylethene units and the porosity of frameworks, 1a and 1b have been successfully used as fluorescent platforms and energy donors to fabricate efficient artificial light-harvesting materials with two fluorescent acceptors (Nile Red and Sulforhodamine 101) via noncovalent interactions in aqueous solution. Furthermore, these light-harvesting materials have been applied for promoting cancer cell imaging with a full shift of imaging channels from blue/green channels to the red channel. Thus, this study provides an effective approach to fabricate functional frameworks as fluorescent platforms for developing more fluorescent materials.

Shape inducer-free polygonal angle platinum nanoparticles in graphene oxide as oxygen reduction catalyst derived from gamma irradiation.

In this report, polygonal angle platinum nanoparticles (PtNPs) anchored on nitrogen doping reduced graphene oxide (NrGO) as oxygen reduction reaction (ORR) catalyst was synthesized by gamma irradiation assisted with in situ hydrolysis of urea without using any shape inducer, seed, or template. Urea was not only employed as the nitrogen source, but also offered more reductive radicals in the gamma system. The uniform dispersion and homogeneous size distribution of PtNPs are obtained on reduced graphene oxide (rGO), which is attributed to the synergy of restriction effects of GO and crush capacity of high energy gamma rays. In addition, the method simultaneously offers PtNPs with polygonal angle structure and doping nitrogen in rGO, thus provides more surface and corner defects on PtNPs and heteroatomic defects on rGO, which synergistically improve the ORR performance of the samples. The obtained polygonal angle PtNPs modified NrGO exhibit fantabulous ORR activity in alkaline media with enhanced onset potential (906 mV), half-wave potential (783 mV) and superior limit current density (6.74 mA·cm-2) compared to the commercial Pt/C and those PtNPs supported on rGO composites. The results indicate that gamma irradiation assisted with in situ hydrolysis of urea can be a promising candidate method for preparation of high performance Pt-based catalysts in practical application.

Coiled Plant Tendril Bioinspired Fabrication of Helical Porous Microfibers for Crude Oil Cleanup.

Fabrication of the helical fibers with sheath/core structure comprising 3D interconnected porous polystyrene (PS) and ductile polyvinylidene fluoride is inspired by coiled plant tendril. The key innovation point applied in this study is to produce a helical porous system based on sheath/core structure that can come into being a huge storage space in the sorption process for crude oil. More importantly, the mechanical properties confirm to have a more excellent improvement than that of the initial PS fibers, which make it become a possible candidate for the large-area sorption and reuse of crude oil from the ocean or industry. The bioinspired fabricating strategy opens a significant avenue between the coaxial electrospinning and crude oil contamination cleanup. It is also expected that the unique structure can make it a promising candidate for applications in energy conversion, tissue engineering, and intelligent devices.

Cellulose nanofibrils extracted from the byproduct of cotton plant.

Cotton stalk bark, as the byproduct of cotton plant, was usually discarded and/or combusted, leading to waste of resources and environment pollution. How to efficiently utilize this kind of cellulosic materials is of significative to energy saving and environment protection. Herein, we report on the extraction of cellulose nanofibrils (CNF) from the cotton stalk bark for the first time by a combination of TEMPO-oxidation and mechanical disintegration method. The obtained CNF showed a yield more than 20 wt%. The morphologies, crystalline structures and thermal properties of CNF were extensively investigated by the transmission electron microscopy, scanning electron microscopy, synchrotron radiation wide-angle X-ray scattering, Fourier transform infrared spectra and differential scanning calorimetry, respectively. The results showed that the final extracted CNF have similar polymorphs with their starting materials and a significantly increased crystallinity. This work will provide a new way to utilize the cotton stalk barks.