Fabrication of Dual pH/Reduction-Responsive P(CL-co-ACL)-Based Cross-Linked Polymeric Micelles for PTX Delivery.

To enhance the stability of the polymeric micelles and optimize their drug-controlled release ability, three disulfide-linked polyethylene glycol methyl ether methacrylate-disulfide-poly(ε-caprolactone-co-γ-amine-ε-caprolactone) (PPEGMA-SS-P(CL-co-ACL)) polymers were synthesized and characterized by 1H NMR, GPC, and FT-IR successfully, and their dual pH/reduction-responsive cross-linked polymeric micelles were prepared for paclitaxel (PTX) delivery by using 2,3-dimethylmaleic anhydride (DMMA) as the cross-linking agent. The PTX loading capacity (LC) and encapsulation efficiency (EE) values of the cross-linked micelles formed by PPEGMA8-SS-P(CL47-co-ACL15) achieved were 23.96% and 71.58%, slightly higher than those of un-cross-linked micelles. Both particle sizes of blank micelles and in vitro drug release of PTX-loaded micelles confirmed that compared with those un-cross-linked micelles, the cross-linked micelles were more stable at pH 7.4 + 0 mM DTT, with a PTX cumulative release of 13% at 120 h, while the PTX cumulative release of the cross-linked micelles at pH 5.0 + 10 mM DTT were close to that of un-cross-linked micelles after 60 h, indicating the successful reversible cross-linking and smooth drug release of the cross-linked micelles. The cytotoxicity assay showed that PPEGMA8-SS-P(CL47-co-ACL15) and its cross-linked micelles had low cell cytotoxicity, and both PTX-loaded micelles revealed a certain inhibitory effect on HepG2 cells. These results revealed that the dual pH/reduction-responsive cross-linked polymeric micelles prepared from PPEGMA8-SS-P(CL47-co-DCL15) were a promising candidate for PTX delivery.

Efficient adsorption of bulky reactive dyes from water using sustainably-derived mesoporous carbons.

Hazardous reactive dyes can cause serious environmental problems, as they are difficult to remove from water using conventional adsorbents due to their large molecular sizes and bulky structures. Sustainable mesoporous carbons derived from alginic acid demonstrated promising adsorbent capacity for several representative industrial bulky reactive dye molecules that account for almost 30% of the global textile dye market: Procion Yellow H-XEL (PY), Remazol Black (RB), Procion Crimson H-XEL (PC) and Procion Navy H-XEL (PN). These new adsorbents showed high mesoporosity (>90%) and large pore diameters (>20 nm) facilitating more straightforward and efficient adsorption and desorption processes when compared with predominately microporous activated carbon (AC), Norit, of similar surface chemistry, or with Silica gel (Sgel) that shows good mesoporosity but is hydrophilic. Their adsorption capacity was also significantly higher than that of both AC and Sgel, verifying suitability for bulky dye elimination from wastewater. Adsorption kinetic studies showed a best fit with the Elovich model, indicating a heterogeneous surface adsorption process. The adsorption isotherm data was best represented via the Toth model for almost all adsorbent/dye systems (R2 ≥ 0.98), validating the results of the Elovich model whereby the adsorbent is structurally heterogenous with multilayer dye coverage. From thermodynamic analysis, the derived parameters of ΔG (-11.6 âˆ¼ -6.2 kJ/mol), ΔH and ΔS demonstrate a spontaneous, enthalpy controlled adsorption process that was exothermic for RB (-10.0 kJ/mol) and PC (-23.9 kJ/mol) and endothermic for PY (3.9 kJ/mol) and PN (13.2 kJ/mol). Overall these alginic acid based mesoporous carbons are cost-effective, sustainable and efficient alternatives to current predominantly microporous adsorbent systems.

DPD simulations and experimental study on reduction-sensitive polymeric micelles self-assembled from PCL-SS-PPEGMA for doxorubicin controlled release.

Delivery of anticancer drugs by amphiphilic polymeric micelles with disulfide bonds as the reduction-responsive groups has potential application in the field of drug-controlled release. In this study, three disulfide-linked polycaprolactone-b-polyethylene glycol methyl ether methacrylate (PCL-SS-PPEGMA) were synthesized and confirmed by 1H NMR and GPC, and then used for doxorubicin (DOX) delivery. The CMC values of the three PCL-SS-PPEGMA micelles were low (0.71-4.56 mg/L), indicative of the good stability of micelles in aqueous solution. The drug loading content (LC) and encapsulation efficiency (EE), together with the DOX accelerated release profiles were determined, with good drug loading capacity and well drug-controlled release performance. And to explore the mesoscopic behavior of reduction-responsive drug-loaded polymeric micelles, by using a dedicated disulfide bond-breaking model and script, dissipative particle dynamics (DPD) simulations were carried out on the three PCL-SS-PPEGMA polymers. Their self-assembled behavior, formation of DOX-loaded micelles, the disulfide bond-breaking process, as well as the DOX reduction-responsive release process were simulated and assessed. Comparing the DPD simulation results with the experimental data, we found that they were in good agreement, effectively demonstrating that the DPD simulation method developed can provide a practical mesoscopic approach for the reduction-responsive drug-loaded polymeric micelles that involved the cleavage of dynamic covalent bonds.

Polycarbonate/Sulfonamide Composites with Ultralow Contents of Halogen-Free Flame Retardant and Desirable Compatibility.

A novel halogen-free flame retardant containing sulfonamide, 1,3,5,7-tetrakis (phenyl-4-sulfonamide) adamantane (FRSN) was synthesized and used for improving the flame retardancy of largely used polycarbonate (PC). The flame-retardant properties of the composites with incorporation of varied amounts of FRSN were analyzed by techniques including limited oxygen index, UL 94 vertical burning, and cone calorimeter tests. The new FR system with sulfur and nitrogen elements showed effective improvements in PC's flame retardancy: the LOI value of the modified PC increased significantly, smoke emission suppressed, and UL 94 V-0 achieved. Typically, the composite with only 0.08 wt% of FRSN added (an ultralow content) can increase the limiting oxygen index (LOI) value to 33.7% and classified as UL 94 V-0 rating. Furthermore, the mechanical properties and SEM morphology indicated that the FRSN has very good compatibility with PC matrix, which, in turn, is beneficial to the property enhancement. Finally, the analysis of sample residues after burning tests showed that a high portion of char was formed, contributing to the PC burning protection. This synthesized flame retardant provides a new way of improving PC's flame retardancy and its mechanical property.

pH-Sensitive Mixed Micelles Assembled from PDEAEMA-PPEGMA and PCL-PPEGMA for Doxorubicin Delivery: Experimental and DPD Simulations Study.

To decrease critical micelle concentration (CMC), improve stability, and keep high drug-loading capacity, three pH-sensitive mixed micelles applied for anticancer drug controlled delivery were prepared by the mixture of polymers poly (N,N-diethylaminoethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PDEAEMA-PPEGMA) and polycaprolactone-b-poly (poly(ethylene glycol) methyl ether methacrylate) (PCL-PPEGMA), which were synthesized and confirmed by 1H NMR and gel permeation chromatographic (GPC). The critical micelle concentration (CMC) values of the prepared mixed micelles were low, and the micellar sizes and zeta potentials of the blank mixed micelles demonstrated good pH-responsive behavior. Combined experimental techniques with dissipative particle dynamics (DPD) simulation, the particle sizes, zeta potentials, drug loading content (LC), encapsulation efficiency (EE), aggregation morphologies, and doxorubicin (DOX) distribution of the mixed micelles were investigated, and the high DOX-loading capacity of the mixed micelles was found. Both in vitro DOX release profiles and DPD simulations of the DOX dynamics release process exhibited less leakage and good stability in neutral conditions and accelerated drug release behavior with a little initial burst in slightly acidic conditions. Cytotoxicity tests showed that the polymer PDEAEMA-PPEGMA and the blank mixed micelles had good biocompatibility, and DOX-loaded mixed micelles revealed certain cytotoxicity. These results suggest that the drug-loaded mixed micelles that consisted of the two polymers PDEAEMA-PPEGMA and PCL-PPEGMA can be new types of pH-responsive well-controlled release anticancer drug delivery mixed micelles.

Electrospun Silver Nanoparticles-Embedded Feather Keratin/Poly(vinyl alcohol)/Poly(ethylene oxide) Antibacterial Composite Nanofibers.

Feathers, which contain >90% keratin, are valuable natural protein resources. The aim of this study is to prepare antimicrobial feather keratin (FK)-based nanofibers by incorporating silver nanoparticles (AgNPs). A series of AgNPs-embedded feather keratin/poly(vinyl alcohol)/poly(ethylene oxide) (FK/PVA/PEO) composite nanofibers with varying amounts of AgNPs content were fabricated by electrospinning. Their morphology, crystallinity, thermal stability, tensile property, and antibacterial activity were systematically investigated. The average diameters of composite nanofibers gradually decreased with increases in the amount of AgNPs. The crystallinity, thermal stability, and antibacterial activity of FK/PVA/PEO nanofibers were enhanced by embedding AgNPs. When embedded with 1.2% AgNPs, both the tensile strength and elongation-at-break reached the highest level. This work has the potential to expand the application of FK-based nanofibers in the biomaterial field.

Exceptionally Stable Microporous Organic Frameworks with Rigid Building Units for Efficient Small Gas Adsorption and Separation.

Three microporous organic frameworks (hereafter denoted as MPOF-Ads) based on a rigid adamantane core have been successfully synthesized via Sonogashira-Hagihara polycondensation coupling in high yields, 83.7-94.6%. The obtained amorphous MPOF-Ads networks have high Brunauer-Emmett-Teller surface areas (up to 737.3 m2 g-1), narrow pore size distribution (0.95-1.06 nm), and superior thermal (the initial decomposition temperature T5% under an N2 atmosphere can reach 410 °C) and chemical stability (no apparent degradation in common organic solvents or strong acid/base solutions after 7 days). At 273 K and 1.0 bar, these MPOF-Ads networks present good uptake capacities for small gas molecules (13.9 wt % CO2 and 1.66 wt % CH4) for which the presence of high surface area, predominant microporosity, and narrow pore size distribution are beneficial. In addition, the as-prepared MPOF-Ads networks possess moderate isosteric heats for CO2 (Qst = 19.5-30.3 kJ mol-1) and show desired CO2/N2 and CO2/CH4 selectivity (36.3-38.4 and 4.1-4.3 based on Henry's law and 17.88-24.92 and 4.24-5.70 based on ideal adsorbed solution theory, respectively). With the demonstrated properties, the synthesized MPOF-Ads networks display potential for small gas storage and separation that can be used in harsh environments because of their superior physical and chemical stability.

Adamantane-Based Micro- and Ultra-Microporous Frameworks for Efficient Small Gas and Toxic Organic Vapor Adsorption.

Microporous organic polymers and related porous materials have been applied in a wide range of practical applications such as adsorption, catalysis, adsorption, and sensing fields. However, some limitations, like wide pore size distribution, may limit their further applications, especially for adsorption. Here, micro- and ultra-microporous frameworks (HBPBA-D and TBBPA-D) were designed and synthesized via Sonogashira⁻Hagihara coupling of six/eight-arm bromophenyl adamantane-based "knots" and alkynes-type "rod" monomers. The BET surface area and pore size distribution of these frameworks were in the region of 395⁻488 m² g-1, 0.9⁻1.1 and 0.42 nm, respectively. The as-made prepared frameworks also showed good chemical ability and high thermal stability up to 350 °C, and at 800 °C only 30% mass loss was observed. Their adsorption capacities for small gas molecules such as CO2 and CH4 was 8.9⁻9.0 wt % and 1.43⁻1.63 wt % at 273 K/1 bar, and for the toxic organic vapors n-hexane and benzene, 104⁻172 mg g-1 and 144⁻272 mg g-1 at 298 K/0.8 bar, respectively. These are comparable to many porous polymers with higher BET specific surface areas or after functionalization. These properties make the resulting frameworks efficient absorbent alternatives for small gas or toxic vapor capture, especially in harsh environments.

DPD studies on mixed micelles self-assembled from MPEG-PDEAEMA and MPEG-PCL for controlled doxorubicin release.

In order to better understand and improve the drug loading capacity and release behavior of the pH-responsive mixed micelles in well controlled pH environments, dissipative particle dynamics (DPD) simulations are employed. This is performed by studying the co-micellization behavior of these materials produced from the two specific diblock polymers, poly(ethylene glycol) methyl ether-b-poly(N, N diethylamino ethyl methacrylate) (MPEG-PDEAEMA) and poly(ethylene glycol) methyl ether-b-polycaprolactone (MPEG-PCL) for doxorubicin (DOX) delivery. With the use of appropriate interaction parameters, the formation mechanism of (drug-loaded) mixed micelles, particle sizes, morphology, and composition are investigated. Simulation results show that compared with pure MPEG-PDEAEMA or MPEG-PCL, the mixed MPEG-PDEAEMA and MPEG-PCL system can combine to form multifunctional mixed micelles with larger particle sizes that lead to improved stability, higher drug loading capacity and better-controlled drug release performance. Simulations of the drug release process using the mixed micelles show that, when the environment is acidic, the tertiary amine group of PDEAEMA and DOX3 lead to rapid diffusion and release of the DOX in the aqueous solution. It is found that the presence of MPEG-PCL has a great influence in avoiding the fast release of the drug inside the core of micelles. Therefore, this study offers a deeper understanding of the mechanism on the co-micellization behaviors, the pH-responsive and drug controlled release behaviors of mixed micelles.

Macroscopic CNT fibres inducing non-epitaxial nucleation and orientation of semicrystalline polymers.

In the presence of macroscopic fibres of carbon nanotubes (CNT), various semicrystalline polymers are shown to present accelerated crystallisation through the formation of a transcrystalline (TC) layer perpendicular to the fibre axis. From differential scanning calorimetry, polarized optical microscopy and X-ray diffraction we establish this to be due to much faster nucleation rates at the fibre surface. The formation of a TC layers is demonstrated for polyvinyldene fluoride, isotactic polypropylene and poly(lactic acid) in spite of the large differences in their chemistry and structure unit cells, suggesting that epitaxy in terms of lattice type or size matching is not a prerequisite. For the three polymers as well as poly(ether ether ketone), the TC layer is identically oriented with the chain axis in the lamella parallel to the CNTs, as observed by wide and small angle X-ray scattering. These results point to polymer chain orientation at the point of adsorption and the formation of a mesomorphic layer as possible steps in the fast nucleation of oriented lamella, with wetting of the CNT fibre surface by the molten semi-crystalline polymer a key condition for heterogeneous nucleation to take place.