Poly(ethylene oxide)-b-poly(l-lactide) Diblock Copolymer/Carbon Nanotube-Based Nanocomposites: LiCl as Supramolecular Structure-Directing Agent

Easy, Flexible and Standardizable Anti-Nascent Biofilm Activity Assay to Assess Implant Materials

Medical implants have improved the quality of life of many patients. However, surgical intervention may eventually lead to implant microbial contamination. The aims of this research were to develop an easy, robust, quantitative assay to assess surface antimicrobial activities, especially the anti-nascent biofilm activity, and to identify control surfaces, allowing for international comparisons. Using new antimicrobial assays to assess the inhibition of nascent biofilm during persistent contact or after transient contact with bacteria, we show that the 5 cent Euro coin or other metal-based antibacterial coins can be used as positive controls, as more than 4 log reduction on bacterial survival was observed when using either S. aureus or P. aeruginosa as targets. The methods and controls described here could be useful to develop an easy, flexible and standardizable assay to assess relevant antimicrobial activities of new implant materials developed by industries and academics.

Design of Thermoplastic Polyurethanes with Conferred Antibacterial, Mechanical, and Cytotoxic Properties for Catheter Application

Thermoplastic polyurethanes (TPUs) are proposed as suitable solution for the fabrication of biocompatible catheters with appropriate mechanical parameters and confirmed antibacterial and cytocompatible properties. For this purpose, a series of quaternary ammonium salts (QASs) and quaternary phosphonium salts (QPSs) based monomers were prepared followed by the determination of their minimal inhibitory concentrations (MICs) against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Pseudomonas aeruginosa (P. aeruginosa). A combination of the most active ammonium (QAS-C₁₄) and phosphonium (QPS-TOP) salts led to a MIC down to 2.4 μg/mL against S. aureus and 9 μg/mL against P. aeruginosa, corroborating the existence of a synergistic effect. These quaternary onium salt (QOS) units were successfully incorporated along the polymer chain, as part of a two-step synthesis approach. The resulting TPU-QOS materials were subsequently characterized through thermal, mechanical, and surface analyses. TPU-Mix (combining the most active QAS-C₁₄ and QPS-TOP units) showed the highest antibacterial efficiency, confirming the synergistic effect between both QOS groups. Finally, an MTT assay on the SiHa cell line revealed the low cytotoxicity level of these polymeric films, making these materials suitable for biomedical application. To go one step further in the preindustrialization approach, proof of concept regarding the catheter prototype fabrication based on TPU-QAS/QPS was validated by extrusion.

Interfacial Compatibilization into PLA/Mg Composites for Improved In Vitro Bioactivity and Stem Cell Adhesion

The present work highlights the crucial role of the interfacial compatibilization on the design of polylactic acid (PLA)/Magnesium (Mg) composites for bone regeneration applications. In this regard, an amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymer with predefined composition was synthesised and used as a new interface to provide physical interactions between the metallic filler and the biopolymer matrix. This strategy allowed (i) overcoming the PLA/Mg interfacial adhesion weakness and (ii) modulating the composite hydrophilicity, bioactivity and biological behaviour. First, a full study of the influence of the copolymer incorporation on the morphological, wettability, thermal, thermo-mechanical and mechanical properties of PLA/Mg was investigated. Subsequently, the bioactivity was assessed during an in vitro degradation in simulated body fluid (SBF). Finally, biological studies with stem cells were carried out. The results showed an increase of the interfacial adhesion by the formation of a new interphase between the hydrophobic PLA matrix and the hydrophilic Mg filler. This interface stabilization was confirmed by a decrease in the damping factor (tanδ) following the copolymer addition. The latter also proves the beneficial effect of the composite hydrophilicity by selective surface localization of the hydrophilic PEO leading to a significant increase in the protein adsorption. Furthermore, hydroxyapatite was formed in bulk after 8 weeks of immersion in the SBF, suggesting that the bioactivity will be noticeably improved by the addition of the diblock copolymer. This ceramic could react as a natural bonding junction between the designed implant and the fractured bone during osteoregeneration. On the other hand, a slight decrease of the composite mechanical performances was noted.

Recent developments in short- and medium-chain- length Polyhydroxyalkanoates: Production, properties, and applications

Developing renewable resource-based plastics with complete biodegradability and a minimal carbon footprint can open new opportunities to effectively manage the end-of-life plastics waste and achieve a low carbon society. Polyhydroxyalkanoates (PHAs) are biobased and biodegradable thermoplastic polyesters that accumulate in microorganisms (e.g., bacterial, microalgal, and fungal species) as insoluble and inert intracellular inclusion. The PHAs recovery from microorganisms, which typically involves cell lysis, extraction, and purification, provides high molecular weight and purified polyesters that can be compounded and processed using conventional plastics converting equipment. The physio-chemical, thermal, and mechanical properties of the PHAs are comparable to traditional synthetic polymers such as polypropylene and polyethylene. As a result, it has attracted substantial applications interest in packaging, personal care, coatings, agricultural and biomedical uses. However, PHAs have certain performance limitations (e.g. slow crystallization), and substantially more expensive than many other polymers. As such, more research and development is required to enable them for extensive use. This review provides a critical review of the recent progress achieved in PHAs production using different microorganisms, downstream processing, material properties, processing avenues, recycling, aerobic and anaerobic biodegradation, and applications.

Halogen bonding for molecular recognition: new developments in materials and biological sciences

This review highlights recent developments of halogen bonding in materials and biological sciences with a short discussion on the nature of the interaction.

Molecular Engineering of the Cellulose-Poly(Caprolactone) Bio-Nanocomposite Interface by Reactive Amphiphilic Copolymer Nanoparticles

A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.

Polyhydroxyalkanoates: Properties and chemical modification approaches for their functionalization

Polyhydroxyalkanoates (PHAs) have become an attractive biomaterial in research in the past few years due to their extensive potential industrial applications. Being long chain hydroxyl fatty acid molecules, the PHAs are hydrophobic in nature, and have less functional groups. These features limit their applications in various areas. To enhance their usage, these polymers may need to be modified including surface and chemical modifications. Such modifications may alter their mechanical properties, surface structure, amphiphilic character and rate of degradation to fulfil the requirements for their future applications. Chemical modifications allow incorporation of functional groups to PHAs that could not be introduced through biotechnological methods. These chemically reformed PHAs, with enhanced properties, could be used for broad range of applications. This review aims to introduce different chemical modification approaches including some recent methods that had not been explored or discussed so far for PHAs as possible technologies for widening the range of product and application potentials. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:29-41, 2018.

Preparation of Cellulose Nanocrystal-Reinforced Poly(lactic acid) Nanocomposites through Noncovalent Modification with PLLA-Based Surfactants

Cellulose nanocrystal (CNC)-reinforced poly(lactic acid) (PLA) nanocomposites were prepared by twin-screw extrusion followed by injection-molding using a masterbatch approach. Noncovalent modification of CNCs was performed with two different poly(l-lactide) (PLLA)-based surfactants to improve the filler/matrix compatibility. They both have a PLLA block that is expected to improve the compatibility with the PLA matrix and differ by the polar head. It consists of either a poly(ethylene glycol) (PEG) block (PEG-b-PLLA) or an imidazolium group (Im-PLLA), that is able to interact with the surface of the CNCs. The morphological, structural, thermal, rheological, and mechanical properties of the nanocomposites were investigated. The different modes of interaction of the polar head of the surfactant lead to different properties. However, the global decrease in the molecular weight of PLA, induced by the short PLLA blocks from the surfactants and the possible degradation during melt processing, results in a plasticization effect and impacts the crystallization of the matrix.

Fabrication of ultra-dense sub-10 nm in-plane Si nanowire arrays by using a novel block copolymer method: optical properties

The use of a low-χ, symmetric block copolymer as an alternative to the high-χ systems currently being translated towards industrial silicon chip manufacture has been demonstrated. Here, the methodology for generating on-chip, etch resistant masks and subsequent pattern transfer to the substrate using ultra-small dimension, lamellar, microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) is described. Well-controlled films of a perpendicularly oriented lamellar pattern with a domain size of ∼8 nm were achieved through amplification of an effective interaction parameter (χeff) of the BCP system. The self-assembled films were used as 'templates' for the generation of inorganic oxides nanowire arrays through selective metal ion inclusion and subsequent processing. Inclusion is a significant challenge because the lamellar systems have less chemical and mechanical robustness than the cylinder forming materials. The oxide nanowires of uniform diameter (∼8 nm) were isolated and their structure mimics the original BCP nanopatterns. We demonstrate that these lamellar phase iron oxide nanowire arrays could be used as a resist mask to fabricate densely packed, identical ordered, good fidelity silicon nanowire arrays on the substrate. Possible applications of the materials prepared are discussed, in particular, in the area of photonics and photoluminescence where the properties are found to be similar to those of surface-oxidized silicon nanocrystals and porous silicon.

Effect of ionic liquid-containing poly(ε-caprolactone) on the dispersion and dielectric properties of polymer/carbon nanotube composites

A compatilizer containing imidazolium segment was used to improve the compatibility of CNTs with PCL matrix.

Folate-mediated mitochondrial targeting with doxorubicin-polyrotaxane nanoparticles overcomes multidrug resistance

Resistance to treatment with anticancer drugs is a significant obstacle and a fundamental cause of therapeutic failure in cancer therapy. Functional doxorubicin (DOX) nanoparticles for targeted delivery of the classical cytotoxic anticancer drug DOX to tumor cells, using folate-terminated polyrotaxanes along with dequalinium, have been developed and proven to overcome this resistance due to specific molecular features, including a size of approximately 101 nm, a zeta potential of 3.25 mV and drug-loading content of 18%. Compared with free DOX, DOX hydrochloride, DOX nanoparticles, and targeted DOX nanoparticles, the functional DOX nanoparticles exhibited the strongest anticancer efficacy in vitro and in the drug-resistant MCF-7/ Adr (DOX) xenograft tumor model. More specifically, the nanoparticles significantly increased the intracellular uptake of DOX, selectively accumulating in mitochondria and the endoplasmic reticulum after treatment, with release of cytochrome C as a result. Furthermore, the caspase-9 and caspase-3 cascade was activated by the functional DOX nanoparticles through upregulation of the pro-apoptotic proteins Bax and Bid and suppression of the antiapoptotic protein Bcl-2, thereby enhancing apoptosis by acting on the mitochondrial signaling pathways. In conclusion, functional DOX nanoparticles may provide a strategy for increasing the solubility of DOX and overcoming multidrug-resistant cancers.

Pyrene-end-functionalized poly(L-lactide) as an efficient carbon nanotube dispersing agent in poly(L-lactide): mechanical performance and biocompatibility study

In order to improve the mechanical properties of poly(L-lactide) (PLLA) based implants, a study was made of how far well dispersed multi-walled carbon nanotubes (MWCNTs) within a PLLA matrix were able to positively affect these properties. To this end, pyrene-end-functionalized poly(L-lactide) (py-end-PLLA) was evaluated as a dispersing agent. Transmission electron microscopy (TEM) analyses and mechanical tests of MWCNTs-based materials demonstrated an enhancement of MWCNT dispersion in the PLLA matrix and improved Young's modulus (E) when 4 wt% of py-end-PLLA was used as the dispersing agent. Subsequently, the bioacceptance of PLLA/py-end-PLLA/MWCNTs nanocomposites was evaluated using human bone marrow stromal cells (HBMC) in vitro. The inclusion of py-end-PLLA and MWCNTs supported HBMC adhesion and proliferation. The expression levels of the bone-specific markers indicated that the cells kept their potential to undergo osteogenic differentiation. The results of this study indicate that the addition of MWCNT combined with py-end-PLLA in PLLA/py-end-PLLA/MWCNTs nanocomposites may widen the range of applications of PLLA within the field of bone tissue engineering thanks to their mechanical strength and cytocompatibility.

Pengaruh Penambahan Polivinil Alkohol pada Biomassa Tongkol Jagung-Bulu Ayam sebagai Adsorben Campuran Ion Logam Timbal (Pb2+) dan Ion Logam Krom Total

Penelitian tentang pengaruh penambahan polivinil alkohol (PVA) pada biomassa tongkol jagung-bulu ayam untuk adsorben campuran ion timbal (Pb2+) dan ion krom total telah dilakukan. Tujuan penelitian ini adalah untuk mendapatkan adsorben tongkol jagung-bulu ayam yang terikat silang (A1) dan adsorben tongkol jagung bulu ayam-PVA (A2), memperoleh data karakter menggunakan FTIR dan BET serta mendapatkan data efektivitas adsorben dalam menyerap campuran ion Pb2+ dan ion krom total. Penelitian dilakukan melalui beberapa tahap yaitu pembuatan adsorben A1, pembuatan adsorben A2, karakerisasi menggunakan FTIR dan BET. Selanjutnya adsorben A1 dan A2 digunakan untuk penyerapan campuran ion logam Pb2+ dan ion logam krom total dengan variasi waktu kontak dan konsentrasi. Data FTIR menunjukkan bahwa adsorben A1 mempunyai gugus OH yang lebih banyak dibandingkan A2. Hasil analisis BET menunjukkan adsorben A2 mengalami penurunan luas permukaan dan total volume pori sebesar 39,83% dan 21,95% serta peningkatan rata-rata ukuran pori sebesar 30,12%. Daya adsorpsi adsorben A1 adalah sebesar 5,22 x 10-5 mol/g untuk Pb2+ dan 1,05 x 10-4 mol/g untuk ion logam krom total, sedangkan oleh adsorben A2 adalah sebesar 4,10x 10-5 mol/g untuk Pb2+ dan 7,77 x 10-5 mol/g untuk ion logam krom total. Berdasarkan hasil penelitian dapat disimpulkan bahwa adsorben A2 mempunyai kemampuan adsorpsi ion logam yang lebih baik dibandingkan adsorben A1.

Halogen bonding in polymer science: from crystal engineering to functional supramolecular polymers and materials

The applications of halogen bonding in surface functionalization, soft, luminescent and magnetic materials, interpenetrated networks, synthetic methods, and separation and inclusion techniques are reviewed.

Rheology of polymer carbon nanotubes composites

In this review paper the rheology of polymer nanocomposites with dispersed carbon nanotubes is presented. The major factors controlling the rheology of these nanocomposites are the overall concentration of the nanotubes and their state of dispersion. Percolation of anisotropic nanotubes and the transition from isotropic to nematic structures bound the range of concentrations over which the rheological properties of these nanocomposites is dominated by the meso-scale structure and dispersion and are of significance to the processing of nanotube based polymer nanocomposites. The percolation threshold and the concentration for the isotropic to nematic transition are strong functions of the inverse of the effective aspect ratio of the dispersed nanotubes and therefore restrict the range of concentrations over which such nanocomposites can be deployed. In this review we briefly describe the rheology in the dilute regime, where especially for the case of polymer nanocomposites the rheology is dominated by that of the polymer. Subsequently, the percolation phenomenon and rheological significances are presented. Finally, both linear and non-linear rheologies of semi-dilute dispersions with random orientation of nanotubes are discussed in detail. Where possible, the rheological responses are contextualized through the underlying structure of the nanocomposites and interplay of different forces.