Dual Thermo- and Photo-Responsive Micelles Based on Azobenzene-Containing Random Copolymer

Amphiphilic random copolymer poly(methacrylamido-azobenzene)-ran-poly(2-hydroxyethylacrylate) (PMAAAB-ran-PHEA) was synthesized via hydrolysis of poly(methacrylamido-azobenzene)-ran-poly[2-((2′-tetrahydropyranyl)oxy)ethylacrylate] (PMAAAB-ran-P(THP-HEA)), which was prepared by conventional radical polymerization. PMAAAB-ran-PHEA micelles were then prepared via dialysis method against water with DMF as solvent. The structure, morphology, size, and low critical solution temperature (LCST) of PMAAAB-ran-PHEA and its micelles were determined by 1H-NMR, GPC, TEM, and DLS. The thermo- and photo-responsive behaviors of the resulting polymer micelles were investigated with Nile red as a fluorescence probe. The results showed that PMAAAB-ran-PHEA micelles were porous or bowl-shaped and its size was 135–150 nm, and its LCST was 55 °C when FMAAAB of the random copolymer was 0.5351; the hydrophobicity of the micellar core was changed reversibly under the irradiation of UV light and visible light without release of Nile red or disruption of micelles; the size and solubilization capacity of the micelles were dependent on temperature, and Nile red would migrate for many times between the water phase and the micelles, and finally increasingly accumulated during the repeated heating and cooling processes.

Aggregation of Gold Nanoparticles in Presence of the Thermoresponsive Cationic Diblock Copolymer PNIPAAM48-b-PAMPTMA6

The adsorption of the thermoresponsive positively charged copolymer poly(N-isopropylacrylamide)-block-poly(3-acrylamidopropyl)trimethylammonium chloride, PNIPAAM48-b-PAMPTMA6(+), onto negatively charged gold nanoparticles can provide stability to the nanoparticles and make the emerging structure tunable by temperature. In this work, we characterize the nanocomposite formed by gold nanoparticles and copolymer chains and study the influence of the copolymer on the expected aggregation process that undergoes those nanoparticles at high ionic strength. We also determine the lower critical solution temperature (LCST) of the copolymer (around 42 °C) and evaluate the influence of the temperature on the nanocomposite. For those purposes, we use dynamic light scattering, UV-vis spectroscopy and transmission electron microscopy. At the working PNIPAAM48-b-PAMPTMA6(+) concentration, we observe the existence of copolymer structures that trap the gold nanoparticles and avoid the formation of nanoparticles aggregates. Finally, we discuss how these structures can be useful in catalysis and nanoparticles recovery.

Inverse Vulcanization of a Natural Monoene with Sulfur as Sustainable Electrochemically Active Materials for Lithium-Sulfur Batteries

A novel soluble copolymer poly(S-MVT) was synthesized using a relatively quick one-pot solvent-free method, inverse vulcanization. Both of the two raw materials are sustainable, i.e., elemental sulfur is a by-product of the petroleum industry and 4-Methyl-5-vinylthiazole (MVT) is a natural monoene compound. The microstructure of poly(S-MVT) was characterized by FT-IR, 1H NMR, XPS spectroscopy, XRD, DSC SEM, and TEM. Test results indicated that the copolymers possess protonated thiazole nitrogen atoms, meso/macroporous structure, and solubility in tetrahydrofuran and chloroform. Moreover, the improved electronic properties of poly(S-MVT) relative to elemental sulfur have also been investigated by density functional theory (DFT) calculations. The copolymers are utilized successfully as the cathode active material in Li-S batteries. Upon employment, the copolymer with 15% MVT content provided good cycling stability at a capacity of ∼514 mA h g−1 (based on the mass of copolymer) and high Coulombic efficiencies (∼100%) over 100 cycles, as well as great rate performance.

Artificial polyhydroxyalkanoate poly[2-hydroxybutyrate-block-3-hydroxybutyrate] elastomer-like material

The first polyhydroxyalkanoate (PHA) block copolymer poly(2-hydroxybutyrate-b-3-hydroxybutyrate) [P(2HB-b-3HB)] was previously synthesized using engineered Escherichia coli expressing a chimeric PHA synthase PhaCAR with monomer sequence-regulating capacity. In the present study, the physical properties of the block copolymer and its relevant random copolymer P(2HB-ran-3HB) were evaluated. Stress–strain tests on the P(88 mol% 2HB-b-3HB) film showed an increasing stress value during elongation up to 393%. In addition, the block copolymer film exhibited slow contraction behavior after elongation, indicating that P(2HB-b-3HB) is an elastomer-like material. In contrast, the P(92 mol% 2HB-ran-3HB) film, which was stretched up to 692% with nearly constant stress, was stretchable but not elastic. The differential scanning calorimetry and wide-angle X-ray diffraction analyses indicated that the P(2HB-b-3HB) contained the amorphous P(2HB) phase and the crystalline P(3HB) phase, whereas P(2HB-ran-3HB) was wholly amorphous. Therefore, the elasticity of P(2HB-b-3HB) can be attributed to the presence of the crystalline P(3HB) phase and a noncovalent crosslinked structure by the crystals. These results show the potential of block PHAs as elastic materials.

Bioactive coating for tissue-engineered smalldiameter vascular grafts

Objective: to develop a method for modifying composite small-diameter porous tubular biopolymer scaffolds based on bacterial copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and gelatin modified with a double-layered bioactive coating based on heparin (Hp) and platelet lysate (PL) that promote adhesion and proliferation of cell cultures.Materials and methods. Composite porous tubular biopolymer scaffolds with 4 mm internal diameter were made by electrospinning from a 1 : 2 (by volume) mixture of a 10% solution of poly(3-hydroxybutyrateco- 3-hydroxyvalerate) copolymer, commonly known as PHBV, and a 10% solution of gelatin, respectively, in hexafluoro-2-propanol. The structure of the scaffolds was stabilized with glutaraldehyde vapor. The scaffolds were modified with a bioactive Hp + PL-based coating. The surface morphology of the samples was analyzed using scanning electron microscopy. Biological safety of the modified scaffolds in vitro (hemolysis, cytotoxicity) was evaluated based on the GOST ISO 10993 standard. Interaction with cultures of human endothelial cell line (EA. hy926) and human adipose-derived mesenchymal stem cells (hADMSCs) was studied using vital dyes.Results. We developed a method for modifying small-diameter composite porous tubular biopolymer scaffolds obtained by electrospinning from a mixture of PHBV and gelatin modified with double-layered bioactive coating based on covalently immobilized Hp and human PL. The modified scaffold was shown to have no cytotoxicity and hemolytic activity in vitro. It was also demonstrated that the developed coating promotes hADMSC adhesion and proliferation on the external surface and EA.hy926 on the internal surface of the composite porous tubular biopolymer scaffolds in vitro.Conclusion. The developed coating can be used for the formation of in vivo tissueengineered small-diameter vascular grafts.

Biosynthesis of poly(glycolate-co-3-hydroxybutyrate-co-3-hydroxyhexanoate) in Escherichia coli expressing sequence-regulating polyhydroxyalkanoate synthase and medium-chain-length 3-hydroxyalkanoic acid coenzyme A ligase

Chimeric polyhydroxyalkanoate synthase PhaCAR is characterized by the capacity to incorporate unusual glycolate (GL) units and spontaneously synthesize block copolymers. The GL and 3-hydroxybutyrate (3HB) copolymer synthesized by PhaCAR is a random-homo block copolymer, poly(GL-ran-3HB)-b-poly(3HB). In the present study, medium-chain-length 3-hydroxyhexanoate (3HHx) units were incorporated into this copolymer using PhaCAR for the first time. The coenzyme A (CoA) ligase from Pseudomonas oleovorans (AlkK) serves as a simple 3HHx-CoA supplying route in Escherichia coli from exogenously supplemented 3HHx. NMR analyses of the obtained polymers revealed that 3HHx units were randomly connected to 3HB units, whereas GL units were heterogeneously distributed. Therefore, the polymer is composed of two segments: P(3HB-co-3HHx) and P(GL-co-3HB-co-3HHx). The thermal and mechanical properties of the terpolymer indicate no contiguous P(3HB) segments in the material, consistent with the NMR results. Therefore, PhaCAR synthesized the novel block copolymer P(3HB-co-3HHx)-b-P(GL-co-3HB-co-3HHx), which is the first block PHA copolymer comprising two copolymer segments.

The influence in difference of compatibilizers on the mechanical and rheological properties of LDPE/PLST blends

In this present study, low density polyethylene/plasticizer starch (LDPE/PLST) blends were prepared as a product to be used in disposable packaging (film applications), reducing the negative polymeric environmental effect. Because of their different molecular structures, LDPE blends with starch are fully immiscible; therefore, a compatibility agent is required. Three different polymer and/or copolymer: poly (vinyl alcohol) hydrolyzed 75% (PVOH), styrene-allyl alcohol copolymer (SAA) and polyethylene glycol (PEG) were selected as compatibilizers containing –OH groups. The effects of compatibilizer on the mechanical and rheological properties of LDPE/PLST blends were investigated and compared to LDPE/PLST without compatibilzer. The blends are also characterized by FTIR, which strongly indicates the existence of compatibilizers that can enhance phase interaction and promote compatibility in the blends of LDPE/PLST. Comparing to the blend without a compatibilizer, the tensile strengths of the blends containing PVOH and SAA increased significantly. The elongation at break results shows similar observation. The rheological measurement results suggested that the addition of a compatibilizer exhibited an increase in the shear stress and apparent viscosity comparing to the uncompatibilized blend except the blend with PEG which exhibited phase separation.

Effects of the Manufacturing Methods on the Mechanical Properties of a Medical-Grade Copolymer Poly(L-Lactide-co-D,L-Lactide) and Poly(L-Lactide-co-ε-Caprolactone) Blend

Biocompatible and biodegradable polymers represent the future in the manufacturing of medical implantable solutions. As of today, these are generally manufactured with metallic components which cannot be naturally absorbed within the human body. This requires performing an additional surgical procedure to remove the remnants after complete rehabilitation or to leave the devices in situ indefinitely. Nevertheless, the biomaterials used for this purpose must satisfy well-defined mechanical requirements. These are difficult to ascertain at the design phase since they depend not only on their physicochemical properties but also on the specific manufacturing methods used for the target application. Therefore, this research was focused on establishing the effects of the manufacturing methods on both the mechanical properties and the thermal behavior of a medical-grade copolymer blend. Specifically, Injection and Compression Molding were considered. A Poly(L-lactide-co-D,L-lactide)/Poly(L-lactide-co-ε-caprolactone) blend was considered for this investigation, with a ratio of 50/50 (w/w), aimed at the manufacturing of implantable devices for tendon repair. Interesting results were obtained.

Flash nanoprecipitation for the production of endosomolytic polymersomes for cytosolic drug delivery

The delivery of biomacromolecular drugs to cytosolic targets has been a long-standing engineering challenge due to the presence of multiple biological barriers including cellular and endosomal membranes. Although many promising carriers designed to facilitate endosomal escape have been developed, the clinical translation of these carriers is often limited by complex production processes that are not amenable to scaled-up manufacturing. In this study, we employed flash nanoprecipitation (FNP) for the rapid, scalable, and reproducible assembly of nanocarriers composed of the pH-responsive, endosomolytic diblock copolymer poly[(ethylene glycol)x-block-[((2-diethylamino) ethyl methacrylate)0.6-co-(butyl methacrylate)0.4]y (PEG-b-DEAEMA-co-BMA). We found that varying the second block molecular weight, while holding the first block molecular weight constant, significantly influenced nanoparticle self-assembly and hence nanocarrier properties and function – including drug encapsulation, endosomolytic capacity, cytotoxicity, and in vitro activity of a cytosolically-active drug cargo, a cyclic dinucleotide (CDN) stimulator of interferon genes (STING) agonist. We found that while increasing second block molecular weight enhanced the capacity of nanocarriers to induce endosomal destabilization, larger second block molecular weights also lead to increased cytotoxicity, increased particle size and heterogeneity, increased the encapsulation efficiency of small (<0.5 kDa) hydrophilic drugs, decreased the encapsulation efficiency of large (10 kDa) hydrophilic biomacromolecules, and decreased long-term particle stability. Collectively, these results demonstrate the utility of FNP for the rapid and scalable production of uniform PEG-b-DEAEMA-co-BMA nanocarriers and implicate an optimal hydrophilic mass fraction for balancing desirable nanoparticle properties with cytosolic cargo delivery efficiency.

Upconversion Nanoparticles Encapsulated with Molecularly Imprinted Amphiphilic Copolymer as a Fluorescent Probe for Specific Biorecognition

A fluorescent probe for specific biorecognition was prepared by a facile method in which amphiphilic random copolymers were encapsulated with hydrophobic upconversion nanoparticles (UCNPs). This method quickly converted the hydrophobic UCNPs to hydrophilic UNCPs. Moreover, the self-folding ability of the amphiphilic copolymers allowed the formation of molecular imprinting polymers with template-shaped cavities. LiYF4:Yb3+/Tm3+@LiYF4:Yb3+ UCNP with up-conversion emission in the visible light region was prepared; this step was followed by the synthesis of an amphiphilic random copolymer, poly(methacrylate acid-co-octadecene) (poly(MAA-co-OD)). Combining the UCNPs and poly(MAA-co-OD) with the templates afforded a micelle-like structure. After removing the templates, UCNPs encapsulated with the molecularly imprinted polymer (MIP) (UCNPs@MIP) were obtained. The adsorption capacities of UCNPs@MIP bound with albumin and hemoglobin, respectively, were compared. The results showed that albumin was more easily bound to UCNPs@MIP than to hemoglobin because of the effect of protein conformation. The feasibility of using UCNPs@MIP as a fluorescent probe was also studied. The results showed that the fluorescence was quenched when hemoglobin was adsorbed on UCNPs@MIP; however, this was not observed for albumin. This fluorescence quenching is attributed to Förster resonance energy transfer (FRET) and overlap of the absorption spectrum of hemoglobin with the fluorescence spectrum of UCNPs@MIP. To our knowledge, the encapsulation approach for fabricating the UCNPs@MIP nanocomposite, which was further used as a fluorescent probe, might be the first report on specific biorecognition.