Different Degrees Of Polymerization Research Articles

Poly(vinyl pyrrolidone) derivatives as PEG alternatives for stealth, non-toxic and less immunogenic siRNA-containing lipoplex delivery

The recent approval of Onpattro® and COVID-19 vaccines has highlighted the value of lipid nanoparticles (LNPs) for the delivery of genetic material. If it is known that PEGylation is crucial to confer stealth properties to LNPs, it is also known that PEGylation is responsible for the decrease of the cellular uptake and endosomal escape and for the production of anti-PEG antibodies inducing accelerated blood clearance (ABC) and hypersensitivity reactions. Today, the development of PEG alternatives is crucial. Poly(N-vinyl pyrrolidone) (PNVP) has shown promising results for liposome decoration but has never been tested for the delivery of nucleic acids. Our aim is to develop a series of amphiphilic PNVP compounds to replace lipids-PEG for the post-insertion of lipoplexes dedicated to siRNA delivery. PNVP compounds with different degrees of polymerization and hydrophobic segments, such as octadecyl, dioctadecyl and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE), were generated. Based on the physicochemical properties and the efficiency to reduce protein corona formation, we showed that the DSPE segment is essential for the integration into the lipoplexes. Lipoplexes post-grafted with 15% DSPE-PNVP30 resulted in gene silencing efficiency close to that of lipoplexes grafted with 15% DSPE-PEG. Finally, an in vivo study in mice confirmed the stealth properties of DSPE-PNVP30 lipoplexes as well as a lower immune response ABC effect compared to DSPE-PEG lipoplexes. Furthermore, we showed a lower immune response after the second injection with DSPE-PNVP30 lipoplexes compared to DSPE-PEG lipoplexes. All these observations suggest that DSPE-PNVP30 appears to be a promising alternative to PEG, with no toxicity, good stealth properties and lower immunological response.

Induction of plant disease resistance by mixed oligosaccharide elicitors prepared from plant cell wall and crustacean shells.

Basal plant immune responses are activated by the recognition of conserved microbe-associated molecular patterns (MAMPs), or breakdown molecules released from the plants after damage by pathogen penetration, so-called damage-associated molecular patterns (DAMPs). While chitin-oligosaccharide (CHOS), a primary component of fungal cell walls, is most known as MAMP, plant cell wall-derived oligosaccharides, cello-oligosaccharides (COS) from cellulose, and xylo-oligosaccharide (XOS) from hemicellulose are representative DAMPs. In this study, elicitor activities of COS prepared from cotton linters, XOS prepared from corn cobs, and chitin-oligosaccharide (CHOS) from crustacean shells were comparatively investigated. In Arabidopsis, COS, XOS, or CHOS treatment triggered typical defense responses such as reactive oxygen species (ROS) production, phosphorylation of MAP kinases, callose deposition, and activation of the defense-related transcription factor WRKY33 promoter. When COS, XOS, and CHOS were used at concentrations with similar activity in inducing ROS production and callose depositions, CHOS was particularly potent in activating the MAPK kinases and WRKY33 promoters. Among the COS and XOS with different degrees of polymerization, cellotriose and xylotetraose showed the highest activity for the activation of WRKY33 promoter. Gene ontology enrichment analysis of RNAseq data revealed that simultaneous treatment of COS, XOS, and CHOS (oligo-mix) effectively activates plant disease resistance. In practice, treatment with the oligo-mix enhanced the resistance of tomato to powdery mildew, but plant growth was not inhibited but rather tended to be promoted, providing evidence that treatment with the oligo-mix has beneficial effects on improving disease resistance in plants, making them a promising class of compounds for practical application.

An efficient protocol for preparing linear β-manno-oligosaccharides

Linear β-manno-oligosaccharides (l-β-MOS) are widely used to investigate oligo- and poly-saccharide structures and mannanolytic enzyme activities. l-β-MOS are also being used as prebiotic agents with potential bio-active properties. In this study, we developed an efficient protocol to prepare a series of l-β-MOS by hydrolyzing cassia gum (CG) using mannanolytic enzymes (endo-1,4-β-mannanase, α-galactosidases and β-glucosidases). By using medium pressure liquid chromatography (MPLC), we purified l-β-MOS with different degrees of polymerization (DPs). HPAEC-PAD, MALDI-TOF-MS and NMR studies confirmed that these l-β-MOS species ranged from 1,4-β-d-mannobiose to 1,4-β-d-mannononaose (DP 2–9) with >95% purity. Our results provide a robust approach to preparing l-β-MOS, thus enabling l-β-MOS to be further used in the fields of chemistry, life science, and nutritional food.

Modulation of tryptophan metabolism via AHR-IL22 pathway mediates the alleviation of DSS-induced colitis by chitooligosaccharides with different degrees of polymerization

Oral administration of chitooligosaccharides (COS) has been reported to alleviate colitis in mice. However, the mechanism of action of COS with specific polymerization degree on gut inflammation and metabolism remains unclear. This study aimed to investigate the effects of chitobiose (COS2), chitotetraose (COS4), and chitohexaose (COS6) on colitis, and to elucidate their underlying mechanisms. COS2, COS4, and COS6 were able to significantly alleviate colonic injury and inflammation levels. COS6 has the best anti-inflammatory effect. Furthermore, COS6 could down-regulate the level of indoleamine-2,3-dioxygenase1 (IDO1) and restore the levels of indole, indoleacetic-3-acid (IAA), and indole-3-carbaldehyde (I3A) in the cecum of chronic colitis mice (p < 0.05), thereby regulating tryptophan metabolism. In the aromatic hydrocarbon receptor-IL-22 (AHR-IL-22) pathway, although there were differences between chronic colitis and acute colitis mice, COS intervention could restore the AHR-IL-22 pathway to normal, promote the expression of MUC2, and repair the intestinal mucosal barrier. In conclusion, the results of this study suggested that COS had a good inhibitory effect on IDO1 under inflammation and the changes of AHR and IL-22 levels at different stages of disease development. This provides new insights into the potential use of COS as a functional food for improving intestinal inflammation and metabolism.

Polysialic acid promotes remyelination in cerebellar slice cultures by Siglec-E-dependent modulation of microglia polarization.

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system. Spontaneous restoration of myelin after demyelination occurs, but its efficiency declines during disease progression. Efficient myelin repair requires fine-tuning inflammatory responses by brain-resident microglia and infiltrating macrophages. Accordingly, promising therapeutic strategies aim at controlling inflammation to promote remyelination. Polysialic acid (polySia) is a polymeric glycan with variable chain lengths, presented as a posttranslational modification on select protein carriers. PolySia emerges as a negative regulator of inflammatory microglia and macrophage activation and has been detected on oligodendrocyte precursors and reactive astrocytes in multiple sclerosis lesions. As shown recently, polySia-modified proteins can also be released by activated microglia, and the intrinsically released protein-bound and exogenously applied free polySia were equally able to attenuate proinflammatory microglia activation via the inhibitory immune receptor Siglec-E. In this study, we explore polySia as a candidate substance for promoting myelin regeneration by immunomodulation. Lysophosphatidylcholine-induced demyelination of organotypic cerebellar slice cultures was used as an experimental model to analyze the impact of polySia with different degrees of polymerization (DP) on remyelination and inflammation. In lysophosphatidylcholine-treated cerebellar slice cultures, polySia-positive cells were abundant during demyelination but largely reduced during remyelination. Based on the determination of DP24 as the minimal polySia chain length required for the inhibition of inflammatory BV2 microglia activation, pools with short and long polySia chains (DP8-14 and DP24-30) were generated and applied to slice cultures during remyelination. Unlike DP8-14, treatment with DP24-30 significantly improved remyelination, increased arginase-1-positive microglia ratios, and reduced the production of nitric oxide in wildtype, but not in Siglec-E-deficient slice cultures. In vitro differentiation of oligodendrocytes was not affected by DP24-30. Collectively, these results suggest a beneficial effect of exogenously applied polySia DP24-30 on remyelination by Siglec-E-dependent microglia regulation.

Effect of hemicellulose content on the solution properties of cellulose carbamates in NaOH/ZnO aqueous system

Hemicellulose removal from bleached bamboo pulp is key to produce qualified dissolving pulps. In this work, alkali/urea aqueous solution was firstly applied to remove hemicellulose in bleached bamboo pulp (BP). The effect of urea usage, time and temperature on the hemicellulose content of BP was studied. The reduction of hemicellulose content from 15.9 to 5.7 % was achieved in 6 wt% NaOH/1 wt% urea aqueous solution at 40 °C for 30 min. Cellulose carbamates (CCs) were obtained from the esterification of BP with urea. The dissolution behavior of CCs in NaOH/ZnO aqueous solutions with different degree of polymerization (DP), hemicellulose and nitrogen contents were studied by using optical microscope and rheology. The highest solubility was up to 97.7 % when the hemicellulose was 5.7 % and Mη was 6.5 × 104 (g/mol). With the decrease of hemicellulose content from 15.9 % to 8.60 % and 5.70 %, the gel temperature increased from 59.0, 69.0 to 73.4 °C. The apparent gelation time increased from 5640 to 12,120 s with the hemicellulose content increased from 8.60 % to 15.9 %. CC solution with 5.70 % hemicellulose always keeps a liquid-state (G" > G') until the test time reached 17,000 s. The results showed that the removal of hemicellulose, the decrease of DP and the increase of esterification endowed CC with higher solubility and solution stability.

Biochemical characterization and elucidation of the action mode of a GH16 family κ-carrageenase for efficient preparation of carrageenan oligosaccharides.

κ-Carrageenan oligosaccharides have a variety of biological activities. Degradation of κ-carrageenan by κ-carrageenase leads to degradation products with different degrees of polymerization (DPs). A novel gene (CecgkA) encoding a new κ-carrageenase was cloned from Colwellia echini and heterologously expressed in Escherichia coli BL21 (DE3). The enzyme is 1104bp in length, encodes 367 amino acid residues and has a molecular weight of 41.30kDa. Multiple alignment analysis showed that CeCgkA belongs to the glycoside hydrolase (GH16) family and has the highest homology with the κ-carrageenase of Rhodopirellula maiorica SM1, with 58% homology. The CeCgkA showed maximum activity (453.15 U/mg) at pH 8.0 and 35°C. Determination of biochemical properties showed that CeCgkA was a thermal recovery enzyme, and 51.6% of the initial enzyme activity was recovered by immediately placing the sample at 35°C for 60min after enzymatic inactivation by boiling for 10min. K+, Na+, and EDTA had an activating effect on the enzyme activity, while Ni2+, Cu2+, and Zn2+ inhibited the activity of the enzyme. In addition, TLC and ESI-MS analysis showed that the maximum recognition unit of CecgkA was decasaccharide and that the main degradation products were disaccharides, tetrasaccharides and hexasaccharides, indicating that the enzyme is an endo-type carrageenase.

Polysaccharides from Dioscoreaopposita Thunb.: isolation, structural characterization, and anti-inflammatory and anti-tumor effects against hepatocellular carcinoma

BackgroundDioscoreaopposita Thunb, as a dual-purpose edible plant with excellent nutritional and medical value, accumulates abundant bioactive compounds, including polysaccharides. Polysaccharides from D.opposita have been widely recognized and studied due to various biological activities, such as anti-inflammatory and anti-cancer, which are influenced by their complex structures. In recent years, numerous studies have investigated the structures and activities of D.opposita polysaccharides, and the relationships between them. However, the detailed structures remain different because the structures are susceptible to various species, producing areas, growth conditions (weather, soil, temperature, moisture, etc.), and extraction and separation methods. In this study, the structures of purified polysaccharides from D.opposita were determined and the biological activities were preliminarily investigated including anti-inflammatory and anti-tumor activities.ResultsThe crude polysaccharides DOP1 and DOP2 were isolated and purified via DEAE-52 and Sephadex G-100 to obtain two purified polysaccharides fractions (DOP1-1 and DOP2-1), with the molecular weights of 15.63 kDa and 32.32 kDa, respectively. The structures of DOP1-1 and DOP2-1 were analyzed by HPLC, FT-IR, methylation, and 1D (1H, 13C) and 2D (HSQC, COSY, TOCSY, and ROESY) NMR spectra. The results indicated the presence of → 2)-β-Manp-(1 → 4)-α-Glcp-(1 → 2)-β-Manp-(1 → , → 1)-β-Manp-(2 → 1)-α-GalpA-(4 →, and → 2)-β-Manp-(1 → 2)-β-Manp-(1 → in DOP1-1, and the ratio was 2:11:5. The bone structure of DOP2-1 was predicted as → 1)-β-d-Galp-(4 → , along with two main branching structures composed of arabinose of different degrees of polymerization. Preliminary anti-inflammatory and anti-tumor activities were investigated. DOP1-1 and DOP2-1 demonstrated inhibitory effects on macrophages cells (RAW264.7). DOP2-1 exhibited anti-tumor effects against hepatocellular carcinoma (SNU-739 and HepG2).ConclusionsThe structures and bioactivities of DOP1-1 and DOP2-1 were analyzed to provide a basis for the establishment of structure/function relationships. The polysaccharides derived from Dioscoreaopposita could be potentially employed in functional food, health care, and pharmaceutical industries.Graphical

STUDY OF THE RHEOLOGICAL AND PHYSICOCHEMICAL PROPERTIES OF FRUCTAN FRACTIONS OF Agave tequilana cv. cenizo

The physico-mechanical properties of fructan fractions in different agave species without Tequila Denomination of Origin (DOT) need to be studied to identify and expand industrial applications. The rheological and physicochemical characterization of three fractions of Agave tequilana cv. cenizo fructans without DOT, with different degree of polymerization (DP) was carried out to propose their use as an additive in the food industry. Fractions were obtained by apparent DP enrichment (DPa) by stepwise ultradiafiltration with 10, 5 and 1 kilodalton (kDa) membranes and classified on the basis of the enriched fraction evidenced by HPLC profiling with amperometric detector. The ultradiafiltrate of the membrane with 10 kDa, called High Degree of Polymerization (HDP), showed enrichment of fructans with high DPa ≥ 30, the one with 5 kDa called Intermediate Degree of Polymerization (IDP), presents enrichment in DPa between 10 to 30, these fractions dried by spray, showed a modal particle size distribution (D [4,3] &lt; 20 µm). In the ultradiafiltrate of the 1 kDa membrane, called Low Polymerization Grade (LDP), fructo-oligosaccharides (FOS) and fructans with maximum DPa of 15 were enriched; this sample was concentrated to 72 °Brix. The glass transition (Tg) showed a DPa-dependent increase (LDP = 152.17 °C, IDP = 216.12 °C and HDP = 227.5 °C). Viscosity was dependent on the degree of polymerization, exhibiting thermo-mechanically stable flow behavior. The reconstituted powders exhibited Newtonian and flow-stable behavior in a concentration range of 2-50 %, temperature of 5-45 °C and pH of 2-9. The macro and micro structural properties identified in the respective fractions of agave fructans, diversify possible applications with potential interest as encapsulating material, stabilizer and prebiotic sweetener, among others that agave fructans have in the food and nutraceutical industry.

Structural and binding studies of a new chitin-active AA10 lytic polysaccharide monooxygenase from the marine bacterium Vibrio campbellii.

Vibrio spp. play a crucial role in the global recycling of the highly abundant recalcitrant biopolymer chitin in marine ecosystems through their ability to secrete chitin-degrading enzymes to efficiently hydrolyse chitinous materials and use them as their major carbon source. In this study, the first crystal structures of a complete four-domain chitin-active AA10 lytic polysaccharide monooxygenase from the chitinolytic bacterium Vibrio campbellii type strain ATCC BAA-1116 are reported. The crystal structures of apo and copper-bound VhLPMO10A were resolved as homodimers with four distinct domains: an N-terminal AA10 catalytic (CatD) domain connected to a GlcNAc-binding (GbpA_2) domain, followed by a module X domain and a C-terminal carbohydrate-binding module (CBM73). Size-exclusion chromatography and small-angle X-ray scattering analysis confirmed that VhLPMO10A exists as a monomer in solution. The active site of VhLPMO10A is located on the surface of the CatD domain, with three conserved residues (His1, His98 and Phe170) forming the copper(II)-binding site. Metal-binding studies using synchrotron X-ray absorption spectroscopy and X-ray fluorescence, together with electron paramagnetic resonance spectroscopy, gave consistently strong copper(II) signals in the protein samples, confirming that VhLPMO10A is a copper-dependent enzyme. ITC binding data showed that VhLPMO10A could bind various divalent cations but bound most strongly to copper(II) ions, with a Kd of 0.1 ± 0.01 µM. In contrast, a Kd of 1.9 nM was estimated for copper(I) ions from redox-potential measurements. The presence of ascorbic acid is essential for H2O2 production in the reaction catalysed by VhLPMO10A. MALDI-TOF MS identified VhLPMO10A as a C1-specific LPMO, generating oxidized chitooligosaccharide products with different degrees of polymerization (DP2ox-DP8ox). This new member of the chitin-active AA10 LPMOs could serve as a powerful biocatalyst in biofuel production from chitin biomass.

Effect of Oligomers Derived from Biodegradable Polyesters on Eco- and Neurotoxicity.

Biodegradable polymers are eco-friendly materials and have attracted attention for use in a sustainable society because they are not accumulated in the environment. Although the characteristics of biodegradable polymers have been assessed well, the effects of their degradation products have not. Herein, we comprehensively evaluated the chemical toxicities of biodegradable polyester, polycaprolactone (PCL), and synthetic oligocaprolactones (OCLs) with different degrees of polymerization. While the PCL did not show any adverse effects on various organisms, high levels of shorter OCLs and the monomer (1 μg/mL for freshwater microorganisms and 1 mg/mL for marine algae and mammalian cells) damaged the tested organisms, including freshwater microorganisms, marine algae, and mammalian cells, which indicated the toxicities of the degradation products under unnaturally high concentrations. These results highlight the need for a further understanding of the effects of the degradation products resulting from biodegradable polyesters to ensure a genuinely sustainable society.

Development and catalytic mechanism of ionic liquid catalysts for polyoxymethylene dimethyl ethers

In this paper, Gaussian calculation and acid strength determination were used to analyze the acid strength of ionic liquid catalysts, and to design ionic liquids with different anions and cations. The synthesis experiment of polyoxymethylene dimethyl ether (PODEn) using paraformaldehyde and methanol as raw materials was used as the catalyst evaluation experiment. Among them, the ionic liquid catalyst [PY-PS][PA] had the best catalytic performance, the conversion rate of methanol was 96%, and the selectivity of PODE3-5 was 49%. The chemical reactivity of the ionic liquid [PY-PS][PA] was analyzed using DFT theory, and the reaction mechanism and rate constant of the process were calculated at the molecular level. Paraformaldehyde is decomposed into formaldehyde and water by chain scission under the action of a catalyst; Formaldehyde and methanol are catalyzed to form hemiacetal (CH3OCH2OH); The hemiacetal is chain-extended by formaldehyde and then dehydrated with methanol to form PODEn with different degrees of polymerization. On the basis of the transition state, the kinetic parameters of the PODE3 synthesis process were calculated.

Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhibition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer α-helices and more β-sheets, β-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural antioxidants for reducing the HCAs in fried foods.

Conserved Protein-Polymer Interactions across Structurally Diverse Polymers Underlie Alterations to Protein Thermal Unfolding.

Protein-polymer conjugates are widely used in many clinical and industrial applications, but lack of experimental data relating protein-polymer interactions to improved protein stability prevents their rational design. Advances in synthetic chemistry have expanded the palette of polymer designs, including development of nonlinear architectures, novel monomer chemical scaffolds, and control of hydrophobicity, but more experimental data are needed to transform advances in chemistry into next generation conjugates. Using an integrative biophysical approach, we investigated the molecular basis for polymer-based thermal stabilization of a human galectin protein, Gal3C, conjugated with polymers of linear and nonlinear architectures, different degrees of polymerization, and varying hydrophobicities. Independently varying the degree of polymerization and polymer architecture enabled delineation of specific polymer properties contributing to improved protein stability. Insights from NMR spectroscopy of the polymer-conjugated Gal3C backbone revealed patterns of protein-polymer interactions shared between linear and nonlinear polymer architectures for thermally stabilized conjugates. Despite large differences in polymer chemical scaffolds, protein-polymer interactions resulting in thermal stabilization appear conserved. We observed a clear relation between polymer length and protein-polymer thermal stability shared among chemically different polymers. Our data indicate a wide range of polymers may be useful for engineering conjugate properties and provide conjugate design criteria.

Combined quantum mechanics and molecular dynamics study on the calcite scale inhibition mechanism of carboxymethyl dextran

The scale inhibition mechanism of carboxymethyl dextran (CMD), a new green scale inhibitor, was studied via quantum mechanical calculations and molecular dynamics (MD) simulations. Specifically, the interactions between the functional groups of CMD and calcite (104), (110), and (1–10) surfaces in aqueous solution were modelled at different degrees of polymerization (DP) of CMD (2, 4, 6, 8, and 10, respectively). The adsorption configuration, radial distribution function, deformation energy, binding energy, and relative concentration distribution of water molecules near the surface of calcite were calculated. The results showed that the carboxyl functional groups in CMD were strongly electronegative and able to form strong chemisorption bonds with calcium ions on the calcite surface. This can change the regular arrangement of the surface and prevent the combination of carbonate particles and calcium ions to form calcite scale. Furthermore, as the DP increased, the binding energy and the peak value of the radial distribution function increased, indicating an increase in the probability and strength of adsorption of CMD on the calcite surface, which can further enhance the scale inhibition efficiency.

Preparation of high-quality alkylated gasoline with low alkane-to-alkene ratio catalyzed by polyether-based Brønsted-Lewis acidic deep eutectic solvent

In this study, the solubility of isobutane in different types of polyethers was evaluated. Macroscopic and microscopic simulations of molecular bonding of isobutane to polyethers such as PEG200 and PPG200 were performed. The solubility of isobutane in different polyethers with different degrees of polymerization was investigated. The solubility of isooctane—the main alkylated gasoline product—in different polyethers was also determined. Based on the solubility ratios of isobutane and isooctane in the same polyether, PEG200 was selected as a component of a deep eutectic solvent (DES), which was then used for catalyzing the alkylation of isobutane and isobutene to prepare alkylated gasoline. Owing to the good solubility of isobutane in polyether, a three-component Brønsted–Lewis acidic DES catalyst, InCl3/PEG200/TfOH, could be used to prepare high-quality alkylated gasoline (conversion rate: 89.12%, C8 selectivity: 82.83%) at a low alkane-to-alkene ratio (5:1). Moreover, owing to its poor solubility to isooctane, the DES catalyst could be easily separated from alkylated gasoline. This DES catalyst retains its high catalytic activity over seven cycles.

Exploration of the Product Specificity of chitosanase CsnMY002 and Mutants Using Molecular Dynamics Simulations.

Chitosanase CsnMY002 is a new type of enzyme isolated from Bacillus subtilis that is used to prepare chitosan oligosaccharide. Although mutants G21R and G21K could increase Chitosan yield and thus increase the commercial value of the final product, the mechanism by which this happens is not known. Herein, we used molecular dynamics simulations to explore the conformational changes in CsnMY002 wild type and mutants when they bind substrates. The binding of substrate changed the conformation of protein, stretching and deforming the active and catalytic region. Additionally, the mutants caused different binding modes and catalysis, resulting in different degrees of polymerization of the final Chitooligosaccharide degradation product. Finally, Arg37, Ile145 ~ Gly148 and Trp204 are important catalytic residues of CsnMY002. Our study provides a basis for the engineering of chitosanases.

Naphthyl-Poly(S-((2-carboxyethyl)thio)-l-cysteine) Peptide Amphiphiles with Different Degrees of Polymerization: Synthesis, Self-Assembly, pH/Reduction-Triggered Drug Release, and Cytotoxicity.

Four peptide amphiphiles (PA1-4) with different degrees of polymerization (DP = 40, 15, 10, and 6) were synthesized by Fuchs-Farthing and ring-opening polymerization followed by post-polymerization modification, as fully characterized by 1H NMR, FT-IR, gel permeation chromatography, and circular dichroism (CD) spectroscopy. It was found that PAs could self-assemble to form regular spherical micelles in low-concentration (about 1 mg/mL) aqueous solution, which had different contents of secondary structures and mainly adopted random coil conformations. The water solubility of PAs increases with the increase of DP, the polypeptide chain stretches randomly in water, the β-sheets decrease, and the random coil conformations dominate. When the pH of PA solution decreases or increases, intramolecular hydrogen bonds break, and molecular chains stretch, leading to a decrease of α-helix, turn conformations, and an increase of β-sheets. Meanwhile, the particle size of micelles increases. At around 0.4 mg/mL, the hemolysis ability of PA2 is negligible at pH 7.4 and 6.5 and about 33% at pH 5.5. Cisplatin (CDDP) was linked to micelles by coordination bonds to explore their potential as drug carriers, exhibiting controlled pH and reduction in dual drug release effects. MTT assay showed that the HeLa cell viability was 78% when cultured in the 13.5 μg/mL PA2 blank micelles for 2 days, while the cell viability was 60% in the CDDP-loaded micelles. Furthermore, a high concentration of PA2 (about 100 mg/mL) could self-assemble into a fibrous hydrogel at pH 5.5, which self-healed 2 h after incision and self-degraded 71% within 14 days. The CDDP-loaded fiber hydrogel exhibited a sustained release effect similar to the CDDP-loaded micelles. The cytotoxicity of CDDP-loaded fibers at 48 h was detected to be the same as that of the same amount of CDDP, and the cell viability was 7%. Therefore, we provide a new strategy for the synthesis of amphiphilic peptides with potential applications in nano-drug carriers and cancer therapy.

4D Printing of Hydrogels Controlled by Hinge Structure and Spatially Gradient Swelling for Soft Robots

In 4D printing, structures with gradients in physical properties are 3D printed in order to dramatically increase deformation. For example, printing bilayer structures with passive and active layers has been proposed, however, these methods have the disadvantages that the material of each layer is mixed, and the modeling process is complicated. Herein, we present a method of creating gradient gels with different degrees of polymerization on the UV-exposed side and the other side using a single material by simply increasing the amount of initiator. This gel is the first example in which the differential swelling ratio between two sides causes the gradient to curl inward toward the UV-exposed side. The mechanical properties (swelling ratio and Young’s modulus) were measured at different material concentrations and structures, and the effects of each on deformation were analyzed and simulated. The results show that adding an initiator concentration of 0.2 (mol/L) or more causes deformation, that increasing the crosslinker concentration by a factor of three or more increases deformation, and that adding a hinge structure limits the gradient gel to deformation up to 90°. Thus, it was found that the maximum deformation can be predicted to some extent by simulation. In the future, we will be able to create complex structures while utilizing simulation.

Effects of alkali metal catalysts on the melt fluidity of polycarbonates with different degrees of polymerization

AbstractThe melt fluidity of polycarbonate (PC) significantly influences the processing, while the melt viscosity depends on the molecular structure. Specifically, the melt viscosity increases sharply with the increase of polymerization degree. However, the influence mechanism of alkali metal catalysts on the fluidity by affecting the molecular structure remains unclear. Herein, high and low concentrations of NaOH catalysts were used to synthesize PC with different polycondensation degrees. The effect of NaOH catalyst content on the molecular structure and thus melt fluidity of PC were systematically characterized and discussed employing NMR spectroscopy, absolute and relative molecular weight, intrinsic viscosity, melt flow index, and thermal analysis. The results show that a random branched structure of the PC molecular chain caused by excess NaOH improves the melt flowability. However, the residual NaOH promotes the degradation of carbonate bonds during thermal processing, resulting in poor PC stability. Based on the above discussion, empirical fitting equations are proposed to describe the relationship between molecular structure and flow properties, which provides a new way to judge PC performance.