Chemical and Biomolecular Engineering - Research Publications
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ItemAn Atom-Economic Enzymatic Cascade Catalysis for High-Throughput RAFT Synthesis of Ultrahigh Molecular Weight Polymers(WILEY-V C H VERLAG GMBH, 2022-11-14)High-throughput synthesis of well-defined, ultrahigh molecular weight (UHMW) polymers by green approaches is highly desirable but remains unexplored. We report the creation of an atom-economic enzymatic cascade catalysis, consisting of formate oxidase (FOx) and horseradish peroxidase (HRP), that enables high-throughput reversible addition-fragmentation chain transfer (RAFT) synthesis of UHMW polymers at volumes down to 50 μL. FOx transforms formic acid, a C1 substrate, and oxygen to CO2 and H2 O2 , respectively. CO2 can escape from solution while H2 O2 is harnessed in situ by HRP to generate radicals from acetylacetone for RAFT polymerization, leaving no waste accumulation in solution. Oxygen-tolerant RAFT polymerization using enzymatic cascade redox cycles was successfully performed in vials and 96-well plates to produce libraries of well-defined UHMW polymers, and represents the first example of high-throughput synthesis method of such materials at extremely low volumes.
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ItemStar-Peptide Polymers are Multi-Drug-Resistant Gram-Positive Bacteria Killers(AMER CHEMICAL SOC, 2022-06-08)Antibiotic resistance in bacteria, especially Gram-positive bacteria like Staphylococcus aureus, is gaining considerable momentum worldwide and unless checked will pose a global health crisis. With few new antibiotics coming on the market, there is a need for novel antimicrobial materials that target and kill multi-drug-resistant (MDR) Gram-positive pathogens like methicillin-resistant Staphylococcus aureus (MRSA). In this study, using a novel mixed-bacteria antimicrobial assay, we show that the star-peptide polymers preferentially target and kill Gram-positive pathogens including MRSA. A major effect on the activity of the star-peptide polymer was structure, with an eight-armed structure inducing the greatest bactericidal activity. The different star-peptide polymer structures were found to induce different mechanisms of bacterial death both in vitro and in vivo. These results highlight the potential utility of peptide/polymers to fabricate materials for therapeutic development against MDR Gram-positive bacterial infections.
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ItemNo Preview AvailableThin film composite membranes for postcombustion carbon capture: Polymers and beyond(PERGAMON-ELSEVIER SCIENCE LTD, 2022-03)
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ItemNo Preview AvailableHigh chain-end fidelity in sono-RAFT polymerization(Royal Society of Chemistry, 2022-10-15)The chain-end fidelity of polymers synthesized via the sono-RAFT technique in an aqueous medium was investigated by performing chain extension studies and preparation of multi-block copolymers. Sono-RAFT polymerization of N,N-dimethylacrylamide (DMA), 2-hydroxyethyl acrylate (HEA) and N-acryloyl morpholine (NAM) exhibited higher conversion values, low dispersity and excellent chain-end fidelity. MALDI-TOF analysis indicated that the fraction of dead chains observed was almost negligible indicating high livingness of the polymer end groups. The sono-RAFT technique was compared to the photo-iniferter method by performing chain extension experiments. Polymers prepared via sono-RAFT were identical to those prepared via the photo-iniferter RAFT method in terms of livingness, and the polymer reached very high conversion within a fraction of the time compared to the latter method. An icosapenta block copolymer (25 blocks) was synthesized at room temperature within 46 h. The resulting block copolymer displayed a controlled molecular weight and a final dispersity of 1.39.
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Item3D nanoprinting via spatially controlled assembly and polymerization(NATURE PORTFOLIO, 2022-04-11)Macroscale additive manufacturing has seen significant advances recently, but these advances are not yet realized for the bottom-up formation of nanoscale polymeric features. We describe a platform technology for creating crosslinked polymer features using rapid surface-initiated crosslinking and versatile macrocrosslinkers, delivered by a microfluidic-coupled atomic force microscope known as FluidFM. A crosslinkable polymer containing norbornene moieties is delivered to a catalyzed substrate where polymerization occurs, resulting in extremely rapid chemical curing of the delivered material. Due to the living crosslinking reaction, construction of lines and patterns with multiple layers is possible, showing quantitative material addition from each deposition in a method analogous to fused filament fabrication, but at the nanoscale. Print parameters influenced printed line dimensions, with the smallest lines being 450 nm across with a vertical layer resolution of 2 nm. This nanoscale 3D printing platform of reactive polymer materials has applications for device fabrication, optical systems and biotechnology.
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ItemMechanochromophore-Linked Polymeric Materials with Visible Color Changes(WILEY-V C H VERLAG GMBH, 2022-05)Mechanical force as a type of stimuli for smart materials has obtained much attention in the past decade. Color-changing materials in response to mechanical stimuli have shown great potential in the applications such as sensors and displays. Mechanochromophore-linked polymeric materials, which are a growing sub-class of these materials, are discussed in detail in this review. Two main types of mechanochromophores which exhibit visible color change, summarized herein, involve either isomerization or radical generation mechanisms. This review focuses on their synthesis and incorporation into polymer matrices, the type of mechanical force used, factors affecting the mechanochromic properties, and their applications.
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ItemCrosslinked Polypeptide Films via RAFT-Mediated Continuous Assembly of Polymers(WILEY-V C H VERLAG GMBH, 2022-02-21)Polypeptide coatings are a cornerstone in the field of surface modification due to their widespread biological potential. As their properties are dictated by their structural features, subsequent control thereof using unique fabrication strategies is important. Herein, we report a facile method of precisely creating densely crosslinked polypeptide films with unusually high random coil content through continuous assembly polymerization via reversible addition-fragmentation chain transfer (CAP-RAFT). CAP-RAFT was fundamentally investigated using methacrylated poly-l-lysine (PLLMA) and methacrylated poly-l-glutamic acid (PLGMA). Careful technique refinement resulted in films up to 36.1±1.1 nm thick which could be increased to 94.9±8.2 nm after using this strategy multiple times. PLLMA and PLGMA films were found to have 30-50 % random coil conformations. Degradation by enzymes present during wound healing reveals potential for applications in drug delivery and tissue engineering.
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ItemVernetzte Polypeptide durch RAFT‐vermittelte Polymerisation zum kontinuierlichen Aufbau von Polymerfilmen(Wiley, 2022-02-21)Abstract Polypeptidbeschichtungen spielen aufgrund ihres großen biologischen Potentials eine wichtige Rolle in der Oberflächenmodifizierung von Materialien. Da ihre Eigenschaften durch ihren strukturellen Aufbau mitbestimmt werden, ist eine Kontrolle der Struktur durch entsprechende Herstellungsstrategien notwendig. In diesem Artikel berichten wir über eine einfache Methode zur präzisen Herstellung von dicht vernetzten Polypeptidfilmen mit ungewöhnlich hoher β‐Faltblatt – und Zufallsknäuel Konformation durch eine kontinuierliche Assemblierungspolymerisation (CAP, continuous assembly polymerization) mittels reversibler Addtitions‐Fragmentierungs‐Kettenübertragungspolymerisation (RAFT Polymerisation, reversible‐addition‐fragmentation chain‐transfer polymerization), kurz CAP‐RAFT. CAP‐RAFT wurde bereits grundlegend mit methacryliertem Poly‐l‐Lysin (PLLMA) und methacrylierter Poly‐l‐Glutaminsäure (PLGMA) untersucht. Eine sorgfältige Anpassung der Methode führte hier zu Filmen mit einer Schichtdicke von bis zu 36.1±1.1 nm, die durch mehrfache Anwendung dieser Strategie auf 94.9±8.2 nm erhöht werden konnte. PLLMA‐ und PLGMA‐Filme wiesen überraschenderweise bis zu 30–50 % Zufallsknäuel Konformation auf. Durch den enzymatischen Abbau mit einem Protease‐Mix, der Proteasen im Wundheilungsmileu repräsentiert, konnte das Potential diesen Strukturen für Anwendungen im Wirkstofftransport und in der Gewebezüchtung gezeigt werden.
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ItemImmobilization and Intracellular Delivery of Structurally Nanoengineered Antimicrobial Peptide Polymers Using Polyphenol-Based Capsules(WILEY-V C H VERLAG GMBH, 2022-02-02)Structurally nanoengineered antimicrobial peptide polymers (SNAPPs) are an emerging class of antimicrobials against multidrug-resistant bacteria. Their encapsulation in particle carriers can improve their therapeutic efficacy by preventing peptide degradation, reducing clearance, and enhancing intracellular delivery and dosage to bacteria-infected host cells. Herein, two template-mediated strategies are reported for immobilizing SNAPPs in microcapsules through 1) complexation of SNAPPs with tannic acid (TA) onto porous CaCO3 templates and subsequent removal of the templates (SNAPP–TA capsules) and 2) adsorption of SNAPPs onto CaCO3 templates and subsequent encapsulation within a metal–phenolic (FeIII–TA) coating and template removal (SNAPP–FeIII–TA capsules). The loading amounts of SNAPPs are 0.8 and 4.4 pg per SNAPP–TA and SNAPP–FeIII–TA capsule, respectively. At pH 7.4, there is sustained release of SNAPPs, which retain high antimicrobial activity with minimum inhibitory concentration values of ≈30 µg mL−1 in Escherichia coli. Both capsule systems are internalized by alveolar macrophages in vitro, with negligible cytotoxicity and are amenable to nebulization, remaining stable in nebulized droplets. This study demonstrates the potential of engineered polyphenol-based capsules for peptide drug immobilization and intracellular delivery, which have prospective application in the pulmonary delivery of antimicrobials against respiratory bacterial infections (e.g., pneumonia, tuberculosis).