Chemical and Biomolecular Engineering - Research Publications
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Item3D nanoprinting via spatially controlled assembly and polymerization.(Springer Science and Business Media LLC, 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, 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, 2022-01-12)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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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).
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ItemFenton-RAFT Polymerization: An "On-Demand" Chain-Growth Method(WILEY-V C H VERLAG GMBH, 2017-05-29)Fine control over the architecture and/or microstructure of synthetic polymers is fast becoming a reality owing to the development of efficient and versatile polymerization techniques and conjugation reactions. However, the transition of these syntheses to automated, programmable, and high-throughput operating systems is a challenging step needed to translate the vast potential of precision polymers into machine-programmable polymers for biological and functional applications. Chain-growth polymerizations are particularly appealing for their ability to form structurally and chemically well-defined macromolecules through living/controlled polymerization techniques. Even using the latest polymerization technologies, the macromolecular engineering of complex functional materials often requires multi-step syntheses and purification of intermediates, and results in sub-optimal yields. To develop a proof-of-concept of a framework polymerization technique that is readily amenable to automation requires several key characteristics. In this study, a new approach is described that is believed to meet these requirements, thus opening avenues toward automated polymer synthesis.
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ItemAntifogging Surface Facilitated by Nanoscale Coatings with Controllable Hydrophobicity and Cross-Linking Density(WILEY-V C H VERLAG GMBH, 2017-01-01)
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ItemSono‐RAFT Polymerization in Aqueous Medium(Wiley, 2017-09-25)The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition–fragmentation chain transfer (RAFT) agent. This allows for a highly “green” method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.
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ItemSono-RAFT Polymerization in Aqueous Medium(WILEY-V C H VERLAG GMBH, 2017-09-25)The ultrasonic irradiation of aqueous solution is demonstrated to be a suitable source of initiating radicals for a controlled radical polymerization when conducted in the presence of a thiocarbonylthio-containing reversible addition-fragmentation chain transfer (RAFT) agent. This allows for a highly "green" method of externally regulated/controlled polymerization with a potentially broad scope for polymerizable monomers and/or polymer structures.
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ItemAn Exciting Time for Polymer Chemists in Australia(John Wiley & Sons, Inc., 2019-09-15)Over the last 50 years, Australian researchers have made significant contributions to polymer science. Australian scientists have participated in the discovery of many polymerization techniques such as nitroxide‐mediated polymerization (NMP), addition‐fragmentation polymerization (AFT), and the well‐known Reversible Addition‐Fragmentation Chain Transfer polymerization (RAFT), as well as the successful commercialization of products utilizing polymers, most notably the plastic banknote. These contributions have been led by the Australian scientists working at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Australian universities. Despite previous attempts by other reserve banks in different countries, the Reserve Bank of Australia introduced the first plastic banknote developed by the CSIRO in collaboration with Note Printing Australia.