Lee A. Fielding

Self-assembling peptides (SAPs) provide a versatile, biocompatible platform for soft biomaterials, but their application in mechanically robust, processable polymers remains limited. We report a peptide–polyethylene glycol (PEG) multiblock copolymer (MBCP) using the amphipathic β-sheet-forming SAP K(FEFK)2K as a physical cross-linker. Synthesized via copper-free strain-promoted azide–alkyne cycloaddition (SPAAC), the MBCP was solution-cast from water into free-standing films whose properties were governed by the peptide’s ability to form stable β-sheet fibers and aggregates. Films were tough and plastic at room temperature, but elastomeric above PEG’s melting point (>60 °C). At high temperature, a micro- and nano-scale phase-separated morphology emerged, with peptide fiber-rich domains embedded in a soft, amorphous PEG matrix. At room temperature, only microphase separation persisted, while PEG crystallization produced a semicrystalline matrix in which peptide fibers restricted large crystal growth and were likely segregated at crystallite interfaces. Extensive mechanical testing revealed resilient films with shape-recovery behavior.

Gene delivery is a cornerstone of both basic research and gene therapy, where it holds the key to treating genetic disorders at their source. However, it does not adhere to one-size-fits-all solutions. Cargo-tailored and time-saving approaches are urgently needed for different applications. Photoinduced electron/energy transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization is a technique that enables the synthesis of a wide range of well-defined polymers, allowing for rapid reaction condition screening in small volumes. In this work, polymerization-induced electrostatic self-assembly (PIESA) based on PET-RAFT polymerization is demonstrated to facilitate the simultaneous synthesis and assembly of pDNA polyplexes for transfection. The as-prepared polyplexes are shown to be less cytotoxic than their conventionally assembled counterparts and act as more effective gene delivery vehicles in transfection trials. This strategy provides a versatile platform that facilitates rapid screening of cell-compatible copolymer nanoparticle compositions for gene delivery in ultralow volumes.

PH-responsive nanogels prepared via RAFT-mediated PISA show tunable swelling, high colloidal stability, and reversible behaviour, highlighting their potential for smart delivery, biosensing, and adaptive biomaterials.

A series of well-defined polymers were synthesised and utilised to adjust the rheology and improve the printability of iron oxide nanoparticle inks, resulting in collapse- and crack-free 3D printed structures.

This paper reports polymer-nanoparticle-based complex coacervate (PNCC) hydrogels prepared by mixing anionic nanogels synthesized by polymerization-induced self-assembly (PISA) and cationic branched poly(ethylenimine) (bPEI). Specifically, poly(3-sulfopropyl methacrylate)₅₈-b-poly(2-(methacryloyloxy)ethyl succinate)₅₀₀ (PKSPMA₅₈-PMES₅₀₀) nanogels were prepared by reversible addition-fragmentation chain-transfer (RAFT)-mediated PISA. These nanogels swell on increasing the solution pH and form free-standing hydrogels at 20% w/w and pH ≥ 7.5. However, the addition of bPEI significantly improves the gel properties through the formation of PNCCs. Diluted bPEI/nanoparticle mixtures were analyzed by dynamic light scattering (DLS) and aqueous electrophoresis to examine the mechanism of PNCC formation. The influence of pH and the bPEI-to-nanogel mass ratio (MR) on the formation of these PNCC hydrogels was subsequently investigated. A maximum gel strength of 1300 Pa was obtained for 20% w/w bPEI/PKSPMA₅₈-PMES₅₀₀ PNCC hydrogels prepared at pH 9 with an MR of 0.1, and shear-thinning behavior was observed in all cases. After the removal of shear, these PNCC gels recovered rapidly, with the recovery efficiency being pH-dependent.

This article reports the preparation of multifunctional magnetic nanocomposite hydrogels formed from wormlike micelles. Specifically, iron oxide nanoparticles were incorporated into a temperature responsive block copolymer, poly(glycerol monomethacrylate)-b-poly(2-hydroxypropyl methacrylate) (PGMA-b-PHPMA), and graphene oxide (GO) dispersion at a low temperature (∼2 °C) through high-speed mixing and returning the mixture to room temperature, resulting in the formation of nanocomposite gels. The optimal concentrations of iron oxide and GO enhanced the gel strength of the nanocomposite gels, which exhibited a strong magnetic response when a magnetic field was applied. These materials retained the thermoresponsiveness of the PGMA–PHPMA wormlike micelles allowing for a solid-to-liquid transition to occur when the temperature was reduced. The mechanical and rheological properties and performance of the nanocomposite gels were demonstrated to be adjustable, making them suitable for a wide range of potential applications. These nanocomposite worm gels were demonstrated to be relatively adhesive and to act as strain and temperature sensors, with the measured electrical resistance of the nanocomposite gels changing with applied strain and temperature sweeps. The nanocomposite gels were found to recover efficiently after the application of high shear with approximately 100% healing efficiency within seconds. Additionally, these nanocomposite worm gels were injectable, and the addition of GO and iron oxide nanomaterials seemed to have no significant adverse impact on the biocompatibility of the copolymer gels, making them suitable not only for 3D printing in nanocomposite engineering but also for potential utilization in various biomedical applications as an injectable magnetic responsive hydrogel.

Colloidal nanogels formed from a pH-responsive poly(succinate)-functional core and a poly(sulfonate)-functional corona were prepared via a previously unreported reversible addition-fragmentation chain-transfer (RAFT)-mediated aqueous emulsion polymerization-induced self-assembly (PISA) route. Specifically, a poly(potassium 3-sulfopropyl methacrylate) (PKSPMA₅₀) macromolecular chain-transfer agent (macro-CTA) was synthesized via RAFT solution polymerization followed by chain-extension with a hydrophobic, carboxylic acid-functional, 2-(methacryloyloxy) ethyl succinate (MES) monomer at pH 2. Colloidal nanoparticles with tunable diameters between 66 to 150 nm, depending on the core composition, and narrow particle size distributions were obtained at 20% w/w solids. Well-defined pH-responsive nanogels that swell on increasing the pH could be prepared even without the addition of a cross-linking comonomer, and introducing an additional cross-linker to the core led to smaller nanogels with lower swelling ratios. These nanogels could reversibly change in size on cycling the pH between acidic and basic conditions and remain colloidally stable over a wide pH range and at 70 °C.

There is a high demand for rapid, sensitive, and accurate detection methods for pathogens. This paper demonstrates a method of detecting the presence of amplified DNA from a range of pathogens associated with serious infections including Gram-negative bacteria, Gram-positive bacteria, and viruses. DNA is amplified using a polymerase chain reaction (PCR) and consequently detected using a sterically stabilized, cationic polymer latex. The DNA induces flocculation of this cationic latex, which consequently leads to rapid sedimentation and a visible change from a milky-white dispersion to one with a transparent supernatant, presenting a clear visible change, indicating the presence of amplified DNA. Specifically, a number of different pathogens were amplified using conventional or qPCR, including Staphylococcus aureus, Escherichia coli, and Herpes Simplex Virus (HSV-2). This method was demonstrated to detect the presence of bacteria in suspension concentrations greater than 380 CFU mL-1 and diagnose the presence of specific genomes through primer selection, as exemplified using methicillin resistant and methicillin susceptible Staphylococcus aureus. The versatility of this methodology was further demonstrated by showing that false positive results do not occur when a PCR of fungal DNA from C. albicans is conducted using bacterial universal primers.