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The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Molecularly Imprinted Polymers (MIPs) are a class of polymeric materials that exhibit highly specific recognition properties towards a chosen target. These "smart materials" offer robustness to work in extreme environmental conditions and cost effectiveness; and have shown themselves capable of the affinities/specificities observed of their biomolecular counterparts. Despite this, in many MIP systems heterogeneity generated in the polymerisation process is known to affect the performance. Microwave reactors have been extensively studied in organic chemistry because they can afford fast and well-controlled reactions, and have been used for polymerisation reactions; however, their use for creating MIPs is limited. Here we report a case study of a model MIP system imprinted for caffeine, using microwave initiation. Experimental parameters such as polymerisation time, temperature and applied microwave power have been investigated and compared with polymers prepared by oven and UV irradiation. MIPs have been characterised by BET, SEM, DSC, TGA, NMR, and HPLC for their physical properties and analyte recognition performance. The results suggest that the performance of these polymers correlates to their physical characteristics These characteristics were significantly influenced by changes in the experimental polymerisation parameters, and the complexity of the component mixture. A series of trends were observed as each parameter was altered, suggesting that the performance of a generated polymer could be possible to predict. As expected, component selection is shown to be a major factor in the success of an imprint using this method, but this also have significant effect on the quality of resultant polymers suggesting that only certain types of MIPs can be made using microwave irradiation. This work also indicates that the controlled polymerisation conditions offered by microwave reactors could open a promising future in the development of MIPs with more predictable analyte recognition performance, assuming material selection loans itself to this type of initiation.

Microbial keratitis occurs from the infection of the cornea by fungi and or bacteria. It remains one of the most common global causes of irreversible blindness accounting for 3.5% (36 million) of blind people as of 2015. This paper looks at the use of a bacteria binding polymer designed to bind Staphylococcus aureus and remove it from the corneal surface. Mechanical unbinding measurements were used to probe the interactions of a thermo-active bacteria-binding polymer, highly-branched poly(N-isopropyl acrylamide), functionalised with modified vancomycin end groups (HB-PNIPAM-Van) to bacteria placed on rabbit corneal surfaces studied ex-vivo. This was conducted during sequential temperature phase transitions of HB-PNIPAM-Van-S. aureus below, above and below the lower critical solution temperature (LCST) in 3 stages, in-vitro, using a novel micro-bead force spectroscopy (MBFS) approach via atomic force microscopy (AFM). The effect of temperature on the functionality of HB-PNIPAM-Van-S. aureus showed that the polymer-bacteria complex reduced the work done in removing bacterial aggregates at T > LCST (p p 2.5 µm) increased (p 2.5 µm) compared to S. aureus aggregates only. Here, we present the first study using AFM to assess the reversible mechanical impact of a thermo-active polymer-binding bacteria on a natural corneal surface.

Graphical abstract, This study shows how highly branched poly(N-isopropyl acrylamide) (HB-PNIPAM) with a chain pendant solvatochromic dye (Nile red) could provide a fluorescence signal, as end groups bind to bacteria and chain segments become desolvated, indicating the presence of bacteria. Vancomycin was attached to chain ends of HB-PNIPAM or as pendant groups on linear polymers each containing Nile red. Location of the dye was varied between placement in the core of the branched polymer coil or the outer domains. Both calorimetric and fluorescence data showed that branched polymers responded to binding of both the peptide target (D-Ala-D-Aa) and bacteria in a different manner than analogous linear polymers; binding and response was more extensive in the branched variant. The fluorescence data showed that only segments located in the outer domains of branched polymers responded to binding of Gram-positive bacteria with little response when linear analogous polymer or branched polymer with the dye in the inner core was exposed to Staphylococcus aureus.

Branched poly( N - iso propylacrylamide) was functionalized with Amphotericin B (AmB) at the chain ends to produce an antifungal material. The polymer showed antifungal properties against AmB-sensitive strains of Candida albicans , Fusarium keratoplasticum and Aspergillus flavus (minimal inhibitory concentration ranged from 5 to 500 µg ml −1 ) but was not effective against an AmB resistant strain of C. albicans nor against Candida tropicalis . The polymer end groups bound to the AmB target, ergosterol, and the fluorescence spectrum of a dye used as a solvatochromic probe, Nile red, was blue shifted indicating that segments of the polymer became desolvated on binding. The polymer was less toxic to corneal and renal epithelial cells and explanted corneal tissue than the free drug. Also, the polymer did not induce reactive oxygen species release from peripheral blood mononuclear cells, nor did it cause a substantial release of the proinflammatory cytokines, tumour necrosis factor-α and interleukin-1 β (at 0.5 mg ml −1 ).

Hydroxyapatite and fluorhydroxyapatite (F)HA nanoparticles were synthesised in the presence of branched poly(acrylic acid)s (PAA) synthesised via reversible addition–fragmentation chain transfer polymerisation and compared to those synthesised in the presence of linear PAA. Analysis of the resulting nanoparticles using Fourier transform infrared spectroscopy, powder X-ray diffraction and transition electron microscopy found that the polymer was included within the nanoparticle samples and affected their morphology with nanoparticles synthesised in the presence of branched PAA being more acicular and smaller overall.

In this investigation, we report a non-covalent (ionic interlocking and hydrogen bonding) strategy of self-healing in a covalently crosslinked organic-inorganic hybrid nanocomposite hydrogel, with specific emphasis on tuning its properties fitting into a muscle mimetic material. The hydrogel was prepared via an in situ free radical polymerization of sodium acrylate (SA) and successive crosslinking in the presence of starch grafted with poly(2-(methacryloyloxy)ethyl trimethyl ammonium chloride) (PMTAC) and montmorillonite modified with cetyl ammonium bromide (OMMT). This hydrogel shows stimuli triggered self-healing following damage in both neutral and acidic solutions (pH = 7.4 and pH = 1.2). This behavior was reported using stress-strain experiments and rheological analyses of the hydrogel segments joined at their fracture points. The hydrogel was also able to display shape memory properties in the presence of water as well as stimuli (salt, acid and electric impulse) driven actuation behavior. It was observed that the ultimate tensile strength (UTS) of the self-healed hydrogel at pH = 7.4 was comparable to the extensor digitorum longus (EDL) muscle of a New Zealand white rabbit and the as synthesized self-healable hydrogel was found to be non-cytotoxic against NIH 3T3 fibroblast cells.

We present here a quantification of the sorption process and molecular conformation involved in the attachment of bacterial cell wall lipopolysaccharides (LPSs), extracted from Escherichia coli, to silica (SiO2) and alumina (Al2O3) particles. We propose that interfacial forces govern the physicochemical interactions of the bacterial cell wall with minerals in the natural environment, and the molecular conformation of LPS cell wall components depends on both the local charge at the point of binding and hydrogen bonding potential. This has an effect on bacterial adaptation to the host environment through adhesion, growth, function, and ability to form biofilms. Photophysical techniques were used to investigate adsorption of fluorescently labeled LPS onto mineral surfaces as model systems for bacterial attachment. Adsorption of macromolecules in dilute solutions was studied as a function of pH and ionic strength in the presence of alumina and silica via fluorescence, potentiometric, and mass spectrometry techniques. The effect of silica and alumina particles on bacterial growth as a function of pH was also investigated using spectrophotometry. The alumina and silica particles were used to mimic active sites on the surface of clay and soil particles, which serve as a point of attachment of bacteria in natural systems. It was found that LPS had a high adsorption affinity for Al2O3 while adsorbing weakly to SiO2 surfaces. Strong adsorption was observed at low pH for both minerals and varied with both pH and mineral concentration, likely in part due to conformational rearrangement of the LPS macromolecules. Bacterial growth was also enhanced in the presence of the particles at low pH values. This demonstrates that at a molecular level, bacterial cell wall components are able to adapt their conformation, depending on the solution pH, in order to maximize attachment to substrates and guarantee community survival.

Uniform onion micelles formed from up to ten nano-structured polymer layers were produced by the aqueous self-assembly of highly-branched copolymers. Highly-branched poly(alkyl methacrylate)s were chain extended with poly(acrylic acid) in a two-step reversible addition–fragmentation chain transfer-self-condensing vinyl polymerization (RAFT-SCVP) in solution. The resulting polymers were dispersed into water from oxolane (THF) using a self-organized precipitation-like method and the self-assembled particles were studied by phase-analysis light scattering, small-angle neutron scattering, and electron microscopy techniques. The relative hydrophobicity of the blocks was varied by changing the alkyl methacrylate (methyl, butyl, or lauryl) and this was found to affect the morphology of the particles. Only the poly(butyl methacrylate)-containing macromolecule formed an onion micelle structure. The formation of this morphology was observed to depend on: the evaporation of the good solvent (THF) during the self-assembly process causing kinetic trapping of structures; the pH of the aqueous phase; and also on the ratio of hydrophobic to hydrophilic segments within the copolymer. The lamellar structure could be removed by annealing the dispersion above the glass transition temperature of the poly(butyl methacrylate). To exemplify how these onion micelles can be used to encapsulate and release an active compound, a dye, rhodamine B (Rh B), was encapsulated and released. The release behaviour was dependent on the morphology of the particles. Particles formed containing the poly(methyl methacrylate) or poly(lauryl methacrylate) core did not form onions and although these materials absorbed Rh B, it was continuously released at room temperature. On the other hand, the lamellar structure formed from branch-poly(butyl methacrylate)-[poly(butyl methacrylate)-block-poly(acrylic acid)] allowed for encapsulation of approximately 45% of the dye, without release, until heating disrupted the lamellar structure.

In this work we report a facile method to prepare a fluorescence active self-healable hydrogel via incorporation of fluorescence responsive ionic block copolymers (BCPs). Ionic block copolymers were prepared via a combined effect of ring opening polymerization (ROP) of e-caprolactone and xanthate mediated reversible addition–fragmentation chain transfer (RAFT) polymerization. Here polycaprolactone (PCL) was modified with xanthate to prepare a PCL based macro-RAFT agent and then it was utilized to prepare block copolymers with cationic poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PCL-b-PMTAC) and anionic poly(sodium 4-vinylbenzenesulfonate) (PCL-b-PSS). During the block formation, the cationic segments were randomly copolymerized with a trace amount of fluorescein O-acrylate (FA) (acceptor) whereas the anionic segments were randomly copolymerized with a trace amount of 9-anthryl methylmethacrylate (AMMA) (donor) to make both the segments fluorescent. The block copolymers form micelles in a DMF : water mixture (1 : 4 volume ratio). The ionic interaction of two BCPs was monitored via Forster resonance energy transfer (FRET) and zeta potential measurements. The oppositely charged BCPs were incorporated into a polyacrylamide (PAAm) based hydrogel that demonstrated self-healing behavior and is also highly fluorescent.

Interpolymer complexes of homopolymer macromolecules are often described as ‘laddered’ or ‘ribbon’ type structures. The proposition of the existence of these ladder structures seems to us not reasonable and here we examine this hypothesis. To address this we have used polymers enabled for Forster Energy Transfer (FRET). Chromophores bound to a macromolecular backbone can transfer energy across short distances via FRET. The close binding of poly(acrylamide) and poly(acrylic acid) interpolymer complex formation at low pH forms a structure compact enough for significant energy transfer to occur between different chains containing naphthalene and anthracene labels. In the context of the proposition that ladder polymers can form it was surprising that the distance between labels on the same polymer back-bone was equivalent regardless of whether the polymer was complexed or not. The data indicated that the bicomponent structure may be more compact than previously supposed: I.e. the complexes are not ladders composed of extended chains. This evidence suggests formation not of ordered ‘ladder’ systems but colloidal ‘co-globules’.

Interpolymer complex formation of poly(acrylic acid) with other macromolecules can occur via several mechanisms that vary depending on the pH. At low pH the protonated acid functional group can form bonds with both donor and acceptor moieties, resulting in desolvated structures consisting of two polymers. Complexes were formed in dilute solutions of PAA, functionalised with acenaphthylene, with a range of other polymers including: poly(NIPAM); poly(ethylene oxide) (PEO); poly(dimethylacrylamide) (PDMA); poly(diethyl acrylamide) (PDEAM) poly(vinyl alcohol) (PVA) and poly(vinyl pyrolidinone) (PVP). Fluorescence anisotropy was used to demonstrate complex formation in each case by monitoring the reductions in segmental motion of the chain as the complexes formed. Considerations of the molecular structures of the complexing moieties suggest that solvation energies and pKas play an important role in complex formation.

Thermally responsive highly branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared and end-functionalised to give polymers with acid or trihistidine end groups. These polymers exhibit a broad coil-to-globule transition across a wide temperature range which can be measured using covalently attached fluorescent tags. The acid chain ends provided a material with a distinct change in solution behaviour at pH close to the pKa of the carboxylate group. At pH 11 this polymer did not show a cloud point up to 50 °C but fluorescence measurements on the labelled polymers showed that a coil to globule transition did take place. The globular state, above the LCST, appeared to be more swollen if the end group carried charge then when it was uncharged. A polymer with trihistidine and free carboxylate chain ends, which contained multiple charges at various pH, did show LCSTs at all pH and the polymer globule was shown to be swollen at each pH.

Microbial keratitis can arise from penetrating injuries to the cornea. Corneal trauma promotes bacterial attachment and biofilm growth, which decrease the effectiveness of antimicrobials against microbial keratitis. Improved therapeutic efficacy can be achieved by reducing microbial burden prior to antimicrobial therapy. This paper assesses a highly-branched poly(N-isopropyl acrylamide) with vancomycin end groups (HB-PNIPAM-van), for reducing bacterial attachment and biofilm formation. The polymer lacked antimicrobial activity against Staphylococcus aureus, but significantly inhibited biofilm formation (p = 0.0008) on plastic. Furthermore, pre-incubation of S. aureus cells with HB-PNIPAM-van reduced cell attachment by 50% and application of HB-PNIPAM-van to infected ex vivo rabbit corneas caused a 1-log reduction in bacterial recovery, compared to controls (p = 0.002). In conclusion, HB-PNIPAM-van may be a useful adjunct to antimicrobial therapy in the treatment of corneal infections.

The behavior of a linear copolymer of N-isopropylacrylamide with pendant vancomycin functionality was compared to an analogous highly branched copolymer with vancomycin functionality at the chain ends. Highly branched poly(N-isopropylacrylamide) modified with vancomycin (HB-PNIPAM-van) was synthesized by functionalization of the HB-PNIPAM, prepared using reversible addition-fragmentation chain transfer polymerization. Linear PNIPAM with pendant vancomycin functionality (L-PNIPAM-van) was synthesized by functionalization of poly(N-isopropylacrylamide-co-vinyl benzoic acid). HB-PNIPAM-van aggregated S. aureus effectively, whereas the L-PNIPAM-van polymer did not. It was found that when the HB-PNIPAM-van was incubated with S. aureus the resultant phase transition provided an increase in the intensity of fluorescence of a solvatochromic dye, nile red, added to the system. In contrast, a significantly lower increase in fluorescence intensity was obtained when L-PNIPAM-van was incubated with S. aureus. These data showed that the degree of desolvation of HB-PNIPAM-van was much greater than the desolvation of the linear version. Using microcalorimetry, it was shown that there were no significant differences in the affinities of the polymer ligands for d-Ala-d-Ala and therefore differences in the interactions with bacteria were associated with changes in the probability of access of the polymer bound ligands to the d-Ala-d-Ala dipeptide. The data support the hypothesis that generation of polymer systems that respond to cellular targets, for applications such as cell targeting, detection of pathogens etc., requires the use of branched polymers with ligands situated at the chain ends.

Highlights • One of first examples of stable Methanol based SEC system for polymer analysis. • Universal Calibration determined using DOSY NMR to get intrinsic viscosity. • Analysis of difficult to characterise branched polyacrylamides., Size Exclusion Chromatography is traditionally carried out in either aqueous or non-polar solvents. A system to present molar mass distributions of polymers using methanol as a mobile phase is presented. This is shown to be a suitable system for determining the molar mass distributions poly(N-isopropylacrylamide)s (PNIPAM); a polymer class that is often difficult to analyze by size exclusion chromatography. DOSY NMR was used to provide intrinsic viscosity data that was used in conjunction with a viscometric detector to provide absolute calibration. Then the utility of the system was shown by providing the absolute molar mass distributions of dispersed highly branched PNIPAM with biologically functional end groups.

A set of water-swollen core–shell particles was synthesized by emulsion polymerization of a 1,3-dioxolane functional monomer in water. After removal of the 1,3-dioxolane group, the particles’ shells were shown to swell in aqueous media. Upon hydrolysis, the particles increased in size from around 70 to 100–130 nm. A bicinchoninic acid assay and ζ-potential measurements were used to investigate the adsorption of lysozyme, albumin, or fibrinogen. Each of the core–shell particles adsorbed significantly less protein than the noncoated core (polystyrene) particles. Differences were observed as both the amount of difunctional, cross-linking monomer and the amount of shell monomer in the feed were changed. The core–shell particles were shown to be resistant to protein adsorption, and the degree to which the three proteins adsorbed was dependent on the formulation of the shell.

Composites have clinical application for their ability to mimic the hierarchical structure of human tissues. In tissue engineering applications the use of degradable biopolymer matrices reinforced by bioactive ceramics is seen as a viable process to increase osteoconductivity and accelerate tissue regeneration, and technologies such as additive manufacturing provide the design freedom needed to create patient-specific implants with complex shapes and controlled porous structures. In this study a medical grade poly( l -lactide) (PLLA) was used as matrix while apatite-wollastonite (AW) was used as reinforcement (5 wt% loading). Premade rods of composite were pelletized and processed to create a filament with an average diameter of 1.6 mm, using a twin-screw extruder. The resultant filament was 3D printed into three types of porous woodpile samples: PLLA, PLLA reinforced with AW particles, and PLLA with short AW fibres. None of the samples degraded in phosphate buffered solution over a period of 8 weeks, and an average effective modulus of 0.8 GPa, 1 GPa and 1.5 GPa was obtained for the polymer, particle and fibre composites, respectively. Composite samples immersed in simulated body fluid exhibited bioactivity, producing a surface apatite layer. Furthermore, cell viability and differentiation were demonstrated for human mesenchymal stromal cells for all sample types, with mineralisation detected solely for biocomposites. It is concluded that both composites have potential for use in critical size bone defects, with the AW fibre composite showing greater levels of ion release, stimulating more rapid cell proliferation and greater levels of mineralisation.

The clinical application of composites seeks to exploit the mechanical and chemical properties of materials which make up the composite, and in researching polymer composites for biomedical applications the aim is usually to enhance the bioactivity of the polymer, while maintaining the mechanical properties. To that end, in this study medical grade Poly(L-lactic) acid (PLLA) has been reinforced with short phosphate-based glass fibers (PGF). The materials were initially mixed by melting PLLA granules with the short fibers, before being extruded to form a homogenous filament, which was pelletized and used as feedstock for compression moulding. As made the composite materials had a bending strength of 51 MPa ± 5, and over the course of eight weeks in PBS the average strength of the composite material was in the range 20–50 MPa. Human mesenchymal stromal cells were cultured on the surfaces of scaffolds, and the metabolic activity, alkaline phosphatase production and mineralization monitored over a three week period. The short fiber filler made no significant difference to cell proliferation or differentiation, but had a clear and immediate osteoinductive effect, promoting mineralization by cells at the material surface. It is concluded that the PLLA/PGF composite material offers a material with both the mechanical and biological properties for potential application to bone implants and fixation, particularly where an osteoinductive effect would be valuable.

Thermal desolvation of poly(N-isopropylacrylamide) (PNIPAM) in the presence of a low concentration of gold nanoparticles incorporates the nanoparticles resulting in suspended aggregates. By covalently incorporating1% acenaphthylene into the polymerization feed this copolymer is enabled to be used as a model to study the segmental mobility of the PNIPAM backbone in response to gold nanoparticles both below and above the desolvation temperature, showing that there is a physical conformational rearrangement of the soluble polymer at ultralow nanoparticle loadings, indicating low affinity interactions with the nanoparticles. Thermal desolvation is capable of extracting99.9% of the nanoparticles from their solutions and hence demonstrates that poly(N-isopropylacrylamide) can act as an excellent scrubbing system to remove metallic nanomaterial pollutants from solution.