The role of algal organic matter in the separation of algae and cyanobacteria using the novel "Posi" - Dissolved air flotation process.

Algae and cyanobacteria frequently require separation from liquid media in both water treatment and algae culturing for biotechnology applications. The effectiveness of cell separation using a novel dissolved air flotation process that incorporates positively charged bubbles (PosiDAF) has recently been of interest but has been shown to be dependent on the algae or cyanobacteria species tested. Previously, it was hypothesised that algal organic matter (AOM) could be impacting the separation efficiency. Hence, this study investigates the influence of AOM on cell separation using PosiDAF, in which bubbles are modified using a commercially available cationic polyelectrolyte poly(N, N-diallyl-N,N-dimethylammonium chloride) (PDADMAC). The separation of Chlorella vulgaris CS-42/7, Mychonastes homosphaera CS-556/01 and two strains of Microcystis aeruginosa (CS-564/01 and CS-555/1), all of which have similar cell morphology but different AOM character, was investigated. By testing the cell separation in the presence and absence of AOM, it was determined that AOM enhanced cell separation for all the strains but to different extents depending on the quantity and composition of carbohydrates and proteins in the AOM. By extracting AOM from the strain for which optimal separation was observed and adding it to the others, cell separation improved from <55% to >90%. This was attributed to elevated levels of acidic carbohydrates as well as glycoprotein-carbohydrate conjugations, which in turn were related to the nature and quantity of proteins and carbohydrates present in the AOM. Therefore, it was concluded that process optimisation requires an in-depth understanding of the AOM and its components. If culturing algae for biotechnology applications, this indicates that strain selection is not only important with respect to high value product content, but also for cell separation.

Surface Modification of Polydivinylbenzene Microspheres with a Fluorinated Glycopolymer Using Thiol-Halogen Click Chemistry.

Distillation-precipitation polymerization of divinylbenzene was applied to obtain uniform-sized polymeric microspheres. The microspheres were then modified with polypentafluorostyrene chains utilizing surface-initiated atom transfer radical polymerization techniques. The hydrophobic fluoropolymer-coated microsphere was then converted to a hydrophilic biopolymer by performing thiol-halogen click chemistry between polypentafluorostyrene and 1-thio-ß-D-glucose sodium salt. The semi-fluorinated glycopolymer showed good binding ability with Concanavalin A as determined by confocal microscopy and turbidity experiments.

Copolymerization of an indazole ligand into the self-polymerization of dopamine for enhanced binding with metal ions.

5,6-Dihydroxy-1H-indazole (DHI) is able to self-polymerize through the same mussel-inspired chemistry responsible for generating poly(dopamine) (PDA), demonstrating the potential to expand this class of catecholamine-exclusive chemistry onto heterocyclic catechol derivatives for the preparation of functional materials. Although DHI exhibits slower polymerization kinetics compared to dopamine, the two chemical species are compatibly polymerizable under the same reaction conditions and allow the preparation of copolymer coatings in different molar ratios. Of these copolymers, the 1 : 3-copolymer (DHI-to-dopamine ratio) has demonstrated adequate structural stability as a polymer coating. While PDA performs as an intact framework, the incorporated DHI enhances the colloidal stability and provides additional coordinating functionality through the pyrazole moieties. The 1 : 3-copolymer was fabricated into polymer capsules which exhibit negligible cytotoxicity towards murine dermal fibroblasts (L929) and enhanced binding behaviour towards copper(ii). This represents a new channel for fabricating cargo carriers for biomedical applications that involve the use of transition metal-based species.

Tailoring Stimuli Responsiveness using Dynamic Covalent Cross-Linking of Poly(vinyl alcohol)-Heparin Hydrogels for Controlled Cell and Growth Factor Delivery.

Heparin-based hydrogels are attractive for cell encapsulation and drug delivery because of the ability of heparin to bind native proteins. However, heparin-based hydrogels have received little attention for their potential as stimuli-sensitive materials. Biosynthetic, poly(vinyl alcohol) (PVA)-heparin hydrogels were formed using dynamic, covalent cross-linking. Hydrogel stimuli-sensitivity was tailored by tuning the concentration of heparin to PVA. Relatively thermally and pH stable hydrogels were produced when formed from only the synthetic, nonionic PVA polymer cross-linked via hydrazone bonds. Cross-linking in the ionic biopolymer heparin, to form PVA-heparin gels, has a profound impact on thermal stability, with degradation ranging from over 6 months to only 4 days across 25-50 °C. PVA-heparin hydrogels degrade within 18 days at basic pH (10), while not fully degrading over 6 months at lower pH (4, 7.4). This finding is attributed to the anionic repulsion of carboxyls and sulfates in heparin. PVA-heparin macromers were cytocompatible and enabled mild cell encapsulation, in addition to providing pH-controlled growth factor release. Overall, it is demonstrated that the biopolymer heparin can be used to create pH and temperature-responsive hydrogel biomaterials for cell and drug delivery.

Incorporation of 5-hydroxyindazole into the self-polymerization of dopamine for novel polymer synthesis.

Investigation into the mussel-inspired polymerization of dopamine has led to the realization that other compounds possessing potential quinone structures could undergo similar self-polymerizations in mild buffered aqueous conditions. To this end, 5-hydroxyindazole was added to a dopamine polymerization matrix in varying amounts, to study its incorporation into a polydopamine coating of silica particles. Solid-state (13) C NMR spectroscopy confirmed the presence of the indazole in the polymer shell when coated onto silica gel. SEM and DLS analysis also confirmed that the presence of the indazole in the reaction matrix yielded monodisperse polymer-coated particles, which retained their polymer shell upon HF etching, except when high levels of the indazole were used. Characterization data and examination of incorporation mechanism suggests that the 5-hydroxyindazole performs the function of a chain-terminating agent. Cytotoxicity studies of the polymer particles containing 5-hydroxyindazole showed dramatically lower toxicity levels compared to polydopamine alone.