A biocoating confines nongrowing, metabolically active bacteria within a synthetic colloidal polymer (i.e., latex) film. Bacteria encapsulated inside biocoatings can perform useful functions, such as a biocatalyst in wastewater treatment. A biocoating needs to have a high permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. Tuning the porosity architecture is a challenge. Here, we exploited rigid tubular nanoclays (halloysite) and nontoxic latex particles (with a relatively high glass transition temperature) as the colloidal "building blocks" to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of a yellow fluorescent protein. A custom-built apparatus was used to measure the permeability of a fluorescein sodium salt in the biocoatings. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 1 × 10 −4 m h −1 . The effects of this increase in permeability was demonstrated through a specially developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a nonoptimized coating made from latex particles alone.
Catalytic chain transfer emulsion polymerization (CCTP) and subsequent chain extension via reversible addition− fragmentation chain transfer (RAFT) were used to synthesize amphiphilic macromonomers (MM), in the form of polymer latexes. The macromonomers consisted of two blocks whose first was a random copolymer of methacrylic acid and methyl methacrylate, at 35:65 mol:mol, while the second block was n-butyl methacrylate P[(MAA-co-MMA)-block-PBMA]. The block copolymer colloids were disintegrated and micellized upon addition of ammonia. The resulting nanosized polymer dispersions were used as reactive surfactants in the emulsion polymerization of n-butyl methacrylate. For this, a dual stage slow−fast monomer feed profile was used. The final polymer latexes were in the sub-100 nm range for the particle diameter at 30% w/w total polymer content. The emphasis of the work is to discuss and find an explanation for the observed particle size distributions in the three consecutive emulsion polymerization steps. The particle size distribution of the ω-unsaturated macromonomer latex synthesized by CCTP emulsion polymerization was found to be much broader than expected. This discrepancy is attributed to an extended particle nucleation period. The chain extension step in the macromonomer latex preparation showed considerable secondary nucleation. The presence of water-soluble macromonomer species from the CCTP emulsion polymerization step assured that control of chain growth persisted. The use of the amphiphilic macromonomers as reactive surfactants in the form of a nanosized aggregate seed dispersion showed that the average particle diameter could be tuned and that the molecular weight distributions could be regulated, when monomer starved conditions were used in the emulsion polymerizations.
Polymer latexes of poly(benzyl methacrylate) P(BzMA) were synthesized by mini-emulsion polymerization, using hexadecane as the hydrophobe and ω-unsaturated methacrylate-based macromonomers as a reactive stabilizer. The amphiphilic macromonomers were synthesized by...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.