ABSTRACT
Chemical fertilizers have been crucial for sustaining the current global population by supplementing overused farmland to support consistent food production, but their use is unsustainable. Pseudomonas chlororaphis is a nitrogen-fixing bacterium that could be used as a fertilizer replacement, but this microbe is delicate. It is sensitive to stressors, such as freeze-drying and high temperatures. Here, we demonstrate protection of P. chlororaphis from freeze-drying, high temperatures (50 oC), and high humidity using self-assembling metal-phenolic network (MPN) coatings. The composition of the MPN is found to significantly impact its protective efficacy, and with optimized compositions, no viability loss is observed for MPN-coated microbes under conditions where uncoated cells do not survive. Further, we demonstrate that MPN-coated microbes improve germination of seeds by 150% as compared to those treated with fresh P. chlororaphis. Taken together, these results demonstrate the protective capabilities of MPNs against environmental stressors and represent a critical step towards enabling the production and storage of delicate microbes under nonideal conditions.
ABSTRACT
Bacillus subtilis are important probiotic microbes currently formulated for delivery as spores, but their ability to germinate in the gut remains debatable. To optimize their application, cells should be delivered in their vegetative state, but the sensitivity of B. subtilis prevents this. Through the application of self-assembled metal-phenolic network (MPN) cellular coatings, B. subtilis are protected from lyophilization stresses. These MPNs are an important class of self-assembled materials comprised of polyphenols and metal ions, and the efficacy of MPN protection was found to be dependent on the MPN components used for assembly. Both the size of the polyphenol and stability of the metal-phenol coordination were important factors that influenced their cellular protection; the smallest polyphenol, gallic acid, and the most stable chelated ion, FeIII, were found to provide the highest level of protection. Further, delivery to the gut involves exposure to acidic conditions in the form of stomach acid and intestinal fluid. MPN coatings rapidly disassemble upon mild acid treatment but were found to protect B. subtilis from the negative impacts of the acid. Overall, optimized MPNs were found to protect vegetative B. subtilis cells from lyophilization stress and enable a more complete understanding of the role of each component in MPNs.
Subject(s)
Polyphenols , Spores, Bacterial , Ferric Compounds , Gallic Acid , Metals , PhenolsABSTRACT
Polyphenols are naturally derived organic compounds that have long been used as food additives, antioxidants, and adhesives owing to their intrinsic physicochemical properties. Recently, there has been growing interest in the fabrication of coordination networks based on the self-assembly of polyphenols and metal ions, termed metal-phenolic networks (MPNs), for multiple biological applications including bioimaging, drug delivery, and cell encapsulation. The as-synthesized MPN complexes feature pH responsiveness, controllable size and rigidity, and tunable permeability based on the choice of polyphenol-metal ion pairs. The aim of this Review is to introduce the physicochemical properties of MPNs, highlight their recent biological applications in cancer theranostics and single-cell encapsulation, and discuss the future utility of MPNs for biomedical applications.
ABSTRACT
The gut microbiome is essential to maintain overall health and prevent disease, which can occur when these microbes are not in homeostasis. Microbial biotherapeutics are important to combat these issues, but they must be alive at the time of delivery for efficacy. Many potentially therapeutic species are anaerobes and thus are difficult to manufacture because of the limited efficacy of existing protective methods, making their production nearly impossible. We have developed a self-assembling cellular coating to improve the viability and stability of the next-generation biotherapeutic Bacteroides thetaiotaomicron. We show protection from both harsh processing conditions and oxygen exposure, even in the absence of canonical cryoprotectants. This advance will increase the range of microbes that can be stably manufactured and facilitate the development of emerging strains of interest by ensuring their postproduction viability.
ABSTRACT
Biomimetic catalysts, ranging from small-molecule metal complexes to supramolecular assembles, possess many exciting properties that could address salient challenges in industrial-scale manufacturing. Inspired by natural enzymes, these biohybrid catalytic systems demonstrate superior characteristics, including high activity, enantioselectivity, and enhanced aqueous solubility, over their fully synthetic counterparts. However, instability and limitations in the prediction of structure-function relationships are major drawbacks that often prevent the application of biomimetic catalysts outside of the laboratory. Despite these obstacles, recent advances in synthetic enzyme models have improved our understanding of complicated biological enzymatic processes and enabled the production of catalysts with increased efficiency. This review outlines important developments and future prospects for the design and application of bioinspired and biohybrid systems at multiple length scales for important, biologically relevant, clean energy transformations.
