Encapsulation of E. coli in biomimetic and Fe3O4-doped hydrogel: structural and viability analyses

Silver Nanoparticles Prepared Using Magnolia officinalis Are an Effective Antimicrobial Agent on Candida albicans, Escherichia coli, and Staphylococcus aureus

Silver nanoparticles (AgNPs) prepared by plants are simple, eco-friendly, and economical. In this study, Magnolia officinalis (MO) extract was applied to synthesize MO@AgNPs. Ultraviolet-visible (UV-vis) spectrum analysis indicated a peak at 440 nm. Most of the particles were spherical with sizes from 1 to approximately 60 nm based on transmission electron microscopy (TEM). X-ray diffraction (XRD) patterns showed a face-centered cubic crystal structure. The zeta value of MO@AgNPs was - 36.5 ± 0.6 mV, which was stable at 25 °C and 4 °C. Growth kinetic studies and the Kirby-Bauer diffusion method showed significant inhibitory activity on Candida albicans (ATCC 10231), Escherichia coli (ATCC BAA-2340), and Staphylococcus aureus (ATCC 25923); the minimum inhibitory concentrations (MIC) were 3, 9, and 9 μg/mL, and corresponding minimum bactericidal concentrations (MBC) were 5, 11, and 9 μg/mL, respectively. MO@AgNPs exhibited better antifungal activity compared to AgNPs prepared using sodium citrate. Further research revealed that MO@AgNPs increased the permeability of bacterial cell membranes. Moreover, the effect of MO@AgNPs on Candida albicans was significantly enhanced by blocking autophagy. The reactive oxygen species (ROS) induced by MO@AgNPs in Candida albicans was limited and may be related to its good antioxidant activity. Finally, MO@AgNPs have no significant cytotoxicity to the human liver LO2 cell line under 20 μg/mL.

Specific nanoantibiotics for selective removal of antibiotic-resistant bacteria: New insights in bacterial imprinting based on interfacial biomimetic mineralization

Antibiotic resistance has been a worsening global concern and selective elimination of antibiotic-resistant bacteria (ARB) while retaining the co-existed beneficial bacteria has been essential in environmental protection, which having attracted considerable interest. In this work, by integrating the whole cell imprinting and epitope imprinting strategy, magnetic bacterial imprinted polymers (BIPs) towards ARB were synthesized with interfacial biomimetic mineralization followed by a screening process. The binding data showed that the BIPs owned highly specific affinity towards the target bacteria. Taking advantage of this specific binding ability of BIPs, a two-step selective antimicrobial approach was developed. Remarkably, the BIP nanoantibiotics (nAbts) could efficiently destroy ARB without harming the beneficial bacteria. In comparison with the non-bacterial imprinted polymers, the biocompatible BIP nAbts showed a 12.5-fold increase in the survival percentage for the beneficial bacteria in wastewater. To the best of our knowledge, this is the first time that bacterial imprinting via interfacial biomimetic mineralization was developed, and also the first report of killing ARB without harming the beneficial bacteria in wastewater. We believe that this strategy provides a new insight into the design of novel affinity materials for the selective elimination of ARB in biological treatment for environmental protection.

Microencapsulation of Lacticaseibacillus rhamnosus GG for Oral Delivery of Bovine Lactoferrin: Study of Encapsulation Stability, Cell Viability, and Drug Release

Probiotics are delivered orally for treating gastrointestinal tract (GIT) infections; thus, they should be protected from the harsh environment of the GIT, such as through microencapsulation. Here, we microencapsulated cells of the probiotic Lacticaseibacillus rhamnosus GG via the liquid-droplet-forming method and evaluated them for oral delivery of bovine lactoferrin (bLf). Briefly, sodium alginate capsules (G-capsules) were first prepared, crosslinked with calcium chloride (C-capsules), and then modified with disodium hydrogen phosphate (M-capsules). All capsules showed good swelling behavior in the order of G-capsules > C-capsules > M-capsules in simulated gastric fluid (SGF, pH 2) and simulated intestinal fluid (SIF, pH 7.2). FE-SEM observations showed the formation of porous surfaces and successful microencapsulation of L. rhamnosus GG cells. The microencapsulated probiotics showed 85% and 77% viability in SGF and SIF, respectively, after 300 min. Compared to the 65% and 70% viability of gelation-encapsulated and crosslinking-encapsulated L. rhamnosus GG cells, respectively, the mineralization-encapsulated cells showed up to 85% viability after 300 min in SIF. The entrapment of bLf in the mineralization-encapsulated L. rhamnosus GG cells did not show any toxicity to the cells. FTIR spectroscopy confirmed the successful surface modification of L. rhamnosus GG cells via gelation, crosslinking, and mineralization, along with the entrapment of bLf on the surface of microencapsulated cells. The findings of these studies show that the microencapsulated L. rhamnosus GG cells with natural polyelectrolytes could be used as stable carriers for the oral and sustainable delivery of beneficial biotherapeutics without compromising their viability and the activity of probiotics.

Cell-based biocomposite engineering directed by polymers

Biological cells such as bacterial, fungal, and mammalian cells always exploit sophisticated chemistries and exquisite micro- and nano-structures to execute life activities, providing numerous templates for engineering bioactive and biomorphic materials, devices, and systems. To transform biological cells into functional biocomposites, polymer-directed cell surface engineering and intracellular functionalization have been developed over the past two decades. Polymeric materials can be easily adopted by various cells through polymer grafting or in situ hydrogelation and can successfully bridge cells with other functional materials as interfacial layers, thus achieving the manufacture of advanced biocomposites through bioaugmentation of living cells and transformation of cells into templated materials. This review article summarizes the recent progress in the design and construction of cell-based biocomposites by polymer-directed strategies. Furthermore, the applications of cell-based biocomposites in broad fields such as cell research, biomedicine, and bioenergy are discussed. Last, we provide personal perspectives on challenges and future trends in this interdisciplinary area.

Biomineralization: An Opportunity and Challenge of Nanoparticle Drug Delivery Systems for Cancer Therapy

Biomineralization is a common process in organisms to produce hard biomaterials by combining inorganic ions with biomacromolecules. Multifunctional nanoplatforms are developed based on the mechanism of biomineralization in many biomedical applications. In the past few years, biomineralization-based nanoparticle drug delivery systems for the cancer treatment have gained a lot of research attention due to the advantages including simple preparation, good biocompatibility, degradability, easy modification, versatility, and targeting. In this review, the research trends of biomineralization-based nanoparticle drug delivery systems and their applications in cancer therapy are summarized. This work aims to promote future researches on cancer therapy based on biomineralization. Rational design of nanoparticle drug delivery systems can overcome the bottleneck in the clinical transformation of nanomaterials. At the same time, biomineralization has also provided new research ideas for cancer treatment, i.e., targeted therapy, which has significantly better performance.

Third Generation Whole-Cell Sensing Systems: Synthetic Biology Inside, Nanomaterial Outside

Whole-cell sensing systems (WCSSs) are highly anticipated in the field of on-site detection. However, due to their low specificity, poor stability, and potential environmental problems, their commercial application is unrealistic. Recently, synthetic biology and nanomaterials have provided potential solutions to these problems, propelling WCSSs into a new generation. Synthetic biology provides a complete solution for the intelligent design and assembly of elements, modules, and genetic circuits. Nanomaterials covering the exterior of the cells provide stable protection, remote control capability, and catalytic ability for the WCSSs, and they can limit the horizontal transfer of genetic elements. These advancements enable personalized customization, intelligent control, and self-destruction in the next generation of cell sensors, promoting their industrialization.

Impact of structural features of Sr/Fe co-doped HAp on the osteoblast proliferation and osteogenic differentiation for its application as a bone substitute

The potential of external ions doped biomaterials has been extensively explored; however, the co-doped biomaterials remain typically unexplored for their biological properties for precise biomedical applications. The current study was aimed to explore the impact of structural features of Sr/Fe co-doped hydroxyapatite (HAp) bionanomaterial on osteoblastic proliferation and osteogenic differentiation for its application as a bone substitute. A 10 mol% isomorphous co-doping of strontium and iron with respect to calcium was carried into HAp in the solid solution. Raman spectroscopy verified the presence of major functional groups of apatite structure together with the carbonate peaks. The Sr/Fe co-doped HAp bionanomaterials showed slightly negative zeta potential (at neutral pH), versatile DLS particle size (140-205 nm), high BET surface area (186 m²/g), and narrow width pore size (13-19 nm). TG/DTA analysis showed low thermal stability of the Sr/Fe co-doped HAp groups. The nanoparticles showed an initial burst release of amoxicillin for 15 h followed by extended-release up to 81 h and demonstrated an excellent antibacterial activity by producing inhibition zones of 17.6 ± 0.3 mm and 19.5 mm ± 0.4 mm for Escherichia coli and Staphylococcus aureus. Live/dead cell staining and MTT assay confirmed the non-toxic nature of Sr/Fe co-doped HAp bionanomaterial towards MC3T3-E1 cells. Further, an improved ALP activity, increased calcium deposition, enhanced RUNX2 expression, and regulated OPN and OCN expression levels suggest in MC3T3-E1 cells demonstrate the maturation of osteoblasts. This study provides the unique advantages of the co-doping approach for the applications Sr/Fe co-doped HAp bionanomaterials as a bone substitute.

Degradation of 3-fluoroanilne by Rhizobium sp. JF-3

The interest of fluoroanilines in the environment is due to their extensive applications in industry and their low natural biodegradability. A pure bacterial strain capable of degrading 3-fluoroaniline (3-FA) as the sole source of carbon and energy was isolated from a sequencing batch reactor operating for the treatment of 3-FA. The strain (designated as JF-3) was identified by 16S rRNA gene analysis as a member of the genus Rhizobium. When grown in 3-FA medium at concentrations of 100-700 mg/L, strain JF-3 almost completely removed 3-FA within 72 h. However, the obvious cell growth inhibition was observed in cultures treated with 3-FA concentrations greater than 500 mg/L. The degradation kinetics of 3-FA were consistent with Haldane's model with the maximum degradation rate as 67.66 mg/(g dry cell h). The growth kinetics of strain JF-3 followed Andrew's model with the maximum growth rate as 30.87 h^-1. Also, strain JF-3 was able to degrade 4-fluoroaniline, aniline, and catechol, but hardly grew on 2-fluoroaniline, 2,4-dfluoroaniline, 2,3,4-trifluoroaniline, 3-fluorocatechol, and 4-fluorocatechol. Additionally, it was able to grow over a wide pH range (pH 6-10), and also showed tolerance to salinity with lower than 1.0%. This result, in combination with the enzyme assays and analysis of metabolite intermediates, indicated an unconventional pathway for 3-fluoroaniline metabolism that involved conversion to 3-aminophenol and resorcinol by monooxygenase, and which was subsequently metabolized via the ortho-cleavage pathway. To our knowledge, this is the first report on the utilization of 3-FA as a growth substrate by Rhizobium sp.

Current Trends and Potential Applications of Microbial Interactions for Human Welfare

For a long time, it was considered that interactions between microbes are only inhibitory in nature. However, latest developments in research have demonstrated that within our environment, several classes of microbes exist which produce different products upon interaction and thus embrace a wider scope of useful and potentially valuable aspects beyond simple antibiosis. Therefore, the current review explores different types of microbial interactions and describes the role of various physical, chemical, biological, and genetic factors regulating such interactions. It further explains the mechanism of action of biofilm formation and role of secondary metabolites regulating bacteria-fungi interaction. Special emphasis and focus is placed on microbial interactions which are important in medicine, food industry, agriculture, and environment. In short, this review reveals the recent contributions of microbial interaction for the benefit of mankind.