Biointerphases最新文献

Self-healing cement takes advantage of microbial induced carbonate precipitation (MICP), a meritorious biological process, to achieve automatic healing of cement cracks. In this study, two beneficial factors, optimization of the bacteria culture medium and encapsulation of bacterial spores, were used to improve the MICP efficiency of Sporosarcina pasteurii in self-healing cement. On the one hand, in medium optimization, we compared the growth of Sporosarcina pasteurii fed with two generally used nitrogen sources, e.g., urea and ammonium chloride, and found that ammonium chloride can promote biomineralization more efficiently than urea. It was also confirmed that nickel (0.1 mg/l) and manganese ions (10 mg/l) benefit the MICP process through enhancement of urease activity and promotion of spore production. On the other hand, spores encapsulated in sodium alginate-gelatin gel beads prepared by using a flow nozzle device can have excellent swelling performance triggered by water. As an application demonstration, self-healing of cement cracks with consideration of the above beneficial factors was successfully verified without substantial influence on the cement compressive strength.

In order to properly satisfy biomedical constraints for cardiovascular applications, additively manufactured NiTi scaffolds required further process and metallurgical engineering. Additively manufactured NiTi materials for cardiovascular use will have to undergo surface finishing in order to minimize negative surface interactions within the artery. In this study, we sought to understand biocompatibility from chemically etched additively manufactured NiTi scaffolds by laser powder bed fusion (LPBF). Although two distinct oxide films were created in the surface etching process (labeled CP-A and CP-B), no qualitative changes in microroughness were seen between the two conditions. CP-A possessed significantly less Ni at the surface (0.19 at. %) than the CP-B group (3.30 at. %), via x-ray photoelectron spectroscopy, alongside a concomitant shift in the O1 s peak presentation alluding to a greater formation of a Ni based oxide in the CP-B group. Our live dead staining revealed significant toxicity and reduced cellular attachment for the CP-B group, in addition to inducing more cell lysis (20.9 ± 5.1%), which was significantly increased when compared to CP-A (P < 0.01). Future practices of manufacturing NiTi scaffolds using LPBF should focus on producing surface films that are not only smooth, but free of cytotoxic Ni based oxides.

Microbially induced corrosion (MIC) is an emerging topic that has huge environmental impacts, such as long-term evaluation of microbial interactions with radioactive waste glass, environmental cleanup and disposal of radioactive material, and weathering effects of microbes. Time-of-flight secondary ion mass spectrometry (ToF-SIMS), a powerful mass spectral imaging technique with high surface sensitivity, mass resolution, and mass accuracy, can be used to study biofilm effects on different substrates. Understanding how to prepare biofilms on MIC susceptible substrates is critical for proper analysis via ToF-SIMS. We present here a step-by-step protocol for preparing bacterial biofilms for ToF-SIMS analysis, comparing three biofilm preparation techniques: no desalination, centrifugal spinning (CS), and water submersion (WS). Comparisons of two desalinating methods, CS and WS, show a decrease in the media peaks up to 99% using CS and 55% using WS, respectively. Proper desalination methods also can increase biological signals by over four times for fatty acids using WS, for example. ToF-SIMS spectral results show chemical compositional changes of the glass exposed in a Paenibacillus polymyxa SCE2 biofilm, indicating its capability to probe microbiologically induced corrosion of solid surfaces. This represents the proper desalination technique to use without significantly altering biofilm structure and substrate for ToF-SIMS analysis. ToF-SIMS spectral results showed chemical compositional changes of the glass exposed by a Paenibacillus bacterial biofilm over 3-month inoculation. Possible MIC products include various phosphate phase molecules not observed in any control samples with the highest percent increases when experimental samples were compared with biofilm control samples.

Organic modification can generally endow inorganic materials with novel and promotional characteristics to fit into new functionalities. In this paper, new cement-based composite materials, with Portland cement as the substrate and polyacrylamide (PAM, alone) and PAM/chitosan as the functional components mixed with cement (bulk modified) or served as the surface coating (surface modified), were prepared and engineered as sampling substrates for biofilm and coral co-culture. In comparison to the bulk modified substrate and pure cement material, the surface modified substrate showed a balanced mechanical property, considering both bending and compressive strengths and distinctive surface features toward facilitating biofilm and coral growth, as characterized by spectroscopic, morphological, mechanical, and biofilm and coral co-culture experiments. We, thus, believe that the as-prepared surface modified substrate has the very potential to be applied as a substitute/alternative for the conventional cement material in the construction and engineering of artificial facilities with ecological protection functions.

Atomic force microscopy was utilized to estimate the adhesion strengths to silicon nitride as well as the cellular elasticities of pathogenic Listeria monocytogenes EGDe cells cultured in media adjusted to five different pH conditions of growth (5, 6, 7, 8, and 9) under water with 0.0027 fixed ionic strength. Particularly, the role of adhesion on the bacterial elastic properties was investigated. The nonadhesive Hertz model of contact mechanics was used to extract Young's moduli of elasticity of bacterial cells from the approach force-indentation data. Additionally, the adhesive models of contact mechanics: Johnson-Kendall-Roberts (JKR) and Derjaguin-Muller-Toporov (DMT) were used to estimate Young's moduli of elasticity of bacterial cells from the retraction force-indentation data. Our results indicated that adhesion to silicon nitride was the highest for cells cultured at a pH of 7. Similarly, bacterial cells cultured at pH 7 were characterized by the highest Young's moduli of elasticities compared to the lower or higher pH conditions of growth. Young's moduli of elasticities estimated from the Hertz model were stiffer than those estimated using JKR or DMT models. As the adhesion between bacterial cells and indenters increased, the difference between the Hertz model and JKR or DMT models estimates of Young's moduli of elasticity increased as well. Contradicting the current norm of using the Hertz model to quantify bacterial elasticity in the literature, our results highlight the extreme importance of utilizing contact mechanics models with adhesion components in them such as the JKR and DMT models to estimate bacterial elasticity.

Zinc is a critical trace element in the human body, playing a key role in regulating various protein functions and cellular metabolism. Thus, maintaining zinc homeostasis is essential for human health, as zinc deficiency can directly contribute to the onset of numerous diseases. Effective supplementation with zinc ions offers a viable treatment for zinc deficiency. Polysaccharides, particularly natural polysaccharides, exhibit extensive physiological activities and serve as efficient systems for delivering zinc ions. Fucoidan (F) is an affordable, widely available polysaccharide with significant bioactivity and safety, attracting growing research interest. However, most studies focus on its physiological functions, while few explore the structure and effects of fucoidan-metal complexes. In this study, fucoidan (F) was chosen to complex with Zn2+ to form the fucoidan-zinc (F-Zn) complex, whose structure was characterized. The zinc ion content reached 9.15%, with zinc (II) predominantly complexed with sulfate groups in the F-Zn (II) complex. Evaluation demonstrated that the prepared fucoidan-zinc system, at a concentration of 110 μg/ml, exhibited no significant cytotoxicity toward HT22 cells. Furthermore, both F and F-Zn exhibited significant neuroprotective effects in an HT22 cell model induced by cisplatin. Additional investigations revealed that F and F-Zn could mitigate cisplatin-induced increases in reactive oxygen species levels and alleviate mitochondrial damage. The fucoidan-zinc complex presents itself as a promising zinc ion delivery system for treating zinc deficiency.

In this work, the adsorption behavior of cytochrome c (Cyt-c) on five different self-assembled monolayers (SAMs) (i.e., CH3-SAM, OH-SAM, NH2-SAM, COOH-SAM, and OSO3--SAM) was studied by combined parallel tempering Monte Carlo and molecular dynamics simulations. The results show that Cyt-c binds to the CH3-SAM through a hydrophobic patch (especially Ile81) and undergoes a slight reorientation, while the adsorption on the OH-SAM is relatively weak. Cyt-c cannot stably bind to the lower surface charge density (SCD, 7% protonation) NH2-SAM even under a relatively high ionic strength condition, while a higher SCD of 25% protonation promotes Cyt-c adsorption on the NH2-SAM. The preferred adsorption orientations of Cyt-c on the negatively-charged surfaces are very similar, regardless of the surface chemistry and the SCD. As the SCD increases, more counterions are attracted to the charged surfaces, forming distinct counterion layers. The secondary structure of Cyt-c is well kept when adsorbed on these SAMs except the OSO3--SAM surface. The deactivation of redox properties for Cyt-c adsorbed on the highly negatively-charged surface is due to the confinement of heme reorientation and the farther position of the central iron to the surfaces, as well as the relatively larger conformation change of Cyt-c adsorbed on the OSO3--SAM surface. This work may provide insightful guidance for the design of Cyt-c-based bioelectronic devices and controlled enzyme immobilization.

Staphylococcus aureus (S. aureus) is a potentially pathogenic bacterium that commonly colonizes surfaces through the formation of biofilms. Silica glass is a common material in the built environment, especially in laboratory and medical spaces. The chemical and physical mechanisms by which S. aureus initially adheres to surfaces are unclear. In this study, the adsorption of several S. aureus biofilm associated compounds on silica is probed using molecular dynamics simulations. Model compounds containing a phosphorylated backbone, N-acetylglucosamine (GlcNAc), or D-alanine (D-Ala) were simulated across a range of pH. GlcNAc adsorption is unfavorable and insensitive to pH. D-Ala adsorption is unfavorable across the range of tested pH. Phosphorylated backbone adsorption is unfavorable at low pH but favorable at high pH. Adsorbate titration and solution salt concentration were probed to establish effects of molecular charge and charge screening. Hydrogen bonding between compounds and the silica surface is a key factor for stronger adsorption. The findings of this study are important for the rational design of improved silica surfaces through chemical functionalization or through the application of optimal chemical disinfectants that discourage the initial stages of biofilm growth.

In this study, bovine serum albumin (BSA) is used as a globular protein model to examine the conformational changes that occur during the interaction of BSA with N-hydroxysulfo-succinimide (sodium salt)-functionalized gold nanourchins (GNUs), for which dynamic spectroscopic techniques are employed. The results showed that the absorbance of phosphate-buffered saline-BSA at 278 nm decreased when a GNU was added to the solution due to adsorption, and it decreased further when the GNU was increased. The intensity and width of the peak of local surface plasmon resonance increased, indicating the effect of corona formation. Dynamic UV-vis spectroscopy and scattering revealed a nonlinear behavior of BSA-GNU interaction. The bioplasmonic solution resulted in higher transmission and scattering than the BSA solution. Fourier transform-near-infrared spectra exhibited several bands due to overtones and combinations of the amide group and different proportions of α-helix and β-sheet components in BSA before and after the addition of the GNU. Time-resolved fluorescence spectroscopy demonstrated an initial increase in blueshifted emission, followed by a redshifted quenching of two major peaks of Tyr and tryptophan (Trp). The binding and dissociation constants were determined as Kb = 2.17 × 1010 M-1 and Kd = 4.6 × 10-11, respectively, using the Stern-Volmer relation. Both the dynamic CMOS-based imaging and the cadmium sulfide sensors demonstrated a nonlinear response of bioplasmonic solution. By increasing the GNU, the resistance of the solution decreased in the order of A > S1 > S3, where S3 exhibited the highest initial transmission with a longer desorption time. MATLAB modeling showed 80% surface coverage by the protein in 15 s at 0.05M, equivalent to a thickness of 1.7 nm, which was in agreement with the value determined by using the Stokes-Einstein relation.