Phosphate Buffer Research Articles

Diverse Role of Buffer Mediums and Protein Concentrations to Mediate the Multimodal Interaction of Phenylalanine-Functionalized Gold Nanoparticle and Lysozyme Protein at Same Nominal pH.

Recently, buffer molecules have been known to affect intermolecular protein-protein interactions at physiological pH. However, the roles of buffer molecules and different monolayer protein concentrations remain elusive in controlling the interaction of gold nanoparticles (Au NPs) with protein molecules. Herein, for the first time taking phenylalanine functionalized gold nanoparticles (Au-Phe NPs) and lysozyme (Lyz) protein as model systems, we report that buffer molecules of different charges (at a particular pH) play diverse roles in protein-Au NPs interaction, particularly in protein induced Au NPs aggregation. Among different buffers, negatively charged buffer (citrate and phosphate) induces aggregation of both Au-Phe NPs and Lyz protein, whereas zwitterionic and positive buffer (HEPES, MOPS, and Tris) only cause the Au NPs aggregation. Taking the diverse role of buffer into account, we propose multimodal models for stability and protein induced aggregation mechanism of NPs at different monolayer (sub-, near-, and excess) concentrations of Lyz in different medium.

Enhanced Experimental Setup and Methodology for the Investigation of Corrosion Fatigue in Metallic Biodegradable Implant Materials.

Biodegradable implants as bone fixations may present a safe alternative to traditional permanent implants, reducing the risk of infections, promoting bone healing, and eliminating the need for removal surgeries. Structural integrity is an important consideration when choosing an implant material. As a biodegradable implant is being resorbed, until the natural bone has regrown, the implant material needs to provide mechanical stability. However, the corrosive environment of the human body may affect the fatigue life of the material. Conversely, mechanical stress can have an effect on electrochemical corrosion processes. This is known as corrosion fatigue. In the presented work, an experimental setup and methodology was established to analyze the corrosion fatigue of experimental bioresorbable materials while simultaneously monitoring the electrochemical processes. A double-walled measurement cell was constructed for a three-point bending test in Dulbecco's Phosphate-Buffered Saline (DPBS- -), which was used as simulated body fluid (SBF), at 37 ± 1 °C. The setup was combined with a three-electrode setup for corrosion measurements. Rod-shaped zinc samples were used to validate the setup's functionality. Preliminary static and dynamic bending tests were carried out as per the outlined methodology to determine the test parameters. Open-circuit as well as potentiostatic polarization measurements were performed with and without mechanical loading. For the control, fatigue tests were performed in an air environment. The tested zinc samples were inspected via scanning electron microscopy (SEM). Based on the measured mechanical and electrochemical values as well as the SEM images, the effects of the different environments were investigated, and the setup's functionality was verified. An analysis of the data showed that a comprehensive investigation of corrosion fatigue characteristics is feasible with the outlined approach. Therefore, this novel methodology shows great potential for furthering our understanding of the effects of corrosion on the fatigue of biodegradable implant materials.

Greenness assessment of a molecularly imprinted polymeric sensor based on a bio-inspired polymer

Methyldopa, a synthesized dopamine substitute with phenolic, amine, and carboxylic groups, was used to create a selective molecular imprinted polymer (MIP) for detecting formoterol fumarate dihydrate (FFD), a long-acting beta2-agonist for asthma and COPD. The bio-inspired polymer (MD) was electro-grafted onto a pencil graphite electrode (PGE) using cyclic voltammetry in a phosphate buffer (pH 6.5). An indirect method involving a redox probe (ferrocyanide/ferricyanide) and differential pulse voltammetry measured FFD binding to the MIP’s 3D cavities. The sensor showed a linear response range from 1 × 10⁻⁹ M to 2 × 10⁻¹⁰ M, with a detection limit of 1.7 × 10⁻¹¹ M. The polymethyldopa (PMD) and FFD interaction was assessed by UV spectroscopy, and the method was validated per ICH guidelines. Green analytical approaches, including RGB and GAPI, were also implemented. The goal was to use advances in molecularly imprinted polymers to develop a more precise and selective electrochemical sensor for FFD quantification.

Electrospun Nanofiber Dopped with TiO2 and Carbon Quantum Dots for the Photocatalytic Degradation of Antibiotics.

Novel photocatalysts were synthesized through the association of carbon quantum dots (CQDs) with commercial (P25) titanium dioxide (TiO2) by sonication. The resulting TiO2/CQDs composite was then incorporated into the polyamide 66 (PA66) biopolymer nanofibers using the electrospinning technique, considering a composite nanoparticles-to-polymer ratio of 1:2 in the electrospinning precursor solution. The produced nanofibers presented suitable morphology and were tested for the photocatalytic degradation under simulated solar radiation of 10 mg L-1 of amoxicillin (AMX) and sulfadiazine (SDZ), in phosphate buffer solution (pH 8.06) and river water, using 1.5 g L-1 of photocatalyst. The presence of the photocatalyst increased the removal of AMX in phosphate buffer solution by 30 times, reducing the AMX degradation half-life time from 62 ± 1 h (without catalyst) to 1.98 ± 0.06 h. Moreover, SDZ degradation half-life time in phosphate buffer solution was reduced from 5.4 ± 0.1 h (without catalyst) to 1.87 ± 0.05 h in the presence of the photocatalyst. Furthermore, the PA66/TiO2/CQDs were also efficient in river water samples and maintained their performance in at least three cycles of SDZ photodegradation in river water. The presented results evidence that the produced photocatalyst can be a promising and sustainable solution for antibiotics' efficient removal from water.

The Role of Extracellular Vesicles Derived from MicroRNA-146a–modified Mesenchymal Stem Cells in Modulating Inflammation in Experimental Glenohumeral Osteoarthritis

Glenohumeral osteoarthritis (GOA) is characterized by chronic inflammation leading to joint damage. Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) are promising therapies because of their immunomodulatory functions. The anti-inflammatory effects of EVs from human Adipose-derived MSCs (hADSCs) overexpressing microRNA (miR)-146a were investigated in experimental GOA in this study. hADSCs were transfected with a mimic negative control or miR-146a mimics. GOA was induced in C57/Bl6j mice, and subsequently, the animals were treated intra-articularly with phosphate-buffered saline, miR-146a EVs, or miR-control EVs. The expression of miR-146a and its targeted cytokines interleukin (IL)-4, IL-10, tumor necrosis factor-alpha (TNF-α), IL-17, and interferon-gamma (IFN-γ) were analyzed in the spleen of mice by enzyme-linked immunosorbent assay and in the articular cartilage by real-time polymerase chain reaction. miR-146a EVs showed enrichment of miR-146a. In GOA mice, miR-146a EV treatment significantly reduced expression levels of inflammatory cytokines IFN-γ, IL-17, and TNF-α and increased the anti-inflammatory cytokine IL-10 and IL-4 compared to controls. miR-146a EV treatment raised the anti-inflammatory cytokines and reduced the pro-inflammatory cytokines of the spleen in treated mice. This study demonstrates that EVs derived from hADSCs overexpressing miR-146a have enhanced anti-inflammatory potential in GOA by modulating cytokine expression and production. EVs engineered with inflammation-related miRNAs could be a cell-free therapeutic approach for GOA.

Antibacterial activity of Savory (Satureja hortensis) extract against pure culture strains of

The paper presents the results of a study of the antibacterial activity of supercritical carbon dioxide extract of the aboveground part of Savory (Satureja hortensis) against Escherichia coli, Salmonella spp. and Staphylococcus aureus bacteria.To study the antibacterial properties of Savory extract (Satureja hortensis) against infections caused by Staphylococcus aureus, Escherichia coli and Salmonella spp.In the course of the experiment, Savory extract obtained by supercritical carbon dioxide extraction was studied for antimicrobial activity against these bacteria. The component composition of the extract was determined by chromatography–mass spectrometry. To determine the antibacterial activity, we used the method of dilution in a liquid medium with subsequent measurement of the growth of the suspension culture biomass. The activity of the extract was compared with certified drugs included in the protocols for the treatment of bacterial infections. DMSO and potassium phosphate buffer were used as a negative control.The studies showed that the extract exhibits high antibacterial activity against all the studied bacterial strains and has a direct positive correlation with its concentration. Chromatographic mass‐spectrometry analysis showed that the extract of garden Savory contains 28 substances, the main ones being thymol (30.51 %), gamma‐terpinene (15.27 %), para‐ cymene (14.25 %) and Carvacrol (9.18 %), which both individually and in combination could exhibit antibacterial activity.Supercritical carbon dioxide extract exhibits pronounced antimicrobial activity against reference strains of S. aureus, Escherichia coli and Salmonella spp.

Elucidating the effect of strain path-dependent crystallographic texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy

This research provides insight into the effect of strain path-dependent texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy in a phosphate buffer solution (pH = 8.3). To achieve this, AA2024 alloy sheets were processed using two methods: accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), i.e., rotating the sheets 90° around the normal direction (ND) axis between each cycle. The ARB-processed AA2024 alloy exhibited a pancake-shaped structure and included texture components of Copper {112}<111>, Brass {011}<211>, P {110}<221>, and S {123}<634>. Meanwhile, the CARB-processed AA2024 alloy had extremely fine and equiaxed nano-grains (< 100 nm) and texture components of S {123}<634>, Brass {011}<211>, Goss {011}<100>, Rotated Cube {001}<110>, and P {110}<221> after eight cycles. Electrochemical studies demonstrated an increase in corrosion current density due to high imposed strains in the ARB route, which in effect made the conditions of passive layer formation more difficult and lowered the corrosion resistance. Additionally, achieving a more uniform distribution of extremely fine grains and {011} orientation textures such as Brass {011}<211>, Goss {011}<100>, and P {110}<221> texture components in the CARB route, provided ideal conditions for forming oxide passive films with superior protection properties compared to ARB. These unique findings can contribute to the broader application of crystallographic-orientation-dependent electrochemical behavior of alloys in the field of corrosion management.

Using an aqueous solution of hydrolyzed collagen in phosphate buffer (drug Compositron) and vitamin D in patients with osteoarthritis of the knee joint complicated by medial meniscus injury

Using an aqueous solution of hydrolyzed collagen in phosphate buffer (drug Compositron) and vitamin D in patients with osteoarthritis of the knee joint complicated by medial meniscus injury

α-MnO2 with a cryptomelane structure for the non-enzymatic glucose electrooxidation in a neutral medium

A high demand for non-enzymatic glucose sensors and continuous glucose monitoring systems encourages the development of stable and active catalysts for the enzymeless anodic oxidation of glucose in the neutral medium. In regard to this reaction, we analyze the prospects of alpha manganese dioxide with a cryptomelane structure synthesized via an aqueous chemical route. To provide various specific surface area, the hydrated α-MnO2 oxide is annealed in a wide temperature range from 60 to 700 °C. Furthermore, we investigate the influence of the oxide annealing temperature on the amount of crystal water, chemical composition, morphology, electrochemical recharging behavior, electrocatalytic activity and stability in the glucose oxidation carried out in an isotonic NaCl-based phosphate-buffered saline (pH 7.40). To solidly determine potentials of the irreversible cathodic dissolution of α-MnO2 as well as O2/Cl2 evolution on α-MnO2, a rotating ring-disk electrode is applied. For the most active α-MnO2 sample with the 100 μg cm−2geo loading the glucose oxidation current of ca. 40 μA cm−2geo after 1 h at +0.8 V (SCE) for 7 mM of glucose is achieved. The linear concentration dependence in a physiological glucose range (1–30 mM) with the sensitivity of ca. 17.8 μA mM−0.5 cm−2geo at 25 °C is observed. Finally, glucose selectivity of α-MnO2 in relation to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol is revealed.

Biomass Carbon Dots as Fluorescent Probes for Fast and Highly Selective Detection of Fe3 + in Water Media.

In this study, a novel fluorescent probe for the rapid and highly selective detection of Fe3 + based on biomass carbon dots (b-CDs) was developed. The b-CDs were obtained via one-step hydrothermal synthesis by utilizing laurel fallen leaves. And the as-synthesized b-CDs were applied for sensing Fe3+ based on fluorescence (FL) quenching effect both in water and phosphate buffer solution (PBS) with a wide linear range from 1 µM to 300 µM, the detection limits (LODs) respectively to be 0.34 µM in water and 0.48 µM in PBS solution. The FL intensity of b-CDs was quenched fleetly within 1min after adding Fe3+. The sensing mechanism of the b-CDs + Fe3+ system can be attributed to the internal filtration effect (IFE) mechanism and the electron transfer (ET) between b-CDs and Fe3+ in water, and only the IFE mechanism in PBS solution based on multiple experimental evidences. Moreover, the as-proposed probe was successfully adopted for monitoring Fe3+ in lake water and tap water samples. This research shows some merits of economic, simplicity, green, high selectivity, and quick response for Fe3+ determination, and provides an approach for the water quality monitoring of Fe3+ and the effective utilization of waste biological materials.

αB-crystallin mini-peptides support corneal healing in vitro and in vivo in rabbit model.

To evaluate if topical use of αB-crystallin mini-peptides supports corneal healing following flap surgery. Cultured corneal cells were treated with fluorescent tagged αB-crystallin mini-peptides to assess its internalization. Cultured corneal cells pre-treated with or without the mini-peptides were exposed to H2O2 and cell viability was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Elongation of neurites of cultured trigeminal neurones was examined following treatment either with αB-crystallin mini-peptides or protein. Cultured trigeminal neurones were pre-treated either with αB-crystallin mini-peptides or crystallin protein and exposed to H2O2 and presence of beading in the dendrites and axons was assessed. Corneal flap surgery was conducted on rabbit cornea and treated topically either with αB-crystallin peptide (0.5 mg/mL thrice daily for 14d) or phosphate-buffered saline (PBS). Corneal healing was evaluated under slit-lamp biomicroscope, mRNA expression of inflammatory cytokines were assessed and the corneas were evaluated by histopathology. Internalization of αB-crystallin mini-peptides was ascertained by the detection of fluorescence within the corneal cells. The MTT assay revealed that treatment with αB-crystallin mini-peptide reduced cell death induced by H2O2 treatment. The mini-peptides did not influence the elongation of trigeminal neurites, but significantly (P<0.05) reduced beading in the neurites. In rabbit eye, the treated corneas showed reduced hyper-reflective zones (P<0.05) and suppression in the expression of inflammatory cytokines. Histopathological examination also revealed reduction of inflammatory response in treated corneas. The αB-crystallin mini-peptides restrict the damage to corneal cells and neurons and aids in corneal healing.

Layer segmented filamentous bacteria colonize and impact gut health of broiler chickens.

In commercial poultry farms, chicks hatch away from their progenitors from which they acquire key host-specific microbiota, like segmented filamentous bacteria (SFB) involved in gut maturation in early life. This study investigated whether providing chicken SFB to newly hatched broilers would increase their gut maturation and resistance to bacteria relevant to broiler and human health. One-day-old Ross308 broilers were orally treated with either phosphate-buffered saline (CON) or layer-derived SFB (D-SFB). On days 5, 10, 17, and 24, feces were collected to detect and enumerate SFB and Enterobacteriaceae. On days 8, 15, 22, and 29, birds were euthanized, intestinal samples were collected to detect and enumerate SFB through quantitative PCR (qPCR) and microscopy and expression of genes associated with gut immune function through reverse transcription-qPCR. This study showed that, despite their host specificity, layer SFB can colonize their genetically distinct relative broilers. Ileal SFB colonization was accelerated by a week with the SFB treatment and covered the proximal, medial, and distal sections of the ileum. Colonization of the ileum by SFB in early life highly activated gene expression of intestinal barrier proteins and cytokines, e.g., IL-10 and IFNγ but not IL-17. SFB treatment reduced the level of Enterobacteriaceae in the gut and provided superior resistance to intestinal and extraintestinal pathogens as tested in vitro. Overall, early gut colonization of SFB is imperative for the maturation of the gut immune system and the establishment of a homeostatic gut environment. Improving our understanding of gut immune maturation in food-producing animals is crucial for both human and animal health.IMPORTANCEIn commercial farms, newly hatched chicks may lack host-specific microbiota that help mature their gut immune system for lifelong health benefits. Here, introducing an avian segmented filamentous bacteria (SFB) to commercially sourced chickens orally at hatch accelerated SFB colonization of the ileum. Remarkably, SFB from layers were able to colonize broilers and enhance gut immune maturation, and this immunomodulation impacted the ability to increase intestinal and extraintestinal resistance to bacteria relevant to poultry and human health. With the antibiotic restrictions in animal production, strategies that will help mitigate infections are urgently needed. In summary, we developed a live prophylactic for newly hatched chicks to improve animal health and food safety. Due to the host specificity of SFB, our data highlight the importance of investigating the molecular mechanism of SFB interaction in their own host.

Evaluating the greenness, blueness, and whiteness of spectroscopic and UPLC techniques for the simultaneous measurement of anti-glaucoma drugs and the preservation agent

The pursuit of sustainable solutions is increasingly crucial in contemporary times. We propose inventive research that fulfills the criteria of whiteness and greenness in analytical chemistry. The endeavor aims to advance environmentally conscious techniques for the simultaneous detection of timolol maleate (TIM), dorzolamide HCl (DOR), and benzalkonium Cl (BNZ). The first method employed a sustainable mobile phase consisting of 0.02 M phosphate buffer: ethanol (68:32, v/v), and a flow rate of 0.6 mL/min with retention times 1.274, 1.798, and 2.483 min for DOR, TIM, and BNZ, respectively, with a UV detector at 210 nm. This methodology was easy, fast, and accurate. The approach showed low processing times, peak symmetry, and satisfactory resolution, with correlation values of 0.999. The linearity was between 0.001–0.064, 0.001–0.060 µg mL-1, and 0.001–0.050 µg mL-1for DOR, TIM, and BNZ, respectively. Furthermore, employing water as the solvent, complementary spectrophotometric methods such as Mean Centering of Ratio Spectra (MCR) and Successive Derivative Ratio Spectra (SRDS) were investigated as economical and environmentally friendly substitutes. All procedures demonstrated good linearity (r² > 0.9990), acceptable accuracy, and precision (RSD ≤ 2 %). Furthermore, by proving the superiority of the current work over previously published methods regarding sustainability, analytical performance, economics, and practicality, the real-world implementation of four greenness and whiteness algorithms boosts the approval and overall sustainable development of the proposed methods. The suggested techniques offer low-cost, environmentally friendly substitutes for traditional methods, advancing the field of analytical chemistry towards more sustainable practices and fostering a less destructive future for quality control.

Development of bacteriostatic central venous port using photobiomodulation: a comparative in vitro study

Photobiomodulation (PBM) occurs when a cell is exposed to low energy intensities. A novel central venous port (CVP) with light-emitting diodes (LEDs) that emits red light with a wavelength of 680 nm via wireless energy transmission technology has been established. This comparative in vitro study examined whether PBM can reduce the growth of methicillin-resistant Staphylococcus aureus (MRSA), a common cause of central venous (CV) infections, in vitro. In this comparative in vitro study, the red light with a wavelength of 680 nm was used to irradiate an MRSA suspension in phosphate-buffered saline for 7.5, 15, 30, or 60 min in a 3.5 cm Petri dish with an area of 8.5 cm2. The total energy was 85 J at 7.5 min, 170 J at 15 min, 340 J at 30 min, and 680 J at 60 min. Six dishes for each time and 6 temperature-controlled samples were prepared. Each sample was incubated overnight at 37℃. The Shapiro-wilk test was used to determine whether the data were normally distributed. The numbers of colonies were counted and compared using one-factor ANOVA and Bonferroni’s post-hoc test. The mean numbers of colonies in the control group were 60.3, where the numbers of colonies in the irradiated group were 51.4 at 7.5 min, 53.5 at 15 min, 44.6 at 30 min, 34.3 at 60 min. The mean number of colonies in the 60 min irradiated group differed significantly from that in the control, 7.5 min, and 15 min groups. The Bonferroni’s post-hoc test showed significant difference in the number of colonies between control vs. 30 min control vs. 60 min, 7.5 min vs. 60 min, 15 min vs. 60 min. PBM with 680 nm LEDs on MRSA for 340 J at 30 min and 680 J at 60 min inhibited the growth of cell colonies. These findings support the use of photobiomodulation in Central venous port to prevent CV access port-Blood stream infection.

Anthraquinone/Activated Carbon Electrochemical Sensor and its Application in Ofloxacin Analysis

AbstractOfloxacin (OFL) has antibacterial and anti‐inflammatory effects on respiratory tract infection, skin soft tissue infection and urogenital tract infection caused by sensitive bacteria. In this study, an electrochemical sensor on account of glassy carbon electrode (GCE) and anthraquinone (AQ)/Vulcan XC‐72 (C) composite was prosperity prepared for the determination of ofloxacin (OFL) drug. The morphology and structure of C/20%AQ composites were characterized by SEM. The electrochemical behavior of OFL on the C/20%AQ/GCE sensor was tested using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The consequences indicate that the linear response of the sensor to OFL at pH 6.5 in 0.2 M phosphate buffer solution (PBS) was in the scope of 0.1–550.0 μM (R2=0.998) with the limit of detection of 0.01 μM. The prepared C/20%AQ/GCE sensor exhibited good anti‐interference ability and repeatability against OFL. The sensor presents a sensitive, simple and low cost OFL detection method, and has been successfully applied to real samples.

Aging-induced dysbiosis worsens sepsis severity but is attenuated by probiotics in D-galactose-administered mice with cecal ligation and puncture model.

Despite the well-established effects of aging on brain function and gut dysbiosis (an imbalance in gut microbiota), the influence of aging on sepsis-associated encephalopathy (SAE) and the role of probiotics in this context remain less understood. C57BL/6J mice (8-week-old) were subcutaneously administered with 8 weeks of D-galactose (D-gal) or phosphate buffer solution (PBS) for aging and non-aging models, respectively, with or without 8 weeks of oral Lacticaseibacillus rhamnosus GG (LGG). Additionally, the impact of the condition media from LGG (LCM) was tested in macrophages (RAW 264.7 cells), microglia (BV-2 cells), and hippocampal cells (HT-22 cells). Fecal microbiome analysis demonstrated D-gal-induced dysbiosis (reduced Firmicutes and Desulfobacterota with increased Bacteroidota and Verrucomicrobiota), which LGG partially neutralized the dysbiosis. D-gal also worsens cecal ligation and puncture (CLP) sepsis severity when compared with PBS-CLP mice, as indicated by serum creatinine (Scr) and alanine transaminase (ALT), but not mortality, neurological characteristics (SHIRPA score), and serum cytokines (TNF-α and IL-6). Additionally, D-gal-induced aging was supported by fibrosis in the liver, kidney, and lung; however, CLP sepsis did not worsen fibrosis. Interestingly, LGG attenuated all parameters (mortality, Scr, ALT, SHIRPA, and cytokines) in non-aging sepsis (PBS-CLP) while improving all these parameters, except for mortality and serum IL-6, in aging sepsis (D-gal CLP). For the in vitro test using lipopolysaccharide (LPS) stimulation, LCM attenuated inflammation in some parameters on RAW264.7 cells but not BV-2 and HT-22 cells, implying a direct anti-inflammatory effect of LGG on macrophages, but not in cells from the brain. D-gal induced fecal dysbiosis and worsened sepsis severity as determined by Scr and ALT, and LGG could alleviate most of the selected parameters of sepsis, including SAE. However, the impact of LGG on SAE was not a direct delivery of beneficial molecules from the gut to the brain but partly due to the attenuation of systemic inflammation through the modulation of macrophages.

Hierarchical assembly and environmental enhancement of bacterial ice nucleators

Bacterial ice nucleating proteins (INPs) are exceptionally effective in promoting the kinetically hindered transition of water to ice. Their efficiency relies on the assembly of INPs into large functional aggregates, with the size of ice nucleation sites determining activity. Experimental freezing spectra have revealed two distinct, defined aggregate sizes, typically classified as class A and C ice nucleators (INs). Despite the importance of INPs and years of extensive research, the precise number of INPs forming the two aggregate classes, and their assembly mechanism have remained enigmatic. Here, we report that bacterial ice nucleation activity emerges from more than two prevailing aggregate species and identify the specific number of INPs responsible for distinct crystallization temperatures. We find that INP dimers constitute class C INs, tetramers class B INs, and hexamers and larger multimers are responsible for the most efficient class A activity. We propose a hierarchical assembly mechanism based on tyrosine interactions for dimers, and electrostatic interactions between INP dimers to produce larger aggregates. This assembly is membrane-assisted: Increasing the bacterial outer membrane fluidity decreases the population of the larger aggregates, while preserving the dimers. Inversely, Dulbecco's Phosphate-Buffered Saline buffer increases the population of multimeric class A and B aggregates 200-fold and endows the bacteria with enhanced stability toward repeated freeze-thaw cycles. Our analysis suggests that the enhancement results from the better alignment of dimers in the negatively charged outer membrane, due to screening of their electrostatic repulsion. This demonstrates significant enhancement of the most potent bacterial INs.

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) reveals metallic heterogeneity in a macrophage model of infectious diseases.

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) offers an attractive option for rapidly measuring trace metal heterogeneity at the single cell level. Chemical fixation has been previously applied to mammalian cells prior to sample introduction so that they can be resuspended in a solution suitable for SC-ICP-MS. However, the effect of fixation on the elemental composition of suspended cells is unknown, and robust methodologies are urgently needed so that the community can measure the effects of intracellular pathogens on elemental composition of their host cells. We demonstrate that different fixatives impact measured cell elemental composition. We have compared suspensions treated using different fixatives (methanol 60-100% in H2O and 4% paraformaldehyde in phosphate-buffered saline solution), and the number of distinguishable single cell events, keeping a constant particle number concentration. Significantly more single cell events (n = 3, P ≤ 0.05) were observed for Ca and Mg when cells were fixed in 4% paraformaldehyde than for the methanol-based fixatives, confirming the hypothesis that methanol fixatives cause leaching of these elements from the cells. The impact of fixation on Mn and Zn was less pronounced. Microbial and viral infection of eukaryotic cells can have profound effects on their elemental composition, but chemical fixation is necessary to render infected cells safe before analysis. We have successfully applied our methodology to a macrophage model of tuberculosis demonstrating utility in understanding metal homeostasis during microbial infection of mammalian cells.

Renewable Photo-Cross-Linkable Polyester-Based Biomaterials: Synthesis, Characterization, and Cytocompatibility Assessment.

The present work consist of the synthesis of photo-cross-linkable materials, based on unsaturated polyesters (UPs), synthesized from biobased monomers from renewable sources such as itaconic acid and 1,4-butanediol. The UPs were characterized to assess the influence of polycondensation reaction temperature and cross-linking time on their final properties. For this purpose, different UV irradiation exposure periods were tested. Homogeneous, uniform, and transparent films were obtained after 1, 3, and 5 min of UV exposure. These cross-linked films were then characterized. All materials presented high gel content, which was dependent on the reaction's temperature. The thermal behaviors of the UPs were shown to be similar. In vitro hydrolytic degradation tests showed that the materials can undergo degradation in phosphate-buffered saline (PBS) at pH 7.4 and 37 °C, ensuring their biodegradability over time. Finally, to assess the applicability of the polyesters as biomaterials, their cytocompatibility was determined by using human dermal fibroblasts.

Mechanistic insights into multimetal synergistic and electronic effects in a hexanuclear iron catalyst with a [Fe3(μ3-O)(μ2-OH)]2 core for enhanced water oxidation.

Multinuclear molecular catalysts mimicking natural photosynthesis have been shown to facilitate water oxidation; however, such catalysts typically operate in organic solutions, require high overpotentials and have unclear catalytic mechanisms. Herein, a bio-inspired hexanuclear iron(III) complex I, Fe6(μ3-O)2(μ2-OH)2(bipyalk)2(OAc)8 (H2bipyalk = 2,2'-([2,2'-bipyridine]-6,6'-diyl)bis(propan-2-ol); OAc = acetate) with desirable water solubility and stability was designed and used for water oxidation. Our results showed that I has high efficiency for water oxidation via the water nucleophilic attack (WNA) pathway with an overpotential of only ca. 290 mV in a phosphate buffer of pH 2. Importantly, key high-oxidation-state metal-oxo intermediates formed during water oxidation were identified by in situ spectroelectrochemistry and oxygen atom transfer reactions. Theoretical calculations further supported the above identification. Reversible proton transfer and charge redistribution during water oxidation enhanced the electron and proton transfer ability and improved the reactivity of I. Here, we have shown the multimetal synergistic and electronic effects of catalysts in water oxidation reactions, which may contribute to the understanding and design of more advanced molecular catalysts.