A Short Appraisal on Gold Nanoparticles: Recent Advances and Applications

: Owing to their unique characteristics and diverse surface activities, gold nanoparticles (AuNPs) have been widely used in various fields of biology. The ease with which AuNPs can be functionalized makes it a useful platform for nanobiological assemblies containing oligonucleotides, antibodies, and proteins. AuNPs bioconjugates have also emerged as an interesting candidate for the development of novel biomaterials for the study of biological systems. AuNPs' flexibility has made them valuable in a variety of biomedical applications. The binding of analytes to AuNPs can change the physicochemical features of AuNPs, such as surface plasmon resonance, conductivity, and redox activity, resulting in observable signals in diagnostics. AuNPs can also be used as a therapeutic platform because of their large surface area, which allows for a dense presentation of multifunctional moieties (e.g., drugs and targeting agents). We present a brief summary of green synthesis, characteristics, and applications of gold nanoparticles in this paper, as well as their translational potential.

Antimicrobial Applications of Rhamnolipid Biosurfactant Produced from Achromobacter sp. (PS1) Isolate Using Lignocellulosic Hydrolysate

Heterogeneous mixture of partially purified rhamnolipid (RL) produced from Achromobacter sp. (PS1) using lignocellulosic rice straw (RS) sugar hydrolysate medium revealed six different congeners- Rha- C10-C10, Rha-C8-C10/Rha-C10-C8, Rha- C12-C10 / Rha- C10-C12, referring mono-rhamnolipids amounting to total 68.23 % and Rha-Rha-C10-C10, Rha-Rha-C8-C10/Rha-Rha-C10-C8, Rha-Rha-C10-C12/Rha-Rha-C12-C10, referring di-rhamnolipids amounting to 31.73 %, with Mono to Di- RL in the ratio of 2.1:1. This mixture's antimicrobial action containing more mono-rhamnolipids analyzed using broth macro-dilution method exhibited a broad-spectrum antibacterial activity showing ≥ 90 % growth inhibition of both Gram-positive and Gram-negative pathogenic bacteria at MIC ranging from 1.25 mg/mL to 10 mg/mL of total rhamnolipids. This might be due to the more hydrophobic character of mono-rhamnolipids containing a single rhamnosyl group and showing high surface activities. On the other hand, the non-antifungal activity may be attributed to the lower percentage of di-rhamnolipids in the partially purified mixture.

Interaction Energy Analysis of Monovalent Inorganic Anions in Bulk Water Versus Air/Water Interface

Soft anions exhibit surface activity at the air/water interface that can be probed using surface-sensitive vibrational spectroscopy, but the structural implications of this surface activity remain a matter of debate. Here, we examine the nature of anion–water interactions at the air/water interface using a combination of molecular dynamics simulations and quantum-mechanical energy decomposition analysis based on symmetry-adapted perturbation theory. Results are presented for a set of monovalent anions, including Cl−, Br−, I−, CN−, OCN−, SCN−, NO2−, NO3−, and ClOn− (n=1,2,3,4), several of which are archetypal examples of surface-active species. In all cases, we find that average anion–water interaction energies are systematically larger in bulk water although the difference (with respect to the same quantity computed in the interfacial environment) is well within the magnitude of the instantaneous fluctuations. Specifically for the surface-active species Br−(aq), I−(aq), ClO4−(aq), and SCN−(aq), and also for ClO−(aq), the charge-transfer (CT) energy is found to be larger at the interface than it is in bulk water, by an amount that is greater than the standard deviation of the fluctuations. The Cl−(aq) ion has a slightly larger CT energy at the interface, but NO3−(aq) does not; these two species are borderline cases where consensus is lacking regarding their surface activity. However, CT stabilization amounts to <20% of the total induction energy for each of the ions considered here, and CT-free polarization energies are systematically larger in bulk water in all cases. As such, the role of these effects in the surface activity of soft anions remains unclear. This analysis complements our recent work suggesting that the short-range solvation structure around these ions is scarcely different at the air/water interface from what it is in bulk water. Together, these observations suggest that changes in first-shell hydration structure around soft anions cannot explain observed surface activities.

SARA-Based Correlation To Describe the Effect of Polar/Nonpolar Interaction, Salinity, and Temperature for Interfacial Tension of Low-Asphaltene Crude Oils Characteristic of Unconventional Shale Reservoirs

Summary Oil/water interfacial tension (IFT) is an important parameter in petroleum engineering, especially for enhanced-oil-recovery (EOR) techniques. Surfactant and low-salinity EOR target IFT reduction to improve oil recovery. IFT values can be determined by empirical correlation, but widely used thermodynamic-based correlations do not account for the surface-activities characteristic of the polar/nonpolar interactions caused by naturally existing components in the crude oil. In addition, most crude oils included in these correlations come from conventional reservoirs, which are often dissimilar to the low-asphaltene crude oils produced from shale reservoirs. This study presents a novel oil-composition-based IFT correlation that can be applied to shale-crude-oil samples. The correlation is dependent on the saturates/aromatics/resins/asphaltenes (SARA) analysis of the oil samples. We show that the crude oil produced from most unconventional reservoirs contains little to no asphaltic material. In addition, a more thorough investigation of the effect of oil components, salinity, temperature, and their interactions on the oil/water IFT is provided and explained using the mutual polarity/solubility concept. Fifteen crude-oil samples from prominent US shale plays (i.e., Eagle Ford, Middle Bakken, and Wolfcamp) are included in this study. IFT was measured in systems with salinity from 0 to 24% and temperatures up to 195°F.

Amyloid particles facilitate surface-catalyzed cross-seeding by acting as promiscuous nanoparticles

Amyloid seeds are nanometer-sized protein particles that accelerate amyloid assembly as well as propagate and transmit the amyloid protein conformation associated with a wide range of protein misfolding diseases. However, seeded amyloid growth through templated elongation at fibril ends cannot explain the full range of molecular behaviors observed during cross-seeded formation of amyloid by heterologous seeds. Here, we demonstrate that amyloid seeds can accelerate amyloid formation via a surface catalysis mechanism without propagating the specific amyloid conformation associated with the seeds. This type of seeding mechanism is demonstrated through quantitative characterization of the cross-seeded assembly reactions involving two nonhomologous and unrelated proteins: the human Aβ42 peptide and the yeast prion–forming protein Sup35NM. Our results demonstrate experimental approaches to differentiate seeding by templated elongation from nontemplated amyloid seeding and rationalize the molecular mechanism of the cross-seeding phenomenon as a manifestation of the aberrant surface activities presented by amyloid seeds as nanoparticles.

Naturally Derived Silicone Surfactants Based on Saccharides and Cysteamine

Silicone surfactants are widely used in many industries and mostly rely on poly(ethylene glycol) (PEG) as the hydrophile. This can be disadvantageous because commercial PEG examples vary significantly in polydispersity—constraining control over surface activity of the surfactant—and there are environmental concerns associated with PEG. Herein, we report a three-step synthetic method for the preparation of saccharide-silicone surfactants using the natural linker, cysteamine, and saccharide lactones. The Piers–Rubinsztajn plus thiol-ene plus amidation process is attractive for several reasons: if employed in the correct synthetic order, it allows for precise tailoring of both hydrophobe and hydrophile; it permits the ready utilization of natural hydrophiles cysteamine and saccharides in combination with silicones, which have significantly better environmental profiles than PEG; and the products exhibit interesting surface activities.

ERA Acute – Extending an Environmental Risk Assessment Model to the Marginal Ice Zone

ERA Acute is a globally applicable method and software tool for environmental risk assessment (ERA) of acute oil spills (Stephansen et. al, 2017a and 2017b; Libre et al, 2018), and is to be implemented as the new industry standard ERA methodology on the Norwegian Continental Shelf (NCS). This paper describes the proposed adaptation and further development of the established ERA Acute method to enhance the functionality for ERA of acute oil spills in the Marginal Ice Zone (MIZ). Due to the highly dynamic nature of the MIZ, the pilot ERA Acute MIZ proposes to use high temporal resolution data on ice concentrations and presence of Valued Ecosystem Components (VECs) in newly developed functions to calculate impacts in the MIZ. Based on literature and preliminary sensitivity tests; parameter values and risk functions have been proposed for the MIZ (ice concentrations in intervals between 10–80 %). The functions reflect that presence of ice reduces the available space for surface activities; foraging, diving, entering and exiting the water and concentrates the oil in the same space between ice floes. These functions will now be further revised, tested and implemented in a software tool. This paper presents the proposed ERA Acute MIZ methodology.