Application of cuminaldehyde and ciprofloxacin for the effective control of biofilm assembly of Pseudomonas aeruginosa: A combinatorial study

Pseudomonas aeruginosa is widely associated with biofilm-mediated antibiotic resistant chronic and acute infections which constitute a persistent healthcare challenges. Addressing this threat requires exploration of novel therapeutic strategies involving the combination of natural compounds and conventional antibiotics. Hence, our study has focused on two compounds; cuminaldehyde and ciprofloxacin, which were strategically combined to target the biofilm challenge of P. aeruginosa. The minimum inhibitory concentration (MIC) of cuminaldehyde and ciprofloxacin was found to be 400 μg/mL and 0.4 μg/mL, respectively. Moreover, the fractional inhibitory concentration index (FICI = 0.62) indicated an additive interaction prevailed between cuminaldehyde and ciprofloxacin. Subsequently, sub-MIC doses of cuminaldehyde (25 μg/mL) and ciprofloxacin (0.05 μg/mL) were selected for an array of antibiofilm assays which confirmed their biofilm inhibitory potential without exhibiting any antimicrobial activity. Furthermore, selected doses of the mentioned compounds could manage biofilm on catheter surface by inhibiting and disintegrating existing biofilm. Additionally, the test combination of the mentioned compounds reduced virulence factors secretion, accumulated reactive oxygen species and increased cell-membrane permeability. Thus, the combination of cuminaldehyde and ciprofloxacin demonstrates potential in combating biofilm-associated Pseudomonal threats.

Piperine, a phytochemical prevents the biofilm city of methicillin-resistant Staphylococcus aureus: A biochemical approach to understand the underlying mechanism

Methicillin-resistant Staphylococcus aureus (MRSA), a drug-resistant human pathogen causes several nosocomial as well as community-acquired infections involving biofilm machinery. Hence, it has gained a wide interest within the scientific community to impede biofilm-induced MRSA-associated health complications. The current study focuses on the utilization of a natural bioactive compound called piperine to control the biofilm development of MRSA. Quantitative assessments like crystal violet, total protein recovery, and fluorescein-di-acetate (FDA) hydrolysis assays, demonstrated that piperine (8 and 16 μg/mL) could effectively compromise the biofilm formation of MRSA. Light and scanning electron microscopic image analysis confirmed the same. Further investigation revealed that piperine could reduce extracellular polysaccharide production by down-regulating the expression of icaA gene. Besides, piperine could reduce the cell-surface hydrophobicity of MRSA, a crucial factor of biofilm formation. Moreover, the introduction of piperine could interfere with microbial motility indicating the interaction of piperine with the quorum-sensing components. A molecular dynamics study showed a stable binding between piperine and AgrA protein (regulator of quorum sensing) suggesting the possible meddling of piperine in quorum-sensing of MRSA. Additionally, the exposure to piperine led to the accumulation of intracellular reactive oxygen species (ROS) and potentially heightened cell membrane permeability in inhibiting microbial biofilm formation. Besides, piperine could reduce the secretion of diverse virulence factors from MRSA. Further exploration revealed that piperine interacted with extracellular DNA (e-DNA), causing disintegration by weakening the biofilm architecture. Conclusively, this study suggests that piperine could be a potential antibiofilm molecule against MRSA-associated biofilm infections.

Cuminaldehyde and Tobramycin Forestall the Biofilm Threats of Staphylococcus aureus: A Combinatorial Strategy to Evade the Biofilm Challenges

Staphylococcus aureus, an opportunistic Gram-positive pathogen, is known for causing various infections in humans, primarily by forming biofilms. The biofilm-induced antibiotic resistance has been considered a significant medical threat. Combinatorial therapy has been considered a reliable approach to combat antibiotic resistance by using multiple antimicrobial agents simultaneously, targeting bacteria through different mechanisms of action. To this end, we examined the effects of two molecules, cuminaldehyde (a natural compound) and tobramycin (an antibiotic), individually and in combination, against staphylococcal biofilm. Our experimental observations demonstrated that cuminaldehyde (20 μg/mL) in combination with tobramycin (0.05 μg/mL) exhibited efficient reduction in biofilm formation compared to their individual treatments (p < 0.01). Additionally, the combination showed an additive interaction (fractional inhibitory concentration value 0.66) against S. aureus. Further analysis revealed that the effective combination accelerated the buildup of reactive oxygen species (ROS) and increased the membrane permeability of the bacteria. Our findings also specified that the cuminaldehyde in combination with tobramycin efficiently reduced biofilm-associated pathogenicity factors of S. aureus, including fibrinogen clumping ability, hemolysis property, and staphyloxanthin production. The selected concentrations of tobramycin and cuminaldehyde demonstrated promising activity against the biofilm development of S. aureus on catheter models without exerting antimicrobial effects. In conclusion, the combination of tobramycin and cuminaldehyde presented a successful strategy for combating staphylococcal biofilm-related healthcare threats. This combinatorial approach holds the potential for controlling biofilm-associated infections caused by S. aureus.

First Study on Nihonium (Nh, Element 113) Chemistry at TASCA

Nihonium (Nh, element 113) and flerovium (Fl, element 114) are the first superheavy elements in which the 7p shell is occupied. High volatility and inertness were predicted for Fl due to the strong relativistic stabilization of the closed 7p 1/2 sub-shell, which originates from a large spin-orbit splitting between the 7p 1/2 and 7p 3/2 orbitals. One unpaired electron in the outermost 7p 1/2 sub-shell in Nh is expected to give rise to a higher chemical reactivity. Theoretical predictions of Nh reactivity are discussed, along with results of the first experimental attempts to study Nh chemistry in the gas phase. The experimental observations verify a higher chemical reactivity of Nh atoms compared to its neighbor Fl and call for the development of advanced setups. First tests of a newly developed detection device miniCOMPACT with highly reactive Fr isotopes assure that effective chemical studies of Nh are within reach.

Mass Equilibration and Fluctuations in the Angular Momentum Dependent Dynamics of Heavy Element Synthesis Reactions

Mass and angle distributions for the ^{52}Cr+^{198}Pt and ^{54}Cr+^{196}Pt reactions (both forming ^{250}No) were measured and subtracted, giving new information on fast quasifission mass evolution, and the first direct determination of the dependence of sticking times on angular momentum. TDHF calculations showed good agreement with average experimental values, but experimental mass distributions unexpectedly extended to symmetric splits while the peak yield remained close to the initial masses. This implies a strong role of fluctuations in mass division early in the collision, giving insights into the transition from fast energy dissipative deep-inelastic collisions to quasifission.

Elastic Scattering and Reaction Cross-section of 8Li on 209Bi

Nuclear physics in the 21st century is driven by a quest to understand the properties of ever more exotic nuclear systems. Unusual structural phenom- ena are observed to arise in light weakly bound nuclei such as 8Li. 8Li has a cluster structure core of 7Li surrounded by a loosely bound neutron which is observed to influence reaction mechanisms near the fusion barrier. Elastic scat- tering provides a vital step towards understanding more complicated reaction mechanisms. In this work, elastic scattering was measured for 8Li + 2°9Bi at energies 2% to 34% above the barrier, allowing extraction of reaction cross- sections. The systematics of the reaction cross-sections of 8Li compared to neighbouring nuclei 6,7,9,11Li are discussed.

Systematic Study of Quasifission in 48Ca-induced reactions

The production of superheavy elements through the fusion of two heavy nuclei is severely hindered by the quasifission process, which results in the fission of heavy systems before an equilibrated compound nucleus (CN) can be formed. The heaviest elements have been synthesised using 48Ca as the projectile nucleus. However, the use of 48Ca in the formation of new superheavy elements has been exhausted, thus a detailed understanding of the properties that made 48Ca so successful is required. Measurements of mass-angle distributions allow fission fragment mass distribution widths to be determined. The effect of the orientation of prolate deformed target nuclei is presented. Closed shells in the entrance channel are also shown to be more important than the stability of the formed CN in reducing the quasifission component, with reduced mass widths for reactions with the closed shell target nuclei 144Sm and 208Pb. Comparison to mass widths for 48Ti-induced reactions show a significant increase in the mass width compared to 48Ca-induced reactions, highlighting the difficulty faced in forming new superheavy elements using projectiles with higher atomic number than 48Ca.

Measuring precise fusion cross sections using an 8T superconducting solenoid

A novel fusion-evaporation residue separator based on a gas-filled superconducting solenoid has been developed at the Australian National University. Though the transmission efficiency of the solenoid is very high, precision cross sections measurements require this efficiency to be accurately known and vitally, requires knowledge of the angular distribution of the evaporation residues. We have developed a method to deduce the angular distribution of the evaporation residues from the laboratory-frame velocity distribution of the evaporation residues transmitted by the solenoid. The method will be discussed, focusing on benchmarking examples for 34S+89Y, where the angular distributions have been independently measured using a velocity filter (A. Mukherjee et al., Phys. Rev. C. 66, 034607 (2002)) . The establishment of this method now allows the novel solenoidal separator to be used to obtain reliable, precise fusion cross-sections.

Mechanisms Suppressing Superheavy Element Yields in Cold Fusion Reactions

Superheavy elements are formed in fusion reactions which are hindered by fast nonequilibrium processes. To quantify these, mass-angle distributions and cross sections have been measured, at beam energies from below-barrier to 25% above, for the reactions of ^{48}Ca, ^{50}Ti, and ^{54}Cr with ^{208}Pb. Moving from ^{48}Ca to ^{54}Cr leads to a drastic fall in the symmetric fission yield, which is reflected in the measured mass-angle distribution by the presence of competing fast nonequilibrium deep inelastic and quasifission processes. These are responsible for reduction of the compound nucleus formation probablity P_{CN} (as measured by the symmetric-peaked fission cross section), by a factor of 2.5 for ^{50}Ti and 15 for ^{54}Cr in comparison to ^{48}Ca. The energy dependence of P_{CN} indicates that cold fusion reactions (involving ^{208}Pb) are not driven by a diffusion process.

Origins of Incomplete Fusion Products and the Suppression of Complete Fusion in Reactions of ^{7}Li

Above-barrier complete fusion involving nuclides with low binding energy is typically suppressed by 30%. The mechanism that causes this suppression, and produces the associated incomplete fusion products, is controversial. We have developed a new experimental approach to investigate the mechanisms that produce incomplete fusion products, combining singles and coincidence measurements of light fragments and heavy residues in ^{7}Li+^{209}Bi reactions. For polonium isotopes, the dominant incomplete fusion product, only a small fraction can be explained by projectile breakup followed by capture: the dominant mechanism is triton cluster transfer. Suppression of complete fusion is therefore primarily a consequence of clustering in weakly bound nuclei rather than their breakup prior to reaching the fusion barrier. This implies that suppression of complete fusion will occur in reactions of nuclides where strong clustering is present.

Exploring Zeptosecond Quantum Equilibration Dynamics: From Deep-Inelastic to Fusion-Fission Outcomes in ^{58}Ni+^{60}Ni Reactions

Energy dissipative processes play a key role in how quantum many-body systems dynamically evolve toward equilibrium. In closed quantum systems, such processes are attributed to the transfer of energy from collective motion to single-particle degrees of freedom; however, the quantum many-body dynamics of this evolutionary process is poorly understood. To explore energy dissipative phenomena and equilibration dynamics in one such system, an experimental investigation of deep-inelastic and fusion-fission outcomes in the ^{58}Ni+^{60}Ni reaction has been carried out. Experimental outcomes have been compared to theoretical predictions using time dependent Hartree-Fock and time dependent random phase approximation approaches, which, respectively, incorporate one-body energy dissipation and fluctuations. Excellent quantitative agreement has been found between experiment and calculations, indicating that microscopic models incorporating one-body dissipation and fluctuations provide a potential tool for exploring dissipation in low-energy heavy ion collisions.

Evidence for the Role of Proton Shell Closure in Quasifission Reactions from X-Ray Fluorescence of Mass-Identified Fragments

The atomic numbers and the masses of fragments formed in quasifission reactions are simultaneously measured at scission in ^{48}Ti+^{238}U reactions at a laboratory energy of 286 MeV. The atomic numbers are determined from measured characteristic fluorescence x rays, whereas the masses are obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasifission fragments on a broad angular range, the important role of the proton shell closure at Z=82 is evidenced by the associated maximum production yield, a maximum predicted by time-dependent Hartree-Fock calculations. This new experimental approach gives now access to precise studies of the time dependence of the N/Z (neutron over proton ratios of the fragments) evolution in quasifission reactions.

Interplay between quantum shells and orientation in quasifission

The quasifission mechanism hinders fusion in heavy systems through breakup within zeptoseconds into two fragments with partial mass equilibration. Its dependence on the structure of both the collision partners and the final fragments is a key question. Our original approach is to combine an experimental measurement of the fragments' mass-angle correlations in (40)Ca+(238)U with microscopic quantum calculations. We demonstrate an unexpected interplay between the orientation of the prolate deformed (238)U with quantum shell effects in the fragments. In particular, calculations show that only collisions with the tip of (238)U produce quasifission fragments in the magic Z=82 region, while collisions with the side are the only ones that may result in fusion.

48Ca+249Bk fusion reaction leading to element Z = 117: long-lived α-decaying 270Db and discovery of 266Lr

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."