A two-stage design enhanced biodegradation of high concentrations of a C16-alkyl quaternary ammonium compound in oxygen-based membrane biofilm reactors.

Quaternary ammonia compounds (QAC), such as hexadecyltrimethyl-ammonium (CTAB), are widely used as disinfectants and in personal-care products. Their use as disinfectants grew during the SARS-CoV-2 (COVID-19) pandemic, leading to increased loads to wastewater treatment systems and the environment. Though low concentrations of CTAB are biodegradable, high concentrations are toxic to bacteria. Sufficient O2 delivery is a key to achieve high CTAB removal, and the O2-based Membrane Biofilm Reactor (O2-MBfR) is a proven means to biodegrade CTAB in a bubble-free, non-foaming manner. A strategy for achieving complete biodegradation of high-concentrations of CTAB is a two-stage O2-MBfR, in which partial CTAB removal in the Lead reactor relieves inhibition in the Lag reactor. Here, more than 98 % removal of 728 mg/L CTAB could be achieved in the two-stage MBfR, and the CTAB-removal rate was 70 % higher than for a one-stage MBfR with the same O2-delivery capacity. CTAB exposure shifted the bacterial community toward Pseudomonas and Stenotrophomonas as the dominant genera. In particular, P. alcaligenes and P. aeruginosa were enriched in the Lag reactor, as they were capable of biodegrading the metabolites of initial CTAB monooxygenation. Metagenomic analysis also revealed that the Lag reactor was enriched in genes for CTAB and metabolite oxygenation, due to reduced CTAB inhibition.

EthoLeciplex: a new tool for effective cutaneous delivery of minoxidil.

This work designates EthoLeciplex, a vesicular system consisting of phospholipid, CTAB, ethanol and water, as an innovative vesicular system for cutaneous/transfollicular minoxidil (MX) delivery. MX-loaded EthoLeciplex was fabricated by one-step fabrication process. Formulations were designed to study the effects of drug/phospholipid ratio, CTAB/phospholipid ratio, and ethanol concentration on vesicular size, PDI, surface charge and EE%. The optimized formulation was characterized by in vitro release, drug/excipient compatibility, ex vivo skin permeability and safety. A size of 83.6 ± 7.3 to 530.3 ± 29.4 nm, PDI of 0.214 ± 0.01 to 0.542 ± 0.08 and zeta potential of +31.6 ± 4.8 to +57.4 ± 12.5 mV were observed. Encapsulation efficiency was obtained in its maximum value (91.9 ± 16.2%) at the lowest drug/phospholipid ratio, median CTAB/phospholipid and the highest ethanol concentration. The optimized formulation was consisted of 0.3 as drug/lipid ratio, 1.25 as CTAB/lipid ratio and 30% ethanol concentration and showed responses' values in agreement with the predicted results. Differential scanning calorimetry studies suggested that EthoLeciplex existed in flexible state with complete incorporation of MX into lipid bilayer. The cumulative amount of MX permeated from EthoLeciplex, conventional liposome and ethanolic solution after 12 h were 36.3 ± 1.5 µg/ml, 21 ± 2.0 µg/ml and 55 ± 4.0 µg/ml respectively. Based on the remaining amount, the amount of MX accumulated in different skin layers can be predicted in descending order as follows; EthoLeciplex > conventional liposome > MX solution. EthoLeciplex produced marked disorder in the stratum corneum integrity and swelling with no features of skin toxicity. This new cationic system is a promising carrier for cutaneous/transfollicular drug delivery.

Exploring molecular dynamics simulation to predict binding with ocular mucin: An in silico approach for screening mucoadhesive materials for ocular retentive delivery systems.

In recent times, molecular dynamic (MD) simulations have been applied in the area of drug delivery, as an in silico tool to predict the behaviour of nanoparticles with respect to their interaction with larger biological entities like bilayer membranes, DNA and dermal surface. However, the predictions must be systematically evaluated by extensive studies with actual biological entities in order to deem the in silico models accurate. Thus, in the present study, MD simulation was used to screen ligands with respect to ocular mucoadhesion. Mucin-4, a cell surface-associated mucin was selected as the substrate for the in silico study due to its abundance across the ocular surface. The ligands were then incorporated into a delivery system like nanostructured lipid carriers (NLC) and assessed for mucoadhesion by relevant in vitro and in vivo techniques. The in silico study suggested chitosan oligosaccharide (COS) to have an extensive mucoadhesive potential towards ocular mucin followed by stearylamine (STA) and cetrimonium bromide (CTAB) which showed intermediate and low mucoadhesion respectively. The corresponding in vitro assessment by spectrophotometry and nanoparticle tracking analysis showed a similar outcome wherein COS was found to be extensively mucoadhesive, followed by both STA and CTAB, which showed mucoadhesion to a nearly equal extent. The findings of in vivo confocal imaging following topical administration to rats showed that while COS and STA adhered extensively to the ocular surface, CTAB showed negligible adhesion. MD simulation was thus found to accurately predict interactions critical to mucoadhesion and the same could be fairly correlated well by relevant mucoadhesion studies both in vitro and in vivo.

Enhanced production of cadaverine by the addition of hexadecyltrimethylammonium bromide to whole cell system with regeneration of pyridoxal-5'-phosphate and ATP.

Cadaverine, also known as 1,5-pentanediamine, is an important platform chemical with a wide range of applications and can be produced either by fermentation or bioconversion. Bioconversion of cadaverine from l-lysine is the preferred method because of its many benefits, including rapid reaction time and an easy downstream process. In our previous study, we replaced pyridoxal-5-phosphate (PLP) with pyridoxal kinase (PdxY) along with pyridoxal (PL) because it could achieve 80% conversion with 0.4 M of l-lysine in 6 h. However, conversion was sharply decreased in the presence of high concentrations of l-lysine (i.e., 1 M), resulting in less than 40% conversion after several hours. In this study, we introduced an ATP regeneration system using polyphosphate kinase (ppk) into systems containing cadaverine decarboxylase (CadA) and PdxY for a sufficient supply of PLP, which resulted in enhanced cadaverine production. In addition, to improve transport efficiency, the use of surfactants was tested. We found that membrane permeabilization via hexadecyltrimethylammonium bromide (CTAB) increased the yield of cadaverine in the presence of high concentrations of l-lysine. By combining these two strategies, the ppk system and addition of CTAB, we enhanced cadaverine production up to 100% with 1 M of l-lysine over the course of 6 h.

Effect of cetyltrimethylammonium bromide (CTAB) on the conformation of a hen egg white lysozyme: A spectroscopic and molecular docking study.

The interactions between cetyltrimethylammonium bromide (CTAB) and hen egg white lysozymes (HEWL) was carried out to investigate protein-surfactant interaction mechanisms while both exist in the overall same charged state. The interactions between CTAB and the HEWL were examined with circular dichroism (CD), dynamic light scattering (DLS), fluorescence spectroscopy, and computational docking at a pH9.0 at room temperature. The far-UV CD and fluorescence results revealed that CTAB at concentrations from 0.15 to 10.0mM influenced the secondary as well as the tertiary structure of HEWL. The secondary structure of the HEWL was retained, while the tertiary structure of the HEWL was disrupted in the CTAB-treated samples at pH9.0. The hydrodynamic radii of the HEWL were also expanded in the presence of CTAB. Molecular docking studies showed that CTAB formed one electrostatic and four hydrophobic interactions, as well as one carbon hydrogen bond with HEWL. The data obtained from spectroscopic and computational studies demonstrated that the positively charged head and 18­carbon alkyl chain of the CTAB interacted through weak electrostatic and strong hydrophobic interactions.

Bare surface of gold nanoparticle induces inflammation through unfolding of plasma fibrinogen.

The surface of nanoparticles (NPs) get coated by a wide range of biomolecules, upon exposure to biological fluids. It is now being increasingly accepted that NPs with particular physiochemical properties have a capacity to induce conformational changes to proteins and therefore influence their biological fates, we hypothesized that the gold NP's metal surface may also be involved in the observed Fg unfolding and inflammatory response. To mechanistically test this hypothesis, we probed the interaction of Fg with gold surfaces using molecular dynamic simulation (MD) and revealed that the gold surface has a capacity to induce Fg conformational changes in favor of inflammation response. As the integrity of coatings at the surface of ultra-small gold NPs are not thorough, we also hypothesized that the ultra-small gold NPs have a capacity to induce unfolding of Fg regardless of the composition and surface charge of their coatings. Using different surface coatings at the surface of ultra-small gold NPs, we validated this hypothesis. Our findings suggest that gold NPs may cause unforeseen inflammatory effects, as their surface coatings may be degraded by physiological activity.

Metagenomic analysis of microbial communities yields insight into impacts of nanoparticle design.

Next-generation DNA sequencing and metagenomic analysis provide powerful tools for the environmentally friendly design of nanoparticles. Herein we demonstrate this approach using a model community of environmental microbes (that is, wastewater-activated sludge) dosed with gold nanoparticles of varying surface coatings and morphologies. Metagenomic analysis was highly sensitive in detecting the microbial community response to gold nanospheres and nanorods with either cetyltrimethylammonium bromide or polyacrylic acid surface coatings. We observed that the gold-nanoparticle morphology imposes a stronger force in shaping the microbial community structure than does the surface coating. Trends were consistent in terms of the compositions of both taxonomic and functional genes, which include antibiotic resistance genes, metal resistance genes and gene-transfer elements associated with cell stress that are relevant to public health. Given that nanoparticle morphology remained constant, the potential influence of gold dissolution was minimal. Surface coating governed the nanoparticle partitioning between the bioparticulate and aqueous phases.