Squaramide-Immobilized Carbon Nanoparticles for Rapid and High-Efficiency Elimination of Anthropogenic Mercury Ions from Aquatic Systems

Synthesis and Structural Analysis of New (-)-Cytisine Squaramides

Derivatives of squaric acid are valuable building blocks with promising applications in the investigation of various bioactivities. In this study, we focus on squaramides functionalized with the (-)-cytisine moiety, an alkaloid known for its bioactivity as a nicotinic acetylcholine receptor agonist and its application in nicotine addiction treatment. Reactions of cytisine-monosquarate with several amines, such as ammonia, propargylamine, and morpholine, led to the formation of novel conjugates of cytisine-squaramides. Additionally, squaramide containing two cytisine moieties was synthesized via the reaction of diethyl squarate with cytisine at a 1:2 molar ratio. All obtained squaramides were thoroughly characterized by MS, FT-IR, and NMR methods and by single-crystal X-ray diffraction analysis. To gain deeper insights into their structural properties and intermolecular interactions, geometry optimizations were performed using DFT calculations, complemented with 3D molecular electrostatic potential maps.

Curcumin-assisted Preparation of α-Fe2O3@TiO2 Nanocomposites for Antibacterial and Photocatalytic Activity

BACKGROUND

Harmful microorganisms like pathogens significantly impact human health. Meanwhile, industrial growth causes pollution and water contamination by releasing untreated hazardous waste. Effective treatment of these microorganisms and contaminants is essential, and nanocomposites may be a promising solution. The present attempt demonstrates the green synthesis of α-Fe2O3@TiO2 nanocomposites (FTNCs) for the effective treatment of pathogens and organic contaminants.

METHODS

The FTNCs have been synthesized through a green approach utilizing curcumin extract. Curcumin (Turmeric) extract (TEx) was prepared by washing, drying, and crushing 5 g of turmeric, then boiling it in 100 mL distilled water at 70°C for 1 hour. Metal salts (Fe3+/Ti4+, 2:1) were added to 100 mL of TEx under continuous stirring at 70°C for 24 h. The solution was rinsed and dried at 80°C overnight and heated at 300°C for 3 h to remove impurities.

RESULTS

Synthesized FTNCs have been tested for the potent antibacterial activity against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Salmonella Abony, Pseudomonas sp.). Observations discovered noteworthy inhibition of both Gram-positive and Gramnegative bacteria by FTNCs. Furthermore, the FTNCs system shows the energy band gap of ~2.6 eV which may suppress electron recombination, thereby enhancing photocatalysis. The photo-degradation is examined against Evans blue (EB) and Congo red (CR) dyes under UV and visible light (125 W) irradiation. The remarkable photocatalytic degradation efficiency (DE) for CR reached ~67.4% in 60 min.

CONCLUSION

A simple green approach has been demonstrated for the synthesis of the FTNCs using curcumin-mediated reduction. As prepared FTNCs have been evaluated for potent antibacterial activity against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Salmonella Abony, Pseudomonas sp.). The results show that the highest zone of inhibition diameter values have been obtained for 5 mg/mL concertation of FTNCs of ~14, 22, 18, 21, and 20 and 29 mm for E. coli, S. abony, S. aureus, B. subtilis, E. faecalis, and Pseudomonas sp., respectively. Additionally, FTNCs demonstrate remarkable photocatalytic degradation efficiency against EB and CR dyes under UV (125 W) irradiation, achieving 56, 67% degradation within 60 min, respectively. The findings indicate that FTNCs show long-term antimicrobial effectiveness and potential for water treatment through photocatalysis. This examination highlights recent advancements in intellectual property rights (IPR) and patent strategies, shedding light on how patents influence eco-friendly synthesis and the development of multifunctional, high-performance nanocomposites.

High-Efficiency Broad-Spectrum Antibacterial Activity of Chitosan/Zinc Ion/Polyoxometalate Composite Films for Water Treatment

The development of multifunctional films with rapidly killing microorganisms and adsorbing residual antibiotics in wastewater remains a challenging endeavor. In this work, the chitosan/zinc ion/polyoxometalate (CS/Zn2+/POM) multifunctional films were prepared by the freeze-drying method using chitosan, ZnO, and POM. Notably, the CS/Zn2+/POM films exhibited excellent bactericidal properties against Gram-positive/negative bacterial strains including Staphylococcus aureus (S. aureus, 99.80%), Escherichia coli (E. coli, 99.82%), and drug-resistant E. coli bacterial strains (kanamycin-resistant E. coli, 87.76% and ampicillin-resistant E. coli, 99.71%). This may be due to the chelation of Zn2+ with CS disrupting the cell membrane and bringing POM into direct contact with bacteria, leading to bacterial death. In addition, the CS/Zn2+/POM films showed good adsorption performance to a tetracycline (TC) solution (adsorption rate 75.2%). Further studies showed that the main process of tetracycline removal by CS/Zn2+/POM films was controlled by a physical adsorption. This POM-based film material has an important potential for the synthesis of broad-spectrum antimicrobial materials for the removal of residual antibiotics from water pollutants such as tetracycline.

New Zein Protein Composites with High Performance in Phosphate Removal, Intrinsic Antibacterial, and Drug Delivery Capabilities

Herein, poly(N-(4-aminophenyl)methacrylamide)-carbon nano-onions [abbreviated as PAPMA-CNOs (f-CNOs)] integrated gallic acid cross-linked zein composite fibers (ZG/f-CNOs) were developed for the removal/recovery of phosphate from wastewater along with controlled drug delivery and intrinsic antibacterial characteristics. The composite fibers were produced by Forcespinning followed by a heat-pressure technique. The obtained ZG/f-CNOs composite fibers presented several favorable characteristics of nanoadsorbents and drug carriers. The composite fibers exhibited excellent adsorption capabilities for phosphate ions. The adsorption assessment demonstrated that composite fibers process highly selective sequestration of phosphate ions from polluted water, even in the presence of competing anions. The ZG/f-CNOs composite fibers presented a maximum phosphate adsorption capacity (qmax) of 2500 mg/g at pH 7.0. This represents the most efficient phosphate adsorption system among all of the reported nanocomposites to date. The isotherm studies and adsorption kinetics of the adsorbent showed that the adsorption experiments followed the pseudo-second-order and Langmuir isotherm model (R2 = 0.9999). After 13 adsorption/desorption cycles, the adsorbent could still maintain its adsorption efficiency of 96-98% at pH 7.0 while maintaining stability under thermal and chemical conditions. The results mark significant progress in the design of composite fibers for removing phosphates from wastewater, potentially aiding in alleviating eutrophication effects. Owing to the f-CNOs incorporation, ZG/f-CNOs composite fibers exhibited controlled drug delivery. An antibiotic azithromycin drug-encapsulated composite fibers presented a pH-mediated drug release in a controlled manner over 18 days. Furthermore, the composite fibers displayed excellent antibacterial efficiency against Gram-positive and Gram-negative bacteria without causing resistance. In addition, zein composite fibers showed augmented mechanical properties due to the presence of f-CNOs within the zein matrix. Nonetheless, the robust zein composite fibers with inherent stimuli-responsive drug delivery, antibacterial properties, and phosphate adsorption properties can be considered promising multifunctional composites for biomedical applications and environmental remediation.

Bifunctional backbone modified squaramide dipeptides as amyloid beta (Aβ) aggregation inhibitors

Alzheimer's disease (AD) is a devastating neurodegenerative condition with complex pathophysiology. Aggregated amyloid beta (Aβ) peptide plaques and higher concentrations of bio-metals such as copper (Cu), zinc (Zn), and iron (Fe) are the most significant hallmarks of AD observed in the brains of AD patients. Therefore simultaneous inhibition of Aβ peptide aggregation and reduction of metal stress may serve as an effective therapeutic approach for treating Alzheimer's disease. A series of bifunctional dipeptides bearing squaramide backbone were synthesized and investigated for their ability to chelate metal ions and prevent Aβ peptide aggregation. Dipeptides with Valine (V) and Threonine (T) substitutions at the C-terminus exhibited preferential chelation with Cu(II), Zn(II), and Fe(III) metal ions in the presence of other metal ions. They were also found to inhibit the aggregation of Aβ peptide in-vitro. A further molecular dynamics (MD) simulation study demonstrated that these two dipeptides interact with the Aβ peptide in the hydrophobic core (KLVFF) region. Circular dichroism (CD) study revealed slight conformational change in the Aβ peptide upon the interactions with dipeptides. Apart from metal chelation and inhibition of Aβ peptide aggregation, the selected dipeptides were found to possess anti-oxidant properties. Therefore, the squaramide backbone-modified dipeptides may serve as an active bifunctional scaffold towards the development of new chemical entities for the treatment of Alzheimer's disease.

Development of fluorescent carbon nanoparticles from Madhuca longifolia flower for the sensitive and selective detection of Cr6+: a collective experimental-computational approach

Herein, blue-emitting carbon nanoparticles (CNPs) were synthesized using the Madhuca longifolia flower for the highly selective and sensitive detection of Cr6+ ions in aqueous media using a simple, green, and cost-effective approach, and computational experiments were also performed. The prepared CNPs were well-dispersed in water with an average diameter of 12 nm and functionalized with carbonyl, hydroxyl and carboxylic acid groups. The decrease in the fluorescence intensity of the CNPs with an increase in the content of Cr6+ provided an important signal for the sensitive and selective detection of Cr6+ in aqueous media. The limit of detection for Cr6+ in an aqueous medium was found to be 103 ppb, which is more sensitive in comparison with the previously reported study. Furthermore, the validation of the proposed higher sensing feature and more selective nature of the CNPs towards Cr6+ was also explained using an in silico approach. The results from the theoretical calculations based on the DFT approach demonstrated that the binding energy (BE) of the CNPs with three transition metal (TM) cations (Cr6+, Fe3+, and Hg2+) follows the order of Cr6+ > Fe3+ > Hg2+, where the Cr6+ TM cation associated with the CNPs possesses the highest valence state, showing the highest sensing feature and highest selectivity among the investigated ions, as expected. The metal ions associated with the CNPs having a higher charge and a smaller radius indicated a higher BE and larger degree of deformation of the CNPs. Moreover, to achieve new insights into the structural, stability/energetics, and electronic features, some useful tools, such as NCI-plot, HOMO-LUMO gap, MESP, and QTAIM analysis were employed, which facilitated noteworthy outcomes.

Synthesis and Investigation of Backbone Modified Squaramide Dipeptide Self-Assembly

Dipeptides are minimalistic peptide building blocks that form well ordered structures through molecular self-assembly. The driving forces involved are cooperative noncovalent interactions such as π-π stacking, hydrogen bonding, and ionic as well as hydrophobic interactions. One of the most intriguing self-assembled motifs that has been extensively explored as a low molecular weight hydrogel for drug delivery, tissue engineering, imaging and techtonics, etc. is Phe-Phe (FF). The backbone of the dipeptide is very crucial for extending secondary structures in self-assembly, and any subtle change in the backbone drastically affect the molecular recognitions. The squaramide (SQ) motif has the unique advantage of hydrogen bonding which can promote the self-assembly process. In this work we have integrated the SQ unit into the dipeptide FF backbone to achieve molecular self-assembly. The resulting carbamate protected backbone modified dipeptide (BocFSAF-OH, 10) has exhibited molecular self-assembly with a fibrilar network. It formed a stable hydrogel (with CAC of 0.024 ± 0.0098 wt %) via the solvent switch method and was found to possess excellent enzymatic stability. The dipeptide and the resulting hydrogel were found to be cytocompatible. When integrated with a polysaccharide based biopolymer, e.g. sodium alginate, the resulting matrix exhibited strong hydrogel character. Therefore, the dipeptide hydrogel of 10 may find its applications in a variety of fields including drug delivery and tissue engineering.