Epsilon-polylysine based magnetic nanospheres as an efficient and recyclable antibacterial agent for Alicyclobacillus acidoterrestris

Enhanced Antibacterial Efficiency and Anti-Hygroscopicity of Gum Arabic-ε-Polylysine Electrostatic Complexes: Effects of Thermal Induction

The aim of this investigation was to scrutinize the effects of a thermal treatment on the electrostatic complex formed between gum arabic (GA) and ε-polylysine (ε-PL), with the goal of improving the antibacterial properties and reducing the hygroscopicity of ε-PL. The heated complex with a ratio of 1:4 exhibited an encapsulation efficiency of 93.3%. Additionally, it had an average particle size of 350.3 nm, a polydispersity index of 0.255, and a zeta potential of 18.9 mV. The formation of the electrostatic complex between GA and ε-PL was confirmed through multispectral analysis, which demonstrated the participation of hydrogen bonding and hydrophobic and electrostatic interactions, as well as the enhanced effect of heat treatment on these forces within the complex. The complex displayed a core-shell structure, with a regular distribution and a shape that was approximately spherical, as observed in the transmission electron microscopy images. Additionally, the heated GA-ε-PL electrostatic composite exhibited favorable antibacterial effects on Salmonella enterica and Listeria monocytogenes, with reduced minimum inhibitory concentrations (15.6 μg/mL and 62.5 μg/mL, respectively) and minimum bactericidal concentrations (31.3 μg/mL and 156.3 μg/mL, respectively) compared to free ε-PL or the unheated electrostatic composite. Moreover, the moisture absorption of ε-PL reduced from 92.6% to 15.0% in just 48 h after being incorporated with GA and subsequently subjected to heat. This research showed a way to improve the antibacterial efficiency and antihygroscopicity of ε-PL, reducing its application limitations as an antimicrobial substance to some extent.

A high-performance fluorescent and ratiometric colorimetric detection of Cu2+ in practice

To monitor Cu2+ efficiently, a kind of D-π-A-π-D conjugated 3,5-di-(2-hydroxyl naphthaldehyde)-iminyl triazole (HNIT) was developed, using triazole as the electron acceptor, 2-hydroxyl naphthaline as the electron donor, and -CN- as the bridging group. The proposed HNIT possessed superior UV-vis and fluorescent spectral property with high molar absorption coefficient of 2.313 × 104 L mol-1 cm-1 and fluorescence quantum yield of 36.2%. Trace Cu2+ could exclusively alter its UV-vis and fluorescent property with clear color change. Under the optimized conditions, a high-performance fluorescent and ratiometric colorimetric detection of Cu2+ based on HNIT was efficient, with low detection limits of 3.3 × 10-8 mol L-1 (S/N = 3) and 9.6 × 10-8 mol L-1 (S/N = 3), respectively. It well satisfied with the safe value of 31.5 μM Cu2+ in drinking water recommended by World Health Organization (WHO). When applied for detection of Cu2+ in real environmental samples, the recovery was in the range of 97.5-105.2%. The recognition mechanism for HNIT to Cu2+ realized quite stable 6-membered rings between electron-deficient Cu2+ and electron-rich N and O atoms in HNIT with 1 : 2 chemical stoichiometry of HNIT to Cu2+.

The Use of Phage Cocktail and Various Antibacterial Agents in Combination to Prevent the Emergence of Phage Resistance

Bacterial food poisoning cases due to Salmonella and E. coli O157:H7 have been linked with the consumption of a variety of food products, threatening public health around the world. This study describes the combined effects of a phage cocktail (STG2, SEG5, and PS5), EDTA, nisin, and polylysine against the bacterial cocktail consisting of S. typhimurium, S. enteritidis, and E. coli O157:H7. Overall, phage cocktail (alone or in combination with nisin or/and polylysine) not only showed great antibacterial effects against bacterial cocktail at different temperatures (4 °C, 24 °C, and 37 °C), but also totally inhibited the emergence of phage resistance during the incubation period. These results suggest that the combination of phages with nisin or/and polylysine has great potential to simultaneously control S. typhimurium, S. enteritidis, and E. coli O157:H7.

Bioconjugation studies of an EGF-R targeting ligand on dendronized iron oxide nanoparticles to target head and neck cancer cells

A major challenge in nanomedicine is designing nanoplatforms (NPFs) to selectively target abnormal cells to ensure early diagnosis and targeted therapy. Among developed NPFs, iron oxide nanoparticles (IONPs) are good MRI contrast agents and can be used for therapy by hyperthermia and as radio-sensitizing agents. Active targeting is a promising method for selective IONPs accumulation in cancer tissues and is generally performed by using targeting ligands (TL). Here, a TL specific for the epidermal growth factor receptor (EGFR) is bound to the surface of dendronized IONPs to produce nanostructures able to specifically recognize EGFR-positive FaDu and 93-Vu head and neck cancer cell lines. Several parameters were optimized to ensure a high coupling yield and to adequately quantify the amount of TL per nanoparticle. Nanostructures with variable amounts of TL on the surface were produced and evaluated for their potential to specifically target and be thereafter internalized by cells. Compared to the bare NPs, the presence of the TL at the surface was shown to be effective to enhance their internalization and to play a role in the total amount of iron present per cell.

Synthesis of silver/Fe3O4@chitosan@polyvinyl alcohol magnetic nanoparticles as an antibacterial agent for accelerating wound healing

Bacterial infection causes wound inflammation and slows wound healing, posing a great threat to human health, which needs to explore more antibacterial nanobiomaterials to promote wound healing. Therefore, this study was conducted to develop low-cost silver/Fe₃O₄@Chitosan@polyvinyl alcohol (Ag/Fe₃O₄@CS@PVA) via a one-pot method to promote healing in bacteria-infected wounds. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) confirmed that Ag/Fe₃O₄@CS@PVA was successfully prepared. In vitro antibacterial experiments demonstrated strong antibacterial activity of Ag/Fe₃O₄@CS@PVA against Escherichia coli and Staphylococcus aureus. The Ag/Fe₃O₄@CS@PVA destroyed the bacterial cell membrane or internal structure, thus resulting in cell death for antibacterial effects. Cytotoxicity and hemolysis rate tests showed that Ag/Fe₃O₄@CS@PVA posed fine biocompatibility. In addition, in vivo assays confirmed that Ag/Fe₃O₄@CS@PVA not only promoted the healing of wound infection caused by bacteria, but also had no toxic effect on mouse organs. Therefore, the low-cost Ag/Fe₃O₄@CS@PVA nanocomposites have great potential in controlling 'bacterial' pathogen.

Continuous preparation of a nontoxic magnetic fluid as a dual-mode contrast agent for MRI

Ultrasmall nanoparticle contrast agents provide dual-mode MRI. However, the application of ultrasmall nanoparticle contrast agents is limited by low manufacturing outputs and cumbersome preparation processes. Herein, we report a novel continuous-flow coprecipitation method for the preparation of the Fe₃O₄ nanoparticles magnetic fluid (CFCPFe) coated with ultrasmall cysteine-terminated polymethacrylic acid (Cys-PMAA). The preparation process is more coherent, simpler, and less expensive. Compared with magnetic fluids prepared by the conventional method (Cys-PMAA@Fe₃O₄), CFCPFe has smaller particle sizes (3.27 ± 0.93 nm). Moreover, CFCPFe demonstrates excellent stability for >180 days with different pH values (pH = 2-12) and salt concentrations (up to 2 mol/L). In addition, HEK293T cytotoxicity tests, hemolysis tests, and H&E tissue sections show excellent in vitro and in vivo biocompatibility. In vitro magnetic resonance imaging (MRI) at 1.5 T shows that the r₂ value (50.51 mM^-1·s^-1) of CFCPFe is slightly lower than that of Combidex (r₂ = 65 mM^-1·s^-1) and that the r₁ value (9.54 mM^-1·s^-1) is 2.7 times higher than that of Gd-DTPA (r₁ = 3.5 mM^-1·s^-1). Finally, in vivo imaging shows that CFCPFe reaches the tumor region of the mouse liver cancer model, and a small tumor can be observed in dual-mode imaging. This work offers an effective method for the preparation of a low-cost, stable, and biocompatible ultrasmall contrast agent exhibiting a strong magnetic-imaging effect for dual-mode imaging.

Silver nanoparticles anchored magnetic self-assembled carboxymethyl cellulose-ε-polylysine hybrids with synergetic antibacterial activity for wound infection therapy

The severe bacterial infection and chronic wound healing caused by the abuse of antibiotics threaten the public health, which calls the need for the development of novel antibacterial agents and alternative therapeutic strategies. Herein, magnetic carboxymethyl cellulose-ε-polylysine hybrids (FCE) were synthesized via a facile one-pot coprecipitation method and further used as matrix to anchor silver nanoparticles (Ag NPs). The as-resulted Ag/FCE hybrids were employed to inactivate pathogenic bacteria and accelerate bacteria-infected wound healing with the assistance of H₂O₂. In vitro investigation revealed the combination of hydroxyl radical (·OH) originated from low concentration of H₂O₂ catalyzed by Ag/FCE and the antimicrobial activity of Ag NPs endowed effective antibacterial performance to the hybrids against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Investigation on antibacterial mechanism indicated antibacterial activity of the synergetic strategy was achieved by destroying bacterial cell integrity, arresting metabolic, producing intracellular ROS, and oxidizing GSH. Additionally, in vivo assay exhibited Ag/FCE possessed satisfactory biocompatibility and effectively accelerated S. aureus-infected wound healing with the presence of low concentration of H₂O₂. Altogether, the presented results supported the great potential application of the synergistic antibacterial strategy for the therapy of bacterial-infected wound healing.