Metallogels from Silver Nanoparticles and Peptide Nanofibers as Antimicrobial Surfaces

Abstract

Peptide amphiphiles (PAs) are elusive candidates to construct soft materials possessing various functionalities, including potent antimicrobial activity. It is imperative to look for a broadspectrum antibiotic against which the genesis of drug resistance is difficult. Herein, a histidine-based PA is found to form a transparent metallohydrogel when AgNO 3 is added to a hot solution of the PA in 2:1 (PA/AgNO 3 ) molar ratio. Exposure to 365 nm UV lamp results in blue light-emitting silver nanocluster (NC) formation inside the hydrogel matrix. Interestingly, when the metallohydrogel is turned in solution through sheer thinning and rested for 12−14 h in ambient light, the gel reforms along with the formation of non-fluorescent silver nanoparticles (NPs). Thus, two different nanomaterials can be synthesized separately inside the gel matrix with modulation of the conditions. As the NC and NP formation takes place, ordered growth of these nanomaterials can be observed along the nanofibrous hydrogel network. Rheological measurements show enhancement of storage modulus in NC-and NP-containing hybrid hydrogels. This new nanohybrid system comprising peptide gel-based nanofibers and silver NC/NPs has potential applications against Gram-positive and Gram-negative bacteria. Furthermore, the plausible mechanism of the antimicrobial effects has been thoroughly investigated. The elevated levels of reactive oxygen species (ROS) found in the bacteria in the presence of the hybrid hydrogels establish that intra-cellular ROS generated in the cytosol of the bacteria is responsible for the death of bacteria. The current work indicates the hybrid hydrogel's utility as a potent antimicrobial agent.

Carbon-Dot-Decorated Silver and Gold Nanocomposites for Antibacterial Activity and Degradation of Organic Dyes

“…ROS generated inside the cells leads to oxidative stress and DNA damage, finally causing cell death. 56,57 As discussed earlier, the increasing amount of CD-AgNP increased the intracellular ROS production, and it is clear from Figure S9a that at MIC an elevated level of ROS in the cells was detected. Therefore, it can be concluded that the complete killing of bacteria by CD-AgNP is attained by a mixed pathway of membrane rupture and intracellular ROS production (Figure 8a).…”

Exploration of Variable Solvent Directed Self-Healable Supramolecular M(II)-Metallogels (M = Co, Ni, Zn) of Azelaic Acid: Investigating Temperature-Dependent Ion Conductivity and Antibacterial Efficiency

“…CFUs observations of the metallogel-treated cell culture in TGE-agar plates evidentially demonstrated the cell viability and also confirmed that all the metallogels have growth inhibition ability but are not fatal to the bacteria cells. In general, metal ions exhibit diverse antimicrobial activities, and these properties have been recognized throughout the history of medicine and healthcare. − In this study, the metallogels showed antimicrobial activity against both Gram-positive and Gram-negative bacteria . However, the effectiveness of antimicrobial activity varies between metallogels. , In the present work, it was found that Ni­(II)-metallogel showed slight antimicrobial efficiency compared to Co­(II)-metallogel and Zn­(II)-metallogel of azelaic acid used as the low molecular weight organic gelator.…”

“…hydrogen bonding interaction, van der Waals forces, dipole–dipole, charge transfer, π–π stacking, etc., are established in literature. − Integration of metal ion with the gelators proposes a noteworthy platform to functionalize soft materials with added superior beneficial functionalities . Few celebrated practical applications of gels such as nonlinear optics, , artificial light-harvesting systems, , molecular sensing, , biomedical applications, drug delivery, − tissue engineering, , cell imaging, antibacterial and antifungal activity, − 3D printing, magnetism, , catalysis, , electronics, − light emitting diodes, biotechnology, , etc. are recognized in the scientific domain.…”

Cationic and amphiphilic peptide-based hydrogels with dual activities as anticancer and antibacterial agents

“…Various studies have shown that antibiotics can kill bacteria either by generation of reactive oxygenase species (ROS) or by specific mechanisms of action. 51,52 To explore the effectiveness of the hydrogels as antibiotics a study is designed to generate ROS through synergistic interaction between antibiotics and ROS producing materials. 51 For the above-mentioned study E. coli is treated with different concentrations of the CP1 hydrogel at 10-200 mg mL À1 and 2 0 ,7 0 -dichlorodihydrofluorescein diacetate (DCFDA) is used as the probe.…”

“…51,52 To explore the effectiveness of the hydrogels as antibiotics a study is designed to generate ROS through synergistic interaction between antibiotics and ROS producing materials. 51 For the above-mentioned study E. coli is treated with different concentrations of the CP1 hydrogel at 10-200 mg mL À1 and 2 0 ,7 0 -dichlorodihydrofluorescein diacetate (DCFDA) is used as the probe. DCFDA is a non-fluorescent dye converted into fluorescent 2 0 ,7 0 -dichlorodihydrofluorescein (DCF) in the presence of ROS to measure the efficiency of the hydrogel.…”